Ultrasound of the Musculoskeletal System

Contents MEDICAL RADIOLOGY Diagnostic Imaging Editors: A. L. Baert, Leuven M. Knauth, Göttingen K. Sartor, Heidelberg...

Author: Stefano Bianchi | Carlo Martinoli | I.F. Abdelwahab | A.L. Baert | L.E. Derchi | G. Rizzatto | M. Valle | M.P. Zamorani

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Contents

MEDICAL RADIOLOGY

Diagnostic Imaging Editors: A. L. Baert, Leuven M. Knauth, Göttingen K. Sartor, Heidelberg

I

Contents

Stefano Bianchi · Carlo Martinoli

Ultrasound of the Musculoskeletal System With Contributions by

L. E. Derchi · G. Rizzatto · M. Valle · M. P. Zamorani Foreword by

A. L. Baert

Introduction by

I. F. Abdelwahab

With 1111 Figures in 3669 Separate Illustrations, 286 in Color

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Contents

Stefano Bianchi, MD Privat-docent Université de Genève Consultant Radiologist Fondation et Clinique des Grangettes 7, ch. des Grangettes 1224 Genève Switzerland

Carlo Martinoli, MD Associate Professor of Radiology Cattedra “R” di Radiologia - DICMI Università di Genova Largo Rosanna Benzi, 8 16132 Genova Italy

Medical Radiology · Diagnostic Imaging and Radiation Oncology Series Editors: A. L. Baert · L. W. Brady · H.-P. Heilmann · M. Knauth · M. Molls · C. Nieder · K. Sartor Continuation of Handbuch der medizinischen Radiologie Encyclopedia of Medical Radiology

Library of Congress Control Number: 2003057335

ISBN 978-3-540-42267-9 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitations, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. Springer is part of Springer Science+Business Media http//www.springer.com ¤ Springer-Verlag Berlin Heidelberg 2007 Printed in Germany The use of general descriptive names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every case the user must check such information by consulting the relevant literature. Medical Editor: Dr. Ute Heilmann, Heidelberg Desk Editor: Ursula N. Davis, Heidelberg Production Editor: Kurt Teichmann, Mauer Cover-Design and Typesetting: Verlagsservice Teichmann, Mauer Printed on acid-free paper – 21/3151xq – 5 4 3 2 1 0

Contents

D e dicat ion

To Maria Pia, Elena and Eugenio, the loves of my life – S.B. To Maura and Roberto, for their love, support and forbearance – C.M.

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Contents

Series Editor’s Foreword

Modern ultrasound has now acquired a very important role in the spectrum of imaging modalities available for the study of the musculoskeletal system. This technique has become an indispensable tool in the clinical management of sports injuries, degenerative and traumatic lesions of the articulations and periarticular soft tissues, as well as – in certain circumstances – clinical management of the bones. Stefano Bianchi and Carlo Martinoli are internationally renowned leaders in their field who, as a long-standing and remarkable team, have acquired an exceptional expertise. This is amply demonstrated by their numerous and outstanding contributions to the literature, as well as by their worldwide lecturing and participation in teaching seminars on musculoskeletal ultrasound. Although some additional chapters have been authored by other well-known ultrasound specialists, most of the chapters have been prepared and written by Stefano Bianchi and Carlo Martinoli. This feature is a guarantee for uniformity and homogeneity of style, concept and presentation throughout the whole volume. An update of our knowledge and the latest insights into this subject are provided for each anatomic area of the musculoskeletal system. I would like to congratulate the authors most sincerely for their superb efforts in preparing this remarkable volume, which comprehensively covers the extensive and varied spectrum of musculoskeletal diseases, in the management of which ultrasound can make an important, if not essential, contribution to better clinical diagnosis and better guidance of therapy. Moreover, this work is superbly and abundantly illustrated by numerous anatomical drawings, photographs and ultrasound images, all realized with state-of-the-art and high-end equipment. These well chosen illustrations strongly enhance the didactic and educational value of this book. Without doubt, this outstanding volume will be of great value to certified general and musculoskeletal radiologists, radiologists in training, as well as orthopedic surgeons and rheumatologists in their daily clinical practice. I am confident that it will meet with the same success among readers as the previous volumes published in this series. Leuven

Albert L. Baert

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Contents

Foreword

Over the last 15 years, musculoskeletal ultrasonography has become an important imaging modality used in sports medicine, joint disorders, and rheumatology. With the rapid development and sophistication of this modality, essential information for a better understanding of the pathophysiologic assessment of many disorders has been established. This, in turn, has aided both in making crucial decisions regarding surgical intervention and in monitoring the effects of therapy. Equally important is the ready availability, affordability, speed, and diagnostic accuracy of ultrasonography. Ultrasound of the Musculoskeletal System is an invaluable text comprising 19 chapters and approximately one thousand pages and figures. The authors have designed unique schematic drawings which aid in better understanding the anatomy of the body part in terms of its sonographic characteristics discussed in each chapter. Correlations of ultrasonography with CT and MRI findings are applied throughout the text, demonstrating not only the exact indications for its use, but also highlighting its limitations. Technical advances continue to improve the utility of ultrasonography as a diagnostic technique in musculoskeletal imaging. Drs. Bianchi and Martinoli have successfully capitalized on the collaboration between radiologists, orthopedists, and rheumatologists as exemplified by their representative images and correlative discussions. Many of the techniques described in the text have been pioneered or improved by Dr. Bianchi and Dr. Martinoli. This text should become a key library reference source for radiologists, orthopedists, and rheumatologists. It is extremely readable and its illustrations help in the clarification of points made in the text. Ultrasound of the Musculoskeletal System is the most comprehensive work of its kind to date. It establishes a higher standard in musculoskeletal imaging and should remain a classic for years to come. Ibrahim Fikry Abdelwahab, MD Formerly Professor of Radiology The Mount Sinai School of Medicine, Weill Medical College, Cornell University, and New York Medical College

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Preface

The use of ultrasound in the assessment of the musculoskeletal system started many years ago. Nevertheless, the continuing innovations in instrumentation and the advances in clinical applications suggest that we have only just started to “peel the onion” in this field. This fact has also been reflected in the length of time needed to prepare this book. The project started some five years ago, with an approximate estimation of 300 pages to cover the whole field. As our personal experience and the literature expanded as a result of new technological improvements, more and more information was added, resulting in a final book size of over 1000 pages. This textbook can be considered the result of a continuing cooperation of two friends and colleagues who started their common practice many years ago publishing scientific papers and teaching at courses and congresses, and then decided to put their experience into a monograph with the aim of sharing their own knowledge and, most importantly, their enthusiasm for this wonderful imaging technique. Given these considerations, this book aims to cover the whole of this field, thus providing both help to those who are already expert in ultrasound and want to acquire further knowledge and skills in this special area, as well as an introduction to beginners, irrespective of whether they are musculoskeletal radiologists, rheumatologists, orthopaedic surgeons, or in-training residents, among others. Since many of the difficulties encountered while learning musculoskeletal ultrasound result from an inability to correctly interpret the images, many figure captions, references for probe placement, oneto-one correlations with clinical photographs, anatomical and operative specimens, as well as images obtained with other modalities were systematically added to the ultrasound illustrations. Schematic drawings have also been extensively used throughout the chapters to emphasize depiction of anatomy, pathomechanisms and biomechanics underlying the disease processes. It was our deliberate intention to compile the book with a uniform style throughout. This is the reason why most of the chapters have been written by the two editors and by a relatively small numbers of authors who have worked or continue to work with the editors. The book begins with an introductory section on the instrumentation and general aspects of musculoskeletal ultrasound, followed by a systematic overview of the applications of this technique in the different areas of the upper and lower extremities. An additional final section devoted to both interventional and pediatric applications has been included. With regard to certain clinical applications, there is still considerable difference of opinion on the role of musculoskeletal ultrasound as compared to that of other imaging modalities, such as magnetic resonance imaging. Obviously, there is a “bias” towards the use of ultrasound in this text. However, every effort has been made to provide accurate accounts of present knowledge and experience, as well as to indicate the most advanced references of emerging applications.

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A new textbook of this size inevitably contains errors and weaknesses -- we welcome corrections and suggestions for future editions. Meanwhile, happy reading! “Nulla res me delectabit, licet sit eximia et salutaris, quam mihi uni sciturus sum”. (Seneca, Epist. 6,4) “I might not be delighted with anything, even eminent and beneficial, if I am the only one to know it”. (Seneca, Epist. 6,4) Genève Genova

Stefano Bianchi Carlo Martinoli

Acknowledgments We are deeply indebted to the many colleagues who have provided information and illustrations of rare pathology, operative and anatomical views, as well as to the models who helped us to obtain correlative photos of anatomical landmarks. These colleagues are listed below. Special thanks go to Alberto Tagliafico (Genova, Italy) for the task of checking the entire book for errors, to the „Subject Index team“, including Enrico Capaccio, Maria Beatrice Damasio, Nunzia Pignataro, Nicola Stagnaro, Alberto Tagliafico and Simona Tosto, and to Jane Farrell for copyediting the manuscript and correcting language errors. Finally, it is a pleasure to acknowledge the skillful help, pleasant cooperation, and patience of the publisher’s staff during the five years of intense work it has taken to prepare this textbook. Elena and Eugenio Bianchi (Geneva, Switzerland) Silvio Boero (Genova, Italy) Gianni Cicio (Genova, Italy) Giovanni Crespi (Genova, Italy) Marino Delmi (Geneva, Switzerland) Jean H Fasel (Geneva, Switzerland) Sergio Gennaro (Genova, Italy) Maurizio Giunchedi (Lavagna, Italy) Claudio Guido Mazzola (Genova, Italy) Vincenzo Migaleddu (Sassari, Italy) Roberto Pesce (Genova, Italy) Nicolò Prato (Genova, Italy) Fabio Pretolesi (Genova, Italy) Maurizio Rubino (Genova, Italy) Federico Santolini (Genova, Italy) Giovanni Serafini (Pietra Ligure, Italy) Stefano Simonetti (Genova, Italy) Enrico Talenti (Padova, Italy) Paolo Tomà (Genova, Italy) Bruno Valle (Rapallo, Italy) Marzia Venturini (Genova, Italy) The Staff of the Institut de Radiologie, Clinique des Grangettes, (Geneva, Switzerland) and the Cattedra di Radiologia “R” – DICMI, Università di Genova (Genova, Italy).

Contents

Contents

Intrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1 Technical Requirements Lorenzo E. Derchi and Giorgio Rizzatto . . . . . . . . . . . . . . . . . . . . . . .

3

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2 Skin and Subcutaneous Tissue Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 19 3 Muscle and Tendon Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 45 4 Nerve and Blood Vessels Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 97 5 Bone and Joint Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 137

Individual Anatomic Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Upper Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 6 Shoulder Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 189 7 Arm Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 333 8 Elbow Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 349 9 Forearm Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 409 10 Wrist Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 425 11 Hand Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 495

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Lower Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 12 Hip Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 551 13 Thigh Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 611 14 Knee Carlo Martinoli and Stefano Bianchi) . . . . . . . . . . . . . . . . . . . . . . . . 637 15 Leg Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 745 16 Ankle Carlo Martinoli and Stefano Bianchi) . . . . . . . . . . . . . . . . . . . . . . . . 773 17 Foot Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 835

Interventional Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889 18 US-Guided Interventional Procedures Stefano BianchI and Maria Pia Zamorani . . . . . . . . . . . . . . . . . . . . . . 891

Pediatric Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919 19 Pediatric Musculoskeletal Ultrasound Carlo Martinoli and Maura Valle . . . . . . . . . . . . . . . . . . . . . . . . . . . 921

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961 List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975

Technical Requirements

Instrumentation

1


Technical Requirements Lorenzo E. Derchi and Giorgio Rizzatto

1.1.1 Transducers

CONTENTS 1.1 1.1.1 1.1.1.1 1.1.1.2 1.1.1.3 1.1.2 1.1.2.1 1.1.2.2 1.1.2.3 1.1.2.4 1.1.2.5 1.1.2.6 1.1.3

Advances in US Technology 3 Transducers 3 Broadband Transducers 3 Focusing 6 Transducer Selection and Handling 6 Imaging Algorithms 7 Advances in Doppler Imaging 8 Compound Imaging 8 Extended Field-of-View Imaging 9 Steering-Based Imaging 11 Three-Dimensional Imaging 13 Elastographic Imaging 14 Ultrasound Contrast Media 14 References

15

1.1 Advances in US Technology US technology is rapidly advancing and being refined, and is aimed at both increasing image quality and opening new fields of applications. This chapter will review the main advances in US technology and address the clinical impact they have had or are likely to have in the future in the field of the musculoskeletal system. New developments in transducer technology and advances in the quality and presentation of US images will be discussed.

L. E. Derchi, MD Professor of Radiology, Cattedra di Radiologia “R” - DICMI – Università di Genova, Largo Rosanna Benzi 8, 16132 Genova, Italy G. Rizzatto, MD Head of Department of Radiology, Ospedale di Gorizia, 34170 Gorizia, Italy

The transducer is an essential element of US equipment, responsible for the generation of a US beam and the detection of returning echoes. It greatly influences spatial resolution, penetration and signal-to-noise ratio. In recent years, research in transducer technology has been focused on the development of piezoelectric crystals with lower acoustic impedances and greater electromechanical coupling coefficients, as well as on improving the characteristics of absorbing backing layers and quarter-wave impedance matching layers (Claudon et al. 2002). Currently, transducer arrays formed by ceramic polymer composite elements of variable shape and thickness and multilayered technology are used, leading to a more accurate shaping of US pulses in terms of frequency, amplitude, phase and length (Whittingham 1999a; Rizzatto 1999). These refinements led to the use of very short pulses and an increased bandwidth (Fig. 1.1).

1.1.1.1 Broadband Transducers

One of the original objectives in designing broadband transducers was to improve axial resolution without changing the emission frequency. This is related to the fact that the shorter transmission pulses used in a broadband emission generate shorter echo pulses which can be faithfully converted into electric signals (Whittingham 1999b). Because short pulses suffer attenuation to a greater extent and are characterized by less penetration than long pulses, some specific techniques have been introduced by different manufacturers to compensate for these drawbacks, including single-pulse and multi-pulse techniques (Claudon et al. 2002). Among single-pulse techniques, the emission of a long, peculiarly shaped transmission pulse, which varies in frequency and

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L. E. Derchi and G. Rizzatto

a

c

b

d

Fig. 1.1a–d. Relationship between spatial pulse length and frequency spectrum. a,b Intensity versus time diagrams illustrate different pulse lengths (λ). Two sine wave pulses are shown lasting 2 µs (four-cycle) and 1 µs (two-cycle) respectively. c,d Corresponding Fourier power (intensity versus frequency) diagrams show the spectrum of frequencies present in the pulses shown in a and b. The bandwidth is measured between the 6 dB points on each side of the spectrum. The longer pulse in a generates a narrower bandwidth (1 MHz) than the shorter pulse (2 MHz) in b

amplitude within the duration of the pulse itself, has been used instead of a simple sinusoidal pulse (Fig. 1.2). When the signal is received, a filter analyzes the signal frequencies as a short pulse, erasing the components introduced to make it long (chirp): the result is increased image penetration with an improved signal-to-noise ratio, without compromising axial resolution. Other multi-pulse techniques make use of a coded-emission mode consisting of transmission of an integrated sequence of many short, high-frequency transmission pulses which vary in terms of phase and are modulated in a code sequence. When the signal is received, the signal frequencies are compared with the transmission pulses by a matching decoding filter working at a high sampling rate. The subtraction process results in increased image penetration without loss of axial resolution or an increase in emission peak pulses (Claudon et al. 2002).

Apart from advances in emission pulse technology, broadband transducers use a spectrum of frequency distribution (i.e., 12–5 MHz) instead of a single fundamental frequency (i.e., 10 MHz): the high-frequency components tend to increase the intensity maximum in the focal zone but cause a prompt decrease in intensity with depth, whereas the low-frequency components extend the penetration depth (Whittingham 1999b). In multiple-frequency imaging, the available broad bandwidth is subdivided into multiple frequency steps for transmission and reception of sound waves: these transducers enable selection of the optimal frequency range in a given scanning plane as though two or more independent transducers – each with a different center frequency – were available (Fig. 1.3). Other systems use the total transducer bandwidth for the transmitted pulse and then adjust the receiver bandwidth to lower frequencies as deeper depths are


a

b

Fig. 1.2a,b. US pulse shaping. a Intensity versus time diagram illustrates a short pulse wave (arrow) characterized by a few oscillations rapidly dampened by the backing material of the transducer. This short-duration pulse is associated with a broad bandwidth but, when transmitted through tissues, it is rapidly attenuated and absorbed resulting in a poor penetration of the US beam. b Intensity versus time diagram illustrates a chirp pulse. This pulse has a longer duration to increase the penetration of the US beam. It is not a simple sine wave: it is modulated in terms of phase and frequency to include a central component (arrow) – that a receive filter reads as a short pulse to obtain high axial resolution – and two sine queues (arrowheads) on each side of the central component to give penetration capabilities. Example of Chirped Emission (Siemens)

* a

b

c

d Fig. 1.3a–d. Multiple-frequency transducers. a,b Longitudinal US images obtained over the palmar aspect of the hand with a 18–6 MHz multiple frequency transducer by setting the center frequency at a 8 MHz and b 16 MHz respectively. Shifting on the lower frequencies of the bandwidth, penetration (large open arrows) of the field-of-view is achieved; on the other hand, the small superficial cyst (arrowheads) overlying metacarpal bone (thin white arrows) does not appear completely anechoic, subcutaneous tissue echoes are coarse and reverberation artifacts (asterisk) appear deep to the bone. Shifting the frequency band upward, a more defined echotexture is appreciated in the superficial part of the image as a result of an increased resolution. In contrast, a strong attenuation affects the deep part of the US image, which loses intensity. c,d Corresponding intensity versus frequency diagrams illustrate how the frequency band is modulated in multiple-frequency transducers. Example of “eXtreme High-Frequencies imaging” technology (Esaote)

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L. E. Derchi and G. Rizzatto

sampled. These systems give increased flexibility to the US examination, enabling the same transducer to change the image acquisition parameters during scanning based on the desired clinical information. In musculoskeletal imaging, this is particularly important when the study focuses on both superficial (i.e., subcutaneous tissue planes) and deep (i.e., muscle tissue layers) tissues in the same study and body area to be explored.

1.1.1.2 Focusing

Reducing the width and thickness of the US beam has definite advantages in terms of contrast and spatial resolution. In modern linear-array transducers, focusing is currently not obtained by means of a fixed lens as in the old mechanical sector probes in which degrading of the image quality occurred at a short distance from the focal zone (Fig. 1.4a). Focusing is now produced electronically by activating a series of elements in the array with appropriate delays, so that the trigger pulses to the inner elements are delayed with respect to the pulses to the outer ones. In this way a curved wavefront results from constructive interference bringing the US beam toward a focus. By adjusting the values of the delays applied to the trigger pulses, the curvature of the wavefront and, therefore, the focal depth can be changed dynamically. As the resulting wavefront has the characteristics of a short excitation pulse, the axial resolution is preserved. When the pulses are received, the US machine continuously refocuses them according to the position from which the echoes come, thus giving real-time focal tracking along the depth axis: synchronization of the received signals is essential to minimize out-of-axis echo interference. An important factor influencing the lateral resolving power of the system is the dynamic aperture: this is achieved by activating variable numbers of elements dynamically to optimize focusing at many depths. As a rule, the higher the number of channels (electric pathways) involved in this process to activate the elements in a combined mode and with appropriate delays, the higher the complexity and the cost of the equipment, but the more accurately the beam can be focused. Recently, the introduction and refinement of matrix (1.5D probes) transducers led to further progress. In these transducers, the single row of long piezoelectric elements found in a conventional probe is replaced by more layers (three to seven) incorporated into a single thin layer to produce parallel

rows of short elements. The slice thickness of the US image is improved by performing dynamic focusing in the elevation plane (Fig. 1.4b). This leads to better spatial and contrast resolution and reduction of partial-volume averaging artifacts (Rizzatto 1999). A less expensive alternative to 1.5D probes is the use of peculiar acoustic lenses –Hanafy lenses –placed in front of the piezoelectric elements. The Hanafy lens has non-uniform thickness and resonance properties: it produces a narrow and uniform image slice thickness and, simultaneously, a very broad bandwidth pulse. The inner portion of the lens is thinner, resonates at higher frequencies and focuses in the near field, whereas its outer portions resonate at lower frequency and are focused in both transmission and reception at the deepest part of the image providing better penetration (Claudon et al. 2002).

1.1.1.3 Transducer Selection and Handling

A variety of linear-array transducers, including large (>40 mm), medium-sized (4 mm in depth has been regarded as highly sensitive and specific for the diagnosis of necrotizing fasciitis (Yen et al. 2002). In addition, US can reveal loculated abscesses in the fascial plane – allowing US-guided diagnostic aspiration – and gas formation in soft tissues in advanced disease (Robben 2004; Wilson 2004). Gas gangrene, which is produced by organisms of bowel origin or by Clostridium, is an ominous sign (Fig. 2.6b). Aggressive surgical debridement and a course of broad-spectrum antibiotics are critical for the patient’s survival.

2.3.2.3 Fatty Atrophy

Focal reabsorption of the subcutaneous tissue and depigmentation of the overlying skin can be observed following local inadvertent injection of long-acting corticosteroids (Canturk et al. 2004). This “sideeffect” is somewhat related to the catabolic effect of the drug: thinning of the subcutaneous fat is dose-related, may be appreciated up to complete reabsorption of the fatty tissue layer and shows a maximal decrease 4–8 weeks after a single injection of steroids (Gomez et al. 1982). US is a reliable means to confirm the presence of focal shrinkage of the subcutaneous fat by comparing the affected side with either the contralateral healthy side or an adjacent normal area. In clinical practice, focal areas of subcutaneous atrophy may occur around the radial head following steroid injection for treatment of tennis elbow and at the buttock secondary to intramuscular injections. Although the US appearance of subcutaneous atrophy is rather specific, awareness of the clinical history is essential to correlate the US findings with a specific causative factor.

2.3.2.4 Traumatic Injuries

In a traumatic setting, and especially in contusion traumas, changes of the subcutaneous tissue are commonly encountered. Depending on the strength and duration of the insult and the patient’s state

a

b Fig. 2.6a,b. Necrotizing fasciitis. Transverse 12–5 MHz US images over the lower anterolateral leg in a severely compromised diabetic patient with necrotizing fasciitis demonstrate accumulation of fluid along fascial planes (arrows) and scattered bright foci in the soft-tissues refl flecting initial gas formation (arrowheads)

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M. Valle and M. P. Zamorani

(anticoagulation therapy, steroids, etc.), soft-tissue abnormalities may range from simple hemorrhagic infiltration of fat lobules, to fat necrosis, hematomas and abscesses. US reveals bloody fat infiltration as an increased echogenicity of fatty lobules that can make the separation from the hyperechoic skin and the connective tissue strands of the subcutaneous tissue undefined (Fig. 2.7a). Hemorrhagic fat infiltration can be readily distinguished from simple edema because of the absence of anechoic fluid distending the connective septa. The differential diagnosis with a superficial hyperechoic lipoma is based on the clinical history and the oval, well-circumscribed appearance of the soft-tissue mass. Following a contusion trauma, subcutaneous fat necrosis may arise with edema, hemorrhage and fibrosis with lack of a discrete soft-tissue mass and volume loss of the subcutaneous tissue (Tsai et al. 1997; Ehara 1998). Fat necrosis appears as a hyperechoic focus containing hypoechoic spaces related to infarcted fat (Fernando et al. 2003) (Fig. 2.7b). In hematomas, the US appearance of the bloody collection varies over time. Soon after the blood leakage, fresh fluid may appear highly reflective up to a pseudosolid appearance because of fibrin and erythrocytes forming multiple acoustic interfaces. With time, the hematoma tends to become completely anechoic as a result of liquefaction of the clot and increases in size (Fig. 2.8a). A network of thin strands may often be seen resulting from fibrin organization (Fig. 2.8b). Fluid levels reflecting separation between serum (anechoic) and cellular com-

a

*

ponents (echogenic) of blood can also be observed. Over a period of months, the hematoma eventually resolves, but a residual fibrous scar and focal retraction of the overlying skin may persist (Fig. 2.8c). As described in Chapter 12, a hematoma that has a peculiar disposition related to the subcutaneous tissue is the Morel-Lavallée lesion. This condition indicates a post-traumatic seroma which derives from local trauma usually located over the lateral aspect of the proximal thigh. The collection typically intervenes between the deep layer of the subcutaneous tissue and the fascia as a result of a shear strain mechanism causing disruption of the rich vascular plexus that pierces the fascia lata (Morel-Lavallée 1863). US depicts a Morel-Lavallée lesion as an elongated fluid collection overlying the straight echogenic appearance of the fascia (Parra et al. 1997; Mellado et al. 2004). In cases of an abscess secondary to trauma, the examiner should attempt to recognize any possible foreign body within it as the causative factor (Fig. 2.9). This is valid even if the patient denies previous open wounds, because the presence of foreign bodies requires surgical removal. In an effort to exclude a more extensive spread of infection that may deserve different treatment, the examiner should check the status of underlying regional muscles, tendon sheaths and joint spaces. Finally, a contusion trauma on the skin by a pointed, sharp object can be transmitted to the subcutaneous tissue causing laceration and focal discontinuity of fat lobules. This category of lesions results in “fat fractures”

*

Fig. 2.7a,b. Subcutaneous tissue contusion trauma and fat necrosis. a Transverse extended-fi field-of-view 12–5 MHz US image of the trochanteric region in a patient with local contusion trauma after a fall demonstrates an undefi fined increased echogenicity of fatty lobules (arrowheads) refl flecting hemorrhagic fat infi filtration. Note that the abnormal area is located just superfi ficial to the osseous prominence of the greater trochanter (asterisk). b Longitudinal 12–5 MHz US image over the anterolateral thigh in another patient with previous local contusion caused by a sharp object. US shows three well-circumscribed hypoechoic areas (arrows) surrounded by ill-defi fined hyperechoic halo (arrowheads) within the subcutaneous tissue (asterisk) representing fat necrosis

b

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Skin and Subcutaneous Tissue

*

*

a

T b

c Fig. 2.8a–c. Superfi ficial hematoma: spectrum of 12–5 MHz US appearances. a Hematoma of the subcutaneous tissue examined a few days after blunt trauma. US demonstrates an echo-free fl fluid collection (asterisks) reflecting fl the phase of clot liquefaction. b Pretibial hematoma (arrowheads) examined 15 days after trauma reveals closely packed fibrous stranding within the collection refl flecting fibrin organization. T T, tibia. c Residual fibrous scar following a large hematoma in the buttock. US shows the scar as a hyperechoic reflection fl (arrows) with posterior acoustic shadowing (open arrowheads) causing distorsion of the adjacent subcutaneous fat (white arrowheads)

that may mimic a tendon gap at physical examination. US can determine whether the discontinuity is limited to the subcutaneous fat or involves the deeper structures too (Thomas et al. 2001) (Fig. 2.10). Subcutaneous scars are easily depicted with US as vertically -oriented thin linear stripes surrounded by hyperechoic halo that interrupt the normal tissue layers. The abnormal tissue can extend deeply across the fascia into the muscles or the ligaments. Scars may eventually calcify (see Fig. 2.8c).

*

2.3.2.5 Foreign Bodies

Foreign bodies can be found in the subcutaneous tissues as the result of traumatic injuries or therapeutic procedures. In a post-traumatic setting, foreign bodies derive from open or penetrating wounds. Most are composed of plant fragments (wood splinters, thorns, etc.), metal or glass. In terms of prevalence, wood fragments are the most frequently found, fol-

*

a

b Fig. 2.9a,b. Foreign-body-related abscess. a Longitudinal and b transverse 12–5 MHz US images over the dorsum of the hand in a patient with signs of local inflammation fl and a recent open wound. US demonstrates a subcutaneous collection (asterisk) with posterior acoustic enhancement (black arrowheads) and fl fluid-debris levels (open arrowheads). A small highly refl flective foreign body (white arrowhead) is contained within the collection. Surgery revealed an abscess containing a small wood splinter

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* *

* *

*

a

b Fig. 2.10a,b. Subcutaneous fat fracture. a Transverse and b longitudinal 12–5 MHz US images of the gluteal region in a patient with previous local blunt trauma reveal a wide fl fluid-fi filled gap (arrowheads) representing a subcutaneous fat fracture. Note the disrupted appearance of fatty lobules (asterisks) and the alignment of the fracture plane with the edge (white arrow) of the iliac bone

a

d

b

c

e

Fig. 2.11a–e. Foreign bodies: US appearance in two patients presenting with a–c wood and d,e glass fragments. a Long-axis and b short-axis 12–5 MHz US images of a carpenter who injured his left hand during manual work show an elongated hyperechoic foreign-body (arrow) inside the subcutaneous tissue. The fragment is surrounded by a hypoechoic rim (arrowheads) representing reactive edema and granulation tissue. c At surgery, a wood splinter 1 cm long was removed. d Sagittal 12–5 MHz US image of the distal forearm with e radiographic correlation in a patient who had an accident during which he broke a glass with his left hand. Initially, physical exploration was negative for foreign bodies and the wound was sutured. At 3 weeks after trauma, US demonstrated two bright linear images (arrows) with posterior reverberation (arrowheads) refl flecting retained glass fragments in the subcutaneous tissue, just superficial fi to the ulnar nerve (arrowheads). e Radiographic correlation


lowed by glass and metal fragments (Anderson et al. 1982). Part of them may remain at the site and unrecognized even after apparent successful removal by the patient at the time of the injury (Peterson et al. 2002). If missed, foreign bodies can results in granuloma formation, secondary soft-tissue infection with formation of an abscess, fistula, purulent tenosynovitis and septic arthritis. Bone destructive changes and damage to adjacent nerves may also occur (Choudhari et al. 2001; Peterson et al. 2002). An early diagnosis and prompt removal of foreign bodies is required to prevent complications. Physical examination has intrinsic limitations for detecting and localizing small foreign bodies due to the associated local soft-tissue swelling and pain. It has been reported that approximately 38% of foreign bodies can be overlooked at the initial clinical investigation (Anderson et al. 1982). The deep position of a fragment makes palpation more difficult and less successful. Plain radiography is the initial imaging modality to identify and localize foreign bodies but it can only show radio-opaque fragments: even if very small, metallic fragments are readily detected on plain films. Detection of glass fragments depends on their size and, less importantly, on their lead content, as even if lead-free, almost all glass material is radio-opaque to some degree on radiographs (Felman and Fisher 1969). Radiolucent fragments, such as wood splinters, plant thorns and plastic fragments, cannot be detected by X-rays. Although radiographs allow an estimate of the fragment’s location and its relationships with adjacent bones and joints, in relation with tendons, vessels and nerves cannot be investigated. In addition, local complications are not recognized. Xeroradiography and low-kilovoltage radiography have been proposed to increase the detection rate of foreign bodies, but these techniques are currently obsolete. US is an excellent means of detecting and evaluating post-traumatic foreign bodies (Dean et al. 2003; Soudack et al. 2003; Friedman et al. 2005; Jacobson 2005). In cases of suspected foreign bodies, the examiner should extend the study to a larger area than that closely surrounding the skin wound, as fragments may migrate far away from the entrance point as a result of repeated muscle contraction (Choudhari et al. 2001). As an example, it is not unrealistic to hypothesize that a retained fragment entered the soft tissues on the volar aspect of the wrist may dislocate proximally to reach the anterior distal forearm. As assessed in cadaveric and in vivo studies, the US appearance of foreign bodies varies to a great extent depending on the composi-

tion (metal, glass, wood, etc.), shape and site of the fragment (Blyme et al. 1990; Horton et al. 2001). Either radio-opaque or radiolucent fragments can be identified with US as reflective structures with posterior acoustic shadowing or reverberation artifact, depending on the surface characteristics and composition of the foreign body (Boyse et al. 2001; Horton et al. 2001). In general, wood fragments are characterized by posterior acoustic shadowing, whereas glass and metal exhibit reverberations and comet tail artifact (Fig. 2.11). Although these findings lack specificity, they can help to identify foreign bodies as such. Detection of posterior acoustic artifact is particularly helpful for locating tiny fragments that, because of their small size, can go unnoticed. Similarly, a hypoechoic halo surrounding the fragments is of the utmost importance to distinguish them from adjacent soft-tissue structures, such as fat strands or muscles. As assessed in a comparative US-pathologic study, the halo correlates with fibrin, granulation tissue and collagenous capsule formation, whereas the hypervascular pattern seen at color Doppler imaging reflects neovasculature (Davae et al. 2003). The examiner should be aware that US is not accurate for evaluating the fragment’s size, as the technique is able only to delineate its surface. On the other hand, the relationship of foreign bodies with adjacent vessels, tendons, muscles and nerves can be precisely assessed. US can recognize a variety of complications, including abscess, granuloma, infectious tenosynovitis and septic arthritis (Fig. 2.12). Generally speaking, the main limitations of this technique occur in the acute phases of trauma, when open wounds or soft-tissue emphysema may make the examination difficult. In an acute setting, care should be taken to avoid contamination of the open wound with gel. In these circumstances, the use of sterile gel and a lateral approach to the skin wound can be recommended to image the fragment. If the foreign body is retained in the distal arm or in the distal leg, US examination can be better performed by placing the affected extremity in a water bath (Blaivas et al. 2004). As determined in an in vitro study, air bubbling can decrease the visibility of foreign bodies, leading to attenuation of the US beam deep to the gas (Lyon et al. 2004). In a preoperative setting, US can identify the foreign body, place a skin mark over it and measure the depth of the fragment relative to the skin. As described in Chapter 18, US can guide the removal of superficial foreign bodies during real-time scanning (Shiels et al. 1990). In summary, when a foreign body is suspected on clinical grounds, the examiner should briefly

29

30


* * a

* T

T

*

T

b

T

*

T

c

Fig. 2.12a–c. Tenosynovial foreign body. a Short-axis and b long-axis 15–7 MHz US images over the palm show an elongated wood fragment (curved arrow) that has penetrated within the synovial sheath of the flexor tendons (T). A thin hypoechoic effusion (asterisks) in the tendon sheath allows the fragment to be precisely located in the synovial space. c Short-axis color Doppler 15–7 MHz US image reveals a hypervascular flow fl pattern in the flexor tendon sheath as an expression of reactive hyperemia

discuss the context of trauma with the patient to hear about the nature of possible fragments (glass, wood, metal, etc.). Radiographs should be always performed before US examination. Then, US scanning should cover a wide tissue area around the wound, as foreign bodies may migrate far away from the penetration site. The examiner should seek for bright echoes in the soft tissues but, even more, for structures with posterior acoustic attenuation. Once detected, the fragment should be measured as regards its size, orientation, distance from the skin, and relationships with adjacent tendons, nerves and vessels. Signs of possible infectious complications, such as fluid collections and tenosynovitis, should be annotated as well. Instead of writing a long descriptive report, we prefer to mark the skin overlying the fragment reproducing its size and orientation and to measure the depth of the foreign body: these are important pieces of information for the surgeon before removal. For foreign bodies in deep locations, we recommend appending a drawing to the written report in an effort to better explain the relationship of the foreign body with the adjacent structures. Orthopaedic implants (screws, pins, etc.) can be found in the soft tissues as a consequence of loosening of orthopaedic devices. Metallic devices appear as bright hyperechoic structures with posterior reverberation artifact (Fig. 2.13). Although they are easily detected on plain films, US allows an excellent analysis of the relationship of loosened implants with adjacent structures, thus helping to plan their removal (Grechenig et al. 1999). Implantable subcutaneous devices are used as long-acting and effective methods of contraception. They consist of a single rod implanted in the subcutaneous tissue of

the medial aspect of the arm to release levonorgestrol into the systemic circulation. Based of physical findings, identification of the rod can be difficult if it has inadvertently been inserted too deep or it has migrated away from the insertion point. If removal is required, US is an efficient modality to precisely localize nonpalpable rods, thus allowing their easy removal (Amman et al. 2003; Piessens et al. 2005). Rods appear as a small, elongated, hyperechoic structures with well-defined definite posterior acoustic shadowing, an appearance that correlate well with in vitro findings (Fig. 2.14) (Amman et al. 2003). MR imaging should be used only if US is unrewarding (Merki-Feld et al. 2001). Tissue expanders are widely used in plastic and reconstructive surgery (Neumann 1957). US can assess twisting of injection ports that are surgically inserted into the subcutaneous tissue (Kohler et al. 2005). Twisting is associated with failure of the injection procedure and fluid accumulation in the subcutaneous tissue. US easily demonstrates the upside-down position of the port by showing the linear hyperechoic appearance of the metallic base tilted toward the skin replacing the normal concave superior face of the soft silicone component (Kohler et al. 2005). Suture granulomas may occur after a surgical intervention in which nonabsorbable stitches are used. These tumor-like lesions usually develop slowly and may cause only vague symptoms or remain asymptomatic for many years. US is an accurate way to identify and characterize them by depicting suture material within (Fig. 2.15). As assessed in an in vitro study, the US appearance of surgical sutures is independent of their chemical composition. Monofilament sutures appear as straight bright double lines (like railway

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a

b

Cor

c Fig. 2.13a–c. Loosened surgical screw. a Anteroposterior radiograph of the shoulder with correlative b transverse and c splitscreen sagittal 12–5 MHz US images over the pectoralis region in a patient with a loosened screw (curved arrow) following previous surgery on the shoulder. a Radiograph reveals the loosened screw projecting over the right chest but it does not indicate its precise location. b At US examination, the screw (curved arrow) appears as a hyperechoic structure with posterior reverberation artifact (straight arrows) presenting a head (white arrowhead) and multiple hyperechoic teeth (open arrowheads) at its anterior aspect corresponding to screw spirals. In c, the screw appears as a small hyperechoic dot (curved arrow) surrounded by fluid collection (arrowhead) due to local inflammatory fl reaction. US allows accurate assessment of the relationship of the screw with the short head of the biceps and the coracobrachialis muscles (open arrows) arising from the coracoid (Cor)

lines) due to high-amplitude reflection of the US beam at the superficial and deep interface of the suture with the surrounding tissue; braided sutures most often produce a single echo (Rettenbacher et al. 2001). Both patterns show posterior reverberation artifacts. In general, the surrounding granuloma appears as an ill-defined hypoechoic mass, containing a liquefied center where the stitch lies. The main differential diagnoses are granulomas containing other foreign bodies and inflamed epidermoid cysts containing a hair.

2.3.3 Tumors and Tumor-Like Conditions Soft tissue masses of the subcutaneous tissue include a variety of lesions, such as calcifications, tophaceous gout or rheumatoid nodules, sebaceous cysts

and tumors, ranging from the common lipomas and hemangiomas to the rare metastasis and primary malignant masses. Scattered calcifications in the subcutaneous tissue are observed in scleroderma and systemic lupus erythematosus. They appear as mottled hyperechoic lesions with posterior acoustic shadowing. US has little value in their assessment as they are manifest on plain films. Subcutaneous calcifications are often the result of drug injections. For the most part, they are encountered in the buttock and appear as well-delimited hyperechoic structures with strong posterior acoustic shadowing (Fig. 2.16a). In rheumatologic patients, subcutaneous nodules are mainly due to tophaceous gout or rheumatoid nodules (Tiliakos et al. 1982; Benson et al. 1983; Nalbant et al. 2003). Tophi are softtissue agglomerates of uric acid crystals that can develop in different areas of the body: the hand, the foot and the elbow the most commonly involved.

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a

b

c Fig. 2.14a–c. Subdermal contraceptive device (Implanon). a Short-axis and b long-axis 12–5 MHz US images over a flexible fl subdermal plastic implant (arrows) for long-acting release of synthetic hormones. In selected cases, US can assist in the localization and minimally invasive removal of the implant. c Photograph of an Implanon rod after surgical removal

a

b Fig. 2.15a,b. Suture granuloma. a Long-axis and b short-axis 12–5 MHz US images show a suture granuloma located in the lower abdominal wall after inguinal herniorrhaphy. Within the hypoechoic granuloma (arrows), the surgical suture appears as a hyperechoic rail-like line (arrowheads) when imaged in its long-axis. On the short-axis image, the suture assumes the appearance of a double dot (arrowhead)

At US examination, tophi appear as heterogeneous masses containing hypoechoic areas related to chalky liquid material surrounded by hyperechoic tissue (Nalbant et al. 2003). Rarely, calcific deposits can be detected within the tophaceous mass in the form of hyperechoic spots with or without posterior acoustic attenuation (Fig. 2.16b) (Gerster et al. 2002). Rheumatoid nodules occur in 20–30% of

rheumatoid patients who have a high serum level of rheumatoid factor and active articular disease (McGrath and Fleisher, 1989). They seem to derive from an immune complex process between rheumatoid factor and immunoglobulin G initiating small vessel abnormalities and then progressing to necrosis and granulation tissue. Gross examination of these nodules reveals a semifluid center sur-

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* a

b

A

* A

*

A

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d Fig. 2.16a–d. Non-neoplastic subcutaneous masses. a Elaioma. Transverse 12–5 MHz US image demonstrates dystrophic calcification (arrows) in the subcutaneous tissue of the buttock, at the site of previous injection therapy. b Tophaceous gout. Longitudinal 12–5 MHz US image over the forefoot reveals tophi as para-articular ill-defi fined hypoechoic masses (asterisks) with posterior acoustic shadowing (open arrowheads) and hyperechoic surrounding halo (arrows), adjacent to the MIP joint. Note the osteoarthritic changes (white arrowheads) in the underlying joint. c,d Rheumatoid nodules. c Transverse and d longitudinal 12-5 MHz US images over the Achilles tendon (A) in an HIV-positive patient affected by longstanding rheumatoid arthritis show a rheumatoid nodule as a hypoechoic mass (arrows) arising from the paratenon and growing into the subcutaneous tissue. The nodule has a mixed echotexture with solid (asterisk) and fl fluid (arrowheads) components

rounded by dense connective tissue. Rheumatoid nodules are usually found at pressure sites, such as the extensor aspect of the elbow, the fingers and the calcaneus, and correlate with a bad prognosis. US displays hypoechoic masses with a central sharply demarcated hypoechoic area reflecting necrosis (Fig. 2.16c,d) (Nalbant et al. 2003).

2.3.3.1 Lipomas

Superficial lipomas typically appear as compressible, palpable soft-tissue masses in the subcutaneous tissue not adherent with the overlying skin. Lipomas have a male and familial predominance and tend to grow in the back, shoulder and upper arms with a predilection for the extensor surface. They are more common in the fifth and sixth decades. Although lipomas most often present as a solitary

oval or rounded mass, they may be multiple (5%– 15%) (Murphey et al. 2004). At US examination, lipomas have a wide range of appearances. Typically, they present as elliptical compressible masses containing short linear reflective striations that run parallel to the skin (Fig. 2.17a). However, their internal echogenicity may vary from hyperechoic to hypoechoic or mixed relative to muscle depending on the degree of connective tissue and other reflective interfaces – such as cellularity, fat and water – within the mass (Fornage and Tassin 1991; Ahuja et al. 1998). At least theoretically, it has been postulated that lipomas composed of pure fat should be echofree lesions due to a low number of tissue acoustic interfaces (Behan and Kazam 1978). Based on different series, the incidence of hyperechoic lipomas, reflecting the so-called fibrolipomas, varies from 20% to 76% (Fornage and Tassin 1991; Ahuja et al. 1998; Inampudi et al. 2004). In a recent retrospective review of 39 US-diagnosed superficial and

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c

b

a

* Muscle d

e

Fig. 2.17a–e. Subcutaneous lipoma: spectrum of typical US appearances. a Long-axis extended-fi field-of-view 12–5 MHz US image of a lipoma of the back shows an elongated well-defi fined compressible mass with its greatest diameter parallel to the skin. The mass has well-defi fined margins and appears slightly hyperechoic relative to adjacent fat. Its echotexture consists of short thin linear striations that run parallel to the skin. b Long-axis 12–5 MHz US image at the border of a nonencapsulated lipoma (arrows) in a patient with a palpable mass at the medial aspect of the left thigh with c correlative contralateral image. d Long-axis 12–5 MHz US image of an intrafascial lipoma shows a lenticular fatty mass (asterisk) contained in a split of the muscle fascia (arrows). Note the fascia dividing into two hyperechoic sheets (arrowheads) to envelop the lipoma. e Transverse 12–5 MHz US image of the left forearm in patient with pathologically-proven angiolipoma demonstrates a hyperechoic rounded mass (arrows) with small internal hypoechoic dots

25 lipomas and 14 nonlipomas, including other benign and malignant histotypes (Inampudi et al. 2004). This indicates that the variable echotexture of lipomas may make their differentiation from other masses subjectively difficult. Although many lipomas have a well-circumscribed appearance with an identifiable thin capsule, a significant proportion (12%–60%) have ill-defined borders blending imperceptibly with the surrounding subcutaneous fat (Fig. 2.17b,c) (Fornage and Tassin 1991; Ahuja et al. 1998; Inampudi et al. 2004). This may lead to difficulties in identifying them with US even if the mass is apparent clinically. Nonencapsulated lipomas may require comparison with the contralateral side to detect significant asymmetry of fat tissue. They should be referred to as “probable lipomas” in the report as long as there are corroborative clinical findings of a discrete mass (Roberts et al. 2003).

In daily practice, the occurrence of a superficial palpable lump suggesting a lipoma in the absence of a definite nodule detectable with US is not uncommon. Graded compression with the probe or combined imaging and palpation may be helpful for detecting these “occult” lipomas. Both maneuvers can increase the detection rate of the mass, which is less compressible than the adjacent subcutaneous tissue. Most superficial lipomas do not present substantial internal vasculature at color and power Doppler imaging, a finding that may enhance the confidence of the examiner that a benign mass is present (Ahuja et al. 1998). Some lipomas grow in the deep subcutaneous tissue, in close contact with the fascia. Care should be taken when reporting on these masses not to lead the surgeon to believe that the lesion can be easily excised, because deep subcutaneous lipomas may adhere to the fascia. A well-delimited mass does not always mean an easily


removable lesion. Lipomas growing inside the deep fascia may also occur. The clinical diagnosis of these lesions may be difficult because they are firm and tethered to the deep plane and may mimic more aggressive tumors. At US examination, intrafascial lipomas appear as lenticular lesions growing into a split of the fascia, which retains a normal hyperechoic appearance (Fig. 2.17d). In these cases, US can rule out abnormalities of the underlying muscles and aggressive growth patterns suggestive of a malignant tumor. Lipomas containing other mesenchymal elements, such as fibrous tissue (fibrous lipomas), cartilage (chondroid lipomas), mucoid component (myxolipoma) and vessels (angiolipoma), may be encountered. In these cases, the presence of nonlipomatous elements may make the US appearance of the lesion less specific. Among these variants, angiolipomas account for 5%–17% of all lipomas (Lin and Lin 1974). They are well-defined hyperechoic subcutaneous masses containing small patchy hypoechoic areas and sparse internal vasculature (Fig. 2.17e) (Choong 2004). Relative to lipomas, angiolipomas have a greater angiomatous component composed of thin-walled capillaries which account for up to 90% or more of the lesion, and occur at an earlier age (early adulthood). Hibernomas (fetal lipomas) are rare benign tumors composed of brown fat. Brown fat is histologically distinct from white adipose tissue and plays a role in nonshivering thermogenesis of hibernating animals and newborn humans. In humans, brown adipose tissue progressively decreases through adulthood. Usual locations of tumors arising from brown fat are the parascapular and interscapular spaces, the mediastinum, the upper thorax and the thighs. US demonstrates a solid well-marginated hyperechoic mass somewhat resembling a lipomatous tumor and Doppler imaging may show a hypervascular pattern reflecting the presence of vascular structures and the increased cellular metabolism of hibernomas. Other rare forms of lipomas, including lipomatosis of nerves (see Chap. 4) and lipoma arborescens (see Chap. 14) are described elsewhere. Other space-occupying nonlipomatous masses containing fat may mimic the US appearance of lipomas. Among them, hemangiomas contain a variable amount of adipose tissue interspersed between abnormal vessels. However, in most cases their typical US appearance made of serpentine or tubular hypoechoic structures contained within the mass, scattered phleboliths and prominent blood flow at

color and power Doppler imaging, allows the correct diagnosis to be made. Lipomatosis represents a diffuse overgrowth of mature adipose tissue histologically similar to simple lipomas. The fatty tissue extensively infiltrates the subcutaneous and muscular tissue and is not associated with nerve involvement. Many entities of superficial lipomatosis are described (Murphey et al. 2004). In multiple symmetric lipomatosis, which is commonly referred to as Madelung or Launois-Bensaude lipomatosis, multiple symmetric lipomas are found in the neck and the shoulder in association with alcoholism, hepatic disease and metabolic disorders (Uglesic et al. 2004). Dercum disease, which is also referred to as lipomatosis dolorosa or adiposis dolorosa, is a rare disorder occurring in middle-aged women, often obese, in which multiple painful subcutaneous lipomas occur (Wortham and Tomlinson 2005).

2.3.3.2 Pilomatricoma and Epidermal Inclusion (Sebaceous) Cysts

Pilomatricoma (pilomatrixoma), also called calcifying epithelioma of Malherbe, is a benign superficial tumor of the hair follicle arising from the hair cortex cells in the deep dermis and extending into subcutaneous tissue as it grows (Malherbe and Chemantais, 1880). Most lesions arise in children less of 10 years of age and appear as small masses (2 kHz) are typically observed and help in distinguishing hemangiomas from other soft-tissue masses (Fig. 2.20b–f) (Dubois et al. 1998, 2002). High-flow malformations are typified by an abnormal network of vascular channels (the nidus), interposed between a prominent feeding artery and a dilated draining


T

b

a

c

d

Fig. 2.19a–d. Epidermal inclusion cyst. a Lateral radiograph of the middle finger in a patient with a palpable mass on the ventral aspect of the proximal phalanx reveals a superfi ficcial oval soft-tissue mass (arrows). b Transverse 12–5 MHz color Doppler US image of the affected finger demonstrates a wellcircumscribed hypovascular mass (arrows) characterized by a homogeneous texture of medium-level echoes in close relationship with the flexor tendons (T). Correlative c fat-suppressed T2-weighted and d gadolinium-enhanced fatsuppressed T1-weighted MR images show a homogeneous lesion (arrow) of high signal intensity on T2-weighted images, central non-enhancement and peripheral thin rim enhancement. Surgery revealed an epidermal inclusion cyst

d

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f

Fig. 2.20a–f. Hemangioma. Transverse a gray-scale and b color Doppler 15–7 MHz US images of the index finger fi in a patient with an indolent palpable mass demonstrate a well-circumscribed solid hypoechoic nodule (arrows) located just superficial fi to the fl flexor tendons (T). The mass reveals several intratumoral vessels. c Coronal fat-suppressed T2-weighted and transverse d T1-weighted, e fat-suppressed T2-weighted and f gadolinium-enhanced T1-weighted MR imaging correlation

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vein. Spectral Doppler analysis demonstrates high systolic arterial flow and arterialization of the veins (Fig. 2.21) (Dubois et al. 1999). Slow-flow (venous) malformations are characterized by abnormally dilated venous spaces and a normal arterial component. Often, they may be suspected on the basis of a subcutaneous bluish or reddish stain. In approximately 15% of cases they contain phleboliths (calcifications in venous thrombosis), which can be seen as hyperechoic foci with posterior acoustic shadowing (Fig. 2.22). Due to slow blood flow, color Doppler imaging may detect only sparse monophasic flow or no blood flow signals at all (Trop et al. 1999). Distinguishing between a slow-flow malformation and an involuted hemangioma may be problematic. In general, vascular malformations are distinguished from hemangiomas owing to the absence of solid tissue (Paltiel et al. 2000). In addition, hemangiomas have similar vessel density and peak systolic velocities but lower venous velocity (Paltiel et al. 2000). Finally, there are capillary malformations limited to the dermis. For the most part, US is unable to display such superficial abnormalities that typically present with a port-wine like stain. In some instances, however, an increased thickness of the subcutaneous tissue and some prominent veins may be demonstrated.

2.3.3.4 Metastases and Lymphomas

Superficial metastases involving the skin and subcutaneous tissue account for approximately 0.5%–9% of tumors. They usually result from seeding of deep tumors during interventional (i.e., needle and surgical biopsy) or surgical procedures or represent a manifestation of end-stage cancer (Galarza and Sosa 2003). In some cases, however, skin metastases can be the first manifestation of an occult cancer, therefore requiring an accurate and early diagnosis (Giovagnorio et al. 2003). Histopathologically, metastases of the skin and subcutaneous tissue can develop from almost any kind of malignancy, but nearly half of them derive from melanoma, lung cancer and breast carcinoma (White 1985). In most cases, metastases appear as well-circumscribed solid hypoechoic masses (Nazarian et al. 1998). A lobulated shape and multiple peripheral vascular pedicles feeding internal irregular vessels seem the most important gray-scale and color Doppler US imaging findings for differentiating them from other benign soft-tissue masses (Fig. 2.23) (Giovagnorio et al. 1999, 2003). In follow-up studies, color Doppler imaging has been proposed as a mean to assess the pharmacodynamic response to chemotherapy

a

b

c Fig. 2.21a–c. Arteriovenous malformation. a Transverse gray-scale 15–7-MHz US image of a 6-month-old infant born with a markedly swollen cheek and upper lip reveals marked thickening of the subcutaneous tissue of the lip (arrows). b Corresponding color Doppler 15–7 MHz US image demonstrates numerous enlarged vessels coursing through the thickened subcutaneous tissue. c Spectral Doppler analysis demonstrates high-velocity arterial waveforms within the vessels

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b Fig. 2.22a–c. Venous malformation. a Longitudinal 12–5 MHz US image of the middle forearm show an ill-defined fi sponge-like subcutaneous mass (arrowheads) containing a network of anechoic channels and a hyperechoic dot (arrow) with posterior acoustic shadowing, likely reflecting fl a phlebolith. b Corresponding 12–5 MHz color Doppler US image reveals only a few, weak signals of flow within the soft-tissue mass (arrowheads). c Radiographic correlation confi firms the presence of a few rounded phleboliths (arrow) within the lesion

* a

c

* b Fig. 2.23a–c. Subcutaneous tissue metastases. a,b Gray-scale and c,d color Doppler 12–5 MHz US images in two patients with previously diagnosed malignancies demonstrate well-defi fined homogeneous hypoechoic nodules (asterisk) located within the subcutaneous tissue. In both nodules, correlative color Doppler imaging shows a hypervascular pattern with peripheral and internal vessels. Postsurgical histologic examination revealed metastases from a,c gut carcinoma and b,d colon adenocarcinoma

d

40


by depicting reduction of intratumoral blood flow (Fig. 2.24) (Nazarian et al. 1996). In patients operated on for melanoma, detection of any nonpalpable mass in the subcutaneous tissue or any suspected regional lymphadenopathy should be ascertained by means of US-guided biopsy (Fornage and Lorigan 1989). The subcutaneous tissue can be the primary site of involvement of peripheral T-cell (non-Hodgkin) lymphoma (Lee et al. 2003; Fujii et al. 2004; Giovagnorio 1997). This kind of lymphoma involves the skin and the subcutaneous tissue in two main forms: the cutaneous T-cell lymphoma, which is also known as mycosis fungoides or Sézary syndrome, and the subcutaneous panniculitis-like T-cell lymphoma (Lee et

a

b

al. 2003). Mycosis fungoides is an indolent disorder presenting with cutaneous patches, plaques or erythroderma. With time, the skin lesions may progress to cutaneous tumors, peripheral lymphadenopathies and widespread extracutaneous involvement, with a corresponding drop in patient survival rate. At the stage of tumor formation, US is able to demonstrate diffuse or focal hypoechoic thickening of the skin; the imaging features of this lymphoma are, however, nonspecific (see Fig. 2.3a) (Fornage et al. 1993). The subcutaneous panniculitis-like T-cell lymphoma is a rare condition which may be a diagnostic challenge as it mimics inflammatory cellulitis associated with connective tissue disease (Lee et al. 2003; Sy et al. 2005). This disorder usually presents with multiple

c

Fig. 2.24a–c. Subcutaneous regional metastasis from melanoma. a Gray-scale and b,c color Doppler 15–7 MHz US images in a patient who had a melanoma in his left foot and some regional relapses reveal a small solid homogeneously hypoechoic nodule (arrow) with spiculated margins in the subcutaneous tissue of the left lower leg. The nodule is hypervascular at color Doppler imaging. c After a course of systemic chemotherapy and immunotherapy, the subcutaneous metastasis appears unchanged in size and echotexture but assumes a hypovascular pattern reflecting fl therapy-related change in tumor perfusion

a

b Fig. 2.25a,b. Subcutaneous panniculitis-like T-cell lymphoma. a Gray-scale and b color Doppler 12–5 MHz US images over an hardened ill-defi fined area in the back show diffuse pseudonodular thickening of the subcutaneous tissue (arrows) with a generalized decrease in echogenicity of the fat lobules and a diffuse hypervascular pattern mimicking cellulitis


palpable subcutaneous nodules, and may undergo rapid deterioration secondary to the onset of the hemophagocytic syndrome (marked anemia due to phagocytosis of red blood cells from monocytes and macrophages). US reveals marked increased echogenicity with swelling of the fat lobules and blurry differentiation between the skin and the subcutaneous tissue, an appearance resembling a diffuse inflammatory infiltrate with edema (Fig. 2.25) (Sy et al. 2005). Hypoechoic nodules surrounded by a hyperechoic rim can also be observed (Fujii et al. 2004). Given the similarity with inflammatory cellulitis, regional enlarged lymph nodes could possibly be misinterpreted as reactive in nature (Sy et al. 2005).

References Ahuja AT, King AD, Kew J et al (1998) Head and neck lipomas: sonographic appearances. AJNR Am J Neuroradiol 19: 505–508 Akesson A, Forsberg L, Hederstrom E (1986) Ultrasound examination of skin thickness in patients with progressive systemic sclerosis (scleroderma). Acta Radiol Diagn 27: 91–94 Amann P, Botta U, Montet X et al (2003) Sonographic detection and localization of a clinically nondetectable subcutaneous contraceptive implant. J Ultrasound Med 22: 855–859 Anderson MA, Newmeyer WL 3rd, Kilgore ES Jr (1982) Diagnosis and treatment of retained foreign bodies in the hand. Am J Surg 144: 63–67 Arslan H, Sakarya ME, Bozkurt M et al (1998) The role of power Doppler sonography in the evaluation of superficial soft tissue abscesses. Eur J Ultrasound 8: 101–106 Behan M, Kazam E (1978) The echographic characteristics of fatty tissues and tumors. Radiology 129: 143–151 Benson CH, Gibson JY, Harisdangkul V (1983) Ultrasound diagnosis of tophaceous and rheumatoid nodules. Arthritis Rheum 26: 696 Blaivas M, Lyon M, Brannam L et al (2004) Water bath evaluation technique for emergency ultrasound of painful superficial structures. Am J Emerg Med 22: 589–593 Blyme PJ, Lind T, Schantz K et al (1990). Ultrasonographic detection of foreign bodies in soft tissue: a human cadaver study. Arch Orthop Trauma Surg 110: 24–25 Boyse TD, Fessell DP, Jacobson JA et al (2001) US of soft-tissue foreign bodies and associated complications with surgical correlation. RadioGraphics 21: 1251–1256 Brenner JS, Cumming WA, Ros PR (1989) Testicular epidermoid cyst: Sonographic and MR findings. AJR Am J Roentgenol 152: 1344 Brocks K, Stender I, Karlsmark T et al (2000) Ultrasonic measurement of skin thickness in patients with systemic sclerosis. Acta Derm Venereol 80: 59–60 Canturk F, Canturk T, Aydin F et al (2004) Cutaneous linear atrophy following intralesional corticosteroid injection in the treatment of tendonitis. Cutis 73: 197–198

Cardinal E, Bureau N, Aubin B et al (2001) Role of ultrasound in musculoskeletal infection. Radiol Clin North Am 39: 191–201 Chau CL, Griffith JF (2005) Musculoskeletal infections: ultrasound appearances. Clin Radiol 60: 49–59 Choong KKL (2004) Sonographic appearance of subcutaneous angiolipomas. J Ultrasound Med 23: 715–717 Choudhari KA, Muthu T, Tan MH (2001) Progressive ulnar neuropathy caused by delayed migration of a foreign body. Br J Neurosurg 15: 263–265 Clements PJ, Hurwitz EL, Wong WK et al (2000) Skin thickness score as a predictor and correlate of outcome in systemic sclerosis. Arthritis Rheum 43: 2445–2454 Davae KC, Sofka CM, DiCarlo E et al (2003) Value of power Doppler imaging and the hypoechoic halo in the sonographic detection of foreign bodies: correlation with histopathologic findings. J Ultrasound Med 22: 1309–1313 Dean AJ, Gronczewski CA, Costantino TG (2003) Technique for emergency medicine bedside ultrasound identification of a radiolucent foreign body. J Emerg Med 24: 303–308 Dubois J, Garel L (1999) Imaging and therapeutic approach of hemangiomas and vascular malformations in the pediatric age group. Pediatr Radiol 29: 879–893 Dubois J, Patriquin HB, Garel L et al (1998) Soft-tissue hemangiomas in children and infants: diagnosis using Doppler ultrasonography. AJR Am J Roentgenol 171: 247–252 Dubois J, Garel L. David M et al (2002) Vascular soft-tissue tumors in infancy: distinguishing features on Doppler sonography. AJR Am J Roentgenol 178: 1541–1545 Ehara S (1998) MR imaging of fat necrosis. AJR Am J Roentgenol 171: 889 Erickson SJ (1997) High-resolution imaging of the musculoskeletal system. Radiology 205: 593–618 Felman AH, Fisher MS (1969) The radiographic detection of glass in soft tissue. Radiology 92: 1529–1531 Fernando RA, Somers S, Edmonson RD et al (2003) Subcutaneous fat necrosis: hypoechoic appearance on sonography. J Ultrasound Med 22: 1387–1390 Fornage BD, Deshayes JL (1986) Ultrasound of normal skin. J Clin Ultrasound 14: 619–622 Fornage BD, Lorigan JG (1989) Sonographic detection and fine-needle aspiration biopsy of nonpalpable recurrent or metastatic melanoma in subcutaneous tissues. J Ultrasound Med 8: 421–424 Fornage BD, Tassin GB (1991) Sonographic appearances of superficial soft tissue lipomas. J Clin Ultrasound 19: 215–220 Fornage BD, McGavran MH, Duvic M et al (1993) Imaging of the skin with 20-MHz US. Radiology 189: 69–76 Friedman DI, Forti RJ, Wall SP et al (2005) The utility of bedside ultrasound and patient perception in detecting soft tissue foreign bodies in children. Pediatr Emerg Care 21: 487–492 Fujii Y, Shinozaki T, Koibuchi H et al (2004) Primary peripheral T-cell lymphoma in subcutaneous tissue: sonographic findings. J Clin Ultrasound 32: 361–364 Galarza M, Sosa FP (2003) Pure subcutaneous seeding from medulloblastoma. Pediatr Neurol 29: 245–249 Gerster JC, Landry M, Dufresne L et al (2002) Imaging of tophaceous gout: computed tomography provides specific images compared with magnetic resonance imaging and ultrasonography. Ann Rheum Dis 61: 52–54 Giovagnorio F (1997) Sonography of cutaneous non-Hodgkin’s lymphomas. Clin Radiol 52: 301–303

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M. Valle and M. P. Zamorani Giovagnorio F, Andreoli C, DeCicco ML (1999) Color Doppler sonography of focal lesions of the skin and subcutaneous tissue. J Ultrasound Med 18: 89–93 Giovagnorio F, Valentini C, Paonessa A (2003) High-resolution and color Doppler sonography in the evaluation of skin metastases. J Ultrasound Med 22: 1017–1022 Gomez EC, Berman B, Miller DL (1982) Ultrasonic assessment of cutaneous atrophy caused by intradermal corticosteroids. J Dermatol Surg Oncol 8: 1071–1074 Grechenig W, Peicha G, Clement HG et al (1999) Ultrasonographic localization of a displaced screw in the carpal canal. A case report. Acta Radiol 40: 625–627 Horton LK, Jacobson JA, Powell A et al (2001) Sonography and radiography of soft-tissue foreign bodies. AJR Am J Roentgenol 176: 1155–1159 Hwang JY, Lee SW, Lee SM (2005) The common ultrasonographic features of pilomatricoma. J Ultrasound Med 24: 1397–1402 Inampudi P, Jacobson JA, Fessell DP et al (2004) Soft-tissue lipomas: accuracy of sonography in diagnosis with pathologic correlation. Radiology 233: 763–767 Jacobson JA (2005) Musculoskeletal ultrasound and MRI: which do I choose? Semin Musculoskelet Radiol 9:135–149 Kohler R, Kritikos N, Poletti PA et al (2005) Sonographic detection of a subcutaneous twisted expander injection port. J Ultrasound Med 24: 1441–1444 Lee HS, Joo KB, Song HT et al (2001) Relationship between sonographic and pathologic findings in epidermal inclusion cysts. J Clin Ultrasound 29: 374–383 Lee HJ, Im JG, Goo JM et al (2003) Peripheral T-cell lymphoma: spectrum of imaging findings with clinical and pathologic features. RadioGraphics 23: 7–28 Lin JJ, Lin F (1974) Two entities in angiolipoma. A study of 459 cases of lipomas with review of literature on infiltrating angiolipoma. Cancer 34: 720–727 Loyer EM, DuBrow RA, David CL et al (1996) Imaging of superficial soft-tissue infections: sonographic findings in cases of cellulitis and abscess. AJR Am J Roentgenol 166: 149–152 Lyon M, Brannam L, Johnson D et al (2004) Detection of soft tissue foreign bodies in the presence of soft tissue gas. J Ultrasound Med 23: 677–681 Malherbe A, Chemantais J (1880) Note sur l’épithélioma calcifie des glandes sebacées. Prog Med 8: 826–837 Maxwell AJ, Mamtora H (1990) Sonographic appearance of epidermoid cyst of the testis. J Clin Ultrasound 18: 188– 190 McGrath MH, Fleisher A (1989) The subcutaneous rheumatoid nodule (1989) Hand Clin 2: 127–135 Mellado JM, Pérez del Palomar L, Diaz L et al (2004) Long standing Morel-Lavallée lesions of the trochanteric region and proximal thigh: MRI features in five patients. AJR Am J Roentgenol 182: 1289–1294 Merki-Feld GS, Brekenfeld C, Migge B, et al (2001) Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging. Contraception 63: 325–328 Morel-Lavallée M (1863) Décollements traumatiques de la peau et des couches sous-jacentes. Arch Gen Med 1: 20–38; 172–200; 300–332 Murphey MD, Carroll JF, Flemming DJ et al (2004) Benign musculoskeletal lipomatous lesions. RadioGraphics 24: 1433–1466

Nalbant S, Corominas H, Hsu B et al (2003) Ultrasonography for assessment of subcutaneous nodules. J Rheumatol 30:1191–1195 Nazarian LN, Alexander AA, Rawool NM et al (1996) Malignant melanoma: impact of superficial US on management. Radiology 199: 273–277 Nazarian LN, Alexander AA, Kurtz AB et al (1998) Superficial melanoma metastases: appearances on gray-scale and color Doppler sonography. AJR Am J Roentgenol 170: 459–463 Nessi R, Betti R, Bencini PL et al (1990) Ultrasonography of nodular and infiltrative lesions of the skin and subcutaneous tissues. J Clin Ultrasound 18: 103–109 Neumann CG (1957). The expansion of an area of skin by progressive distension of a subcutaneous balloon: use of the method for securing skin for subtotal reconstruction of the ear. Plast Reconstr Surg 19: 124–130 Paltiel HJ, Burrow PE, Kozakewich HPW et al (2000) Soft-tissue vascular anomalies: utilities of US for diagnosis. Radiology 214: 747–754 Parra JA, Fernández MA, Encinas B et al (1997) Morel-Lavallée effusions in the thigh. Skeletal Radiol 26: 239–241 Peterson JJ, Bancroft LW, Kransdorf MJ (2002) Wooden foreign bodies: imaging appearance. AJR Am J Roentgenol 178: 557–562 Piessens SG, Palmer DC, Sampson AJ (2005) Ultrasound localization of non-palpable implanon. Aust N Z J Obstet Gynaecol 45:112–116 Rettenbacher T, Macheiner P, Hollerweger A et al (2001) Suture granulomas: sonography enables a correct preoperative diagnosis. Ultrasound Med Biol 27: 343–350 Robben SGF (2004) Ultrasonography of musculoskeletal infections in children. Eur Radiol 14: L65–L67 Roberts CC, Liu PT, Colby TV (2003) Encapsulated versus nonencapsulated superficial fatty masses: a proposed MR imaging classification. AJR Am J Roentgenol 180: 1419–1422 Scheja A, Akesson A (1997) Comparison of high frequency (20 MHz) ultrasound and palpation for the assessment of skin involvement in systemic sclerosis (scleroderma). Clin Exp Rheumatol 15: 283–288 Schmid-Wendtner MH, Burgdorf W (2005) Ultrasound scanning in dermatology. Arch Dermatol 141: 217–224 Shiels WE, Babcock DS, Wilson JL et al (1990) Localization and guided removal of soft-tissue foreign bodies with sonography. AJR Am J Roentgenol 155: 1277–1281 Soudack M, Nachtigal A, Gaitini D (2003) Clinically unsuspected foreign bodies: the importance of sonography. J Ultrasound Med 22: 1381–1385 Struk DW, Munk PL, Lee MJ et al (2001) Imaging of soft-tissue infections. Radiol Clin North Am 39: 277–303 Sy ANL, Lam TPW, Khoo US (2005) Subcutaneous panniculitislike T-cell lymphoma appearing as a breast mass: a difficult and challenging case appearing at an unusual site. J Ultrasound Med 24: 1453–1460 Thomas RH, Holt MD, James SH et al (2001) “Fat fracture”: a physical sign mimicking tendon rupture. J Bone Joint Surg Br 83: 204–205 Tiliakos N, Morales AR, Wilson CH Jr (1982) Use of ultrasound in identifying tophaceous versus rheumatoid nodules. Arthritis Rheum 25: 478–479 Trop I, Dubois J, Guibaud L et al (1999) Soft-tissue venous malformations in pediatric and young adult patients; diagnosis with Doppler US. Radiology 212: 841–845

Skin and Subcutaneous Tissue Tsai TS, Evans HA, Donnelly LF et al (1997) Fat necrosis after trauma: a benign cause of palpable lumps in children. AJR Am J Roentgenol 169: 1623–1626 Uglesic V, Knezevic P, Milic M et al (2004) Madelung syndrome (benign lipomatosis): clinical course and treatment. Scand J Plast Reconstr Surg Hand Surg 38: 240–243 Vincent LM, Parker LA, Mittelstaedt CA (1985) Sonographic appearance of an epidermal inclusion cyst. J Ultrasound Med 4: 609–611

Wilson DJ (2004) Soft-tissue and joint infection. Eur Radiol 14(Suppl 3): 64–71 White JW (1985) Evaluating cancer metastatic to the skin. Geriatrics 40: 67–72 Wortham NC, Tomlinson IP (2005). Dercum’s disease. Skinmed 4: 157–162 Yen ZS, Wang HP, Ma HM et al (2002) Ultrasonographic screening of clinically-suspected necrotizing fasciitis. Acad Emerg Med 9: 1448–1451

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Muscle and Tendon

3

Muscle and Tendon Maria Pia Zamorani and Maura Valle

CONTENTS 3.1 3.1.1 3.1.2 3.1.3 3.1.3.1 3.1.3.2 3.1.4 3.1.4.1 3.1.4.2 3.1.4.3 3.1.5 3.1.5.1 3.1.5.2 3.1.5.3 3.1.6 3.1.6.1 3.1.6.2 3.1.6.3 3.1.6.4 3.1.6.5 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.4.1 3.2.4.2 3.2.5 3.2.5.1 3.2.5.2 3.2.5.3 3.2.6 3.2.6.1 3.2.6.2

Muscle 45 Histologic Considerations 45 Normal US Anatomy and Scanning Technique 46 Anatomical Variants and Heritable Disorders 50 Muscle Agenesis, Anomalous and Accessory Muscles 50 Neuromuscular Disorders 52 Traumatic Lesions 54 Myotendinous Strains 55 Contusion and Laceration 56 Myositis Ossificans 57 Inflammatory and Ischemic Conditions 59 Idiopathic Inflammatory Myopathies 59 Pyomyositis, Abscess, and Hydatid Disease 61 Diabetic Muscle Infarction and Rhabdomyolysis 62 Tumors 64 Intramuscular Hemangioma 64 Deep-Seated Lipoma and Liposarcoma 66 Intramuscular Myxoma 67 Desmoid 69 Rhabdomyosarcoma and Metastases 71 Tendon 71 Histologic Considerations 71 Normal US Anatomy and Scanning Technique 72 Tendon Instability 75 Degenerative Changes and Tendon Tears Tendinosis and Partial Tears 76 Complete Tears and Postoperative Findings Inflammatory Conditions 83 Paratendinitis and Attrition Bursitis 84 Tenosynovitis 85 Enthesopathy 87 Tumors and Tumor-Like Conditions 88 Intratendinous and Tendon Sheath Ganglia Giant Cell Tumor of the Tendon Sheath References

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M. P. Zamorani, MD Unité de Recherche et Dévelopement, Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland M. Valle, MD Staff Radiologist, Reparto di Radiologia, Istituto Scientifico “Giannina Gaslini”, Largo Gaslini 5, 16148 Genova, Italy

3.1 Muscle 3.1.1 Histologic Considerations On the whole, skeletal muscles can be regarded as the largest organ of the human body, accounting for approximately 25–35% of the total body weight in women and 40–50% in men (Hollman and Hettiger 1990). They are made up of two components: the muscle fibers, which are long and cylindrical in structure, representing the cellular unit of muscle, and stromal connective tissue. Individual muscle fibers are grouped together in bundles, which are commonly known as fascicles, and several fascicles join together to form an individual muscle (Fig. 3.1a). Thin connective tissue strands – the endomysium – separate the individual muscle fibers; a more substantial connective sheath with small vessels and nerve endings, the perimysium (also referred to as fibroadipose septa), envelops individual fascicles; a thick fibrous layer, the epimysium, surrounds the entire muscle (Fig. 3.1a). Muscle fibers vary in length and cross-sectional diameter depending on the individual muscle. Fascicles may be either coarse, as in the case of large muscles, or very fine, as in the case of small muscles that coordinate precise movement (Erickson 1997). They insert into the different connective tissue components of the muscle, including the peripheral epimysium and central major septa formed by converging fibroadipose septa. At their distal end, intramuscular septa join into large tendinous layers – commonly referred to as aponeuroses – or directly to tendons. The internal arrangement of the muscle varies according on the fascicular orientation, which reflects gross muscle shape and function. A parallel arrangement is found in strap-like (e.g., sartorius) and quadrilateral (e.g., thyrohyoid) muscles, in which fibers course nearly the full length of the long axis of the muscle; the rectus abdominis shows

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T

a

b Fig. 3.4a,b. Intramuscular aponeuroses. a Long-axis and b short-axis 12–5 MHz US images of the normal tibialis anterior muscle (arrowheads) demonstrate the feather-like arrangement of a circumpennate muscle created by the convergence of the fibroadipose septa upon the internal aponeurosis. The aponeurosis (straight arrows) appears as a highly reflective linear echo within the muscle that is thicker than the fibroadipose septa (curved arrow). T, tibia

a

b Fig. 3.5a,b. Muscle anisotropy. Short-axis 17–5 MHz US images of the biceps brachii muscle (arrows) examined with a perpendicular angle between the transducer face and the orientation of the muscle fibers and b an angle that deviates slightly from the perpendicular. In a, the muscle appears diffusely hyperechoic owing to the highest specular reflectivity from the perimysium interfaces. In b, the overall muscle becomes more hypoechoic with decreased intensity of echoes from the perimysium. On the other hand, the larger fibroadipose septa (arrowhead) are more visible. Tilting the probe over the muscle may be useful to distinguish artifactual hypoechoic patterns from mild strains

fibroadipose septa, US is able to recognize the internal architecture of pennate muscles as semipennate, unipennate, bipennate, or multipennate (Fig. 3.6). Intramuscular vessels coursing within the hyperechoic septa are visible on color and power Doppler imaging. The outer muscle fascia (epimysium) appears as a well-delineated echogenic envelope circumscribing the hypoechoic muscle. Large hyperechoic septa (aponeuroses) directed within the muscle belly can be seen arising from it. In complex muscles, an individual hyperechoic fascial sheath surrounds each muscle belly thus helping the examiner to recognize the different heads. The interstice between juxtaposed fasciae of two adjacent muscles appears

as a hypoechoic band and corresponds to loose connective tissue that allows some sliding of the muscles during contraction. Focal interruptions of the muscle fascia are found at the points where nerves, veins, and arteries (perforating vessels) enter the muscles. When the muscle fascia lies under the subcutaneous tissue, it adheres to the superficial fascia and cannot be distinguished from it. Dynamic US scanning performed during muscle contraction can show changes in size and relationship of fascicles and fibroadipose septa. On short-axis planes, contracted muscles usually appear thicker and more hypoechoic. Intramuscular septa change their appearance and orientation as a result of the action of

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a

b Fig. 3.6a,b. Internal architecture of skeletal muscles. a Fusiform muscle. Long-axis 12–5 MHz US image over the deltoid muscle (arrows) demonstrates the fibroadipose septa (arrowheads) as hyperechoic lines separating the hypoechoic muscle bundles. These septa have a parallel arrangement along the muscle belly. b Pennate muscle. Long-axis 125 MHz US image over the tibialis anterior muscle (arrows) demonstrates the fibroadipose septa (arrowheads) as they converge on the highly reflective aponeurosis (curved arrow), giving the appearance of a feather

the muscle fibers that attach into these structures. In the medial head of gastrocnemius, for instance, pennation angle increases from 15.5° to 33.6° when examined during isometric contraction (Fig. 3.7) (Narici et al. 1996). Shortening of muscles is well appreciated on long-axis images during concentric contraction. Recently, a method to measure muscle tissue perfusion by means of contrast-enhanced power Doppler US has been developed with quantification of intramuscular blood flow performed at rest and after exercise (Krix et al. 2005).

3.1.3 Anatomical Variants and Heritable Disorders 3.1.3.1 Muscle Agenesis, Anomalous and Accessory Muscles

Muscle agenesis indicates the absence of one muscle or one head of a complex muscle as a result of incomplete or imperfect development. In general, the diagnosis is already evident at physical examination. US

α

A a

β

A b

Fig. 3.7a,b. Pennation angle. Long-axis 12–5 MHz US images of the medial head of gastrocnemius obtained a at rest and b during isometric contraction demonstrate an increased pennation angle during muscle activation. The pennation angle is given by the incidence of the muscle fibers (dashed line) relative to the aponeurosis (A), which represents the direction of force generation (double arrow). Note that this angle is greater during contraction (β) than at rest (α)

Muscle and Tendon

causes profound US changes in muscle architecture with increased echogenicity, loss of heterogeneity, and shadowing (Fig. 3.10). The increased echogenicity of muscle reflects an increased number of acoustic interfaces related to fat accumulation, fibrosis, and inflammation. In neuromuscular disorders, the increased reflectivity of muscles is associated with a decreased ability of the US beam to penetrate deeper structures, leading to loss of bone edge definition and bone shadowing (Fischer et al. 1998; Walker et al. 2004). In addition, the disease process blurs the distinction between fibroadipose septa and muscle fascicles, making the image more homogeneously echogenic (Fig. 3.10a). Similarly, peripheral neuropathies are often associated with selective atrophy of the innervated muscles. US is able to evaluate the size and echotexture of the affected muscles by comparing the two extremities (Scholten et al. 2003). A definite loss in bulk of the affected muscle would suggest atrophy. This can be appreciated by simple pattern recognition analysis (concave or straight muscle boundaries instead of the normal convex surface). Because side-to-side differences in muscle thickness rarely exceed 20%, measuring the muscle diameters or cross-sectional area with the electronic calipers of the equipment seems to be a more reliable means

to assess volume changes in a given group of muscles than subjective evaluation (Bargfrede et al. 1999). The ratio of muscle thickness to subcutaneous fat thickness was found to be helpful in specific neuromuscular disorders (decreased ratio in spinal muscle atrophy). In neuromuscular disorders, however, US has shown some limitations compared with MR imaging. The complex distribution of muscle involvement in some dystrophies seems more reliably mapped with MR imaging because of its better anatomic rendering and panoramic view. Based on echotextural pattern analysis, US is not as accurate as MR imaging in distinguishing early neurogenic atrophy (in which changes are mainly related to extracellular edema) from late atrophy (in which muscle tissue is gradually replaced by fat). Unlike MR imaging, in which early denervation is appreciated by a homogeneous hyperintense pattern on T2-weighted and STIR sequences (increase in free-water content) and late denervation by a hyperintense pattern on T1-weighted images (fatty replacement), at US the two processes have a similar hyperechoic pattern and can be hardly differentiated (Fig. 3.11) (Kullmer et al. 1998). Quantification of muscle echotexture to estimate the severity of atrophy would reduce the observer variability but is strongly influenced by the scanner and the

MHG T soleus F

∗ a

∗ b

c

Fig. 3.10a–c. Neuromuscular disorders. a,b Transverse 12-5 MHz US images obtained over the a posteromedial and b posterolateral aspect of the middle third of the leg in a 12-year-old child with Duchenne dystrophy. The affected medial head of the gastrocnemius (MHG) and soleus exhibits a diffusely hyperechoic pattern with strong US beam attenuation (asterisks) and blurred distinction of fibroadipose septa. The acoustic shadowing leads to inability of the US beam to penetrate deep structures. In b, there is loss of bone edge definition of the fibula (F) caused by the abnormal muscle reflectivity (arrows). T, tibia. c Photograph showing calf muscle pseudohypertrophy. The patient had progressive symmetric muscle weakness associated with elevated serum CK levels, myalgia, cramps, and stiffness after exercise

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T

T a

b

T

T c

d Fig. 3.11a–d. Neurogenic atrophy of muscles in two different patients with a,b recent-onset and c,d long-standing peroneal neuropathy. a Transverse 12–5 MHz US image over the tibialis anterior muscle with b fat-suppressed T2-weighted MR imaging correlation demonstrates normal volume and diffusely hyperechoic appearance of the muscle (arrowheads). The abnormal echotexture is related to intramuscular edema (curved arrow). c Transverse 12-5 MHz US image over the tibialis anterior muscle with d T1-weighted MR imaging correlation reveals decreased volume and hyperechoic appearance of the muscle (arrowheads). Although similar to that seen in a, the abnormal echotexture reflects fatty atrophy (curved arrow). T, tibia

equipment settings (Bargfrede et al. 1999; Pillen et al. 2003; Scholten et al. 2003). Apart from the above limitations, US can be considered a useful tool complementary to electrophysiology to provide information on muscle morphology, which is beyond the scope of electrodiagnosis. In patients with unilateral disorders, US images of the affected muscle can be compared with those of the unaffected side. In these cases, careful positioning of the transducer by surface landmarks is needed to ensure symmetric imaging. Transverse images are best suited for muscle measurements. In patients with bilateral disorders, comparative US evaluation should be conducted by selecting a control muscle in a healthy area, possibly with similar degrees of overlying subcutaneous tissue. Finally, when examining an atrophied fatty-infiltrated muscle, the examiner must be aware that changes may occur not only as a result of a denervation process but also following disuse or a complete tendon tear (Yao and Metha 2003). Then the integrity of the tendon belonging to the affected muscle must be carefully assessed.

3.1.4 Traumatic Lesions Based on their pathomechanism, muscle injuries can be grouped into two main classes: extrinsic and intrinsic. Extrinsic injuries result from external trauma, either a contusion or a penetrating injury (laceration), whereas intrinsic injuries are most often the result of contraction and simultaneous elongation of a given muscle. In the first class, the location of the tear strictly matches the site of the trauma. These lesions typically occur in areas where the muscle is compressed between the applied outer force (direct blow) and an underlying hard bony surface (e.g., quadriceps muscles against the femoral shaft). On the other hand, intrinsic ruptures almost invariably lead to a disruption of muscle fibers near the myotendinous junction, which is considered the weakest ring of the muscle-tendonbone unit because it has less capacity for energy absorption than the other structures (Palmer et al. 1999). The myotendinous junction is the most common site of partial or complete muscle injury

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Clinically, muscle strain injuries can be classified into a four-step grading system: grade 1 indicates a tear affecting a small number of muscle fibers with an intact fascia; grade 2 refers to a moderate tear with the fascia remaining intact; grade 3 injury is a tear of many fibers with partial tearing of the fascia; grade 4 injury indicates a complete tear of the muscle and the fascia (Ryan 1969). Healing and recovery of function takes longer with a high-grade injury, and the long-term outcome is generally worse (Noonan and Garrett 1999). Initially, treatment of a muscle strain injury includes rest, application of ice, and compression for relieve of pain and swelling; nonsteroidal inflammatory drugs may also be administered for pain relief in the first days after trauma. After resolution of the acute pain and swelling, physical therapy performed avoiding excessive fatigue and with adequate warm-up before exercise may contribute to the restoration of muscle strength and flexibility (Noonan and Garrett 1999). The long-term outcome after muscle strain injury is usually good and complications are rare. Muscle strain injuries appear at US as avulsion and retraction of muscle fibers from the tendon or aponeurosis in which they attach (Fig. 3.12b,c) (Bianchi et al. 1998). The examiner must be aware that some muscles (e.g., rectus femoris) have a complex structure with internal tendons: in these cases, the injury may occur in the mid-portion of the muscle belly and not at its distal portion as may be expected (Bianchi et al. 2002). US signs of muscle tear include avulsion and proximal retraction of the fibroadipose septa. In low-grade injuries, the space between the retracted septa and the aponeurosis is filled with a hyperechoic area reflecting extravasation of blood and clots. These small lesions may go unnoticed if an accurate scanning technique with careful and systematic examination of the distal portion of the fibroadipose septa is not employed. On the other hand, larger muscle tears are characterized by a more substantial blood collection which makes them easily detectable. This does not occur immediately after the trauma, but 1–2 days later, when the collection tends to become more hypoechoic. A widely accepted classification of muscle injuries is based on a four-grade scale (Peetrons 2002). Grade 0 injury corresponds to a normal US appearance in spite of the presence of local clinical findings; in grade 1 injury, subtle US findings may be observed, including ill-defined hyperechoic or hypoechoic intramuscular areas or a swollen aponeurosis (Fig. 3.13); grade 2 and grade 3 correspond to partial and complete muscle

tears, in which incomplete or full discontinuity of the muscle occurs. In mild trauma, an early assessment with US can lead to false negative results because the hematoma is diffuse and manifests as scattered blurred hyperechoic areas within muscle rather than as a focal well-defined hypoechoic collection: fat-suppressed T2-weighted MR imaging is superior to US in depicting mild strains soon after the trauma. During healing, the hemorrhagic cavity shrinks and its walls progressively thicken and collapse. The time at which the lesion is filled in can be considered an indicator for restarting low-level activity with care. However, this should be only decided in the absence of clinical symptoms and when a sufficient delay has occurred between the injury and the resumption of sports activities (never less than 4–6 weeks after the end of symptoms) (Peetrons 2002). In late phases, fibrous scars are seen as blurred hyperechoic zones within muscle: they are often observed in significant trauma or when the sporting activity was resumed too early (Fig. 3.14) (Peetrons 2002). Usually, scars are weakly symptomatic, but the risk of recurrent injury seems to be proportional to their extent in the muscle.

3.1.4.2 Contusion and Laceration

Direct external trauma may result in local hematoma, contusion, and partial and complete muscle laceration. Although virtually all muscles can be involved during sporting or recreational activities, the most frequently injured are the vastus intermedius and the vastus lateralis. These anterior thigh muscles are particularly predisposed to injury in athletes whose sports require direct hard contact (e.g., soccer, football, rugby, and hockey). The mechanism of injury often consists of crushing of the muscle against the femoral shaft by the knee of another player. Contusion injuries following extrinsic trauma are depicted with US as muscle swelling with focal irregularities and echotextural changes. The muscle architecture is no longer recognized as it is altered by disruption of the muscle fibers and hematoma (Fig. 3.15a). Depending on the overall strength of the applied force, partial or complete tears can occur. Abnormalities are typically located at the actual site of trauma and not at the myotendinous junction: this helps in distinguishing a contusion injury from a muscle strain. If a large fluid collection is present,

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b

∗ c

d

e

Fig. 3.13a–e. Myotendinous strains. Two different cases of central aponeurosis strain of the rectus femoris muscle following minimal trauma. a,b Case 1. a Short-axis and b long-axis 12–5 MHz US images over the middle third of the rectus femoris muscle demonstrate an ill-defined hyperechoic area (arrowheads) surrounding the aponeurosis related to edema and hemorrhagic changes. Note the normal-appearing external portion of the muscle (arrows). c–e Case 2. Short-axis 12–5 MHz US images obtained from c proximal to e distal over the rectus femoris reveal progressive swelling and hypoechoic appearance (arrowheads) of the central aponeurosis (straight arrows) and adjacent muscle fibers (curved arrow) with a small hematoma (asterisk) reflecting a myotendinous strain

the muscle ends can be seen floating within the hematoma. Closed muscle trauma by a sharp object may be associated with laceration of the subcutaneous tissue. In these cases, the hematoma expands vertically through the subcutaneous layer and the muscle (Fig. 3.15b). A direct shock injury may also result in disruption of the muscle fascia causing a muscle hernia (Bianchi et al. 1995a; Beggs 2003). In these patients, US demonstrates interruption of the hyperechoic fascial layer and focal extrusion of muscle tissue within the subcutaneous fat (see Chapter 15). Muscle lacerations are much less common and are more often encountered after trauma than after sports accidents. In these instances, irrigation and debridement followed by suture repair of the fascia is indicated.

3.1.4.3 Myositis Ossificans

There are three main complications of muscle tear: cysts and myositis ossificans and, more rarely, calcific myonecrosis (Peetrons 2002). Intermuscular and intramuscular cysts may be encountered after muscle trauma as well-defined echo-free masses with posterior acoustic enhancement. These cysts have an elongated shape and represent the residue of a local hematoma. Their most common location is the calf (see Chapter 15). In selected cases, they may require percutaneous needle evacuation. Calcific myonecrosis is a space-occupying calcified mass that typically develops in the anterior compartment of the leg late after a closed lower extremity

57

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a

b

c Fig. 3.14a–c. Healing rectus femoris strain. a Long-axis extended field-of-view and b short-axis 17–5 MHz US images of the rectus femoris muscle in a patient with prior myotendinous strain reveal an intramuscular echogenic area (arrows) in proximity to the central aponeurosis (arrowheads) representing residual scar tissue. c Correlative axial gradient-echo T2*-weighted MR image

s

s m

m

m a

b Fig. 3.15a,b. Closed contusion trauma. Two different cases of thigh muscle injuries following blunt trauma by sharp objects. a Transverse 12–5 MHz US image over the vastus lateralis (m) reveals an extensive laceration of muscle tissue filled in with hypoechoic hematoma (arrowheads). Note the intact subcutaneous tissue (s). b Transverse 12-5 MHz US image over the medial thigh demonstrates combined laceration of the subcutaneous tissue (s) and the gracilis muscle (m) with interruption of the fascia (arrows). The defect is filled in with hypoechoic hematoma (arrowheads)

Muscle and Tendon

trauma, and is often seen in association with vascular injury or a compartment syndrome (Dhillon et al. 2004). In this condition, the injured muscle may be replaced with a complex mass consisting of a central cystic core containing necrotic muscle, fibrin, cholesterol, and organizing thrombus, together with a peripheral calcified rim. US demonstrates calcified myonecrosis as an intramuscular extensive calcified mass with posterior acoustic shadowing and may help to guide the aspiration of the fluid component as an aid in management (Batz et al. 2006). The main differential diagnosis of calcific myonecrosis is the more common myositis ossificans, given the fact that the extensive calcified shell may mask the internal fluid component at US examination. Myositis ossificans is a benign self-limiting condition presenting as an intramuscular mass with predominant involvement of the large muscles of the extremities, the large muscles of the thigh and the anterior muscles of the arm being the most commonly affected (Thomas et al. 1991). The term “myositis” is a misnomer because this condition is not inflammatory. It usually results from a severe contusion trauma or chronic microtrauma, but may also be seen in patients with other disease or may develop spontaneously. There is, however, debate as to whether unrecollected trauma is present in these cases. From the histologic point of view, this condition exhibits a typical maturation pattern that allows a proliferative mesenchymal response (early pseudosarcomatous phase) to evolve toward formation of heterotopic mature bone. During maturation of the lesion, a zonal pattern develops with three concentric zones: the inner zone is characterized by areas of hemorrhage and necrotic muscle with proliferating fibroblasts; the middle zone consists of immature osteoid formation and islets of cartilage preceding bone formation; and the outer zone is formed by mature bone (Gindele et al. 2000). Peripheral bone formation usually starts 6–8 weeks after the trauma, but it can occur earlier. In the late phase, the lesion can ossify as a whole with formation of a cortex and marrow spaces (Ackermann 1958). As it matures the lesion regresses in size, disappearing spontaneously in approximately 30% of cases (Schulte et al. 1995). Development of peripheral calcifications is a peculiar feature of myositis ossificans and makes this condition more easily diagnosed with X-ray modalities, including plain films and CT, than with US and MR imaging. In the early stages of disease (before the sixth week of evolution), when formation of calcifications has not yet occurred, the imaging diagnosis is not straightforward: it can be difficult to distinguish lesions at this stage from a soft-tissue malignancy.

The US findings of myositis ossificans change with the lesion’s age, reflecting the evolving histology (Fornage and Eftekhari, 1989; Peck and Metreweli, 1988). Initially, the US appearance of myositis ossificans has been described as that of an intramuscular hypoechoic ovoid mass with an echogenic center, and even a so-called zone phenomenon matching the maturation process has been reported (Kramer et al. 1979; Thomas et al. 1991; Gindele et al. 2000). In more detail, early lesions are characterized by a peripheral thin hypoechoic zone enveloping a broader highly reflective zone within which a third central hypoechoic zone is found (Fig. 3.16a) (Thomas et al. 1991). With progressive maturation, the peripheral hypoechoic rim may become hyperechoic as a result of increasing ossification: a sheet-like or eggshell-like calcified rim is considered very suggestive of myositis ossificans (Peck and Metreweli, 1988). Then, visualization of the lesion center and the separation of the lesion from the underlying bony cortex may become more difficult because of the acoustic shadowing from peripheral calcifications (Gindele et al. 2000). The process of ossification is apparent with US approximately 2 weeks earlier than with plain radiographs (Peetrons 2002). Although the typical pattern of calcifications is characteristic, we believe that a standard radiograph must always be obtained to confirm the diagnosis and to exclude more aggressive calcified lesions, including paraosteal and soft-tissue sarcomas (Fig. 3.16b,c). After surgical resection, US has proved able to detect recurrence of myositis ossificans and to differentiate this condition from extraosseous sarcomas (Okayama et al. 2003).

3.1.5 Inflammatory and Ischemic Conditions Inflammatory myopathies include a heterogeneous group of acquired and potentially treatable disorders caused by an autoimmune process (idiopathic inflammatory myosites) or infectious agents (pyomyositis). Among ischemic conditions, we focus here mainly on diabetic muscle infarction and rhabdomyolysis. As previously stated, compartment syndromes are addressed in Chapter 15.

3.1.5.1 Idiopathic Inflammatory Myopathies

Based on their unique clinical, histopathologic, immunologic, and demographic features, idio-

59

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Muscle and Tendon

a

b Fig. 3.17a,b. Polymyositis and associated scleroderma. a Long-axis and b short-axis 12–5 MHz US images over the medial head of gastrocnemius reveal an intramuscular ill-defined hypoechoic area (arrows) with loss of the fibroadipose pattern, reflecting edema and fatty tissue infiltration. The subcutaneous tissue appears normal

fications (Mulier et al. 1999; Wlachovska et al. 2004). This lesion has been described as having a “scaffolding” pattern between continuous muscle bundles on long-axis scans and a “checkerboard” pattern on short-axis images (Sarteschi et al. 1997). Longitudinal US images may also demonstrate muscle swelling with preservation of the normal fibrillar pattern, disrupted by hypoechoic lines in a geometric shape, somewhat resembling “dry cracked mud” (Fig. 3.18) (Pagonidis et al. 2005). Although imaging studies may suggest such an inflammatory process (very rapidly growing mass in a muscle compartment), incisional biopsy is usually needed to rule out soft-tissue malignancy and to avoid radical excision. Sarcoidosis, a systemic granulomatous disease, may occasionally involve the skeletal muscles, leading to either palpable nodules or chronic progressive wasting and muscle atrophy or acute myositis (Otake 1994; Tohme-Noun et al. 2003). The muscles of the proximal portions of the extremities are predominantly involved. In nodular-type sarcoidosis, US is able to display well-defined hypoechoic nodules elongated along the muscle fibers and to guide percutaneous biopsy to the appropriate site (Levine et al. 1996; Tohme-Noun et al. 2003). Histologic detection of noncaseating granulomas surrounded by normal muscle tissue allows a definitive diagnosis. In large sarcoid nodules, a hyperechoic center can be depicted with US (Otake 1994). In patients with pulmonary sarcoidosis and painful leg muscles, the possibility of muscular sarcoidosis should be taken into account by the examiner. Color Doppler imaging may be helpful to rule out phlebitis.

3.1.5.2 Pyomyositis, Abscess, and Hydatid Disease

Pyomyositis is a suppurative bacterial infection of muscle, most commonly affecting the larger muscles of the lower limb (Chau and Griffith 2005). This condition most often occurs in immunocompromised patients with HIV-AIDS or diabetes and has a higher prevalence in tropical countries, where it is responsible for 3–5% of all hospital admissions (Canoso and Barza 1993; Trusen et al. 2003). However, it may follow even minor blunt trauma and local hematoma. The major causative agent is Staphylococcus aureus followed by Mycobacterium tuberculosis (psoas muscle infection following tuberculous spondylodiscitis), and Streptococcus pyogenes (Bickels et al. 2002). From the clinical point of view, pyomyositis presents with or without fever, dull cramping pain for 10–21 days, and localized muscle tenderness (Trusen et al. 2003). The US appearance of infection of the muscles has been described both in adults (Chau and Griffith 2005) and in children (Trusen et al. 2003). Initially (inflammatory phase), US reveals muscle swelling, a diffuse hyperechoic appearance reflecting edema, and hyperemia (Fig. 3.19) (Bureau et al. 1999; Chau and Griffith 2005). Small hypoechoic foci within the abnormal muscle related to early necrosis and small abscesses may be noted. At this stage, pyomyositis usually responds well to antibiotic therapy. Later in the course of the disease, an overt muscle abscess develops (suppurative phase). Muscle abscesses appear as fluid collections with well-defined posterior enhancement and variable echotexture, ranging from hypoechoic to hyper-

Muscle and Tendon

∗ a

b

c

d Fig. 3.19a-d. Pyomyositis in a 65-year-old man with fever and left thigh pain after sustaining blunt trauma to this area. a,b Transverse a gray-scale and b color Doppler 12–5 MHz US images reveal a swollen vastus lateralis muscle with heterogeneous echotexture consisting of increased echogenicity (arrows) as well as hypoechoic areas (asterisk) in which fibroadipose echoes are lost or spaced out. Posterior to this abnormal area, muscle tissue retains a normal appearance (arrowheads). Diffuse intramuscular hyperemia is detected at color Doppler imaging. c,d Correlative axial c T1-weighted and d T2-weighted MR images demonstrate marked hyperintense T2 signal and swelling of the vastus lateralis with irregular borders and diffuse fascial involvement (arrows)

∗

∗ a

F

b

c

Fig. 3.20a–c. Muscle abscess. a Transverse 12–5 MHz US image over the anterior thigh in a middle-aged immunocompromised patient with fever, pain, and local signs of infection with b T2-weighted and c Gd-enhanced T1-weighted MR imaging correlation shows a swollen heterogeneous vastus intermedius muscle (arrows) with internal fluid-filled areas (asterisks) and debris, consistent with local abscess formation. F, femoral shaft. US-guided aspiration yielded purulent fluid that grew Staphylococcus aureus up. Symptoms resolved with percutaneous drainage and antibiotic therapy

63

Muscle and Tendon

b

∗ a

c

d

Fig. 3.22a–d. Diabetic infarction. a Anteroposterior plain film of the right leg in a 60-year-old patient with diabetic infarction of the distal lower extremity shows discrete soft-tissue swelling (arrows) in the anterolateral compartment musculature. b Longitudinal 12–5 MHz US image reveals a hypoechoic intramuscular area with deranged echotexture (arrows), which is limited to the tibialis anterior muscle. c,d Axial fat-suppressed c gradient-echo T2* and d gadolinium-enhanced T1-weighted MR images show diffuse edema of the tibialis anterior muscle (arrow) and a ring of high signal intensity after gadolinium administration surrounding an unenhanced central core (asterisk)

the muscle fibers. As already described in Chapter 2, the term “hemangioma” encompasses a wide spectrum of lesions from capillary forms to vascular malformations – including capillary, cavernous, arteriovenous, venous, and mixed types – based on the predominant type of vascular channel involved (Olsen et al. 2004). In addition to their vascular components, hemangiomas can contain thrombus, calcification, hemosiderin, fat, smooth muscle, and fibrous tissue, reactive fat being the most common association. The variety of tissues found in muscular hemangiomas explains their heterogeneous appearance. US demonstrates a complex ill-defined mass within the affected muscle, characterized by a mixture of hypoanechoic and hyperechoic (reactive fat overgrowth) components (Fig. 3.23) (Derchi et al. 1989). Prominent vascular channels can be identified on gray-scale and Doppler imaging as well. One-toone correlation between US and MR images shows good correspondence between intratumor hyper-

echoic areas and fat (high T1 signal), and hypoechoic components and blood-filled cavities (high T2 signal). Phleboliths within the mass are present in approximately 50% of cases and are best identified on plain films (Fig. 3.23f) (Murphey et al. 1995). At US, they appear as bright dots with posterior acoustic shadowing that are usually located within the hypoechoic component of the hemangioma. Doppler imaging characteristics of hemangiomas are described in Chapter 2. Overall, US can diagnose hemangiomas, especially when phleboliths are detected within the mass. During prolonged observation, very slow blood motion in the hypoechoic cavities of the mass can be appreciated on gray-scale imaging, like a “swarming mass”. In some instances, however, the assessment of hemangiomas may be difficult: in particular, the boundaries of the lesion are usually undefined, especially in large masses infiltrating more than one muscle or blending imperceptibly with the intermuscular fatty planes.

65

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Muscle and Tendon

∗ b

∗

∗

∗

a

c Fig. 3.24a–c. Intramuscular lipoma: infiltrative type. a Transverse 12–5 MHz US image over the anterior shoulder in a patient with a painless slowly growing mass with b,c axial T1-weighted MR imaging correlation demonstrates a large mass within the deltoid muscle characterized by a hyperechoic background (asterisks) and a striated pattern (arrowheads) due to intermingled muscle fibers with fat. The lipoma is delimited by a thin hypoechoic rim (arrows) reflecting peripherally displaced muscle tissue

fat, in our experience MR imaging is much superior to US for the confident identification of adipose tissue in infiltrative lipomas. After fibrous and fibrohistocytic malignancies, liposarcoma represents the second most common type of soft-tissue sarcoma, accounting for approximately 10–25% of all soft-tissue sarcomas (Murphey et al. 2005). It is predominant in men around the fifth and sixth decades of life and does not represent the result of malignant transformation of a lipoma. Histopathologically, liposarcomas are grouped in five subtypes: well-differentiated, myxoid, round cell, pleomorphic, and dedifferentiated. Well-differentiated liposarcoma is the most common type (50%); it lacks metastatic potential but tends to recur locally. US shows large, multilobulated, well-defined masses which, in most cases, are indistinguishable from mature lipomas (Fig. 3.25) (Futani et al. 2003; Murphey et al. 2005). Based on gray-scale US findings, lipoma-like lesions with a complex appearance (containing thick septa and nodular or globular foci with echotexture other than that of fat) always merit further investigation with contrast-enhanced MR imaging (Fig. 3.26). Finding blood flow signals in a lipoma-like mass with color and power Doppler imaging should also alert the examiner (Bodner et al. 2002; Futani et al. 2003). Unlike well-differentiated liposarcoma, myxoid liposarcoma presents as a well-circumscribed multinodular mass whose gross pathologic appearance includes a smaller volume of

fat (often 5 mm between the suprapatellar fat and the prefemoral fat (Fig. 14.115). This sign has been reported positive even for effu-

sions of 2 ml (Hall 1975). MR imaging has proved to be an excellent modality for detecting small amounts of fluid. Based on the intra-articular injection of cadaveric knees, some authors have documented so high a sensitivity of this technique as to detect even a 1 ml effusion (Schweitzer et al. 1992). Such a small quantity of fluid is delineated as a thin rim lying between the condyles and the Hoffa fat pad. With increasing amounts (3 ml), the fluid is consistently detected in the suprapatellar recess. We routinely assess fluid effusions with US in this recess (Fig. 14.116). A careful scanning technique avoiding excessive pressure with the probe on the skin should be used for this purpose because there may be a shift of fluid toward other synovial recesses. The smallest collections can occasionally be demonstrated only at the level of the medial and lateral parapatellar

723

Knee

recesses, as these are the most dependent recesses of the knee while the patient is supine. When looking for a knee effusion, the examiner should be aware that changes in the patient’s position can cause a shift of the fluid toward sites not subjected to pressure (Singer 1985). When a discrete effusion is present, US may be helpful to select the best site for puncture as well as to prove the correct intra-articular positioning of the needle. Usually, US-guided arthrocentesis is less painful than blind punctures. The suprapatellar recess is the preferred site for synovial membrane assessment in knee disorders. Its routine examination is almost always completed using transverse US images obtained over the lateral and medial parapatellar recesses (Backhaus et al. 2001). In normal conditions, the synovial membrane is too thin to be detected at US examination. Following a variety of local or systemic disorders, the synovium can undergo hypertrophy to reach a thickness detectable at US (Fig. 14.117). The appearance of synovial membrane hypertrophy should be considered nonspecific, and it does not allow a precise differentiation among various pathologies (Wang et al. 1999a). The thickened synovium leads to a hypoechoic appearance of the recess walls and may show projections within the joint cavity. Depending on the degree of hypertrophy, the synovial pannus can fill the articular cavity in part or completely. Synovial proliferation is one of the early manifesta-

tions of rheumatoid arthritis and its detection has practical importance because it can indicate early aggressive treatment to try to limit extensive erosive changes, tears of para-articular ligaments and tendons as well as functional disabilities. Somewhat similar to gadolinium-enhanced MR imaging, color and power Doppler techniques have been proved to be useful means of distinguishing active (hypervascular) from fibrous (hypovascular) pannus. Demonstration of a hypervascular pannus has therapeutic implications as it correlates with disease activity (Carotti et al. 2002). Microbubble-based contrast agents seem promising in this field to enhance the sensitivity of US to detect synovial blood flow and assess the response to therapy in patients with rheumatoid arthritis (Doria et al. 2001; Taylor et al. 2004). As for the suprapatellar recess, US can assess similar pathologic changes at the level of the lateral and medial parapatellar pouches (Fig. 14.118).

14.5.5.2 Lipohemarthrosis

Lipohemarthrosis can be defined as the occurrence of blood and fat within an articular cavity. This is a common finding in acutely injured knees with a fracture involving the articular surfaces or a severe

*

*

1T

1T

*

*

a Fig. 14.117a,b. Subquadriceps recess: synovial hypertrophy. a Longitudinal 12–5 MHz US image obtained over the quadriceps tendon (Qt) in a child with juvenile idiopathic arthritis with b sagittal T2-weighted MR imaging correlation demonstrates nodular thickenings (asterisks) of the synovial membrane associated with intra-articular effusion (asterisk). Synovial hypertrophy must be distinguished from the suprapatellar (arrow) and prefemoral (arrowhead) fat pads based on its location and echotexture

b

724

C. Martinoli and S. Bianchi

a

c

0 b

d Fig. 14.118a–d. Parapatellar recess: synovial hypertrophy. a Transverse gray-scale and b color Doppler 12–5 MHz US image obtained over the medial aspect of the knee at the level of the patella in a child with juvenile idiopathic arthritis shows abundant synovial pannus filling the parapatellar recess as a band of hypoechoic tissue (arrowheads) intermingled with fluid. P, patella. Marked synovial hyperemia is observed at color Doppler examination indicating active pannus. c,d Corresponding transverse T1-weighted MR images obtained c before and d after intravenous contrast material administration confirm thickening of the synovium (arrowhead) in the parapatellar recess. In the postcontrast scan, note the marked enhancement of the pannus which parallels the color Doppler image

capsuloligamentous injury. In patients with intraarticular fractures, the fat found inside the joint cavity derives from yellow bone marrow, whereas in capsuloligamentous tears it derives from the synovial membrane or from the intra-articular fat pads. The clinical importance of lipohemarthrosis relies on the fact that its presence in a traumatized patient with negative radiographic studies suggests a nondisplaced fracture or a severe intra-articular lesion which warrants further imaging evaluation. Standard radiographs recognize lipohemarthrosis by demonstrating a fat-fluid level resulting from floating of the fat on the blood (Fig. 14.119a) (Butt et al. 1983). A double fat-fluid level can be seen when a suprapatellar plica or lobulations of the capsule are present (Sandretto and Carrera 1983). Both MR and CT imaging can easily reveal lipohemarthrosis. CT shows a fat-fluid level with the typical negative density of fat overlying the blood (Fig. 14.119b). On the other hand, MR imaging may depict a four-layer effusion which includes, from superficial to deep: fat, chemical shift artifact, serum and red blood cells (Kier and McCarthy 1990). Similar to these techniques, US can identify a layered appearance of

the intra-articular effusion (Bianchi et al. 1995b). In a routine posttraumatic study, the incidental detection of lipohemarthrosis with US should alert the examiner to the possibility of an intra-articular fracture. An experimental setting demonstrated that the US appearance of lipohemarthrosis critically depends on the time of examination (Bianchi et al. 1995b). In this study a mixture of cooking oil and fresh blood in a bag was examined at various time intervals. Early US images (obtained at 1 and 5 min) revealed a two-layered appearance consisting of a hyperechoic superior band corresponding to the fat floating inside the bag and an inferior band of intermediate echogenicity related to the blood. Delayed images (obtained at 30 min) displayed a three-layered pattern with an intermediate thin anechoic band corresponding to the serum over the cellular blood component. In practice, patients immobilized for long periods of time (more than 30 min) reveal a three-layered pattern while those mobilized have only a two-layered pattern (Fig. 119c,d). While examining post-traumatic knees, care should be taken not to confuse the normal suprapatellar fat pad with free fat floating on the effusion. In these

726


that can ultimately result in secondary osteoarthritis and chronic disability. In a traumatic setting, the sites from which intra-articular loose bodies more commonly arise include the articular surfaces of the patella, the lateral trochlea and the weight-bearing surfaces of the femoral condyles. The main differential diagnosis of intra-articular loose bodies is displaced meniscal fragments, a common cause of intermittent joint locking. US has proved to be an effective imaging modality for detection and characterization of intra-articular loose bodies (Bianchi and Martinoli. 1999). Because the suprapatellar recess is the widest recess of the knee, it is not surprising that it is the most common location for intra-articular loose bodies (Fig. 14.120). Fragments may appear as hyperechoic structures with posterior acoustic shadowing (osseous and chondral calcified fragments), hypoechoic structures without posterior attenuation of the US beam (purely chondral nature) and hyperechoic images covered by a hypoanechoic rim (osteochondral fragments) (Figs. 14.98, 14.99). The presence of anechoic fluid surrounding the fragments greatly enhances the diagnostic confidence (Fig. 14.121). Consequently, all efforts should be made to shift as large an amount of fluid as possible into the recess to be examined. This can be achieved by asking the patient to contract the quadriceps or simply by push-

*

ing the fluid in a cranial direction with the hand. Then, examining the knee in an extended position can avoid squeezing the fluid away from the suprapatellar recess. If a retropatellar fragment is suspected on standard radiographs, examining the knee with different degrees of flexion can move the patella distally from over the fragment (Fig. 14.122). Overall, a conclusive US diagnosis of intra-articular loose bodies basically relies on demonstration of fluid surrounding the fragment or fragment displacement. Flexion and extension movements of the knee and a change in the patient’s position (standing vs. supine) can induce mobilization of the fragments. Display of motion excludes synovial and capsular calcifications. If the recess does not contain fluid, intra-articular loose bodies can be found between the prefemoral fat pad and the quadriceps tendon. In this cases, fragments are more difficult to see. Osteophytes of the superior edge of the trochlea can be imaged on longitudinal US images just deep to the patella and should be differentiated from intraarticular loose bodies. Because they are formed by hyperechoic cortical bone covered by a thin layer of cartilage, trochlear osteophytes may mimic a loose body positioned underneath the patella. Correlation of US findings with standard radiographs and examining the trochlea during forced flexion of the knee allow a correct diagnosis.

* b

* a

c Fig. 14.120a–c. Intra-articular loose body. a Longitudinal 12–5 MHz US image of the suprapatellar recess performed with the knee flexed shows a calcified loose body (asterisk) as a hyperechoic fragment with posterior acoustic shadowing (arrowheads) located within the suprapatellar recess. b Corresponding laterolateral radiograph and c sagittal T2-weighted MR image obtained with mild knee flexion confirm the presence of a calcified intra-articular fragment (asterisk)

730


&EMUR 4IBIA

4IBIA

&EMUR

a

b

&EMUR

4IBIA

c Fig. 14.126a–c. Osteoarthritis of the medial compartment. a,b Longitudinal 12–5 MHz US images obtained over the medial joint line during a varus and b valgus stress test. a The medial joint space is narrowed (curved arrow) due to cartilage thinning. Note marginal bone spurs (white arrowheads) related to osteophytes. b During valgus stress, the joint space opens due to ligament instability. c Anteroposterior radiograph shows typical findings of medial knee osteoarthritis, including joint space narrowing, marginal osteophytes (white arrowheads) and subchondral sclerosis

&EMUR

4IBIA

&EMUR

4IBIA

a

b Fig. 14.127a,b. Meniscal extrusion. a Coronal 12–5 MHz US image over the medial joint line demonstrates the normal appearance of the meniscus (M), a triangular-shaped hyperechoic fibrocartilaginous structure located between the articular surfaces of the femur and tibia which are covered by a layer of hypoechoic hyaline cartilage (rhombi). b Coronal 12–5 MHz US image of meniscal extrusion in severe medial femorotibial joint space narrowing. Note the severe narrowing of the medial joint space (arrow) due to cartilage thinning and the presence of marginal osteophytes (white arrowheads). The medial meniscus (M) is extruded and stretches the overlying superficial layer of the medial collateral ligament (black arrowheads)

Knee

a

b

c

Fig. 14.135a–c. Schwannoma of the tibial nerve. a Transverse and b longitudinal 12–5 MHz US images over the popliteal fossa reveal a well-defined oval hypoechoic mass (arrows) in continuity with the tibial nerve (arrowheads). In a, note some unaffected fascicles (arrowhead) displaced at the periphery of the tumor. c Transverse color Doppler US image demonstrates a hypervascular pattern of the tumor (arrows) consisting of peripheral and central blood flow signals

et al. 1996). Its origin is undetermined although this mass is believed to represent more a reactive than a neoplastic entity. It can be an isolated condition or can be found in association with chronic arthropathies, such as rheumatoid arthritis or osteoarthritis. In some patients, lipoma arborescens presents clinically as a painless slow-growing mass, whereas in other cases it is painful and can be associated with a decreased range of knee motion and joint effusion. US reveals an intra-articular compressible mass characterized by multiple frond-like projections that allow its differentiation from hypertrophic synovitis

* a

(Fig. 14.136) (Learch et al. 2000; Martinez et al. 1992). Correlation with laboratory and clinical data may help to distinguish lipoma arborescens from synovitis. Following the US study, MR imaging allows a conclusive diagnosis so that the adequate treatment, a synovectomy, can be performed (Martin et al. 1998; Vilanova et al. 2003). Differentiation of this condition from the normal superolateral fat pad is based on the typical location, the smaller size and the smooth margins of the fat pad and the larger size and macroscopic villus-like appearance of the lipoma arborescens (Armstrong and Watt 1989).

* b

c

Fig. 14.136a–c. Lipoma arborescens. a Transverse 12–5 MHz US image over the lateral parapatellar recess (arrows) demonstrates a large effusion (asterisks) and villous hyperechoic fatty synovial proliferations (arrowheads) with a clearly frond-like morphology inside the pouch, resembling the image of a branched tree. b,c Correlative b transverse T1-weighted and c T2-weighted MR images reveal signal intensity similar to that of subcutaneous fat within the mass (arrows)

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BM

BM

SM

SM a

b

c

SM

LHG

MHG

d

e

Fig. 14.139a–e. Tensor fasciae suralis muscle. a Transverse and b longitudinal 12–5 MHz US images obtained over the popliteal space show the accessory belly of the tensor fasciae suralis (arrows) which lies superficial to the semimembranosus muscle (SM). Note the characteristic internal structure of the muscle made up of hypoechoic bundles and hyperechoic fibroadipose septa. c Cranial and d caudal transverse T1-weighted MR images confirms the US finding. Note the distal tendon of the tensor fasciae suralis (arrowhead) located superficial to the medial head of the gastrocnemius (MHG). BM, biceps femoris muscle; LHG, lateral head of the gastrocnemius. e Photograph of the posterior thigh obtained during resisted flexion of the knee shows an anomalous lump (arrow) produced by the contracted muscle

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Leg

15

Leg Stefano Bianchi and Carlo Martinoli

CONTENTS 15.1

15.2 Clinical and US Anatomy

Introduction 745

15.2 Clinical and US Anatomy 15.2.1 Anterolateral Leg 745 15.2.2 Posteromedial Leg 749

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15.3 Leg Pathology 755 15.3.1 Anterolateral Leg 755 15.3.1.1 Muscle Hernias 755 15.3.1.2 Medial Tibial Stress Syndrome 757 15.3.1.3 Compartment Syndromes 757 15.3.1.4 Superficial Peroneal Neuropathy 759 15.3.2 Posteromedial Leg 759 15.3.2.1 Tears of the Medial Head of the Gastrocnemius 759 15.3.2.2 Plantaris Tendon Tears 765 15.3.2.3 Calf Vein Thrombosis 767 15.3.2.4 Phlebitis of the Calf Veins 768 15.3.2.5 Sural Neuropathy 769 15.3.3 Leg Masses 769 References

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Two space compartments can be considered in the lower leg: anterolateral and posteromedial. They are separated by a plane passing through the tibia, the fibular shaft, a strong interosseous membrane connecting these bones and the posterior crural intermuscular septum, which is located lateral to the fibula. The anterolateral compartment can be further subdivided into an anterior crural compartment and a lateral crural compartment separated by the anterior crural intermuscular septum, located between the extensors and the peroneal muscles. The posterolateral compartment includes two groups of muscles – superficial and deep – separated by the transverse crural intermuscular septum. A brief description of the normal and US anatomy of the anterolateral and posteromedial compartments is included here.

15.1 Introduction Similar to the thigh, typical clinical manifestations in the soft tissue of the leg are mainly related to muscle pathology, including traumatic injuries and muscle hernias, the first most often affecting the posteromedial compartment, the latter the anterolateral one. Pathology of nerves and vessels of the lower leg is less common but should be recognized by the examiner nevertheless due to important clinical implications and possible association with other musculoskeletal abnormalities.

S. Bianchi, MD Privat-docent, Université de Genève, Consultant Radiologist, Fondation et Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland C. Martinoli, MD Associate Professor of Radiology, Cattedra “R” di Radiologia – DICMI – Università di Genova, Largo Rosanna Benzi 8, 16132 Genova, Italy

15.2.1 Anterolateral Leg The anterolateral compartment of the leg is located between the anterior edge of the tibia and the lateral aspect of the fibula. This space houses muscles involved in dorsal flexion, pronation and supination of the ankle The anterior muscles of the lower leg lie in a more medial position. From medial to lateral, they are: the tibialis anterior, the extensor hallucis longus and the extensor digitorum longus (Fig. 15.1). The tibialis anterior is a strong muscle which arises just lateral to the anterior border of the superior two thirds of the tibia (Fig. 15.2a). It has a circumpennate structure with an internal aponeurosis oriented in a coronal oblique plane. The aponeurosis continues downward in a strong oval tendon which courses along the anterior edge of the tibia and the anterior aspect of the ankle joint. The anterior tibialis muscle is the stron-

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Dynamic scanning during passive extension–flexion movements of either the greater or the lesser toes in a group may be helpful to distinguish them. Longitudinal planes may show the circumpennate appearance of the tibialis anterior muscle. Deep to the anterior muscles, US is able to depict the interosseous membrane as a thin, continuous line joining the tibia and the fibula (Fig. 15.3a) (Durkee et al. 2003). The lateral muscles of the lower leg include the peroneus longus and the peroneus brevis (Fig. 15.4). These muscles are separated from the anterior leg muscles by the anterior crural intermuscular septum. The peroneus longus takes its origin from the lateral aspect of the superior tibiofibular joints and the upper two thirds of the lateral fibular shaft (Fig. 15.4a). The peroneus brevis arises more distally from the lower half of the lateral aspect of the fibula. It descends more distally than the peroneus longus and continues in a flat tendon located anteromedially to that of the peroneus longus (Fig. 15.4b). Both peroneal muscles are powerful everters of the foot and participate in plantar flexion of the ankle. Transverse US images obtained at the upper third of the leg reveal the cranial peroneus longus which lies on the lateral side of the fibula (Fig. 15.5a). More caudal images demonstrate its flat tendon located in the external portion of the muscle. More distally, the peroneus longus tendon becomes oval and courses on the external surface

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Fig. 15.4a,b. Schematic drawings of the lateral compartment of the leg showing the peroneal muscles. a The peroneus longus muscle (PL) takes its origin more cranially and is located superficial to the peroneus brevis (PB). It continues down into the medial aspect of a tendon located posteriorly and then inferiorly to the tendon of the peroneus brevis. b The peroneus brevis muscle arises from the caudal half of the posterolateral aspect of the fibula. Its belly descends down to the lateral malleolus ending on the posterior aspect of the tendon

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Fig. 15.5a,b. Peroneal muscles. Transverse 12– 5 MHz US images obtained over the middle (a) and distal (b) third of the lateral leg. The peroneus longus muscle (PL) is larger in size and lies more anteriorly than the peroneus brevis (PB). Note that the flat tendon (arrowheads) of the peroneus longus arises from the superficial aspect of the muscle and, more caudally, overlies the belly of the peroneus brevis. The photograph at the right of the figure indicates probe positioning

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cular septum, which is also referred to as the deep transverse fascia of the leg. From medial to lateral, the deep muscles are: the flexor digitorum longus, the tibialis posterior and the flexor hallucis longus (Figs 15.1, 15.7). The flexor digitorum longus takes its origin from the middle third of the posterior face of the tibia, just distal to the soleal line and medial to the origin of the tibialis posterior (Fig. 15.7b). The tibialis posterior muscle, the most deeply seated, lies between the flexor digitorum longus and the flexor hallucis longus (Fig. 15.7a,b). It arises from the middle third of the posterior aspect of the tibia, the posterior surface of the interosseous membrane and the upper two thirds of the medial aspect of the fibula. The tibialis posterior muscle has a bipennate appearance consisting of a central aponeurosis which continues downward in a strong tendon reflecting over the medial malleolus. It acts as an extensor of the foot and also plays a role as a foot inverter in antagonism with the peroneal muscles. The flexor hallucis longus is the most lateral of the deep muscles (Fig. 15.7b). It arises from the posterior aspect of the distal two thirds of the fibula, the posterior surface of the interosseous membrane and the posterior crural septum which separates it from the peroneal muscles. The flexor hallucis longus sends a

strong posterior tendon which reflects in an osteofibrous tunnel grooved in the posterior talus. The flexor digitorum and flexor hallucis longus are flexors of the toes. Superficial to these muscles, the triceps surae, the largest and most powerful muscle of the leg, is composed of the soleus and the gastrocnemius. The soleus is a broad and flat muscle which lies deep and bulges on each side of the gastrocnemius extending more caudally than it (Fig. 15.7c). It has a wide origin from the middle third of the medial tibial surface, the proximal third of the posterior aspect of the fibular shaft including a strong fibrous arcade which joins the tibial and fibular insertions. Its fibers are oriented obliquely from anterior to posterior and attach down into the deep face of a broad aponeurosis. Just superficial and posterior to the soleus, the gastrocnemius consists of two heads – medial and lateral – which join together in the midline (Fig. 15.7d). As a rule, the medial head is thicker and extends more distally than the lateral. The proximal tendons of the gastrocnemius take their origin from the posterior aspect of the medial and lateral epicondyles. In each head of the muscle, the proximal tendon forms a flat “superficial aponeurosis.” Muscle fibers arise from the deep surface of this aponeurosis and insert

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Fig. 15.7a–d. Posterior leg muscles. Schematic drawings of a coronal view of the posterior leg showing the (a,b) deep and (c,d) superficial muscles of the posteromedial compartment. a The tibialis posterior muscle (TP) is the deepest muscle, located between the tibia and fibula. Note that its long, central tendon (in black) arises at the proximal third of the muscle. b The flexor digitorum longus (FDL) and the flexor hallucis longus (FHL) lie more superficially, on the medial and lateral aspect of the tibialis posterior muscle respectively. c The soleus (So) is a large flat muscle joining the tibia and the fibula through a strong fibrous arcade (arrowhead). It inserts into a distal broad aponeurosis (SDA) that continues downward to form the deep (anterior) contribution of the Achilles tendon (AT). The small plantaris muscle (Pl) and its long thin tendon (black arrow) lies on the dorsal aspect of the soleus. d The gastrocnemius muscle, consisting of the medial (MH) and lateral (LH) heads, is located posterior to the soleus. The medial head descends more caudally than the lateral. Both attach to a broad distal aponeurosis (GDA) which forms the superficial (posterior) contribution of the Achilles tendon

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complex. Given the considerable extension of the posterior muscles, extended field-of-view images are well suited to display the relationships among the muscles of this compartment in a panoramic view. The superficial location of the triceps surae makes it easier to be examined with US. The gastrocnemius overlies the flat soleus and is separated from it by two well-defined hyperechoic layers reflecting the apposition of the distal aponeuroses of these muscles separated by a thin hypoechoic cleavage plane filled with loose connective tissue (Fig. 15.8b). In the distal gastrocnemius, intramuscular fibroadipose septa appear as a series of parallel hyperechoic lines arranged obliquely to reach their insertion into the distal aponeurosis. On the other hand, the fibers of the soleus are less evident because of the deep location of this muscle and its less organized internal

structure. Between the medial head and the soleus, the thin plantaris tendon can be appreciated as a very small flattened hyperechoic structure. Moving the transducer back and forth over it in a transverse plane can improve the confidence in its detection. A hyperechoic intermuscular septum is usually visible at the point where the two heads join together in the midline. More deeply, the flexor digitorum longus, tibialis posterior and flexor hallucis longus muscles can be assessed with US as well (Fig. 15.9). Especially in obese patients with thick legs, a careful adjustment of image setting parameters, including penetration and focus positioning, may be required for this purpose. As for the anterior muscles, dynamic scanning during flexion and extension movements of the greater and lesser toes can help to distinguish the flexor muscles from one other.

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Fig. 15.9a–c. Posterior leg muscles. a Transverse extended field-of-view 12–5 MHz US image shows a panoramic view of the medial (MH) and lateral (LH) heads of the gastrocnemius, the soleus (So) and the three deep muscles, the flexor digitorum longus (FDL), the flexor hallucis longus (FHL) and the tibialis posterior (TP). Note the deeper position of the tibialis posterior muscle, which lies between the tibia (T) and the fibula (F), relative to the other muscles. b,c Transverse medial (b) and lateral (c) 12–5 MHz US images give full depiction of the tibialis posterior muscle (TP) and its central aponeurosis (open arrowhead). Note the relationship of this muscle with the other flexors, the soleus (So) and the gastrocnemius (G). The posterior tibial artery (white arrowhead) and the tibial nerve (black arrowhead) intervene between the superficial and deep layers of these muscles. FDL, flexor digitorum longus; FHL, flexor hallucis longus. The photograph at the right of the figure indicates probe positioning

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The most common accessory muscle in the lower leg is the accessory soleus, which is located between the Achilles tendon and the soleus muscle (Bianchi et al. 1995b). In most cases, this muscle takes its origin from the posterior aspect of the tibia and the anterior aspect of the soleus. Five types of distal insertions have been described in this muscle (Kouvalchouk and Fisher 1998). In type 1, the muscle inserts directly into the Achilles tendon at approximately 1–2 cm from the calcaneus (Fig. 15.10); in types 2 and 3, the muscle inserts onto the superior face of the calcaneus directly (type 2) or through a short tendon (type 3); in types 4 and 5, the muscle attaches on the medial face of the calcaneus directly (type 4) or by its tendon (type 5) (Fig. 15.11). Clinically, the accessory soleus presents as an indolent posteromedial mass which becomes tense during contraction (patient standing on tiptoes). Occasionally, it may become symptomatic as a result of overuse during sporting activities. Diagnostic imaging may be helpful to distinguish the anomalous muscle from a soft tissue tumor. US typically shows a normal-appearing muscle located deep to the Achilles tendon and replacing the fat of Kager’s space (Bianchi et al. 1995b). The posterior tibial artery is the direct continuation of the popliteal artery down to the distal margin of the popliteus muscle. During its course, this artery is accompanied by the tibial nerve and two or more posterior tibial veins. This posterior neurovascular bundle passes deep to the tendinous arch of the soleus and, after giving off the peroneal artery, courses superficial to the tibialis posterior muscle to reach the tarsal tunnel (Fig. 15.12a,b). The posterior tibial artery is a useful landmark to separate the deep from the superficial group of calf

muscles. In the medial head of gastrocnemius, there are two or three pairs of intramuscular veins (each pair enclosing a small artery) characterized by a larger diameter than the other veins in the lateral head and in the soleus (Fig. 15.13). These veins drain into the popliteal vein and, in some instances (especially in sitting subjects), may appear dilated with a hyperechogenic content that may mimic a thrombus (Coulier 2002). This phenomenon is fully reversible and seems related to a decreased intravenous shear rate due to sluggish blood flow. It can be resolved by applying pressure with the probe over the veins, squeezing the distal calf or changing the patient’s position (leg suspended over the edge of the table with the foot supported on a rest or tilting the table into a reversed Trendelenburg position) (Coulier 2002). These maneuvers are essential to avoid falsepositive diagnoses of calf venous thrombosis. In the posterior leg, the superficial venous system consists of the great saphenous vein, which courses along the medial aspect of the calf, and the small saphenous vein, which runs along the lateral aspect of the Achilles tendon. Normal venous drainage is directed from the superficial to the deep system. US evaluation of the calf veins in patients with suspected acute deep or superficial venous thrombosis may require compression in a stepwise fashion every 2–3 cm. In addition to the tibial nerve, another nerve running in the posterior calf is the sural nerve. This small sensory nerve descends between the two heads of the gastrocnemius and then pierces the deep fascia around the middle third of the posterior leg to course in the subcutaneous tissue in close association with the small saphenous vein on the lateral aspect of the Achilles tendon. During its course, the sural nerve joins the peroneal communicating nerve. The small

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Fig. 15.10a,b. Accessory soleus muscle (type 1). a Longitudinal extended field-of-view 12–5 MHz US image over the Achilles tendon (arrowheads) reveals the aberrant soleus muscle (arrows) inserting into the deep surface of the tendon. The muscle ends in proximity to the calcaneus and occupies a large part of Kager‘s space. b Axial CT scan confirms the presence of an accessory muscle (arrows) located between the distal Achilles tendon (At) and the flexor hallucis longus muscle (FHL)

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Fig. 15.11a–g. Accessory soleus muscle (type 5). a Physical examination shows a soft tissue lump (arrows) on the posteromedial aspect of the distal leg. In this particular case, the lump became painful when the patient ran. b Lateral radiograph of the ankle reveals an area of soft tissue density (arrow) replacing the fatty tissue in Kager‘s space reflecting the accessory muscle. Arrowhead indicates the flexor hallucis longus muscle. c–e Transverse T1-weighted MR images obtained from cranial (c) to caudal (e) demonstrate the aberrant muscle (arrows) and its tendon (arrowhead). Note that the accessory soleus is located superficial to the medial retinaculum: this latter feature may help to distinguish it from the accessory flexor digitorum muscle (see Fig. 3.9). f Transverse extended field-of-view 12–5 MHz US image depicts the bulk of the accessory muscle (arrows) located between the Achilles tendon (At) and the flexor hallucis longus (FHL). TP, tibialis posterior tendon. g Coronal 12–5MHz US image over the lump demonstrates the thin eccentric tendon (arrowheads) of the accessory soleus (arrows) inserting into the medial face of the calcaneus

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Fig. 15.12a–d. Normal nerves of the posterior leg. a,b Tibial nerve. a Transverse 12–5 MHz US image obtained over the medial aspect of the distal leg with b T1-weighted MR imaging correlation demonstrates the tibial nerve (arrows) as a honeycombed structure made up of hypoechoic rounded areas reflecting the fascicles. Observe the anatomic relationships of the nerve with the tibialis posterior (tp) and the flexor digitorum longus (fdl). t, tibia. c,d Sural nerve. c Transverse 17–5 MHz US image obtained over the lateral aspect of the distal leg with d T1-weighted MR imaging correlation reveals the few fascicles of the sural nerve (open arrow) embedded in the subcutaneous fat. The nerve courses in close proximity to the small saphenous vein (white arrow)

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Fig. 15.13a–d. Intramuscular veins of the medial head. a Schematic drawing of a coronal view of the posterior leg demonstrates a series of gemellary veins which course inside the medial head (MH) of gastrocnemius upward to reach the popliteal vein. LH, lateral head of gastrocnemius. b Transverse 12–5 MHz US image obtained over the medial head reveals two intramuscular vessel pedicles (1 and 2), each consisting of a central artery (straight arrow) and two satellite veins (arrowheads), running within large stromal septa (curved arrows) of the muscle. c Longitudinal and d transverse color Doppler images obtained over a vessel pedicle of the medial head identify blood flow signals coded in red for the artery (arrow) and in blue for the veins (arrowheads)

saphenous vein is a useful landmark to identify the nerve (Fig. 15.12c,d).

15.3 Leg Pathology Similar to the thigh, the most relevant pathologies of the lower leg in terms of prevalence and clinical importance that are amenable to US examination are muscle abnormalities, which are often correlated with sporting or recreational activities.

15.3.1 Anterolateral Leg 15.3.1.1 Muscle Hernias

Muscle hernias are focal protrusions of muscle tissue through fascial defects. In the lower leg, herniation of muscle is most commonly observed in the middle and lower thirds affecting the tibialis anterior muscle, although involvement of the extensor digitorum longus, peroneal muscles and the lateral head of the gastrocnemius have also been reported (Mellado and Peréz del Palomar 1999). The area overlying the anterior intermuscular septum,

between the anterior and lateral compartments of the lower third of the calf, is also a preferred site of muscle hernia. From the pathophysiologic point of view, muscle hernias can be either constitutional or secondary to local blunt trauma. Muscular overuse or hypertrophy may lead to fascial tears at specific weak locations, such as those in which the fascia is traversed by vessels and nerves, and subsequent muscle herniation as a result of an increased pressure within the compartment. On the other hand, repeated contusions, such as those occurring in soccer players as a result of violent impacts against football boots, can cause traumatic damage of the fascial sheaths, leading to hernia formation. Most patients with leg hernias are asymptomatic, although they may present with cramping or vague pain after prolonged exercise. Often, the medical consultation is required for cosmetic purposes or to rule out a small soft tissue tumor. Physical examination demonstrates a focal lump in the anterolateral aspect of the leg which can vary in size from less than 1 to several centimeters. Careful palpation can detect a focal disruption of the fascia. US is an accurate means to identify muscle hernias in the lower leg and assess their size during dynamic scanning (Bianchi et al. 1995a; Beggs 2003). First, the examiner should locate the referred lump, which may be not so evident on the skin while the patient is standing, supine on the examination bed or even contracting the muscle. Examining the patient while

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Fig. 15.14a–g. Muscle hernia. a Photograph showing the examination technique for detecting muscle hernias in the anterolateral compartment of the leg with US. The patient is asked to assume a squatting position to increase the pressure within the compartment and make the extruded muscle palpable. Then, the examiner places the probe over the lump. b,c Schematic drawings illustrate the mechanism of hernia (asterisk) reduction below the fascial defect by applying pressure (black arrows) with the probe over it. Arrowheads, fascial plane. d–g Corresponding transverse 12–5 MHz US images obtained in two different patients with d,e a large hernia of the tibialis anterior muscle and f,g a small hernia of the extensor digitorum longus. In both cases (d and f), part of the muscle (asterisk) bulges through the defect of the fascia (arrowheads). e,g With probe compression over the defect, reduction of the hernia is obtained. Arrow, direction of probe pressure

squatting to increase the pressure within the anterolateral compartment, or immediately after strenuous exercise, can increase the conspicuousness of the lump (Fig. 15.14a) (Bates 2001). Once the lump has been clinically detected, the skin should be marked because the hernia may be difficult to be identified during scanning. US should be performed with the patient in the position most adequate to reveal it. The transducer is applied lightly on the skin to avoid reduction of the hernia and a false negative examination. Abundant coupling gel may be useful. US findings of muscle herniation include focal discontinuity of the fascia covering the involved muscle and a herniated portion of the muscle overlapping the fascial defect (Fig. 15.14b,c). The fascial defect appears as a focal interruption of the superficial echogenic line forming the superficial boundary of the muscle. The disruption of the fascia requires a careful scanning technique because it is often present only as a small opening and can go unnoticed. The fascial defect size, however, does not correlate with the success of medical therapy versus surgical treatment (Bates 2001). In some cases, color and power Doppler imaging demonstrate promi-

nent vessels which traverse the fascia at the site of muscle herniation. This observation could support the hypothesis that hernias originate at areas of fascial weakness, such as the entrance sites of perforating vessels. If the fascia is thinned but no defect is apparent, there may be a shallow muscle bulge with elevation of the overlying fascia during muscle contraction (Beggs 2003). The herniated portion of the muscle has a mushroom-shaped appearance with a superficial convex contour, and can protrude within the subcutaneous tissue for only a few millimeters. The hernia is usually less echogenic than the normal muscle, possibly due to anisotropy or crowding of the fibroadipose septa (Bianchi et al. 1995a; Beggs 2003). Because the hernia is reducible below the fascial defect in most cases, applying varying degrees of pressure with the probe over it dynamically gives a real-time depiction of its intermittent reduction and reherniation and, therefore, confirmation of the diagnosis (Fig. 15.14d-g) (Bates 2001). A less common type of herniation is caused by severe trauma that results in avulsion of the anterior leg fascia from the tibia and muscle fascia rupture (Fig. 15.15).

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Fig. 15.15a–c. Muscle hernia. a–c Transverse 12–5 MHz US images obtained with different degrees of probe pressure over the defect show disruption of the tibialis anterior muscle fascia (open arrowhead) from the tibia (T) and subsequent muscle herniation within the subcutaneous tissue (asterisks). Note progressive reduction of the herniation with graded compression. White arrowhead indicates the internal aponeurosis of the tibialis anterior muscle

Asymptomatic hernias are treated conservatively. For severe pain or cosmetic reasons, surgery can be performed with fasciotomy or fascial patch grafting, whereas simple fascial repair is avoided because it may result in a compartment syndrome.

15.3.1.2 Medial Tibial Stress Syndrome

Similar to thigh splints, medial tibial stress syndrome, also referred to as “shin splints,” reflects an overuse injury presenting with discomfort, pain and tenderness along the medial or posterolateral border of the tibial shaft. Although the exact cause of this syndrome is unclear, this condition is though to be related to a traction-induced periostitis at the posteromedial tibial aponeurotic insertion of the soleus and the flexor digitorum longus muscles. Shin splints may affect athletes at all fitness levels, particularly those who pound the legs, such as long-distance elite runners, sprinters, gymnasts and so forth, and in cases of altered loading biomechanics, such as during overpronation of the foot (Fredericson et al. 1995; Bergmann et al. 2004). Symptoms may vary depending on ankle movements, worsen during rhythmic and repetitive exercise and decline at rest. US reveals a slight focal hypoechoic thickening of the layer of tissue covering the anteromedial or posteromedial tibial cortex, reflecting traumatic inflammation of the deep crural fascia and the periosteum fused together over the bone. Because, in severe cases, the injury may progress to a stress reaction within the bone and even to an actual stress fracture, MR imaging should be performed in patients with acute symptoms (Bergman et al. 2004). In these instances, initial callus formation may be revealed

with US (Bodner et al. 2005). The therapy for shin splints is essentially based on rest. Depending upon severity, it is often necessary for the patient to stop running completely for a period of time.

15.3.1.3 Compartment Syndromes

The anterolateral leg muscles are characteristically subject to compartment syndromes. Clinically, an acute compartment syndrome derives from exerciseinduced muscular overload or significant trauma such as a fracture, and presents with swelling of the compartment, persistent pain associated with exercise – particularly passive stretching – and paresthesias. From the pathophysiologic point of view, the establishment of an acute compartment syndrome is related to an elevated pressure in a confined fascial space. Muscle edema following strenuous exercise or blunt trauma leads to an increased interstitial pressure within the compartment due to the limited compliance of the fascia, and impaired capillary perfusion below a level necessary for viability. Although blood flow at the capillary bed is severely compromised, large arteries remain patent and there are no clinical signs of distal leg ischemia. A compartment syndrome must be diagnosed early and followed by immediate fasciotomy of the affected compartment to prevent extensive damage to the muscles. However, clinical findings may be equivocal and a definite diagnosis may be difficult on clinical grounds. Until recently, direct tissue pressure measurements, which are invasive, helped the diagnosis but these tests are difficult to perform and are not always available. Diagnostic imaging may have a role in the diagnostic investigation to identify early muscle changes and

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exclude other entities in the differential diagnosis, including hematoma, deep venous thrombosis or a ruptured Baker cyst. At early stages, US reveals diffuse swelling, bulging of the fascia and an abnormal echotextural appearance with blurred and less defined visualization of the fibroadipose septa in the affected muscles (Fig. 15.16). When initial findings are ambiguous, one-to-one comparison with the muscles of the contralateral side may be helpful. Later, a patchy hyperechoic appearance of the muscle with loss of recognizable muscle architecture suggests progression of the ischemic condition to frank infarction and rhabdomyolysis (Fig. 15.17). At least in our experience, color and power Doppler imaging are

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not useful modalities for the diagnosis of a compartment syndrome because the ischemic process takes place at the capillary level, beyond the sensitivity of current US equipment. Therefore, care should be taken not to exclude a compartment syndrome when blood flow signals are visible within large intramuscular vessels. In fact, these vessels may remain patent even in cases of severe ischemia. At least theoretically, ultrasonic contrast media could have a value in this field as a means to better identify the level of microvasculature. In late stages, extensive abnormalities of the involved muscles with loss of volume, cystic areas, fibrosis and ossification may be observed with US. In overt compartment syndrome, MR imaging is also

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Fig. 15.16a,b. Acute compartment syndrome: early changes. Long-distance runner with sudden onset of striking pain in the anterolateral leg at the end of a race (marathon). a Transverse and b longitudinal 12–5 MHz US images over the anterolateral muscles show diffuse swelling, bulging of the fascia (arrowheads) and abnormal echotextural appearance with loss of the normal fascicular pattern (asterisks) of the extensor digitorum longus. Only a few dissociated fibroadipose septa (arrows) are still visible within the muscle. Similar abnormalities were also observed in the tibialis anterior. The patient underwent immediate fasciotomy to avoid further progression of muscle damage

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Fig. 15.17a–d. Acute compartment syndrome: late changes. a–c Series of transverse 12–5 MHz US images over the tibialis anterior muscle obtained from caudal (a) to cranial (c). Proceeding from a to c, echotextural changes in the muscle are demonstrated with increasing severity. In c, complete disappearance of the central aponeurosis, that is well evident in a and b (arrows), and diffuse hyperechoic appearance of the muscle fibers with loss of the fibroadipose pattern is observed suggesting rhabdomyolysis. d Correlative coronal T2-weighted MR image reveals signal abnormalities (arrowheads) in the upper third of the muscle reflecting edema and muscle infarction

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able to identify early changes showing a swollen compartment with loss of the normal muscle architecture and abnormal contrast enhancement patterns, whereas in late follow-up it shows fibrosis and cystic and fatty degeneration of the affected compartments (Rominger et al. 2004). In contrast to acute compartment syndrome, in which irreversible loss of muscle function occurs, chronic exertional compartment syndrome is characterized by recurrent onset of cramp-like pain during exercise, is very short-lived and fully reversible. The anterolateral group of muscles in the lower leg is the most often involved. This exercise-induced syndrome may be associated or not with volume changes of the affected compartment and is related to a considerable increase in interstitial fluid in the muscle, at least in part reflecting an increased intramuscular blood flow in the short time of the exercise, which results in an elevated tissue pressure due to the expansion of the compartment volume and in transient ischemic changes. The reasons for this syndrome are still unknown and, in some way, seem related to the inextensibility of the fascia which invests the muscle. Until recently, the diagnosis was essentially based on direct tissue pressure measurements, which are performed during or immediately after the physical exercise. US signs of chronic exertional compartment syndrome may be subtle and include a transitory increase in the volume of the compartment and a hypoechoic appearance of the involved muscles following exercise (van Holsbeeck and Introcaso 2001). US examination performed at rest, immediately after exercise and at 10 minutes recovery time, together with an accurate one-to-one comparison with the contralateral side, are essential steps to demonstrate this condition with US because muscle changes may be very subtle (van Holsbeeck and Introcaso 2001). In our opinion, US is not reliable for diagnosing chronic exertional compartment syndrome and clear-cut threshold values above which this diagnosis can be made have not yet been established with this technique. MR imaging performed at rest and following exercise using T2weighted sequences seems more promising in this field (Verleisdonk et al. 2001).

15.3.1.4 Superficial Peroneal Neuropathy

Superficial peroneal neuropathy is a rare condition encountered in dancers and athletes who have a history of ankle sprains or trauma to the leg leading to vague sensory disturbances on the dorsal aspect of

the ankle and foot which worsen with activity and are relieved at rest. The trauma, usually an inversion or plantar flexion injury of the ankle, overstretches the nerve at the point where it pierces the deep fascia of the leg, approximately 10–12 cm above the tip of the lateral malleolus (Schon 1994; Delfaut et al. 2003). In some individuals, the nerve crosses the fascia in a more distal location, closer to the lateral malleolus. Such a variant has been implicated as a predisposing factor to stretching injuries (Delfaut et al. 2003). At US, the superficial peroneal neuropathy usually presents with a fusiform hypoechoic thickening of the nerve at the point where it is bound by the fascial opening, reflecting a fusiform neuroma related to tension neuropathy and perineural fibrosis (Fig. 15.18a). MR imaging can contribute to better delineation of the relationship of the nerve with the deep fascia of the leg (Fig. 15.18b–e). When conservative measures do not allow the athlete with superficial peroneal neuropathy to continue the agonistic activity, surgical release of the deep fascia may be indicated. Occasionally, the superficial peroneal nerve can be severed by penetrating trauma because of its superficial course along the distal two thirds of the leg.

15.3.2 Posteromedial Leg 15.3.2.1 Tears of the Medial Head of the Gastrocnemius

Rupture of the distal myotendinous junction of the medial head of the gastrocnemius, which is trivially known as “tennis leg,” is one of the most common muscle injuries affecting the middle-aged population during amateur sport practice (Miller 1977; Shields et al. 1985). In the majority of cases, this lesion affects subjects who do not play tennis. Leg trauma during daily or recreational activities, such as while performing a short sprint to catch the bus or while climbing stairs, or following heavy exercise, is frequently implicated. Regardless of the age and type of sporting activity of the subject, the mechanism of the injury is exactly the same and consists of a sudden forceful active plantar flexion of the foot and simultaneous extension of the knee, leading to a simultaneous active contraction and passive stretching of the medial head of the gastrocnemius. Patients complain of local, sharp pain in the middle third of the calf, often associated with a snapping sensation. Calf swelling and local ecchymosis usu-

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Fig. 15.18a–e. Superficial peroneal neuropathy in an athlete complaining of numbness and paresthesias over the dorsolateral aspect of the foot following a severe inversion trauma at the ankle. a Longitudinal 12–5 MHz US image of the lateral leg demonstrates fusiform swelling and hypoechoic appearance (arrows) of the superficial peroneal nerve (arrowheads) at the point where it crosses the fascia. b–e Transverse T1-weighted MR images of the lateral leg obtained from cranial (b) to caudal (e) show the nerve (white arrowhead) as a small hypointense structure deep to the fascia and, more distally, coursing in the subcutaneous tissue close to the anterolateral aspect of the fibular shaft (open arrowhead). At the level of the fascial opening (c,d), the nerve (arrow) appears markedly thickened as a result of traction injury. Note the relationship of the nerve with the extensor digitorum longus (edl), the peroneus brevis muscle (pbm) and the peroneus longus tendon (asterisk)

ally develop 24 hours after trauma. In many cases, patients refer a sensation somewhat similar to that of being kicked on the back of their leg. However, a direct impact is never implicated in the mechanism of injury, which actually derives from detachment of the muscle fibers of the medial head from the distal aponeurosis (Fig. 15.19). Physical examination typically reveals a painful swollen calf with exquisite tenderness along its medial side. Although the Achilles tendon is unaffected, standing on tiptoes and weight-bearing on the affected leg is impractical for the patient. Small tear are treated conservatively with rest and ice, whereas large lesions may require pharmacologic therapy with anti-inflammatory and anticoagulant drugs, prolonged immobilization and elastic dressing. Surgical therapy is limited to the rare instances in which the rupture is complicated by the onset of a compartment syndrome (Gilbert et al. 1996). In these cases, fasciotomy is indicated. Although the value of MR imaging for the diagnosis of tennis leg has been reported (Menz and Lucas 1991; Weishaupt et al. 2001), US is an efficient and accurate modality to diagnose this condition as well as to rule out more serious complications, such as deep venous thrombosis (Bianchi et al. 1998; Delgado et al. 2002). Compared with MR imaging, US has the main advantages of lower costs, shorter examination time and repeatability for follow-up studies. In these patients, US is best performed with transverse and oblique sagittal planes over the posteromedial aspect of the middle third

of the calf. In general, transverse planes are well suited to distinguish partial from complete ruptures because the medial head of the gastrocnemius is entirely seen in the same image, whereas sagittal US images are more reliable to show the extent of proximal retraction. During scanning, sagittal US images are obtained first, followed by transverse planes over the most anterior and internal part of the medial head. If a tear is found, additional US images should be obtained to establish the size and extent of muscle retraction. It is important to point out that the medial head should carefully be examined up its most anteromedial portion, because small ruptures typically affect this area and could be missed if the muscle is not assessed as a whole. If any doubt exists regarding the occurrence of a partial or complete rupture, gentle passive assisted movements with dorsal and plantar flexion of the foot with the patient prone and the foot hanging over the end of the examination bed may be helpful (Fig. 15.20). The probe is placed over the tear on the longitudinal plane. In complete fresh ruptures, dynamic examination demonstrates the intact soleus which glides under an immobile detached medial head. In the acute setting, this maneuver may also be useful if fluid does not fill the tear, such as in those patients seen soon after trauma. A wide spectrum of US appearances of medial head rupture exists. The appearance depends mainly on the size of the tear and the time of examination. Depending on the severity of trauma, a tennis leg

Leg

As the organization progresses, its walls gradually thicken toward the center while the amount of fluid decreases (Fig. 15.25d–i). In these intermediate phases, dynamic scanning with plantar and dorsal flexion of the foot in patients who suffered a complete tear demonstrates the medial head moving again in phase with the soleus. Lastly, the fluid-filled central space disappears and the walls collapse and fuse together (Fig. 15.25j-l). Chronic longstanding lesions appear as a straight thickened hypoechoic fibrous band intervening between the medial head and the soleus on longitudinal images. The fibrous band assumes a typical oval appearance on transverse planes. The differential diagnosis list for a tear of the medial head of the gastrocnemius includes leg thrombophlebitis, recent rupture of a Baker cyst and, occasionally, Achilles tendon tear (Liu et Chen. 1989; Jamadar et al. 2002). As described elsewhere, these conditions can be accurately distinguished with US from a tear of the medial head. Soleus tears can occasionally mimic a tennis leg lesion (Fig. 15.26). Similar to lateral head ruptures, these latter injuries are relatively rare, probably because the soleus is mainly composed of type I fibers which are devoted to slow contraction. On the other hand, there is no clear explanation as to why lateral head

MHG

15.3.2.2 Plantaris Tendon Tears

A plantaris tendon tear may be clinically confused with other pathologic entities leading to calf pain, and especially with tears of the medial head of the

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ruptures have such a low incidence compared with medial ones. In a prospective study based on the MR imaging findings in a series of consecutive patients with gastrocnemius tears, injuries affecting the lateral head were encountered in 14% of cases only (Weishaupt et al. 2001). In our personal experience, we have never encountered cases of isolated avulsion of the lateral head of gastrocnemius. Most traumatic lesions at this level are referred to a direct external blunt trauma (Fig. 15.27). From the clinical point of view, plantaris rupture can closely mimic a medial head tear and, for several years, tennis leg was incorrectly attributed to this tendon. In a series of 141 patients with tennis leg, isolated plantaris tendon tears were observed in 2 cases only, accounting for 1.4% of the total (Delgado et al. 2002). In some instances, however, plantaris rupture can be found in association with distal avulsion of the medial head.

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Fig. 15.26a–d. Soleus muscle disinsertion. Two different cases with partial (a,b) and complete (c,d) muscle injury. a Longitudinal and b transverse 12–5 MHz US images obtained over the medial head–soleus complex reveal partial disinsertion of the muscle fibers of the soleus from its distal aponeurosis (curved arrow) and a localized fusiform hematoma (asterisk). Some hypoechoic wavy images (arrowheads) are seen crossing the medial head: they reflect patent gemellary veins and should not be confused with intramuscular tears. c Longitudinal and d transverse 12–5 MHz US images obtained over the medial head–soleus complex demonstrate complete rupture of the soleus muscle which appears shrunk, heterogeneously hypoechoic and surrounded by intrafascial hematoma (asterisks). Note the convex appearance of the distal aponeurosis (curved arrow) of the soleus secondary to the increased intrafascial pressure related to the bloody effusion. In both cases, note the medial head (MHG) of the gastrocnemius is intact

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gastrocnemius. This tendon typically ruptures at the mid-calf level and presents with a gap in the tendon substance which can be better appreciated on cross-sectional planes (Leekam et al. 1999). A small hematoma typically fills the tendinous bed with a cord-like configuration between the medial head of the gastrocnemius and the soleus. In gen-

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eral, the fluid collection associated with a tear of the plantaris occurs at a more proximal or distal site compared with the level of the hematoma observed in a tear of the medial head (Fig. 15.28). In a patient with tennis leg, the plantaris tendon should always be assessed with US as it can be injured either in isolation or in association with a tear of the medial

b

Fig. 15.27a,b. Contusion trauma on the posterolateral leg. a Longitudinal and b transverse 12–5 MHz US images obtained over the lateral head–soleus complex in a patient who suffered a heavy blow to the leg reveal a large, partially organized hematoma (asterisks) confined to the subcutaneous tissue, whereas the insertion (arrowhead) of the lateral head (LHG) onto its distal aponeurosis (curved arrow) is entirely normal

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Fig. 15.28a–e. Plantaris tendon tear. a,b Transverse 12–5 MHz US images of the distal third of the posterior leg obtained a cranial to and b at the level of the tear in a patient with symptoms suggesting tennis leg. a The normal plantaris tendon is seen as a small flattened image (arrowhead) located in close proximity to the medial edge of the proximal Achilles tendon (arrows), just superficial to the soleus muscle. b Shifting the probe distally over the tendon, a hypoechoic rounded area (curved arrow) reflecting the ruptured plantaris and the associated local hematoma is seen. c–e Correlative transverse T1-weighted MR images obtained from cranial (c) to caudal (e). In c, the normal plantaris tendon is appreciated as a thin hypointense image (arrowhead) in close relationship with the proximal Achilles tendon (arrow). d,e More distally, the injured plantaris (curved arrow) is less clearly delineated as a result of the traumatic injury

Leg

head (Helms et al. 1995). Tears of this tendon are treated conservatively.

15.3.2.3 Calf Vein Thrombosis

In a traumatic setting, careful scanning technique should be needed to analyze not only the leg muscles but also the calf veins, because approximately 10% of patients with tennis leg lesions have a coexistent infrapopliteal deep venous thrombosis, mainly affecting the gemellary veins (Delgado et al. 2002). There are only tentative pathogenetic explanations for this complication. The same stretching mechanism producing the muscle injury has been implicated as a cause of damage to the venous walls. Other hypotheses rely on either the presence of muscle edema or hematoma compressing and then occluding low-pressure intramuscular veins or the prolonged absence of contracture of calf muscles as a result of local pain and immobilization (Slawski 1994). US evaluation of the calf veins should be extended cranially to the level of the tennis leg lesion because vessel involve-

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ment by thrombosis usually occurs at the proximal third of the leg and may reach even the popliteal vein. The collapse of intramuscular veins by compression ultrasound is a simple and reliable means to exclude venous thrombosis (Cronan et al. 1987). However, when vascular pathology is assumed, the gemellary veins should also be evaluated with color Doppler imaging to distinguish partial from complete occlusions. For this purpose, distal compression may be helpful to enhance blood flow signals in these veins. Thrombosis of the medial head veins most commonly involves the medial vascular pedicle of the muscle, which is formed by one artery and two veins on each side. Thrombosed veins may appear quite enlarged and filled with echogenic material (Fig. 15.29). Clots may involve both or a single vein of the pedicle and may extend longitudinally for several centimeters (Fig. 15.30a–c). Compared with medial head veins, thrombosis of the soleus veins is far less common (Fig. 15.30d,e). The examiner should be aware of this condition so as not to confuse vessel pathology with a proximal extension of the muscle injury (Parellada et al. 2006). Gentle local pressure applied with the probe does not show vessel collapse and color Dop-

Fig. 15.29a–d. Tennis leg complicated with calf vein thrombosis. a,b Longitudinal and c,d transverse (a,c) gray-scale and (b,d) color Doppler 12–5 MHz US images of the calf reveal a solid hypoechoic tubular structure (arrows) oriented longitudinally within the medial head, reflecting a thrombosed gemellary vein. Near to the thrombosed vein, the artery (white arrowheads) and the other vein (open arrowhead) forming the intramuscular vessel pedicle remained patent as seen at color Doppler imaging. In this particular case, the thrombosis extended longitudinally for approximately 7 cm and developed in association with complete disinsertion of the medial head. The photograph at the upper right of the figure indicates probe positioning. Note the higher position of the vascular lesion compared with the typical site of the muscle injury (star)

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Fig. 15.30a–e. Calf vein thrombosis: spectrum of appearances in different cases, all presenting with tennis leg injury. a–c Transverse 12–5 MHz US images. a Both veins (arrowheads) of a vessel pedicle of the medial head appear enlarged and filled with echogenic material indicating complete thrombosis. Note the patent artery (arrow) located between these veins. b Only one vein (white arrowhead) is thrombosed, whereas the other (open arrowhead) remains patent. Arrow, artery. c Thrombosis of one gemellary vein which appears markedly swollen and echogenic (arrowheads) compared with the patent one (open arrowhead). Arrow, artery. d,e Longitudinal 12–5 MHz US images over the medial head–soleus complex demonstrate thrombosis of an intramuscular vein (arrowheads) of the soleus. Note the deep position of the affected vein relative to the distal aponeuroses (curved arrow) and the medial head of the gastrocnemius (MHG)

pler imaging confirms the absence of internal flow signal. Detection of vein thrombosis can significantly change the therapeutic strategy. In fact, proximal clot propagation for isolated calf vein thrombosis and muscular calf vein thrombosis has been estimated to be relevant (approximately 20% of cases), suggesting that these veins are a possible source of pulmonary embolism (Hollerweger et al. 2000). In these cases, clinical management includes anticoagulation therapy (low molecular weight heparin) both in the event of isolated calf venous thrombosis and, even more importantly, if proximal propagation of the thrombus to the popliteal vein is detected.

15.3.2.4 Phlebitis of the Calf Veins

Patients with chronic venous thrombosis may present with postphlebitic syndrome, a condition in which

symptoms closely mimic those of acute disease. In these cases, however, anticoagulation therapy is not indicated. US can demonstrate poor visualization of the clot, incomplete venous compression, wall thickening and calcification of the involved venous segment. Color Doppler imaging may be helpful to distinguish acute from chronic changes revealing a decreased diameter of the vessel lumen, atresic venous segments, well-developed venous collaterals and irregular echogenic vein walls (Lewis et al. 1994). Superficial venous thrombosis, which is also known as superficial thrombophlebitis, refers to thrombus located in the large or small saphenous veins or in superficial varicosities. This condition does not have the same clinical implications as deep venous thrombosis and, when the deep system is not involved, can be treated with only heat and anticoagulation drugs (aspirin). The thrombosis of the superficial venous system is more easily recog-

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Fig. 15.31a–e. Spectrum of diseases affecting the superficial venous system of the calf. Different cases. a Longitudinal and b transverse 12–5 MHz US images of a thrombosed great saphenous vein (arrows). Note the reactive hyperechoic subcutaneous fat (arrowheads) surrounding the thrombosed vein. Asterisks, soleus muscle; T, tibia. c,d Transverse 12–5 MHz US images of the calf in a patient with tortuous superficial varicosities (1–3) obtained c without and d with probe compression. Probe compression is a useful means to assess the state of the venous system. In this case, the superficial veins were patent as they were fully compressible. e Transverse 12–5 MHz US image of the calf in a patient with thrombosed superficial varicosities (asterisks)

nized with US (Fig. 15.31a). Distal venous augmentation tests by squeezing the distal calf may be helpful to assess the status of these veins (see Chapter 4). Often, the thrombosed superficial veins appear surrounded by a halo of hyperechoic subcutaneous fat (Fig. 15.31b). Venous valvular damage in patients with deep venous thrombosis may lead to development of venous insufficiency and subcutaneous varicosities which appear as anechoic tortuous channels coursing in the subcutaneous tissue (Fig. 15.31c-e).

15.3.2.5 Sural Neuropathy Due to its superficial position, the sural nerve may be injured anywhere along its course. In the leg, compressive sural neuropathy may occur next to an inflamed and edematous Achilles tendon. However, the most common cause of sural nerve pathology is probably related to penetrating injuries in the posterior leg or iatrogenic trauma (Fig. 15.32).

The value of US in detection of sural nerve lesions following stripping of the adjacent small saphenous vein has been described (Simonetti et al. 1999).

15.3.3 Leg Masses Soft tissue masses are infrequently encountered in the leg. Most are benign lesions, including lipomas and neural tumors, have indolent behavior and can be easily diagnosed with US based on already described criteria (Fig. 15.33). On the other hand, deep-seated lesions may be difficult to be recognized even when large. Clinically, they can cause subtle leg swelling and nonspecific symptoms related to their anatomic relationship with other structures, such as nerve and vessels (Fig. 15.34). In these cases, only a careful scanning technique with focal zone and image magnification appropriately adjusted to the far-field can allow depiction of these deep masses.

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Fig. 15.32a–f. Sural nerve injury in a patient complaining of a sensory deficit over the dorsolateral aspect of the foot following a penetrating wound to his lower leg. a Photograph of the patient’s posterior leg reveals a small lump (arrow) on the skin at the level of injury. b,c Transverse 12–5 MHz US images of the posterior leg obtained b just cranial to and c at the level of the penetrating wound with d,e T1-weighted MR imaging correlation show the sural nerve (small arrows) ending in a bulbous neuroma (large arrow). f MR neurography gives a full depiction of the neuroma (large arrow) connected with the proximal stump of the nerve (small arrow)

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Fig. 15.33a–c. Schwannoma of the tibial nerve at the posterior leg. a Longitudinal extended field-of-view 12–5 MHz US image depicts the tumor as an eccentric round hypoechoic mass (arrowheads) in continuity with the tibial nerve (arrows). b,c Correlative T2-weighted MR images obtained b just proximal to the tumor and c at the tumor level confirm the continuity of the mass (arrowheads) with the tibial nerve (arrow)

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Fig. 15.34a–c. Mixoid liposarcoma of the leg. a Longitudinal and b transverse 12–5 MHz US images with c transverse postcontrast T1-weighted MR imaging correlation reveal a large deep soft tissue neoplasm (T) of the leg developing within the tibialis posterior muscle and causing displacement and compression (arrow) of the tibial nerve (arrowheads) and the posterior tibial artery (a) and veins. In this particular case, the patient was submitted to US examination for a recent onset of tibial neuropathy. Although large, the mass was nonpalpable. At surgery, the tumor was completely resected preserving the integrity of the tibial nerve

References Bates DY (2001) Dynamic ultrasound findings of bilateral anterior tibialis muscle herniation. Pediatr Radiol 31:753– 755 Beggs I (2003) Sonography of muscle hernias. AJR Am J Roentgenol 180:395–399 Bergman AG, Fredericson M, Ho C et al (2004) Asymptomatic tibial stress reactions: MRI detection and clinical follow-up in distance runners. AJR Am J Roentgenol 183:635–638 Bianchi S, Abdelwahab IF, Mazzola CG et al (1995a) Sonographic examination of muscle herniation. J Ultrasound Med 14:357–360 Bianchi S, Abdelwahab IF, Oliveri M et al (1995b) Sonographic diagnosis of accessory soleus muscle mimicking a soft tissue tumor. J Ultrasound Med 14:707–709 Bianchi S, Martinoli C, Abdelwahab IF et al (1998) Sonographic evaluation of tears of the gastrocnemius medial head (tennis leg). J Ultrasound Med 17:157–162 Bodner G, Stöckl, Fierlinger A et al (2005) Sonographic findings in stress fractures of the lower limb: preliminary findings. Eur Radiol 15:356-359 Coulier B (2002) Hyperechogenicity of medial gastrocnemial veins during ultrasound scanning of the calf in sitting patients: a normal variant. Eur Radiol 12:1843–1848 Cronan JJ, Dorfman GS, Scola FH et al (1987) Deep venous thrombosis: US assessment using vein compression. Radiology 162:191–194 Delfaut EM, Demondion X, Bierganski A et al (2003) Imaging of foot and ankle nerve entrapment syndromes: from well-demonstrated to unfamiliar sites. RadioGraphics 23:613–623

Delgado GJ, Chung CB, Lektrakul N et al (2002) Tennis leg: clinical US study of 141 patients and anatomic investigation of four cadavers with MR imaging and US. Radiology 224:112–119 Durkee NJ, Jacobson JA, Jamadar DA et al (2003) Sonographic evaluation of lower extremity interosseous membrane injuries: retrospective review in 3 patients. J Ultrasound Med. 22:1369-1375. Fredericson M, Bergman AG, Hoffman KL et al (1995) Tibial stress reaction in runners. Correlation of clinical symptoms and scintigraphy with a new magnetic resonance imaging grading system. Am J Sports Med 23:472–481 Gilbert TJ, Bullis BR, Griffiths HJ (1996) Tennis calf or tennis leg. Orthopedics 19:179–184 Helms CA, Fritz RC, Garvin GJ (1995) Plantaris muscle injury: evaluation with MR imaging. Radiology 195:201– 203 Hollerweger A, Manheiner P, Rettenbacher T et al (2000) Sonographische Diagnose von Muskelvenenthrombosen des Unterschenkels und deren Bedeutung als Emboliequelle. Ultraschall Med 21:66–72 Jamadar DA, Jacobson JA, Theisen SE et al (2002) Sonography of the painful calf: differential considerations. AJR Am J Roentgenol 179:709–716 Kouvalchouk JF, Fisher M (1998) Les muscles accessoires au niveau de la cheville. Mise au point. J Traumatol Sport 15:101–106 Leekam RN, Agur AM, McKee NH (1999) Using sonography to diagnose injuries of the plantaris muscles and tendons. AJR Am J Roentgenol 172:185–189

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S. Bianchi and C. Martinoli Lewis BD, James EM, Welch TJ et al (1994) Diagnosis of acute deep venous thrombosis of the lower extremities: prospective evaluation of color duplex flow imaging in diagnosis. Radiology 192:651–655 Liu SH, Chen WS. (1989) Medial gastrocnemius hematoma mimicking deep vein thrombosis: report of a case. Taiwan Yi Xue Hui Za Zhi. 88:624-627. Menz MJ, Lucas GL (1991) Magnetic resonance imaging of a rupture of the medial head of the gastrocnemius muscle. A case report. J Bone Joint Surg Am 73:1260–1262 Mellado JM, Perez del Palomar L (1999) Muscle hernias of the lower leg: MRI findings. Skeletal Radiol 28:465-469. Miller WA (1977) Rupture of the musculotendineous juncture of the medial head gastrocnemius muscle. Am J Sports Med 5:191–193 Parellada AJ, Morrison WB, Reiter SB et al (2006) Unsuspected lower extremity deep venous thrombosis simulating musculoskeletal pathology. Skeletal Radiol 35:659-664 Rominger MB, Lukosch CJ, Bachmann GF (2004) MR imaging of compartment syndrome of the lower leg: a case control study. Eur Radiol 14:1432–1439

Schon LC (1994) Nerve entrapment, neuropathy, and nerve dysfunction in athletes. Orthop Clin North Am 25:47– 59 Shields CL Jr, Redix L, Brewster CE (1985) Acute tears of the medial head of the gastrocnemius. Foot Ankle 5:186–190 Simonetti S, Bianchi S, Martinoli C (1999) Neurophysiological and ultrasound findings in sural nerve lesions following stripping of the small saphenous vein. Muscle Nerve 22:1724–1726 Slawski DP (1994) Deep venous thrombosis complicating rupture of the medial head of the gastrocnemius muscle. J Orthop Trauma 8:263–264 Van Holsbeeck MT, Introcaso JH (2001) Sonography of muscle. In: Van Holsbeeck MT, Introcaso JH (eds) Musculoskeletal ultrasound. Mosby, St Louis, pp 23–75 Verleisdonk EJMM, van Gils A, van der Werken C (2001) The diagnostic value of MRI scans for the diagnosis of chronic exertional compartment syndrome of the lower leg. Skeletal Radiol 30:321–325 Weishaupt D, Schweitzer ME, Morrison WB (2001) Injuries to the distal gastrocnemius muscle: MR findings. J Comput Assist Tomogr 25:677–682

Ankle

16

Ankle Carlo Martinoli and Stefano Bianchi

CONTENTS 16.1

Introduction 773

16.2 Clinical Anatomy 773 16.2.1 Joints and Ligament Complexes 16.2.1.1 Distal Tibiofibular Joint 774 16.2.1.2 Ankle Joint 774 16.2.1.3 Subtalar Joint 776 16.2.2 Tendons and Retinacula 776 16.2.2.1 Anterior Tendons 776 16.2.2.2 Lateral Tendons 778 16.2.2.3 Medial Tendons 778 16.2.2.4 Posterior Tendons 779 16.2.3 Neurovascular Structures 779

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Essentials of Clinical History and Physical Examination 781 16.3.1 Ankle Sprains 781 16.3.2 Achilles Tendon Tears 782

16.5.3.5 Tarsal Tunnel Syndrome 814 16.5.4 Posterior Ankle Pathology 817 16.5.4.1 Achilles Tendinopathy 817 16.5.4.2 Achilles Tendon Tear 821 16.5.4.3 Plantaris Tendon 823 16.5.4.4 Bursitis and Haglund Deformity 824 16.5.5 Bone and Joint Disorders 825 16.5.5.1 Synovitis 825 16.5.5.2 Chondral and Osteochondral Damage 826 16.5.5.3 Occult Fractures 829 16.5.6 Ankle Masses 830 16.5.6.1 Ganglia 830 16.5.6.2 Neurogenic Tumors 830 16.5.6.3 Soft-Tissue Abscesses 830 References

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16.4 16.4.1 16.4.2 16.4.3 16.4.4

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Normal US Findings and Scanning Technique 782 Anterior Ankle 783 Lateral Ankle 784 Medial Ankle 790 Posterior Ankle 794

16.5 Ankle Pathology 796 16.5.1 Anterior Ankle Pathology 796 16.5.1.1 Abnormalities of the Anterior Tendons 796 16.5.1.2 Anterior Ankle Impingement 798 16.5.2 Lateral Ankle Pathology 799 16.5.2.1 Lateral Ligamentous Injuries 799 16.5.2.2 Tenosynovitis of the Peroneal Tendons 801 16.5.2.3 Instability of the Peroneal Tendons 802 16.5.2.4 Split of the Peroneus Brevis Tendon 804 16.5.3 Medial Ankle Pathology 807 16.5.3.1 Medial Ligamentous Injuries 807 16.5.3.2 Abnormalities of the Tibialis Posterior Tendon 808 16.5.3.3 Accessory Navicular Bone 811 16.5.3.4 Posterior Impingement and Os Trigonum Syndrome 811 C. Martinoli, MD Associate Professor of Radiology, Cattedra “R” di Radiologia – DICMI – Università di Genova, Largo Rosanna Benzi 8, 16132 Genova, Italy S. Bianchi, MD Privat-docent, Université de Genève, Consultant Radiologist, Fondation et Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland

16.1 Introduction The ankle is the most frequently injured major joint in the body. Although routine radiography still remains crucial to evaluate and diagnose many ankle disorders, US has become increasingly important in the assessment of abnormalities of tendons, joints, ligaments, nerves and other soft-tissue structures. Because there are so many structures to be examined in the ankle joint, the US examination should be focused and guided by the clinical findings in an attempt to save time and increase the efficacy of the study.

16.2 Clinical Anatomy A brief description of the complex anatomy of the ankle with emphasis given to the anatomic features amenable to US examination, including joints and ligament complexes, tendons, retinacula and neurovascular structures, is included here. As the US study of the ankle is a focused examination, this chapter will arbitrarily discuss the tendons, nerves and vessels of the ankle from approximately 5 cm above to 5 cm below the ankle joint, deferring con-

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16.2.1.3 Subtalar Joint

The subtalar joint is formed by two articular cavities – the posterior talocalcaneal joint (posterior subtalar joint) and the talocalcaneonavicular joint (anterior subtalar joint) – separated by the structures housed in the tarsal sinus. The posterior subtalar joint is distal to the ankle joint and lies between the inferior surface of the body of the talus and the superior surface of the calcaneus (Fig. 16.1). It is supported by a fibrous capsule which is attached to the margins of the articular facets and is reinforced by the anterior (interosseous), medial, lateral and posterior talocalcaneal ligaments. In approximately 10–20% of subjects, its synovial cavity communicates with the ankle joint. The subtalar joint coordinates with the talocalcaneonavicular and calcaneocuboid joints to allow inversion and eversion movements of the foot. The anterior subtalar joint lies where the head of the talus articulates with the posterior surface of the navicular bone, the superior aspect of the spring ligament, the sustentaculum tali and the articular surface of the calcaneus. This last joint is reinforced dorsally by the dorsal talonavicular ligament, a thick band connecting the talar neck and the dorsal surface of the navicular. The spring (plantar calcaneonavicular) ligament is a triangular bundle that extends from the anterior margin of the sustentaculum tali to the undersurface of the navicular bone. It blends with the deltoid ligament and plays a major role in stabilizing the longitudinal arch of the foot.

16.2.2 Tendons and Retinacula All tendons which cross the ankle are invested by a synovial sheath with the exception of the Achilles tendon and the plantaris. Based on their location, ankle tendons are subdivided into four groups: anterior, posterior, medial and lateral.

16.2.2.1 Anterior Tendons

In the anterior ankle, four extensor tendons lie alongside each other. From medial to lateral, these are the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus and the peroneus tertius tendons (Fig. 16.4). The tibialis anterior is the largest and the most medial tendon. During dorsiflexion and inversion of the ankle, it can easily be

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b Fig. 16.4 a−c. Anterior tendons. Photographs of the anterior aspect of the ankle in a girl showing the main surface features visible when the foot is (a) dorsiflexed and (b) during foot dorsiflexion and inversion. During these actions, the tendon of the tibialis anterior (ta) may be observed and palpated as it passes anterior to the medial malleolus (MM). The tendons of the extensor hallucis longus (ehl) and extensor digitorum longus (edl) become prominent too on the dorsal aspect of the ankle. c Anterior view of a gross dissection of the ankle showing the position of the tibialis anterior (ta), extensor hallucis longus (ehl), extensor digitorum longus (edl) and peroneus tertius (pt). Note the position of the inferior extensor retinaculum (arrows) which restrains the anterior tendons, preventing them from slipping anteriorly while dorsiflexing the foot

seen and palpated as a cord-like structure lateral to the upper half of the shin (Fig. 16.4c). The tibialis anterior tendon courses along the anterior aspect of the ankle just lateral to the medial malleolus to insert onto the medial surface of the medial cuneiform and the plantar aspect of the base of the first metatarsal. Its primary function is dorsiflexion and inversion of the ankle and foot. The extensor hallucis longus lies between the tibialis anterior and the extensor digitorum longus tendons, being lateral to the former and medial to the latter. Similar to the tibialis anterior it is palpable in front of the ankle joint. The extensor digitorum longus tendon passes over the anterior aspect of the ankle joint lateral to

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16.2.2.2 Lateral Tendons

There are two tendons that can be found lateral to the ankle: the peroneus longus and the peroneus brevis (Fig. 16.6). These tendons course posterior and inferior to the lateral malleolus, which they use as a pulley during contraction of the peroneal muscles, and share a common sheath proximally but have separate sheaths in the inframalleolar region. The peroneus brevis is smaller than the peroneus longus and lies anterior to it coursing in a shallow retromalleolar groove on the posterior border of the lateral malleolus. There is a close relationship of the common peroneal tendon sheath and the adjacent posterior talofibular and calcaneofibular ligament. Two retinacula, superior and inferior, hold the peroneal tendons firmly in place behind the lateral malleolus and against the lateral surface of the calcaneus. Both are fascial thickenings that extend from the lateral malleolus to the calcaneus. The superior peroneal retinaculum converts the peroneal groove into a tunnel and prevents the tendons from bowstringing forward over the lateral malleolus during muscle contraction. A triangular flaring of fibrocartilage usually blends with the retinaculum at its attachment to the fibular periosteum. Distally, the peroneal tendons turn forward below the lateral malleolus to rest on the lateral aspect of the calcaneus. At this level the upper peroneus brevis is separated from the lower peroneus longus by a small bony prominence, the peroneal tubercle. The inferior peroneal retinaculum inserts on the top of the tubercle and creates two separate fibrous tunnels for each of the peroneal tendons. In addition to the peroneus longus and brevis, the peroneus quartus muscle is an accessory muscle of the lateral distal leg which has been reported to be present in up to 22% of cases (Sobel et al. 1990). It

most often originates from the peroneus brevis muscle and inserts onto the retrotrochlear eminence of the calcaneus (a bone prominence located posterior to the peroneal tubercle), passing posteromedial or medial to the tendons of the peroneus brevis and longus. Its action consists in lifting the lateral edge of the foot and assisting hindfoot pronation. Because of variation in the location of the distal myotendinous junction, the appearance of the peroneus quartus varies considerably in the retromalleolar area, ranging from muscle to tendon.

16.2.2.3 Medial Tendons

From anterior to posterior, the medial ankle contains three flexor tendons – the tibialis posterior, flexor digitorum longus and flexor hallucis longus – which travel through the tarsal tunnel surrounded by separate tendon sheaths (Fig. 16.7). The tibialis posterior tendon has an oval shape and is approximately twice as large as the adjacent round flexor digitorum longus. It courses beneath the medial malleolus, which it uses as a pulley, and superficial to the spring ligament to insert onto the tuberosity of the navicular bone, sending extensions to the three cuneiforms and the bases of the first to fourth metatarsals. The tibialis posterior acts as an inverter of the foot. Also, it can be considered a major stabilizer of the hindfoot. In fact, its rupture results in a loss of the height of the medial longitudinal arch and in an acquired flatfoot. At the ankle, the flexor digitorum longus tendon passes just lateral to the tibialis posterior tendon. The flexor hallucis longus tendon is the most lateral of the three flexor tendons. This tendon runs inferomedially grooving the posterior surface of

ta MM tp

MM

fdl

Kfp C

a

b

Fig. 16.7 a,b. Medial tendons. a Photograph of the medial aspect of the ankle in a girl with her foot plantar flexed and inverted showing the prominence on the skin of the tibialis posterior tendon (straight arrows) around the medial malleolus (MM). ta, tibialis anterior tendon. b Medial view of a gross dissection of the ankle showing the position of the tibialis posterior (tp) and flexor digitorum longus (fdl) tendons relative to the medial malleolus (MM). Observe the more posterior and deeper location of the flexor hallucis longus tendon (arrowheads) that curves around the posterior surface of the talus and the Achilles tendon (arrows) that inserts into the calcaneus (C). These latter two tendons are separated by the Kager fat pad (Kfp)

Ankle

a

a 1

2

The posterior ankle houses the sural nerve, a cutaneous sensory branch that supplies the skin of the posterolateral aspect of the inferior third of the leg, the lateral margin of the foot and the lateral side of the small toe. This nerve enters the ankle between the lateral malleolus and the Achilles tendon, accompanied by the small saphenous vein. Over the dorsum of the foot, the sural nerve anastomoses with branches of the superficial peroneal nerve.

16.3 Essentials of Clinical History and Physical Examination A detailed reference note from the referring clinician with the indication of the specific structures to be investigated and a presumptive clinical diagnosis should routinely be obtained before the US examination. Aside from age, sporting activities, such as volleyball, basketball, gymnastics and so forth, are critical points of the patient’s history as they are usually correlated with a higher incidence of ankle injuries. Knowledge of the exact mechanism of injury may be helpful in determining which structures are probably involved. If the reference note is not detailed, a basic clinical examination should be performed by the sonologist before starting the US examination.

Fig. 16.11. Normal tibial nerve at the tarsal tunnel. Gross dissection of the tarsal tunnel gives a closer look to the tibial nerve (arrows) and its divisional branches, the medial (1) and lateral (2) plantar nerves, and the calcaneal branches (arrowheads). a, posterior tibial artery. The insert on the left of the figure indicates the site of the anatomic specimen illustrated

16.3.1 Ankle Sprains The most frequent injuries of the ankle involve the ligaments as a result of pronation and supination trauma. The lateral ligamentous complex is more commonly involved as a result of an inversion (pronation) mechanism, whereas isolated injuries of the deltoid ligament as a result of an eversion (supination) trauma are less frequently observed. Depending on the stress forces involved and the mechanism of trauma, there may be isolated damage of one or more ligaments as well as avulsion of their bony insertions. During inspection, changes in the contour and shape of the different aspects of the ankle should be considered as appropriate landmarks to direct the US examination over the injured structures. Especially in patients with high-grade sprains and marked swelling, physical examination may be difficult to perform due to significant discomfort to palpation. Specific clinical tests in ankle injuries include the anterior drawer and the talar tilt. The anterior drawer maneuver is applied by immobilizing the patient’s distal tibia with one hand while applying pressure against the back of the foot with the other (Fig. 16.12a). In complete tears of the anterior and posterior ligaments, and especially of the anterior talofibular ligament, the talus is shifted anteriorly

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the patient is unable to carry out this movement. It must be stressed, however, that plantar flexion performed without resistance can be possible because the flexors, peroneals and plantaris tendons can compensate, at least partially, for an injured Achilles tendon. Another useful test consists of squeezing the calf, the so-called Thompson’s test (Fig. 16.12b) (Thompson 1962). This maneuver does not result in plantar flexion of the foot when the Achilles tendon is completely torn. One should be careful, however, about relying on this test alone, because in some instances it may fail if the plantaris tendon is intact. a

b

Fig. 16.12 a,b. Clinical tests. a The anterior drawer test (arrows) is carried out by grasping the patient’s distal tibia with one hand while pulling the calcaneus anteriorly with the other. When the anterior talofibular ligament is torn, the talus shifts anteriorly. b Thompson’s test is carried out by squeezing the calf. If the Achilles tendon is intact, this maneuver produces plantar flexion (arrow). Absence of plantar flexion in this test indicates a rupture of the Achilles tendon

against the tibia. The talar tilt stress test is carried out by applying a varus and valgus stress to the ankle by rolling the calcaneus internally and externally with one hand while the patient is supine and relaxed. During varus stress, an excessive opening of the joint space compared with the opposite ankle would indicate damage to the lateral ligamentous complex, including the anterior talofibular and calcaneofibular ligaments. On the other hand, the stability of the deltoid ligament can be assessed with valgus stress.

16.3.2 Achilles Tendon Tears Some clinical signs and physical maneuvers should be recognized by the examiner while evaluating the state of the Achilles tendon. Complete tears of the Achilles tendon usually present with abrupt onset of pain over the posterior aspect of the leg, difficulty in walking and inability to tiptoe on the injured side. In general, a definite tensing defect can easily be felt at the site of the tear. Some tests can be useful to diagnose a complete Achilles tendon tear. Once the foot has been examined while hanging over the edge of the examination bed, the patient is asked to perform a plantar flexion against resistance. In the case of a complete rupture of the Achilles tendon,

16.4 Normal US Findings and Scanning Technique Focusing the US examination on a definite region of interest around the ankle joint reduces the examination time and allows a more accurate assessment of the anatomic structures to be examined. A standard US examination of the ankle usually begins with the anterior compartment of the joint followed by its medial and lateral aspects and by the examination of the posterior ankle structures. Modern linear-array transducers with a frequency band ranging from 5 to 15 MHz are adequate to examine the soft-tissue structures around the ankle joint, including tendons, ligaments, retinacula and joint recesses. As a default setting, the field-of-view of the US image and the focal zone should be adjusted for the examination of small superficial parts, similar to those currently used for the examination of the wrist. With the exception of the posterior compartment, the position of most of the soft-tissue structures of the ankle is actually very superficial and requires a high magnification scale and the optimization of image parameters to increase the spatial resolution capability of US scanning. On the other hand, the evaluation of the posterior joint space and the flexor hallucis longus tendon may require repositioning of the focal zones and adjustment of the size of the field-of-view to increase its depth. Owing to the prominence of bones around the ankle, a thin stand-off pad may be helpful to maintain the probe in full contact with the skin during stress maneuvers. In general, if the examiner is confident in the evaluation of the ankle structures, the examination of the contralateral side is not needed except for comparing the size of a pathologic structure with the healthy one.

Ankle

Before starting the study, the examiner should always be informed regarding the patient’s history, and should request a recent radiographic study of the ankle. Standard radiographs (including anteroposterior and lateral views) clearly demonstrate bone lesions that may be overlooked sonographically and can aid in the correct interpretation of unclear US findings related to disorders that are obvious on plain films.

16.4.1 Anterior Ankle With the patient seated or supine, the examination of the anterior aspect of the ankle is best conducted with the knee flexed 45° so that the plantar surface of the foot lies flat on the examination table. The main anatomic structures in the anterior ankle that are amenable to US examination are the tibialis ante-

rior and extensor tendons, the anterior tibial artery and deep peroneal nerve, and the anterior synovial recess of the ankle joint. The tibialis anterior tendon appears to be approximately twice as large as the other extensor tendons. It can be evaluated on both long-axis and short-axis scanning planes from its myotendinous junction down to its bony insertion (Fig. 16.13). The extensor hallucis longus tendon is examined in a similar fashion (Fig. 16.13a). Sweeping the probe from proximal to distal, US demonstrates the extensor digitorum longus as a single flattened tendon which divides distally into four individual slips, one of which inserts on each of the second through fifth toes (Fig. 16.14). Each extensor tendon can be identified on an anatomic basis using skin landmarks. Dynamic scanning during passive movements of the different toes may also be helpful in differentiating each of them. In normal conditions, the synovial sheath of the ankle tendons cannot be distinguished even with a

U U

U

Talus

a

U

Talus

Tibia U

b Fig. 16.13 a,b. Normal tibialis anterior and extensor hallucis longus tendons. a Transverse 12−5 MHz US image reveals the crosssectional appearance of the tibialis anterior (open arrows) and the extensor hallucis longus (white arrow) tendons. Both are overlain by thin anisotropic bands (arrowheads) relative to the retinacula. Deep to the tendons, note the anterior surface of the talar dome covered by a thin rim of hypoechoic articular cartilage (rhombi). b Longitudinal 12−5 MHz US scan over the ankle joint shows the tibialis anterior tendon (arrows) in its long axis. The internal architecture of this tendon is clearly depicted, reflecting an echogenic fibrillar pattern. Rhombi, talar articular cartilage. The photographs at the upper left of the figures indicate probe positioning

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Talus Talus

U

a

5

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edb

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Cuneiform Cuneiform b Fig. 16.14 a,b. Normal extensor digitorum longus tendon. Transverse 12−5 MHz US images obtained over (a) the talus and (b) the medial cuneiform demonstrate the flattened appearance of the extensor digitorum longus tendon, which is divided into four tendinous slips diverging toward the second through the fifth toes (2−5). Note the inferior extensor retinaculum (white arrowhead) which overlies the tendon as a transverse fibrillar band. In b, the tendon courses superficial to the extensor digitorum brevis muscles (edb). The photographs at the upper left of the figures indicate probe positioning

high-frequency transducer. In normal states, retinacula are identified as thin bands that surround the tendons and insert into the periosteum (Figs. 16.13, 16.14). Owing to anisotropic properties, normal extensor retinacula appear hyperechoic over and hypoechoic at both sides of the underlying tendon. The lateral limbs of the retinacula may assume a curvilinear course deep to the restrained tendon and can be visualized as they insert onto the bone. The anterior tibial artery lies in a deeper position, just lateral to the extensor hallucis longus tendon. Its anechoic appearance and pulsatility allow easy detection of the vessel even without using Doppler imaging modalities (Fig. 16.15a). Arterial wall thickening as well as atherosclerotic calcifications can easily be assessed with US (Fig. 16.15b). Due to its small size, only very high-frequency probes (more than 10 MHz of center frequency) can reliably image the deep peroneal nerve. The anterior tibial artery is the key landmark for identifying it. Transverse scans are the best for depicting the artery, the vein/s and the deep peroneal nerve, which are located in a line with the nerve medial to the vessels and the crossing over them to descends lateral to the artery (Fig. 16.16). Due to its small size, the deep peroneal nerve appears as a homogeneous hypoechoic struc-

ture surrounded by hyperechoic fat without a definite fascicular echotexture and free from color signals of flow at Doppler imaging. Owing to acoustic shadowing from the overlying bones, the ankle joint cavity is poorly imaged with US. Anterior longitudinal scans may be obtained with the ankle in plantar flexion to improve the evaluation of the articular surface of the talar dome, which is covered by a thin layer of hypoechoic cartilage (Fig. 16.17). The anterior capsule of the ankle joint can barely be distinguished from the para-articular hyperechoic soft tissues. In normal conditions, the anterior synovial recess appears as a triangular anechoic structure located just anterior to the talocrural joint and deep to the anterior fat pad (Fig. 16.17) (Jacobson et al. 1998). In normal states, the hypoechoic cartilage of the talar dome is approximately 2−3 mm thick and up to 3 mm of anechoic fluid can be demonstrated in the anterior joint (Nazarian et al. 1995).

16.4.2 Lateral Ankle In order to examine the lateral aspect of the ankle, the patient is asked to roll the forefoot slightly internally.

Ankle

tibia talus

a

tibia b Fig. 16.15 a,b. Anterior tibial artery. a Longitudinal 12−5 MHz US image over the ankle joint demonstrates the normal appearance of the anterior tibial artery (white arrows). b Same scan in a 65 year-old diabetic patient with diffuse atherosclerotic changes involving this artery (black arrow). Note the irregular and hyperechoic appearance of the inner vessel wall due to diffuse deposition of calcified plaques. The photograph at the upper left of the figure indicates probe positioning

a

b

Fig. 16.16a,b. Deep peroneal nerve. Transverse 12−5 MHz US images proximal to the ankle joint demonstrates the deep peroneal nerve (arrow) coursing a on the medial side the anterior tibial artery (a) and then b crossing it to descend along its lateral side. The anterior neurovascular bundle runs between the tibia and the extensor hallucis longus muscle (ehlm). The photograph at the upper left of the figure indicates probe positioning

The anatomic structures in the lateral ankle that are amenable to US examination include the peroneal tendons and retinacula, the lateral ligamentous complex and the anterior tibiofibular ligament, and the lateral aspect of the fibula, talus and calcaneus. The lateral ligamentous complex of the ankle, including the anterior talofibular and the calcaneofibular ligaments, can reliably be depicted with US by means of long axis and short axis scans obtained in the

planes described above in Sect. 16.2.1.2 (Peetrons et al. 2004). The tip of the lateral malleolus is the initial landmark for the examination of the lateral ligaments. US images of thelateral ankle ligaments should also be obtained while stressing the ankle joint during, eversion and the anterior drawer maneuver to increase diagnostic confidence in the detection of tears as well as to differentiate complete from partial ruptures (Campbell et al. 1994). In addition, care should

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always be taken to place the transducer as parallel as possible to the examined ligament to avoid their artifactual hypoechoic appearance that can mimic pathology (Fig. 16.18). One-to-one comparison of US images and anatomic specimens (Brasseur et al. 1994; Friederick et al. 1993; Milz et al. 1996) showed that this technique can accurately detect these ligaments and determine their thickness. Owing to the nearly horizontal orientation of the anterior talofibular ligament, this ligament is best evaluated with the transducer parallel to the examination table. It appears as a straight fibrillar band connecting the

anterior aspect of the tip of the lateral malleolus with the talar neck just anterior the joint line (Fig. 16.18). The calcaneofibular ligament is examined by placing the transducer in an oblique coronal plane with its superior margin at the tip of the malleolus and its inferior margin slightly posterior to it (Fig. 16.19a). The calcaneofibular ligament has a similar appearance but, unlike the anterior talofibular ligament, it has a concave course which makes the evaluation of its malleolar insertion more difficult. Therefore, care should be taken not to evaluate it incompletely. The caudal part of this ligament is 2−3 mm thick and is Fig. 16.17. Normal anterior recess of the ankle joint. Longitudinal 12−5 MHz US image reveals the concave appearance of the anterior recess (arrows) of the ankle joint containing a physiologic small amount of fluid (asterisk). Star, anterior fat pad; rhombi, talar articular cartilage. The photograph at the upper left of the figure indicates probe positioning U

tibia

LM

U

talus

Ta

a

LM Ta b Fig. 16.18 a,b. Normal anterior talofibular ligament. Long-axis 12−5 MHz US images. a If the incidence of the US beam is perpendicular to the anterior talofibular ligament (arrows), this appears as a hyperechoic fibrillar band that connects the lateral malleolus (LM) and the talus (Ta). b Even a slight obliquity in the orientation of the US beam leads to a hypoechoic appearance of the ligament (arrows) relative to the surrounding fat. This is due to anisotropy. The photograph at the upper left of the figure indicates probe positioning

Ankle

pb pl

LM

calcaneus a

pt

b

calcaneus

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Fig. 16.19 a−c. Normal calcaneofibular ligament. a Long-axis 12−5 MHz US image reveals the calcaneofibular ligament (arrows) as a fibrillar band that extends deep to the peroneus brevis (pb) and peroneus longus (pl) tendons, from the apex of the lateral malleolus (LM) to the lateral aspect of the calcaneus. As the ligament approaches the lateral malleolus it tends to become artifactually hypoechoic (asterisk) due to anisotropy. b 12−5 MHz US scan demonstrates the oval cross-section of the calcaneofibular ligament (arrows) that is imaged in its short axis deep to the peroneal tendons (pt) that are imaged in their long axis. c Depending on the orientation of the US beam, the ligament may appear hypoechoic (arrows) as a result of anisotropy. The photographs at the upper left of the figures indicate probe positioning

visualized as a cord-like fibrillar structure which overlies the lateral aspect of the calcaneus, whereas its cranial part courses deep to the peroneal tendons and usually appears hypoechoic as a result of anisotropy (Fig. 16.19). Forced dorsiflexion of the foot tightens the calcaneofibular ligament and allows its better depiction (Fig. 16.20). On short-axis scans, the calcaneofibular ligament has an oval shape and could occasionally mimic an intra-articular loose body in relation to the peroneal tendons, especially when surrounded by fluid (Fig. 16.20b,c). Therefore, the examiner should become familiar with the appearance of this ligament to prevent misdiagnoses (Patel et al. 2002). Because of its deep location, the posterior talofibular ligament cannot be assessed with US. The anterior tibiofibular ligament is studied by placing the transducer obliquely upwards and medially from the anterior aspect of the tip of the lateral malleolus (Fig. 16.21). It appears as a thin flattened band connecting the tibia and the fibula (Milz et al. 1998). Differentiation between the anterior tibiofibular and the anterior talofibular ligaments is accomplished reliably with US owing to theie different orientation. US allows an accurate evaluation of the peroneal tendons in their supramalleolar, retromalleolar and

inframalleolar portions. Owing to their reflection behind the lateral malleolus, US images of the peroneal tendons should first be obtained transversely to their long axis to better assess their location and inner structure (Fig. 16.22). Long-axis planes are more useful when scanning these tendons at the inframalleolar region where they have a straight course. To assess possible anterior subluxation or dislocation relative to the lateral malleolus, peroneal tendons are examined with the foot dorsiflexed and everted. In the supramalleolar region the peroneus longus tendon courses lateral to the peroneus brevis muscle. As the peroneus brevis muscle approaches the lateral malleolus, it continues in a long tendon which has a flattened curvilinear appearance and is located anteromedial and then superior to the peroneus longus tendon. Since the peroneal tendons arc around the tip of the malleolus, the examiner should progressively tilt the transducer upward to maintain the US beam perpendicular to the tendons fibers to avoid false hypoechoic patterns related to anisotropy. In the inframalleolar region, the peroneal tendons appears as oval diverging structures which are separated by the peroneal tubercle of the calcaneus (Fig. 16.23). The peroneus brevis passes superior to the tubercle whereas the peroneus longus is located

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b Fig. 16.20 a,b. Normal calcaneofibular ligament. Long-axis 12−5 MHz US images of the ligament obtained a with the patient’s foot lying flat on the examination table and b during forced dorsiflexion and inversion (positioning indicated in the photographs at the left of the figures). In b observe the calcaneofibular ligament (arrows) just deep to the peroneus brevis (pb) and longus (pl) tendons that tightens and elevates from the calcaneus during dorsiflexion and inversion of the foot. A small amount of intra-articular fluid (asterisk) fills the lateral recess of the ankle joint. This maneuver can be helpful to assess the integrity of the ligament

Tibia

LM

Fig. 16.21. Anterior tibiofibular ligament. Long-axis 12−5 MHz US image demonstrates the anterior tibiofibular ligament (arrows) as a thin hyperechoic band that connects the anterior border of the tibia with the lateral malleolus (LM). In the photograph at the upper left of the figure note the different orientation of the probe with respect to Figure 16.18

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inferior to it. The peroneal tendons have a common synovial sheath which splits distally to surround the diverging tendons. The superior and inferior retinacula can be appreciated as thin laminar bands which overlie the tendons and insert into the bone cortex. A triangular area of hypoechoic thickening or flaring at the attachment of the superior retinaculum to the fibular periosteum can often be demonstrated with US. In subjects with a peroneus quartus, this accessory muscle presents as a discrete structure that is separated from the other peroneal tendons. In general, it lies posteromedial to the peroneals and assumes a variable appearance ranging from hypoechoic muscle to hyperechoic tendon (Fig. 16.24) (Chepuri et al. 2001).

16.4.3 Medial Ankle For examination of the ligamentous complex and tendons of the medial ankle, the patient is supine or seated with the plantar surface of the foot rolled externally or in a “frog-leg” position. The medial ligamentous complex of the ankle, commonly referred to as the deltoid ligament,is best imaged using coronal scans. Due to its marked obliquity, the tibiotalar component appears as a hypoechoic thick structure bridging the medial malleolus and the posteromedial surface of the talus. Often, it exhibits an inhomogeneous striated appearance that can be correlated with areas of fatty tissue interspersed between the ligamentous fibers and should not be mistaken for evidence of a liga-

pl

pq

mentous tear (Fig. 16.25a). The tibiocalcaneal component has a straight vetical course and appears as a thin hyperechoic band connecting the sustentaculum tali and the medial malleolus, and located deep to the tibialis posterior tendon (Fig. 16.25b). The spring ligament is seen inconsistently on US due to its deep and complex course. The tibialis posterior tendon can also be evaluated with the patient prone and the foot plantar flexed overhanging the edge of the examination table (Nazarian et al. 1995). To rule out instability, this tendon is best scanned posterior to the medial malleolus with the foot dorsiflexed and inverted. The tibialis posterior, flexor digitorum longus and flexor hallucis longus tendons are examined by means of short-axis and long-axis scans obtained in the supra- and inframalleolar region. The tibialis posterior tendon appears as an oval hyperechoic structure (Hsu et al. 1997) measuring 4−6 mm in diameter (Miller et al. 1996). It lies in a shallow bony groove on the posterolateral aspect of the medial malleolus covered by a thick retinaculum (Fig. 16.26). Just before its insertion on the tubercle of the navicular, the tendon fans out and often appears thickened and hypoechoic as a result of the multiple diverging slips that attach to the bone: this normal appearance should not be confused with a partial tendon tear (Fig. 16.27a). A small amount (up to 4 mm) of fluid is commonly found in the distal sheath and should not be considered a pathologic finding (Fig. 16.27b) (Nazarian et al. 1995). The tibialis posterior tendon may contain the accessory navicular (os tibiale externum), a sesamoid bone that appears as a curvilinear hyperechoic structure

pb

LM

Fig. 16.24. Peroneus quartus. Short-axis 12−5 MHz US image obtained over the retromalleolar groove demonstrates the peroneus longus (pl) and peroneus brevis (pb) tendons together with an additional element, the peroneus quartus, consisting of a discrete tendon (pq) surrounded by a hypoechoic muscle (asterisks). The peroneus quartus typically lies posteromedial to the peroneals. The increased volume of resident soft-tissue structures in the retromalleolar area may stress the superior peroneal retinaculum (arrowheads) that, in this particular case, appears bulging, thickened and hypoechoic. LM, lateral malleolus. The photograph at the upper left of the figure indicates probe positioning

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a

b

N

c Fig. 16.27 a−c. Normal tibialis posterior tendon. Long-axis 12−5 MHz US images of the distal tibialis posterior tendon (open arrows) obtained in the inframalleolar region. a The tibialis posterior typically shows a broad insertion with diverging slips of fibers that attach to the navicular bone (N). b Small amounts of tenosynovial fluid (asterisks) are visualized in the distal sheath of the tendon. This finding must be considered normal. c The os tibiale externum (white arrow) appears as a discrete hyperechoic structure with posterior acoustic shadowing contained within the substance of the distal tibialis posterior tendon (arrows). In this particular case, this sesamoid (type I accessory navicular) lies proximal to the tendon insertion onto the navicular bone (N). Observe the hypoechoic appearance (asterisk) of the posterior tibialis tendon just before its insertion on the navicular. This finding is related to anisotropy. The photograph at the upper left of the figure indicates probe positioning

surface of the sustentaculum tali. Because of its deep location, US evaluation of the flexor hallucis longus tendon is more difficult. Its supramalleolar portion is well depicted on sagittal US images obtained with the transducer placed over the Achilles tendon or slightly medial to it (Fig. 16.29a). Dynamic scanning during passive flexion and extension movements of the hallux may increase confidence in its detection. At the level of the ankle joint, careful scanning technique is necessary to display the tendon running between the two posterior processes of the talus – medial and lateral(Fig. 16.29b). The inframalleolar portion of the flexor hallucis longus tendon can be visualized underneath the sustentaculum tali. With high-resolution transducers, US can delineate the complex anatomy of the tarsal tunnel and

is able to image the entire course of the tibial nerve and its branches at the medial ankle. The tibial nerve and its two terminal branches – medial and lateral plantar nerves – lie posterior to the flexor digitorum longus and superficial to the flexor hallucis longus tendons, in close proximity to the posterior tibial artery and veins (Fig. 16.30). Identification of the posterior tibial vessels with color and power Doppler imaging may be a useful landmark to identify the position of the nerve, which is typically located deep and slightly posterior to them. Occasionally, US can identify the thin sensitive calcaneal branch. Collapse of the veins obtained by direct compression with the transducer can exclude vein thrombosis and may be helpful for distinguishing the artery without the use of Doppler modalities.

Ankle

calcaneus a

?

Fig. 16.28 a−c. Os tibiale externum (type 2 accessory navicular). a Long-axis 12−5 MHz US image of the distal tibialis posterior tendon (arrowheads) obtained just before its insertion demonstrates partial fusion of the accessory ossicle (asterisk) with the navicular bone (star). Curved arrow indicates the synchondrosis. b Oblique radiograph of the midfoot region demonstrates the accessory ossicle (asterisk). c Transverse arthro-CT image shows the tibialis posterior tendon (tp) that partially inserts onto the os. This ossicle should not be confused with tendon calcification or avulsion fracture

tp ?

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b

fhl LT

Fig. 16.29 a,b. Normal flexor hallucis longus tendon. a Sagittal 12−5 MHz US image of the posterior ankle obtained with the transducer placed over the Achilles tendon (A) demonstrates the flexor hallucis longus (fhl) at its distal myotendinous junction. The tendon (arrows) courses deep to the soleus and the Kager fat space (Kfs) and superficial to the posterior tibial malleolus (PM), the posterior recess of the ankle joint (asterisk) and the posterior process of the talus (Ta). b Short-axis 12−5 MHz image of the flexor hallucis longus tendon (fhl) between the medial (MT) and lateral (LT) tubercles of the talus. Note the more posterior position of the flexor hallucis longus tendon when compared with the tibialis posterior (tp) and flexor digitorum longus (fdl). Superficial to it, the posterior tibial artery (a) and veins (v) and the tibial nerve (arrowheads) can be seen. The photographs at the upper left of the figures indicate probe positioning

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tp

v

fdl

MM

a

v v

a

tp MM

fdl

v

a v

b

16.4.4 Posterior Ankle For optimal depiction of the posterior ankle, the patient is examined prone with the foot hanging freely over the edge of the examination table or resting on the toes to maintain the foot perpendicular to the leg. The Achilles tendon must be examined from its myotendinous junction to its calcaneal insertion by means of short-axis and long-axis scans (Figs. 16.31, 16.32). As a rule, the Achilles tendon tends to be thicker in tall subjects, men and the elderly (Koivunen-Niemela and Parkkola 1995). In addition, there is some degree of correlation between tendon size and body mass. On long-axis scans, the anterior and posterior boundaries of the normal Achilles tendon lie parallel below the soleus insertion. Occasionally, the convergent contributions from the lateral and medial heads of gastrocnemius and the soleus can be visualized proximally as a central thickened echo due to the union of respective peritendinous envelopes (Bertolotto et al. 1995). Short-axis planes allows a better demonstration of the more peripheral portions of the tendon, which are difficult to assess on long-axis scans. Depending on the gender and body habitus of the subject to be examined, the normal average thickness of the Achilles tendon is approximately 5−6 mm (van Holsbeeck and Introcaso 1991). US measurements should be obtained in the short-axis plane, because the long-axis plane tends to overestimate tendon thickness due to the tendon’s oblique course (Fornage 1986). The Achilles insertion on

v

Fig. 16.30 a,b. Normal tarsal tunnel. a Transverse 12−5 MHz US image obtained posterior to the medial malleolus (MM) demonstrates the tibial nerve (arrow) located close to the posterior tibial artery (a) and veins (v) and posterior to the tibialis posterior (tp) and flexor digitorum longus (fdl) tendons. All these structures lies in the tarsal tunnel and are covered by the flexor retinaculum (arrowheads). b Oblique transverse 12−5 MHz US scan at the medial heel shows the medial and lateral plantar nerves (arrows) as a result of division of the main trunk of the tibial nerve. The photographs at the upper left of the figures indicate probe positioning

the calcaneus is approximately 1 cm long. At this level, the tendon fibers assume an oblique course that can cause an artifactual hypoechoic appearance that could mimic tendinous disease: changes in the angle of incidence of the US beam are usually required to evaluate this area correctly (Fig. 16.31c) and to distinguish the narrow band of hypoechoic fibrocartilage that joins the tendon to bone from anisotropy. Close by on the medial aspect of the Achilles tendon, the plantaris tendon can be identified on transverse scans as a small oval hypoechoic structure (Fig. 16.32a) (Wening et al. 1996). It is visualized better at the medial edge of the myotendinous junction of the Achilles tendon and can then be followed upward in the leg along the aponeurosis of the soleus and the medial head of the gastrocnemius. Accessory muscles can be detected with US. The accessory soleus presents as a space-occupying mass with characteristics identical to normal muscle located at the anteromedial side of the Achilles tendon. It is usually asymptomatic although it may lead to a feeling of fullness at the posteromedial ankle or pain and swelling after exercise. Two bursae lie close to the insertion of the Achilles tendon on the calcaneus: the retro-Achilles bursa and the retrocalcaneal bursa. The retro-Achilles bursa is positioned between the skin and the Achilles tendon, whereas the retrocalcaneal bursa lies between the Achilles tendon insertion and the posterosuperior angle of the calcaneus. In normal states, the retro-Achilles bursa is normally imperceptible with US, even using high-frequency transducers, whereas the retrocalcaneal bursa can occasionally be demonstrated as a comma-shaped hypoechoic

Ankle

so

fhl

a

A

A so

Kfs b

A

A

Kfs

calcaneus

c

A

Fig. 16.31 a−c. Normal Achilles tendon. Sagittal 12−5 MHz US images obtained over the posterior ankle demonstrate the Achilles tendon (a) at its myotendinous junction, (b) at the middle third and (c) at its calcaneal insertion. a The Achilles tendon originates from an aponeurosis (arrows) which covers the posterior aspect of the soleus muscle (so). Observe the unipennate arrangement of the muscle fibers of the soleus and the peripheral location of the aponeurosis. Proceeding downward, a gradual thickening of the aponeurosis and reduction of the volume of the soleus can be seen. fhl, flexor hallucis longus muscle. b Below the soleus (so) junction, the normal Achilles tendon (A) exhibits uniform thickness and fibrillar echotexture and lies posterior to the Kager fat space (Kfs). c The insertion of the Achilles tendon (A) on the calcaneus may appear slightly hypoechoic (asterisk) as a result of anisotropy because the tendon fibers change from a horizontal to a more vertical alignment as they approach their insertion. Kfs, Kager fat space. The photographs at the upper left of the figure indicate probe positioning

A

soleus a

A

soleus b

A soleus

c

Fig. 16.32 a−c. Normal Achilles tendon. Transverse 12−5 MHz US images obtained over the posterior ankle demonstrate the Achilles tendon (a) at the medial side of its myotendinous junction, (b) at the middle third and (c) at its calcaneal insertion. The Achilles tendon (A) modifies its cross-sectional shape gradually from its myotendinous junction down to the calcaneus. In a it has an elongated, crescentic shape over the soleus muscle. At its medial side, the plantaris tendon (arrow) is visualized as a small hypoechoic flattened image. In b and c, the Achilles tendon (A) progressively assumes an oval shape. The photogrphs at the upper left of the figures indicate probe positioning

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structure that changes in size and shape during plantar and dorsal flexion of the foot (Mathieson et al. 1988). Because fluid within the retrocalcaneal bursa may be seen in asymptomatic subjects, this bursa is considered normal if its anteroposterior diameter measures is ≤3 mm (Fornage and Rifkin 1988; Nazarian et al. 1995). Deep to the Achilles tendon, the Kager fat pad appears as a soft-tissue space filled with fat lobules (Figs. 16.29a, 16.31b). The posterior ankle recess is a small recess located deeply, between the posterior tibial malleolus and the posterior talus. Usually, its evaluation requires lowering the US frequency and adjustment of the focal zone at the level of the tail of the talus (Fig. 16.33). In large ankles, such as occur in obese or edematous subjects, low-frequency transducers

so

A variety of soft-tissue disorders involve the ankle. They are reviewed here by location.

16.5.1.1 Abnormalities of the Anterior Tendons

fhl

T

16.5 Ankle Pathology

16.5.1 Anterior Ankle Pathology

A

A

(even down to 5 MHz center frequency) may be helpful to image it. Effusions inside this recess are better demonstrated with dorsal flexion of the ankle. The small saphenous vein and the sural nerve course in the subcutaneous tissue along the posterolateral aspect of the ankle. Detection of the vein makes identification of the small sural nerve, which lies on its medial aspect, easier (Fig. 16.34).

?

Ta

Fig. 16.33. Normal posterior recess of the ankle joint. Longitudinal 12−5 MHz US image over the Achilles tendon (A) reveals the concave appearance of the posterior recess (arrows) of the ankle joint that lies between the posterior malleolus of the tibia (T) and the posterior talus (Ta). Note the deep location of this recess relative to the soleus (so) and the flexor hallucis longus (fhl) muscles. It contains a physiologic small amount of fluid (asterisk). Star, posterior fat pad. The photograph at the upper left of the figure indicates probe positioning

v A soleus

The anterior ankle tendons are rarely affected with pathology in comparison with the other ankle tendons. The tibialis anterior tendon is the most likely of all the anterior tendons to be abnormal. Its subcutaneous rupture is rare and can be secondary to local trauma or spontaneous. Acute open or blunt ruptures usually occur in younger patients while spontaneous rupture most frequently affects subjects older than 45 years of age (Dooley et al. 1980). The site of rupture is usually between the extensor retinaculum and the insertion onto the medial cuneiform and base of the first metatarsal. Spontaneous tears are typically well tolerated by the patient, who may report only mild local pain and loss of function. At physical examination, the palpable outline of the normal tendon on the skin is no longer appreciated even during forced ankle

Fig. 16.34. Normal sural nerve. Transverse 12−5 MHz US image obtained at the lateral aspect of the Achilles tendon (A) demonstrates the sural nerve (arrow) adjacent to the small saphenous vein (v). The photograph at the upper left of the figure indicates probe positioning

Ankle

dorsiflexion of the foot. Instead, the retracted tendon stump forms a lump on the anteromedial aspect of the distal leg that may be confused clinically with a tumor or a cyst. Symptoms of a tendon tear include weakness of dorsiflexion and localized tenderness. However, these findings are often misleading since some dorsiflexion is preserved by the action of the other extensor tendons. In complete tears, US can identify the tendinous nature of the palpable lump, that corresponds to the proximal end of the severed tendon and a hypoechoic defect with tendon discontinuity (Fig. 16.35) (Bianchi et al. 1994). In most cases, the distal portion of the severed tendon is not well visualized. An effusion in the tendon sheath can also be appreciated. The

second most frequent abnormality affecting the tibialis anterior is distal tendinopathy (see also Chapt. 17). In this condition, after crossing the ankle joint and just before its insertion, the tibialis anterior tendon appears swollen and hypoechoic (Mengiardi et al. 2005) (Fig. 16.36). Because this abnormality is uncommon it may be overlooked clinically as a cause of chronic anterior pain exacerbated by dorsiflexion. In the anterior ankle, US is able to confirm the uncommon clinical diagnosis of tenosynovitis of the extensor hallucis longus and extensor digitorum longus tendons based on widening of the tendon sheaths by fluid (Fig. 16.37). In these cases, US provides dynamic assessment and direct correlation with the site of pain.

ta

tibia

b,c

f,g

d,e

a

b

d

f

c

e

g

talus

Fig. 16.35a–g. Complete tear of the tibialis anterior tendon. a Extended field-of-view 12−5 MHz US image obtained over the anterior ankle demonstrates the swollen proximal portion of a chronically ruptured tibialis anterior tendon (ta) which appears retracted at the level of the distal tibia. Note the empty tendinous bed (arrowheads) as a thin hypoechoic line in distal continuity with the retracted stump (arrows) of the torn tendon. Asterisk, anterior recess of the ankle joint. b−g Transverse 12−5 MHz images (b,d,f) with CT tenographic (c,e,g) correlation obtained at the levels (vertical white bars) indicated in a show the retracted proximal tendon (narrow arrows) within the synovial sheath. The sheath becomes empty (large arrow) as the scanning plane proceeds distally (f,g)

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a

b

c

d

Fig. 16.36 a–d. Distal tendinopathy of the tibialis anterior tendon. Long-axis (a) and short-axis (b) 12−5 MHz US images over the distal tibialis anterior tendon in a patient with anteromedial pain exacerbated by dorsiflexion demonstrate a swollen hypoechoic distal insertion of the tendon (arrows) on the medial cuneiform relative to tendinosis. The diameter of the affected tendon is markedly increased with respect to the contralateral side (c,d)

5 5

a

4 4

3 3

2 2

b

Fig. 16.37 a,b. Serous tenosynovitis of the extensor digitorum longus tendon. a Long-axis and b short-axis 12−5 MHz US images in a patient who wore narrow shoes and complained of pain over the anterior ankle exacerbated by dorsifl exion show moderate fluid distension of the sheath (asterisks) of the extensor digitorum longus tendon (curved arrow) consistent with tenosynovitis. In b the sheath fluid allows good depiction of the complex anatomic architecture of this tendon composed of several slips to the second (2), third (3), fourth (4) and fifth (5) digits, each joined with a mesotendon (arrowhead)

16.5.1.2 Anterior Ankle Impingement

Anterior ankle impingement is a well-established clinical syndrome associated with anterior tibiotalar spurs, which are typically formed within the joint capsule, most commonly at the margin of the articular cartilage (Robinson and White 2002). These spurs are probably the consequence of damage to the anterior articular cartilage rim that occurs during forced dorsiflexion injuries and direct microtrauma. They are commonly observed in soccer players as the result of repetitive direct trauma due to the impact of the ball over the ante-

rior tibiotalar joint during kicking. Anterior ankle impingement causes chronic ankle pain with a feeling of locking on dorsiflexion and may lead to premature ankle osteoarthritis. US can depict the position of the tibiotalar spurs at the distal end of the anterior tibia or over the talus and assess their intracapsular location (Fig. 16.38). Synovial thickening, scarring and intra-articular effusion can be associated findings. In more advanced cases, the spur can impinge on the tibialis anterior tendon leading to a chronic tendinopathy. Symptomatic anterior ankle impingement can require arthroscopic resection of the osseous spurs and soft-tissue abnormalities.

Ankle

tibia

talus

a

b

Fig. 16.38 a,b. Anterior impingement syndrome. a Longitudinal 12−5 MHz US image with b T2*-weighted MR imaging correlation demonstrates a prominent spur (arrow) at the distal end of the anterior tibia. The spur is intracapsular in location and appears bordered by fluid (asterisk). During ankle movements, it remained still. Note the loss of the thin hypoechoic layer of articular cartilage (arrowheads) that overlies the talar dome in comparison with Figures 16.13b and 16.17

16.5.2 Lateral Ankle Pathology 16.5.2.1 Lateral Ligamentous Injuries

Lateral ligamentous injuries are usually secondary to inversion sprains with internal rotation of the foot combined with ankle plantar flexion. Clinically, lateral ligamentous injuries present with pain, swelling and tenderness over the involved ligaments, and especially over the anterior talofibular and calcaneofibular ligaments (van Dijk et al. 1997). Forward displacement of the talus in the ankle mortise occurs when the anterior talofibular ligament is torn, whereas medial tilting of the talus with progressive widening of the lateral joint space is associated with the concurrent rupture of the anterior talofibular and calcaneofibular ligaments. Lateral ligamentous injuries frequently occur during sporting activities or falls on rough surfaces. Ligamentous lesions are classified on the basis of the severity of the injury and the site or sites of involvement. The severity of an injury to an individual ankle ligament, both lateral and medial, may be categorized into one of three grades of increasing clinical gravity: grade I, mild stretching of the involved ligament without disruption or instability; grade II, partial ligament tears; grade III, complete ligament tears. The anterior talofibular ligament tears most frequently alone (approximately 70% of all ankle ligament ruptures). Severe injuries may lead to the combined rupture of the anterior talofibular and calcaneofibular ligament (20–40% of

cases), whereas the stronger posterior talofibular ligament is rarely involved, except in severe ankle trauma with dislocation. Isolated tears of the calcaneofibular ligament occur rarely. Based on the site of involvement of the ligamentous complex, injuries can also be subdivided into four grades which are useful for determining the prognosis and the treatment strategy: grade I injury is stretching or partial tear of the anterior talofibular ligament; grade II injury consists of complete tear of the anterior talofibular ligament with the other ankle ligaments remaining intact; grade III injury indicates complete tear of the anterior talofibular ligament and partial tear of the calcaneofibular ligament; and grade IV injury is complete tear of both ligaments. After ligamentous injuries, joint incongruity leads to chronic ankle instability in approximately 15−25% of cases. This may cause degenerative changes progressing toward early ankle osteoarthritis. Although there is no consensus in the literature as to whether surgery or conservative treatment may be indicated in lateral ligamentous injuries, grade I and II injuries generally heal without significant instability, whereas grade III and IV injuries may lead to chronic pain and can require surgical therapy. Conservative treatment includes taping, air splints or even casting for at least 3−6 weeks. On the other hand, surgical treatment attempts to reconstruct the injured lateral ligaments. For this purpose, the peroneus brevis tendon can be rerouted to restructure them. At US examination, ankle ligaments with partial tears may appear swollen with focal or diffuse internal hypoechoic areas (Figs. 16.39, 16.40) (Krappel et al. 1997; Peetrons et al. 2004). In complete ruptures,

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LM

LM

talus a

talus b

Fig. 16.39 a,b. Partial rupture of the anterior talofibular ligament. a Long-axis 12−5 MHz US image over the anterior talofibular ligament in a patient following an inversion injury of the ankle. The ligament (arrows) appears thickened and hypoechoic but without signs of macroscopic discontinuity. This finding is consistent with a partial tear. Hypoechoic effusion (asterisk) in the ankle joint underlines the deep aspect of the ligament. b Contralateral normal side. LM, lateral malleolus

LM

pt

pt

calcaneus a

pt

calcaneus b

Fig. 16.40a,b. Partial rupture of the calcaneofibular ligament in a patient with a torn anterior talofibular ligament presenting with pain and swelling over the lateral ankle. a Long-axis and b short-axis 12−5 MHz US scans reveal a markedly swollen and hypoechoic calcaneofibular ligament (arrows), just deep to the peroneal tendons (pt). This appearance is typical of partial or complete rupture of the ligament. In this particular case, while dorsiflexing the foot, the ligament tightened suggesting a partial tear. In b observe the perpendicular course of this ligament relative to the long axis of the peroneal tendons. LM, lateral malleolus

a hypoechoic gap reflecting the hematoma is seen within the ligamentous substance and the free ends of the severed ligament may appear retracted and wavy, in contrast to its normal straight appearance (Fig. 16.41). Anterior talofibular ligament ruptures are associated with capsular breakage and extravasation of joint fluid into the anterolateral soft tissues of the ankle (Fig. 16.41a), whereas complete tearing of the calcaneofibular ligament may result in communication between the ankle joint and the peroneal tendon sheath (Fig. 16.42). Rupture of the calcaneofibular ligament may seldom be associated with tear of the superior peroneal retinaculum. Because the normal calcaneofibular ligament tightens during dorsiflexion and pushes the peroneal tendons laterally, this maneuver can help to assess its integrity (Peetrons et al. 2004). In fact, the absence of peroneal tendon displacement during dorsiflexion of the ankle is a sign of complete tear of this ligament. Calcifications can also be seen within an injured ligament, often reflecting a bony

avulsion fragment (Figs. 16.43, 16.44) (Peetrons et al. 2004). During scanning, stress tests for the detection of joint laxity can be helpful to identify ligamentous injuries. These maneuvers should be performed carefully to avoid pain and reflexed muscle contraction that may cause false negatives. In complete tears of the anterior talofibular ligament, the anterior drawer test can easily be obtained with the foot hanging over the edge of the examination table while pulling the forefoot anteriorly when in plantar flexion and inversion (Fig. 16.45). This maneuver may be helpful in doubtful cases to differentiate partial (grade II) from complete (grade III) tears of the anterior talofibular ligament. When the ligament is completely torn, the anterior shift of the talus against the tibia will open the gap in the substance of the ligament making the lesion more obvious, whereas in partial tears the distance between the talus and the tibia will remain constant. Syndesmotic sprains account for up to 10% of ankle injuries. They can occur with the same mech-

Ankle

tibia

fibula a

b

Fig. 16.46 a,b. Complete rupture of the anterior tibiofibular ligament. a Transverse 12−5 MHz US image of the anterior aspect of the syndesmosis demonstrates a disrupted anterior tibiofibular ligament. Note the hypoechoic cleft which separates the torn ends (asterisks) of the ligament. b Contralateral normal side showing an intact ligament (arrows)

pl

pb

a

b

Fig. 16.47 a,b. Serous tenosynovitis of the peroneal tendons. a The patient presented with diffuse swelling (arrows) and tenderness in the retromalleolar region following an ankle sprain. b Transverse 12−5 MHz US image at the level of the lateral malleolus (asterisk) shows increased fluid (stars) within the common tendon sheath of the peroneus longus (pl) and peroneus brevis (pb) tendons. The hypoechoic effusion makes the mesotendons (arrowheads) visible. Note the flattened appearance of the peroneus brevis compared with the peroneus longus

causes include laxity of the superior peroneal retinaculum, a shallow or convex retromalleolar groove of the fibula, hindfoot valgus and accessory tendons (peroneus quartus). Although the instability of peroneal tendons can be voluntary, it is invariably secondary to the disruption of the superior peroneal retinaculum (Rosenberg et al. 2003; Wang et al. 2005). The injury is typically produced by a sudden, forced dorsiflexion and eversion of the foot. Even in absence of tendon dislocation, episodes of ankle sprains in dorsiflexion and eversion may stretch the superior peroneal retinaculum, which becomes thickened and hypoechoic, apparently representing failure of some of its fibers (Fig. 16.48). The instability of the peroneal tendons can be categorized into four types: type I injury consists of separation of the retinaculum and the periosteum from the bone of the lateral malleolus, forming a pouch within which the peroneals can

dislocate; type II injury presents separation of the insertion of the retinaculum and the posterior fibrous lip from the bone without periosteal stripping; and type III injury is associated with avulsion of a thin flake of bone from the lateral malleolus attached to the stripped retinaculum (Fig. 16.49); type IV injury, the less common, occurs with intrasubstance rupture of the retinaculum (Eckert et al. 1976 ; Oden 1987; Rosenberg et al. 2003). Clinically, palpation of the dislocated tendons over the lateral malleolus or their displacement in dorsiflexion is diagnostic. In acute settings, however, the clinical diagnosis may not be easy because patients complain of pain exacerbated by motion and a diffuse soft-tissue swelling around the lateral malleolus may make the palpation of tendons difficult. Treatment of peroneal tendon dislocation includes deepening of the fibular groove and reinforcement of the superior retinaculum. The

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pl pb

LM

Fig. 16.48. Mild strain injury of the superior peroneal retinaculum in a patient with a history of ankle sprains. Transverse 12−5 MHz US image over the retromalleolar groove reveals a thickened and hypoechoic retinaculum (arrowheads) connected to the periosteum of the lateral malleolus (LM) by a fibrous lip (asterisk). The peroneus longus (pl) and peroneus brevis (pb) tendons appear normal

peroneus quartus can be used for reconstruction purposes. The US diagnosis of peroneal tendon instability is based on detection of the tendons lateral to the distal lateral malleolus, instead of posterior to it (Fig. 16.50) (Magnano et al. 1998). The tendons are often found within a pouch formed by a stripped-off superior peroneal retinaculum. Often, a small flake

a

c

b

d

fracture along the distal fibular metaphysis is associated with avulsion of the superior retinaculum and may be visible at US (Fig. 16.51). Dynamic examination with both dorsiflexion and eversion of the foot can help to detect cases of intermittent subluxation (Fig. 16.52). In longstanding disease, a fusiform thickening of peroneal tendons can be observed at the tip of the malleolus. Complete ruptures of the peroneus brevis and longus tendons are rare and may occur either at the level of the lateral malleolus or at the midfoot (see Chap. 17).

16.5.2.4 Split of the Peroneus Brevis Tendon

Peroneal tendon tears can be observed in patients following ankle sprains or with a history of chronic instability, especially if they are affected by systemic disorders such as rheumatoid arthritis and diabetes mellitus or are receiving corticosteroids (Kraus and Brodsky 1998; Wang et al. 2005). Clinically, the rupture of peroneal tendons leads to inability to evert and cavovarus foot. Tears of the peroneus brevis tendon are most common and present with a typical longitudinal configuration, commonly referred to as “split” or “fis-

e

Fig. 16.49a–e. Schematic drawings of a transverse view through the lateral malleolus (LM) illustrate the mechanisms of peroneal tendon dislocation. a Normal state. The peroneus longus (pl) and peroneus brevis (pb) tendons lie in the retromalleolar groove covered by the superior peroneal retinaculum (dark gray). Asterisk indicates the posterior fibrous lip. b Peroneal tendon dislocation is secondary to the separation (straight arrows) of the retinaculum and the periosteum from the lateral malleolus forming a pouch within which the peroneal tendons dislocate (curved arrow); (type I injury). c Peroneal tendon dislocation (arrow) occurs as a result of detachment of the retinaculum and the fibrous lip from the lateral malleolus without periosteal stripping (type II injury). d Peroneal tendon dislocation follows an avulsion fracture at the insertion of the retinaculum (black arrowhead) (type III injury). Note that he peroneal tendons dislocate under an elevated periosteum (void arrowhead). e Peroneal tendon dislocation is secondary to intrasubstance disruption of the retinaculum (type IV injury)

Ankle

pb pb pl

pl

a

b

Fig. 16.50 a,b. Peroneal tendon instability (type I injury). Transverse 12−5 MHz US images over the retromalleolar groove obtained a at rest and b during forced eversion and dorsiflexion of the foot. In a the superior peroneal retinaculum (arrowheads) is disrupted but still inserted onto the lateral malleolus (asterisk). The peroneus longus (pl) and peroneus brevis (pb) tendons lie posterior to the tip of the malleolus. Note the edematous changes in the soft tissues of the perimalleolar region. In b, the peroneal tendons are seen while subluxing over the lateral malleolus

suration” (Waitches et al. 1998). This condition is usually secondary to recurrent inversion injuries with the supinated foot and is difficult to diagnose on clinical grounds. In fact, peroneus brevis splits may lead to nonspecific and confusing symptoms with pain and swelling around the lateral malleolus and along the

course of the peroneals. In the elderly, this kind of tear may also be asymptomatic. Longitudinal splits of the peroneus brevis are usually 2.5–5 cm in length and arise at the distal end of the lateral malleolus, extending distally and proximally from there (Fig. 16.53). Laxity of the superior peroneal retinaculum, a bony

pl

pb

a

c

pl pb

pb pl

b

d

e

Fig. 16.51 a–e. Peroneal tendon instability (type III injury). a The patient presented with diffuse swelling and tenderness around the lateral ankle and complete inability to place his foot in eversion. b Internal oblique view of the ankle demonstrates a fibular flake fracture (arrowheads). c Transverse 12−5 MHz US scan obtained with the transducer applied transversely over the lateral malleolus (asterisk) reveals the avulsed bony fragment (arrowheads) and the anterior dislocation of the peroneus brevis (pb) and peroneus longus (pl) tendons. d Transverse 12−5 MHz US scan of the contralateral normal side. e Transverse T2-weighted MR imaging correlation confirms the anterior dislocation of the peroneal tendons

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Ankle

PB1

PL PB1 PB1 PL

PB1

PCL PB2

PL

PB

PB2

b

a

PB1 PB2 PL

c

d

e

Fig. 16.54 a–e. Longitudinal split of the peroneus brevis tendon. a Transverse and b longitudinal 12−5 MHz US images obtained over the retromalleolar region demonstrate the peroneus longus (PL) that insinuates within a longitudinal split (arrowhead) of the peroneus brevis. The peroneus brevis is divided into two separate bundles of fibers (PB1, PB2) by compression toward the lateral malleolus (asterisk). c,d CT-tenographic correlation shows the injured peroneus brevis components (arrowheads) and the peroneus longus (arrow) which lies in between them. e Gross operative view of the same case

neus longus, whereas the two tendons on each side of the peroneus longus are the halves of the peroneus brevis. In general, the halves of the peroneus brevis are of equal size. The presence of a synovial sheath effusion greatly facilitates the demonstration of peroneus brevis splits. Dynamic examination during maximal plantar and dorsal flexion of the ankle can enhance the visibility of the split. US scans should be obtained proximal and distal to the split, because the injured peroneus brevis may appear markedly swollen and edematous, even at a distance from the tear. Every time the examiner identifies an effusion in the peroneal tendon sheath, every effort should be made to accurately evaluate the size and echotexture of the peroneus brevis. If the tendon seems to have too small a size relative to normal, the presence of a split must be considered and a careful search for the second half of the tendon should be made. On the other hand, during scanning of the peroneal tendons one should be careful not to misinterpret an accessory peroneus quartus muscle or tendon as a longitudinal split of

the peroneus brevis. Knowledge of the normal course and common insertion of the peroneus quartus onto the retrotrochear eminence of the calcaneus can help one to avoid this pitfall (Patel et al. 2002). In conclusion, a longitudinal split of the peroneus brevis must always be suspected in patients who have a tenosynovial effusion or pain radiating over the peroneal tendons. Demonstration of three tendons can be due either to a complete split or to an accessory peroneus quartus. A careful scanning technique is mandatory to differentiate these two conditions.

16.5.3 Medial Ankle Pathology 16.5.3.1 Medial Ligamentous Injuries

Isolated rupture of the deltoid ligament is rarely encountered without additional injuries to the

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ankle, owing to the uncommon occurrence of eversion ankle sprains and to the intrinsic thickness of the ligament. Often, it is produced during a severe eversion injury in association with fractures of the lateral malleolus and lateral displacement of the talus. Less commonly, deltoid ligament injuries are observed with avulsion fractures of the medial malleolus at the site of attachment of its superficial portion. Widening of the ankle mortise is typically encountered when the deltoid ligament is disrupted. In ligamentous tears that occur without ankle fractures, US can be helpful for differentiating a ligamentous injury from a lesion of the adjacent tibialis posterior tendon, both conditions presenting with pain and swelling over the medial aspect of the ankle. US should examine the deltoid ligament systematically, at any single level. Focal changes of the deltoid ligament without complete disruption of its fibers are seen more commonly than fullthickness tears. In such cases, the US findings are

tibia C

talus Fig. 16.55. Partial-thickness tear of the deltoid ligament. Coronal 12−5 MHz US image over the medial ankle reveals hypoechoic thickening of the cranial portion of the tibiocalcaneal ligament consistent with a partial tear. Note the discrepant size between the injured (arrows) and the intact (arrowheads) portion of the ligament. C, calcaneus

similar to those described in Section 16.5.2.1 for the lateral ligament, including diffuse or focal areas of hypoechoic thickening of the ligament and intrasubstance linear defects in partial-thickness tears (Figs. 16.55, 16.56). Small bone fragments avulsed from the talus can also occur as a result of a traction mechanism. The interruption of the ligament continuity with surrounding hematoma, joint effusion and extravasation of joint fluid in the para-articular soft tissues is observed in acute full-thickness tears. The inability to visualize the ligament could also indicate a tear, but this finding cannot be used as a reliable sign of injury because the deltoid ligament is not always depicted as completely and reliably by US as are the anterior talofibular and calcaneofibular ligaments. In this setting, MR imaging can demonstrate deltoid ligament injuries better than US.

16.5.3.2 Abnormalities of the Tibialis Posterior Tendon

The tibialis posterior tendon is the most commonly injured tendon on the medial side of the ankle. Its rupture is typically encountered in middle-aged obese women or as a result of systemic disease, such as rheumatoid arthritis or seronegative spondyloarthropathy (Johnson 1983). Acute fractures of the ankle may also be responsible for some cases of rupture of this tendon. In most cases, tibialis posterior tendon tears occur around the medial malleolus, but they may also be encountered at the navicular insertion. Rupture of the is frequently overlooked clinically because it often develop with no history of trauma. Initially, the patient complains of pain and swelling around the affected tendon. Then, as the severity of the lesion gradually progresses toward rupture elongation, gradual collapse

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Fig. 16.56 a,b. Partial-thickness tear of the deltoid ligament in a patient presenting with chronic pain and swelling over the medial ankle. a Coronal 12−5 MHz US image over the medial ankle with b arthro-MR imaging correlation reveals a hypoechoic cleft (arrows) involving the deep portion of the deltoid ligament suggesting a partial tear. The superficial portion (arrowheads) of the ligament is swollen but continuous

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of the medial longitudinal arch occurs, resulting in an unilateral valgus deformity of the hindfoot and excessive pronation of the forefoot (Goldner et al. 1974; Funk et al. 1996). The valgus alignment of the heel and abduction at the talonavicular joint can lead to secondary stretching of the spring ligament and lesion of the deltoid ligament and capsule. Surgical repair of a tibialis posterior tendon tear includes several procedures that depend on the site and extent of injury as well as on the duration of the flatfoot deformity, such as end-to-end anastomosis and reconstruction of the tendon with the use of the adjacent flexor digitorum longus tendon as a graft. In general, surgery of partial or complete intrasubstance tendon tears is more successful than surgery of tears occurring at the tendon insertion. On the other hand, the conservative treatment of tibialis posterior tendon tears by supporting the medial longitudinal arch with orthoses may be preferred in the elderly or patients with systemic disorders. Based on the US findings, tibialis posterior tendon tears have been classified into three types of increasing severity of involvement (Rosenberg et al. 1998). The type I tear corresponds to a thickened tendon with longitudinal splits and degeneration (Fig. 16.57);

irregularities of the outer surface of the tendon and adhesions are observed at this stage (Chen and Liang 1997). The type II tear presents with an elongated and focally thinned tendon with abnormal echogenicity corresponding to areas of tearing and fibrosis. The type III tear represents complete rupture of the tendon and presents as a focal gap in the tendon substance that can be filled with hypoechoic fluid (acute) or echogenic granulation tissue (chronic). Usually, shortaxis US planes perform better than long-axis scans to image longitudinal split tears of the tibialis posterior tendon. In chronic disruption of the tibialis posterior tendon, care should be taken not to confuse the presence of hypoechoic debris and granulation tissue filling the tendinous bed with a thinned and degenerated tendon (Fig. 16.58). The absence of a fibrillar pattern and a careful scanning technique based on short-axis planes obtained from the myotendinous junction down to the tendon insertion onto the navicular can be helpful for making a correct US diagnosis. Subtle intratendinous vessels in inflammatory conditions can also mimic a tendon fissuration. Color Doppler imaging may help to avoid confusion in this regard. Another possible pitfall can be encountered when the intact flexor digitorum longus shifts forward in the

Fig. 16.57 a–c. Partial-thickness (type I) tear of the tibialis posterior tendon. a Long and b short-axis 12−5 MHz US images at the level of medial malleolus (MM) with c CT-tenographic correlation demonstrate a swollen tibialis posterior tendon (arrows) with a longitudinal hypoechoic cleft (arrowheads) in its substance consistent with a partial tear

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a medial and anterior direction relative to the medial malleolus, is less common than for peroneals. It is usually due to stripping or tearing of the flexor retinaculum at the level of its anterior insertion onto the medial malleolus (Prato et al. 2004). At US examination, tibialis posterior tendon instability is best assessed in dorsiflexion with forced supination.

16.5.3.3 Accessory Navicular Bone

Two types of accessory bones can be found at the level of the distal insertion of the posterior tibialis tendon: the accessory navicular type I and II (Lawson 1994). The accessory navicular bone (type I), also known as the os tibiale externum, can be enclosed within the tibialis posterior tendon. This sesamoid ranges from 2 to 6 mm in size and is located just proximal to the posteromedial aspect of the navicular bone. In general, it is asymptomatic and should not be confused with tendon calcification or avulsion fracture at US examination (Patel et al. 2002). The accessory navicular bone (type II) is an accessory ossification center of the navicular bone. It is larger than the type I form, ranging from 9 to 12 mm in size, has a triangular shape and articulates with the posterior and

Fig. 16.60 a–d. Chronic tenosynovitis of the tibialis posterior tendon in a patient with rheumatoid arthritis. Short-axis a gray-scale and b power Doppler 12−5 MHz US images over the inframalleolar area show fluid effusion (asterisk) within the synovial sheath of the tibialis posterior tendon (tp). Note the deltoid ligament (dl) that lies just deep to the tibialis posterior. At power Doppler imaging, increased signals of flow are visible at the synovial sheath level and within the tendon substance, suggesting intense hyperemia. c,d Correlative transverse T1-weighted MR images obtained before c and after d intravenous administration of gadolinium demonstrate marked uptake of contrast medium in the tendon (arrow) substance

medial aspect of the navicular by a synchondrosis. The type II anomaly can provide the site of attachment of some of the fibers of the tibialis posterior tendon and is associated with a painful syndrome and higher incidence of tendon rupture caused by altered stresses (Fig. 16.61) (Chen et al. 1997). In addition, it may undergo arthritic changes or injury mimicking a tibialis posterior tendon pathology on clinical grounds. In these cases, US can image irregularities in the synchondrosis compatible with chronic stressrelated injury and exclude injury of the adjacent tendon (Fig. 16.62) (Chen and Liang 1997).

16.5.3.4 Posterior Impingement and Os Trigonum Syndrome

Posterior impingement of the ankle results from compression of the soft tissues between the posterior tibia and the posterior process of the calcaneus that occurs on plantar flexion. This syndrome is more commonly encountered in patients involved in sporting activities such as ballet dancers, soccer players and runners who actively plantar flex their feet, even at extremes of their full range of movement and/or for prolonged periods (Hamilton 1982; Sammarco and Cooper

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tic confidence in this clinical setting (Jacobson et al. 1999). The os trigonum may also be visualized with US as a small hyperechoic area just lateral to the tendon, although this finding may or may not be the source of the problem (Fig. 16.64). In the absence of clinical symptoms, the isolated finding of tenosynovial fluid in the sheath of the flexor hallucis longus tendon should not be considered as a reliable sign of tendon pathology because, somewhat like the long head of the biceps tendon, this sheath communicates with the adjacent ankle joint in approximately 20% of cases. Accordingly, fluid surrounding this tendon may often reflect a joint disease rather than a tendon abnormality, especially when a large ankle joint effusion is also present. Although US can demonstrate fluid accumulation in the sheath of the flexor hallucis longus tendon in posterior impingement syndrome of the ankle, this technique is less sensitive than MR imaging to identify some typical findings of this syndrome, because of the deep location of the abnormal structures and the inability to detect bone bruises and soft-tissue abnormalities which are typically associated to this condition. Other causes of posterior impingement include osteochondral damage of the posterior talar dome and posterior talocalcaneal joint, and thickening and inflammation of the synovial folds of the posterior recesses of the ankle and subtalar joints. US has a limited value in the evaluation of these latter

flexor hallucis longus tendon, which articulates with the talus by a synchondrosis. Both the Stieda process and the os trigonum can precipitate presentation of a posterior impingement syndrome (Robinson and White 2002). In fact, the medial edge of this bone lies on the lateral side of the flexor hallucis longus tendon and may lead to compression of the tendon in this area. Therapy is first conservative. If this fails, surgical excision of the os trigonum and release of the flexor hallucis longus tendon may be indicated. In posterior impingement syndrome of the ankle, the diagnosis is based primarily on the patient’s clinical history and physical examination and is supported by imaging findings. US can identify focal areas of synovitis around the posterior recess of the ankle joint and abnormalities of the flexor hallucis longus tendon (Bureau et al. 2000). Stenosing tenosynovitis of the flexor hallucis longus tendon occurs either as the result of focal areas of synovitis or fibrosis within the tendon sheath that block the normal flow of synovial fluid, or in association with os trigonum syndrome and may lead to triggering and stiffness of the great toe (Oloff and Schulhofer 1998). The fluid can be seen proximal to the talar tubercles, but also insinuating below the retinaculum, and the tendon may appear swollen and may exhibit longitudinal splits (Fig. 16.63). Dynamic scanning of the flexor hallucis longus tendon in plantar and dorsiflexion may add further information and increase diagnos-

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Fig. 16.63 a–d. Stenosing tenosynovitis of the flexor hallucis longus tendon in a ballet dancer who had recent onset of pain during plantar flexion of the foot. a,b Sagittal and c transverse 12−5 MHz US images of the posteromedial ankle obtained a,c at the level of the talar tubercles and b proximal to them reveal a thickened flexor hallucis longus tendon (fhl) with abundant anechoic effusion in its synovial sheath (asterisks). Observe the tenosynovial fluid that insinuates under the retinaculum (arrows). Star, medial talar tubercle. d Correlative transverse T2w tSE MR image confirms abundant effusion (asterisks) in the sheath of the flexor hallucis longus (T)

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conditions and it is obvious that MR imaging is superior for detecting abnormalities of cartilage and subchondral bone plates.

16.5.3.5 Tarsal Tunnel Syndrome

Tarsal tunnel syndrome refers to the entrapment of the main trunk of the tibial nerve and/or of its divisional branches (medial plantar nerve, lateral plantar nerve, calcaneal nerve) at the medial aspect of the ankle. This syndrome has an insidious clinical onset with numbness or pain in the foot and ankle and paresthesias in the sole of the foot, often with the heel being spared. However, clinical and electromyographic diagnosis of tarsal tunnel syndrome is often not straightforward, especially when a soft-tissue swelling on the medial ankle is absent. Depending on the site of compression, tarsal tunnel syndrome produces different clinical syndromes that can be classified as proximal or distal. The proximal syndrome consists of entrapment of the main trunk of the tibial nerve in the

Fig. 16.64 a–d. Os trigonum syndrome. a Long-axis 12−5 MHz US image of the flexor hallucis longus tendon (fhl) shows its tendon sheath distended with fluid (asterisks). b Shifting the transducer lateral from a to obtain a mid-sagittal scan at the level of the Achilles tendon (open arrow), US shows a prominent bone (white arrow) located over the posterior talus (rhombus), just lateral to the flexor hallucis longus, consistent with an os trigonum. Star, posterior tibia. c Lateral radiograph of the ankle demonstrates a well-defined os trigonum tarsi (arrow). d Telethermographic image of the posterior ankle shows a local increase in temperature (yellow-red area) in the soft tissues of the retrotalar area, consistent with inflammation. Note that the Achilles tendon is outside the warm area

retromalleolar region, whereas the distal syndrome involves the divisional branches of the tibial nerve. When addressing tarsal tunnel syndrome, it should be assumed that the pathology exists in both these zones; localized nerve disease may exist, however, involving only one of these nerves. Although the source of tarsal tunnel syndrome cannot be identified on imaging findings in many cases as it results from tension stresses to the nerve without a definite morphologic correlate, the causes of this compression neuropathy that are amenable to US examination are a spaceoccupying mass or a traumatic injury. A variety of space-occupying lesions of the medial ankle, such as flexor tenosynovitis (Fig. 16.65), ganglia related to the subtalar joint (Fig. 16.66), lipomas, venous engorgement of the posterior tibial veins (Fig. 16.67), fascial septa, anomalous tendon or muscle – f lexor digitorum accessorius longus – (see Fig. 3.9), or fracture residuals (Fig. 16.68) may constrict the nerve. Identification of a definite space-occupying lesion in the tunnel is an indication for surgery. In such instances, US can provide exact information on the nature and

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paresthesias and local pain. This test (US-guided Tinel’s test) can increase the confidence that a neurogenic lesion is present. Penetrating injuries in the medial ankle can also cause direct damage to the tibial nerve in the tarsal tunnel. When the nerve is completely torn, terminal neuromas can be identified as small hypoechoic masses in continuity with the opposite edges of the severed nerve. The nerve ends may appear wavy and retracted from the site of injury. In partial tears, a spindle neuroma consisting of fusiform irregular bulging of hypoechoic fibrous tissue without evidence of nerve discontinuity can be appreciated at the site of injury (Fig. 16.69).

16.5.4 Posterior Ankle Pathology 16.5.4.1 Achilles Tendinopathy

Based on histopathologic examination findings, Achilles tendinopathy may be further subdivided into tendinosis and paratendinitis (Maffulli et al. 1998). These conditions should be considered separate entities although they often coexist and present with similar findings. In the acute phases of Achilles tendinopathy the tendon is diffusely swollen and edematous and symptoms include pain and stiffness with limitation in daily activities, whereas in

chronic phases and degenerative settings, the pain is absent or moderate and is typically induced by exercise, especially with running. Nodular or diffuse thickening of the superficial soft tissues can be palpated around the tendon. In the most severe cases, pain and discomfort may become continuous, even with walking. Initially, the treatment of Achilles tendinopathy is conservative with rest of the injured ankle while allowing activity in the uninjured parts of the body, nonsteroidal anti-inflammatory drugs, heel lifts or custom-made orthoses. If the symptoms worsen, surgery should be considered (Rolf and Movin 1997). Usually, the US examination of a patient with isolated paratendinitis demonstrates a normal intratendinous structure, whereas peritendinous effusion, irregularities of tendon margins and adhesions related to scarring of the paratenon, and a heterogeneous appearance of the pre-Achilles tendon fat pad, are the main findings (Fig. 16.70). On the other hand, the main abnormalities recognized with US in patients with Achilles tendinosis are tendon swelling, which is often bilateral, and textural heterogeneity with intratendinous focal hypoechoic areas (Fornage and Rifkin 1988; Martinoli et al. 1993; Movin et al. 1998). US can reveal subtle changes in the fibrillar pattern, including thickening, fragmentation and disappearance of specular echoes, possibly the result of the histologic alteration at the interfaces between endotendineum septa and collagen due to lesion of one or both of these structures (Martinoli

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Fig. 16.69 a–c. Partial tear of the tibial nerve following a penetrating injury caused by scissors. a Long-axis and b,c short axis b gray-scale and c color Doppler 12−5 MHz US images over the tibial nerve at the tarsal tunnel reveal fusiform hypoechoic thickening (asterisks) of the severed nerve (arrowheads) at the site of injury, consistent with a spindle neuroma. In continuity with the abnormal hypoechoic nerve segment, undefined hypoechoic scarring (arrows) is also seen in the superficial soft tissues of the tarsal tunnel. In b the tibial nerve (asterisk) appears markedly swollen in comparison with the adjacent posterior tibial artery (a) and veins (v), the tibialis posterior (tp), flexor digitorum longus (fdl) and flexor hallucis longus (fhl) tendons. c Color Doppler imaging reveals moderate hyperemia in the tibial neuroma (arrowheads)

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et al. 1993). Histopathologic correlation has demonstrated that the abnormal tendon echotexture is most often secondary to degenerative processes and repair rather than a significant inflammatory response (Movin et al. 1997). Because of the absence of a true synovial lining, inflammation is rare in the Achilles tendon and, when present, is most often secondary to an inflamed retrocalcaneal bursa. The pathologic processes leading to Achilles tendon swelling and degeneration include hypoxic (fibromatous), mucoid, tenolipomatosis and osseous degeneration (Kannus and Jozsa 1991). Hypoxic and mucoid degeneration are strongly associated with spontaneous rupture of the Achilles tendon (Kannus and Jozsa 1991). In particular, hypoxic degenerative tendinopathy is the most frequently occurring degenerative finding in torn Achilles tendons (Fox et al. 1975). It seems to be secondary to ischemia resulting from the hypovasculature of the critical zone of the Achilles tendon and usually occurs after multiple symptomatic episodes (Leach et al. 1983). On the other hand, mucoid degeneration is associated in some degree with hypoxic degeneration but, in general, it may be asymptomatic at clinical presentation (Haims et al. 2000). This could explain why abnormally enlarged and hypoechoic Achilles tendons can occasionally be found at US examination in otherwise asymptomatic individuals. In patients with symptomatic chronic Achilles tendinopathy, bilateral abnormalities are identified with US in more than half (62%) the cases (Gibbon et al. 2000). With regard to the distribution pattern, most abnormal findings are confined to the proximal two thirds of the tendon (81%), the distal third (8%) being involved less frequently (Fig. 16.71) (Gibbon et al. 2000). In short-axis planes, focal abnormalities in the proximal two thirds of the Achilles tendon involve the tendon diffusely or are limited to its medial fibers.

Fig. 16.70 a–c. Acute peritendinitis of the Achilles tendon. a Transverse 12−5 MHz US image with b T1-weighted and c T2*weighted MR imaging correlation reveals a thin layer of anechoic fluid (asterisks) along the medial aspect of the Achilles tendon (A)

On the other hand, US abnormalities in distal-third Achilles tendinopathy more commonly involve the deep portion of the Achilles tendon, often in association with retrocalcaneal bursitis (93%) (Gibbon et al. 2000). The distinction between textural abnormalities in tendon degeneration and partial tendon tears is questionable in the absence of a hematoma (Martinoli et al. 1999; Hartgerink et al. 2001). This may be difficult given that degeneration and tears are both part of the same continuum of Achilles tendon problems. Focal tendinosis may, in fact, be the consequence of a healing intrasubstance rupture. In severe longstanding tendinosis, color and power Doppler US may demonstrate abnormal vessels entering from the deep tendon surface leading to an intratendinous hypervascular pattern (Fig. 6.71c) (Zanetti et al. 2003). Although a relationship between the number of vessels and the tendon size exists, it not clear whether such hyperemia is causative or secondary to attempts at healing (Richards et al. 2005). The hypervascular pattern seems to correlate with pain but not with an unfavourable outcome (Zanetti et al. 2003). The Achilles tendon is the tendon most frequently involved in metabolic disorders: in gout, deposition of urate tophi may result in intratendinous nodules or diffuse thickening of the tendon, while in heterozygous familial hypercholesterolemia, an inherited disorder leading to premature atherosclerosis, US can depict striking bilateral tendon swelling and a high-grade textural heterogeneity and disappearance of the fibrillar pattern with focal or diffuse hypoechoic areas, the intratendinous xanthomas, before these become clinically apparent (Fig. 16.72) (Kainberger et al. 1993; Bude et al. 1993, 1998; Bureau and Roederer 1998). Calcifications may occasionally be encountered in the Achilles tendon, although their relation with

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Fig. 16.71 a–c. High-grade tendinopathy in a patient with continuous pain in the Achilles tendon. a Long-axis and b short-axis 12−5 MHz US images demonstrate marked fusiform swelling and hypoechoic appearance of the tendon (arrows) at the level of the distal tibia and approximately 5−6 cm above the insertion on the calcaneus (C). In this particular case, US cannot distinguish with certainty whether these changes are related to severe tendinosis or to a partial-thickness tear. c Color Doppler imaging gives a better depiction of intratendinous flow signals. The pattern distribution of flow is characterized by vessel pedicles that enter the tendon from the paratenon and assume a longitudinal course within it. . In a and c, a split-screen image was used, with the two screens aligned for an extended field-of-view.

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tendon degeneration is not clear (Fig. 16.73). In fact, calcific deposits account for only 3% of ruptured tendons. In the midportion of the Achilles tendon, more extensive plaque-like ossification may occur after severe repetitive trauma (Fig. 16.74) (Yu et al. 1994). Tendon ossification is a process distinct from tendon calcification because it leads to formation of

Fig. 16.72 a–c. Heterozygous familial hypercholesterolemia. a Long-axis extended field-of-view and b short-axis 12−5 MHz US images of the Achilles tendon reveal a markedly swollen tendon (arrowheads) with rounded cross-section despite the patient’s lack of physical activity. The tendon appearance is inhomogeneous and predominantly hypoechoic due to deposition of xanthomatous material within the tendon fibers. This abnormal appearance was recognized bilaterally. C, calcaneus. c Photograph shows surface bulging of the posterior ankle reflecting the enlarged Achilles tendon

intratendinous cortical bone and trabeculae. Calcaneal enthesophytes are the most common osseous abnormalities at the insertion of the Achilles tendon. They often arise in runners and may become painful. At US examination, there is prominent spurring and deformity of the hyperechoic profile of the posterior calcaneus (Fig. 16.75) in comparison with normal (see

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Fig. 16.31c). In addition, subtle linear echoes related to calcific deposits may be encountered at the insertion of tendon into bone (Fig. 16.75). Focal surgical resection of the bony spur is the treatment of choice.

16.5.4.2 Achilles Tendon Tear

Degenerative changes in the Achilles tendon substance, and especially hypoxic and myxoid types of tendon degeneration, may lead to the development of microscopic tears, progressing through multiple symptomatic episodes to interstitial tears (which are usually parallel to the long axis of the tendon), up to partial tears and eventually to complete tears. The rupture of the Achilles tendon has a prevalence of approximately 7×106 new cases per year (Schweitzer and Karasick 2000). It is more common in males, with the left side predominantly involved for unknown reasons. The

effects of aging and reduced blood flow as the result of a sedentary life-style are factors predisposing to tendon rupture. The site of rupture is typically 2−6 cm from the calcaneal insertion, at the so-called “critical zone” of relative hypovasculature. Occasional physical activity that intermittently stresses an ischemic tendon may also lead to spontaneous rupture. Also, a relationship between tendon tear and some running sports, such as jogging and soccer, has been described (Sandelin et al. 1985). There is still controversy as to whether the optimal treatment for complete ruptures of the Achilles tendon is surgical or conservative. Conservative management can be advocated when the torn tendon ends are apposed with the ankle in equine position. Plaster casts or functional bracing are used that allow immediate weight-bearing, plantar flexion of the ankle and graded limited dorsiflexion. (Thermann et al. 1992). At US examination, the complete rupture of the Achilles tendon appears as a focal defect between

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Fig. 16.76. Complete rupture of the Achilles tendon. Long-axis extended field-of-view 12−5 MHz US image demonstrates with difficulty the separation of the torn tendon ends because of an ill-defined hypoechoic hematoma (asterisks). Note the anterior orientation of the distal tendon end (arrow): this is a common finding in Achilles tendon tears. C, calcaneus

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Fig. 16.77 a,b. Complete acute rupture of the Achilles tendon in a patient under therapy with corticosteroids who felt a sudden acute pain in the Achilles tendon while running. a Long-axis 12−5 MHz US image demonstrates a gap between the proximal (open arrowheads) and distal (arrows) ends of the ruptured Achilles tendon (A) filled with anechoic fluid (asterisks) related to the hematoma. Note the intact paratenon (white arrowheads) which appears as a regular envelope surrounding both tendon and hematoma. b Gross operative view of the same case (courtesy of Dr. Mario Delmo, Geneva, CH)

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the torn tendon edges (Fornage 1986; Kainberger et al. 1990). In acute phases, the tendon ends abut one another without an intervening gap (Fig. 16.76). However, a defect created by the tear and filled with anechoic or hypoechoic hematoma can be present (Fig. 16.77). In these cases, it has been found to measure up to 20 mm on long-axis scans (Hollenberg et al. 2000; Hartgerink et al. 2001). In most cases, the paratenon remains intact and appears as a straight echogenic envelope that outlines the site of rupture (Fig. 16.77). Distortion of the normal fibrillar pattern and loss of the parallelism of the tendon fibers can be observed in acute phases (Hollenberg et al. 2000) as an associated finding. Other signs indicative of a complete tear of the Achilles tendon are the tendency to fat herniation into the tendon defect and increased visualization of the plantaris tendon, as well as a posterior acoustic shadowing at the site of the tear, which seems to relate to US beam refraction at the frayed tendon ends (Fig. 16.76) (Hartgerink et al. 2001). This last sign demonstrates a more significant correlation (P=0.007) with complete tears of the tendon and, in doubtful cases, it can be helpful for differentiating full- from partial-thickness tears or tendinosis of the Achilles tendon together with the absence of a detectable tendon at the site of injury and with tendon retraction (Hartgerink et al. 2001). If there is no retraction and the torn tendon ends are curled up, or if fluid does not fill the space created by the tear, gentle passive assisted movements can be helpful, by enhancing the separation of the tendon ends during stretching (Fig. 16.78). Atrophy of the triceps muscle, usually occurring first in the soleus because of its high proportion of slow-twitch fibers, can also be observed in chronic complete tears. US has proved to have 100% sensitivity, 83% specificity, 92% accu-

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racy, 88% positive predictive value and 100% negative predictive value in differentiating full-thickness tears from partial-thickness tears or tendinosis of the Achilles tendon (Hartgerink et al. 2001). As stated before, greater difficulties may arise with US in distinguishing changes related to tendinosis from partial-thickness tears. However, this distinction may not be of critical importance because both conditions, in the absence of a complete tear, are initially treated conservatively. Partial-thickness tears are more likely when the anteroposterior diameter of the tendon is very large (range 10−15 mm) and the intratendinous echotexture is abnormal (Åström et al. 1996), when a hypoechoic interstitial defect in the longitudinal direction parallel to the tendon fibers is visible or a clear discontinuity involves an individual portion of the tendon whereas the other remains unaffected with a preserved fibrillar pattern (Fig. 16.79a,b) (Kalebo et al. 1992; Martinoli et al. 1993). A localized irregularity of the tendon surface or a concavity in the tendon contour filled with fat may be an associated sign of partial tendon tears (Fig. 16.79c) (Kalebo et al. 1993). In patients who have been managed conservatively without surgery, the healed Achilles tendon tear presents with mild residual distortion of the normal fibrillar pattern, slight anterior bulging or irregularity and a hypoechoic area at the site of prior rupture (Hollenberg et al. 2000). Intratendinous calcifications can be observed. After surgical repair, the Achilles tendon appears markedly enlarged, with gross echotextural abnormalities and poor delineation of the reinforcement flap (Fig. 16.80) (Rupp et al. 1995; Karjaleinen et al. 1996). Sutures can be visualized as intratendinous bilaminar bright specular echoes with comet-tail artifact or acoustic shadowing at the site of injury. In a postoperative setting, US can be used

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Fig. 16.78 a–c. Complete rupture of the Achilles tendon. a US scanning technique includes examination of the tendon during plantar and dorsal flexion of the foot to enhance the separation of the torn ends of the Achilles tendon. Arrows, direction of movement. b,c Long-axis 12−5 MHz US images of a torn Achilles tendon obtained during b plantar and c dorsal flexion of foot. The gap (asterisks) between the tendon ends widens with the foot in dorsiflexion

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to monitor the repair process as well as to exclude recurrent tears (Fig. 16.81). After repair, the Achilles tendon remains thickened, whereas the postoperative changes in the structure may regress partially.

16.5.4.3 Plantaris Tendon

In full-thickness tears of the Achilles tendon, the plantaris tendon frequently remains intact. In the context of a complete Achilles tendon tear, an intact

plantaris tendon may lead to a false diagnosis of a partial Achilles tendon tear, thereby affecting appropriate surgical management. In fact, when the Achilles tendon is torn, the plantaris tends to move posteriorly into the defect created by the tear and can be mistaken for residual intact fibers of the Achilles tendon (Fig. 16.82). Knowledge of the normal anatomy and appearance of the intact plantaris in the setting of an Achilles tendon tear helps avoid this pitfall. Assessment of the status of the plantaris tendon is also important for planning surgical repair of the Achilles using the plantaris as a

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Fig. 16.79 a–c. Partial rupture of the Achilles tendon. Longitudinal 12−5 MHz US images demonstrate a spectrum of appearances of partial-thickness tears of the Achilles tendon in three different cases, all surgically proven. a The echotexture of the posterior half of the Achilles tendon is abnormally hypoechoic (asterisks) with loss of the fibrillar pattern. b A hypoechoic interstitial defect (asterisks) in the longitudinal direction is visible within the tendon substance. C, calcaneus c The anterior border of the Achilles tendon is wavy (arrows) and the echotexture appears diffusely hypoechoic. In this case, there was discontinuity of the anterior fibers from the soleus muscle

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Fig. 16.80 a–c. Postoperative Achilles tendon. a After surgical repair, long-axis 12−5 MHz US image reveals a markedly enlarged and heterogeneous Achilles tendon (arrowheads). Adhesions and irregularities (asterisks) in the peritendinous tissues are associated findings. Note the sutures (arrows), which appear as bilaminar straight echoes within the tendon substance. Correlative b transverse and c sagittal T1-weighted MR images confirm the striking swelling of the Achilles tendon, which contains a region of intermediate signal intensity in both images and signs of peritendinitis (asterisks)

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Fig. 16.81 a,b. Recurrent rupture of the Achilles tendon after surgical repair in a patient with sudden onset of pain while walking upstairs. a Long-axis and b short-axis 12−5 MHz US images of the operated Achilles tendon (arrows) reveal an intratendinous fluid collection (asterisks) reflecting recurrence of a partial tendon tear. A suture (arrowheads) is visible in close relationship with the hematoma

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d

Fig. 16.82 a–d. Complete rupture of the Achilles tendon. a Long-axis 12−5 MHz US image of the Achilles tendon obtained with a dorsiflexed foot shows a short hypoechoic gap between the torn tendon ends (asterisks). A split-screen image was used, with the two screens aligned for an extended field-of-view; C, calcaneus. b Long-axis 12−5 MHz US image obtained just medial to a reveals an intact plantaris tendon (arrowheads). c Transverse 12−5 MHz image identifies the intact plantaris (white arrow) within the bed of the ruptured Achilles tendon (open arrows). d Photograph demonstrates the surface prominence of the plantaris tendon (arrowheads), possibly mimicking an intact Achilles tendon

graft (Fessel and Jacobson 1999). Isolated tears of the plantaris tendon are rare and must be distinguished from Achilles tendon injuries and medial gastrocnemius muscle injuries (e.g., tennis leg). Clinically, the torn plantaris tendon is considered a less severe injury than gastrocnemius muscle injury, and requires conservative treatment with ice, rest and anti-inflammatory drugs (see also Chapt. 15).

16.5.4.4 Bursitis and Haglund Deformity

Chronic posterior ankle pain may also be related to bursal pathology, which may occur as an isolated disorder but is more often secondary to inflammatory disorders, such as rheumatoid arthritis and seronegative spondyloarthropathies, or repetitive trauma, usu-

Ankle

C

C

a

b

ally associated with Achilles tendinopathy (runners). Clinically, retrocalcaneal bursitis presents with posterior heel pain exacerbated by passive dorsiflexion of the ankle. Therapy includes rest, heel elevation with a felt heel pad and nonsteroidal anti-inflammatory drugs. Local steroid injections are is not indicated in cases of coexisting insertional Achilles tendinopathy because of the risk of tendon rupture. At US examination, the distended retrocalcaneal bursa appears as a comma-shaped hypoechoic structure intervening between the Achilles tendon and the posterosuperior aspect of the calcaneus (Fig. 16.83). One should be careful not to mistake the adjacent Kager fat space, which may contain oval hypoechoic lobules of fatty tissue, for a fluid collection in the retrocalcaneal bursa (Patel et al. 2002). When bursitis is a manifestation of a synovial inflammatory process, it may appear hypervascular at Doppler imaging. Retro-Achilles bursitis usually presents with a painful and tender subcutaneous swelling that overlies the Achilles tendon. This condition is mostly observed in young women as a result of local irritation from the upper edge of a narrow shoe. At US examination, retro-Achilles bursitis presents with thickening and localized fluid collection within the subcutaneous tissue immediately superficial to the retrocalcaneal

C a

Fig. 16.83 a,b. Retrocalcaneal bursitis in a patient with chronic heel pain. Longitudinal a gray-scale and b color Doppler US images reveal hypoechoic swelling of the retrocalcaneal bursa (arrowheads) deep to a thickened distal Achilles tendon. The peribursal area appears hypervascular at color Doppler imaging. C, calcaneus

portion of the Achilles tendon (Fig. 16.84a). Hyperemic flow signals are often recognized on Doppler imaging (Fig. 16.84b). Excessive pressure with the transducer should be avoided when examining the retro-Achilles bursa because it is easily deformable and its walls may become effaced and difficult to identify. A prominent, convex posterosuperior tuberosity of the calcaneus associated with thickening of the Achilles tendon at its site of insertion, distension of the retro-Achilles bursa and inflammatory changes in the pre-Achilles fat and retrocalcaneal bursa characterize so-called Haglund deformity (Fig. 16.85) (Sella et al. 1998). In this condition, heel protection from shoes is the initial treatment. When conservative measures fail, calcaneal osteotomy with resection of the posterosuperior tuberosity of the calcaneus is performed.

16.5.5 Bone and Joint Disorders 16.5.5.1 Synovitis

US is able to reliably detect mild effusion (>2 ml) within the talocrural joint by scanning over its ante-

C b

825

Fig. 16.84 a,b. Retro-Achilles bursitis in a patient with a painful and swollen heel. Longitudinal a gray-scale and b color Doppler US images show soft-tissue thickening and localized fluid collection (arrowheads) within the subcutaneous tissue immediately superficial to the retrocalcaneal portion of the Achilles tendon. Local hyperemia is demonstrated in the peribursal tissues at color Doppler imaging. C, calcaneus

826


C

a

b

c

rior and posterior recess (Figs. 16.86, 16.87) (Fessel and Jacobson 1999). The US diagnosis of synovitis in the ankle joint is relatively easy and differences in echotexture can allow distinction between synovial hypertrophy and effusion. In large effusions of the ankle joint, the anterior intracapsular fat pad tends to displace anteriorly (Jacobson et al. 1998). US images obtained with different degrees of flexion and extension lead to different degrees of filling of the anterior and posterior synovial recess and can help in evaluating the internal content of the joint. In general, the sensitivity of US for detecting fluid in the anterior recess of the ankle joint is improved with plantar flexion of the foot. This maneuver should always be performed in doubtful cases. Then, color and power Doppler imaging and graded compression with the probe can help to distinguish effusion from synovial pannus. When there is clinical concern for septic arthritis, US-guided aspiration of the joint fluid can easily be performed in the anterior recess (Fessel et al. 2000). During this procedure, care should be taken to check the position of the anterior neurovascular bundle before inserting the needle.

Fig. 16.85 a–c. Haglund deformity. a Longitudinal 12−5 MHz US image in a patient with pain and chronic swelling over the distal Achilles tendon. Textural inhomogeneities (stars) are visible in a thickened Achilles tendon, just adjacent to a convex prominent superior tuberosity of the calcaneus (C). Deep to the tendon, there is concurrent inflammation of the retrocalcaneal bursa (arrows). b Lateral radiograph confirms the bony prominence (arrows) of the calcaneus. c Photograph of the lateral heel of the same case

Synovitis in the anterior subtalar joint can also be assessed with US by placing the transducer just below and anterior to the anterior talofibular ligament to examine the groove between calcaneus and talus; synovitis of the posterior subtalar joint is best evaluated by scanning its posterior recess that is located just caudal to the posterior recess of the ankle joint (Fig. 16.88).

16.5.5.2 Chondral and Osteochondral Damage

In the evaluation of intra-articular loose bodies the active displacement of the bone fragment is an important diagnostic criterion (Bianchi and Martinoli 1999). Intra-articular loose bodies can be demonstrated by showing them surrounded by fluid in a recess of the ankle joint (Fig. 16.89) or in the subtalar joint (Fig. 16.90). Flexion and extension of the joint cause changes in the shape of the recess and, as a consequence, in the position of the loose bodies (Bianchi and Martinoli 1999). In patients without a synovial effusion or in cases of doubtful findings (e.g., a small

Ankle

talus a

b

c

Fig. 16.86 a–c. Synovitis of the ankle joint: anterior recess. a Midsagittal 12−5 MHz US image over the dorsal ankle in a patient with joint effusion reveals a distended anterior joint recess (arrows) filled with hypoechoic fluid between the hyperechoic margins of the distal epiphysis of the tibia (star) and the talar head (asterisk). b Lateral radiograph reveals increased density (arrows) involving the anterior ankle, consistent with a synovial process. c The patient presented with anterior swelling (curved arrow) of the ankle

fhl

fhl

PM talus a

b

Fig. 16.87 a,b. Synovitis of the ankle joint: posterior recess. a Sagittal 12−5 MHz US image over the posterior ankle demonstrates hypoechoic fluid (arrows) within the posterior recess of the ankle joint between the posterior malleolus (PM) and the talus, in close relation to the flexor hallucis longus tendon (fhl). b Lateral radiograph shows increased density (arrows) at the level of the posterior recess, reflecting synovitis

fragment located in a deep posterior recess), the intraarticular injection of saline may enhance the conspicuity of small and radiographically occult loose bodies (Frankel et al. 1998). Small fragments may occasionally occur at the lateral aspect of the joint, under the anterior talofibular ligament. They are difficult to differentiate from post-traumatic ligament calcifications. In addition, bony outgrowths that commonly develop on the anterior aspect of the distal

tibia and on the superior surface of the talar neck as a result of anterior impingement may mimic an intraarticular loose body (Fig. 16.38a). Also, one should be careful not to confuse a residual fracture of the posterior malleolus or an os trigonum tarsi for a loose body. In patients with degenerative osteoarthritis, a reduced thickness, focal irregularities or complete loss of the hypoechoic layer of the articular cartilage can be identified with US as well (Fig. 16.38b).

827

828


A

A

A

calcaneus a

b

Fig. 16.88 a,b. Synovitis of the posterior subtalar joint. a Sagittal 12−5 MHz US image over the Achilles tendon (A) with b T2weighted MR imaging correlation reveals abundant fluid within a distended posterior recess of the posterior subtalar joint (arrows), deep to the Kager fat space (asterisk). Note the close relation of this recess with the superior margin of the calcaneus

talus

talus a

c

talus b

d

Fig. 16.89 a–d. Intra-articular loose body in the ankle joint. a, b Longitudinal 12−5 MHz US images of a distended anterior recess of the ankle joint (open arrows) obtained a in neutral position and b after dorsiflexion of the foot. An intra-articular loose body is visible inside the recess as a hyperechoic fragment (white arrow) with faint posterior acoustic shadowing surrounded by joint effusion. After dorsiflexion of the foot, the bony fragment is seen moving to a more cranial position. A coexisting intracapsular spur (curved arrow) at the distal end of the anterior tibia remains stationary during ankle movements. Note the thin hypoechoic layer of articular cartilage that overlies the talar dome. The articular cartilage of the tibial plafond cannot usually be demonstrated with US. c Transverse 12−5 MHz US image depicts the loose body (arrow) over the articular surface of the talus. d Lateral arthrographic view confirms that the bony fragment (arrow) is intra-articular in location

830


joint is typically present when the fracture involves the articular surfaces of the posterior talocalcaneal joint. In a post-traumatic setting, we believe the US assessment of the lateral process of the talus should be part of the routine examination of the ankle, especially when fluid effusion is detected within the posterior subtalar joint (Copercini et al. 2003; Bonvin et al. 2003). Positive US findings should be confirmed by means of CT or MR imaging.

the ganglia are large and extend circumferentially around ankle tendons.

16.5.6.2 Neurogenic Tumors

Soft-tissue masses in the ankle are uncommon (Ozdemir et al. 1997). They may be asymptomatic or may cause disturbances, such as pain, weakness, swelling, joint impairment or tarsal tunnel syndrome. With US, the diagnosis of a solid or complex mass versus a cystic mass can reliably be performed in the soft tissue of the ankle. The US characteristics of many masses that arise around the ankle joint are reported in the General Section of this book. However, the specific features of some of them, including ganglia, neurogenic tumors and abscesses, warrant additional brief discussion here. Accessory muscles (peroneus quartus, flexor digitorum longus accessorius, accessory soleus) have already been described in previous sections of this chapter.

The US diagnosis of neurogenic tumor is essentially based on detection of an oval homogeneous hypoechoic mass in continuity with the nerve of origin. This sign is virtually pathognomonic for a nerve tumor but requires accurate knowledge of the course of the peripheral nerves in the body area to be examined. In the ankle, the anterior tibial artery can be used as a landmark to identify the deep peroneal nerve as it passes through the anterior compartment; the hyperechoic bony cortex of the distal fibula can be helpful to identify the superficial peroneal nerve; the small saphenous vein that runs just lateral to the Achilles tendon is the main reference for the sural nerve, whereas the posterior tibial vessels and the flexor digitorum and flexor hallucis longus tendons allow easy identification of the tibial nerve across the tarsal tunnel. In such cases, Doppler assessment of vascular landmarks can aid nerve evaluation. With regard to the characteristics of neurogenic tumors of the ankle, these are similar to those already described in Chapter 4 (Figs. 16.93, 16.94) (Pham et al. 2003).

16.5.6.1 Ganglia

16.5.6.3 Soft-Tissue Abscesses

Ankle ganglia have some different characteristics relative to wrist ganglia. Clinically, they are more frequently symptomatic. This seems related primarily to their larger size. In a recent series, ankle ganglia are reported to measure 10−30 mm in diameter (Ortega et al. 2002), whereas most wrist ganglia are 5 mm in size when examined along their short axis (Redd et al. 1989; Pollak et al. 1992; Zanetti et al. 1997). In the rare instances in which a restricted web space prevents an accurate US examination, MR imaging should be performed to detect neuromas and distinguish them from other local disorders of the forefoot (Zanetti and Weishaupt 2005). As detailed in Chapter 18, US can successfully guide steroid or alcohol injections to treat symptomatic Morton neuromas (Dockery 1999; Fanucci et al. 2004). In the postsurgical setting, US has proved useful in detecting recurrences (Levine et al. 1998). However, the interpretation of postsurgical findings is often difficult with US because of local scar tissue.

17.5.4 Foot Masses Most soft-tissue masses of the foot are benign nonneoplastic conditions, including ganglion cysts, bursitis, foreign body granuloma, plantar fibromatosis,

M B M

a

b

M

c

M

Fig. 17.51a–c. Scanning technique for Morton neuroma: transverse plantar approach. a Photograph shows the examiner, who places the transducer over the plantar aspect of the anterior intermetatarsal space applying simultaneous pressure on its dorsal aspect with the other hand. b,c Schematic drawings demonstrate that simultaneous pressure (black arrows) exerted with the probe and the thumb allows the spacing out (light gray arrows) of the metatarsals (M), to displace the neuroma (arrowhead) plantarly – in a closer position to the probe – and squeeze the intermetarsal bursa (B)

879

881

Foot

pigmented villonodular synovitis, and giant cell tumor of the tendon sheath. The foot is the third most common location of ganglion cysts following the wrist and hand (Waldt et al. 2003). In the foot, ganglia most often develop from the tarsal sinus and the tarsal canal (34%), around the Lisfranc joint (14%), and dorsal to the metatarsophalangeal joints (Ashman et al. 2001;

Fig. 17.54. Morton neuroma and intermetatarsal bursitis. Longitudinal 12–5 MHz US image obtained with a dorsal approach shows the neuroma as a fusiform solid hypoechoic mass (n) located just proximal to the bifurcation of the common digital nerve (arrowheads). Dorsal to it, fluid distension of the intermetatarsal bursa (asterisks) is seen, reflecting associated bursitis

Woertler et al. 2005; Weishaupt et al. 2001). Dorsal ganglia usually arise from a tendon sheath, are palpable, and are larger than those located in the hand and wrist (Waldt et al. 2003). Most are clinically asymptomatic (Woertler et al. 2005; Weishaupt et al. 2001). The US appearance of ganglion cysts is variable, ranging from round to oval and lobulated masses (Fig. 17.56).

∗

∗

n

b

a

b Fig. 17.55a,b. Morton neuroma. Shape changes induced by compression. a,b Longitudinal 12–5 MHz US images obtained a without and b with compression by the examiner’s thumb. Without compression (double-headed arrow), a small neuroma (arrowheads) is found in association with a distended bursa (b). With increasing pressure (white arrow) with the thumb, a decreased soft-tissue thickness (double-headed arrow) of the intermetatarsal space is observed, leading to a better assessment of the neuroma and depiction of the nerve continuity at its anterior edge (open arrowhead). The squeezed bursa is no longer appreciated. Dynamic scanning helps to confirm the fluid content of the hypoechoic image referred to the bursa

Fig. 17.53a–e. Morton neuroma. a Longitudinal and b transverse 12–5 MHz US images of the forefoot with c schematic drawing correlation in a 32-year-old woman with longstanding pain referred to the third intermetatarsal space. US images are obtained with a dorsal approach while applying pressure (white arrow) with the thumb (void arrows) on the plantar aspect of the third intermetatarsal space. Depending on the scanning plane, the neuroma (n) appears as a fusiform (a) or rounded (b) well-circumscribed solid hypoechoic mass. Compression with the examiner’s thumb decreases the soft-tissue thickness (double-headed arrow), thus allowing an accurate evaluation of the intermetatarsal space. M, metatarsal. d,e Coronal d T1-weighted and e fatsuppressed T2-weighted MR images confirm the presence of Morton neuroma (n)

882


Cal

Cub

a

b

Tal Cal c

d Fig. 17.56a–d. Ganglion cysts. Spectrum of US appearances in three different patients. Case 1. a Photograph shows a painless stiff lump (arrow) on the dorsolateral aspect of the midfoot with normal overlying skin. b Transverse 12–5 MHz US image obtained over the mass shows a well-marginated cystic lesion (arrowheads) connected with the calcaneocuboid joint through a small pedicle (arrow). Cal, calcaneus; Cub, cuboid. Case 2. c Transverse 12–5 MHz US image over the lateral ankle reveals an occult nonpalpable ganglion (arrows) arising from the tarsal sinus and expanding superficially between the calcaneus (Cal) and the talus (Tal). Case 3. d Longitudinal 12–5 MHz US image over the dorsal aspect of the forefoot in a patient with a palpable softtissue lump demonstrates an elongated cystic mass (arrows) displacing the extensor tendons. Hypoechoic deposits (arrowheads) in the dependent portion of the ganglion reflect hemorrhage or chronic inflammation

Apart from intermetatarsal bursitis, superficial palpable bursitis can occur in the midfoot over a hypertrophied peroneal tubercle and in the forefoot involving the adventitial bursae beneath the metatarsal heads (Ashman et al. 2001). A distended bursa underlying the head of the first metatarsal is often observed in association with hallux valgus (Schweitzer et al. 1999). It can be recognized as a focal mass with mixed echotexture (containing fluid and hypertrophied synovium) interrupting the subcutaneous fat plane focally (Fig. 17.57). Foreign body granulomas develop in response to fragments of wood, thorns, glass or plastic objects that have penetrated the soft tissues of the foot. They are almost invariably found in the subcutaneous fat at the plantar aspect of the foot, particularly in subjects who walk barefoot. The US characteristics of these lesions have been described in Chapters 2 and 11 (Fig. 17.58).

The intra-articular form of pigmented villonodular synovitis is a monoarticular condition that can arise as a single nodule or a diffuse villonodular mass, most often located in the ankle and hindfoot (Fig. 17.59a,b) (Yang et al. 1998; Woertler et al. 2005). In the forefoot, giant cell tumor of the tendon sheath shows a predilection for a location among the toes (Fig. 17.59c–f). In this area, it represents by far the most common solid benign soft-tissue mass (Ashman et al. 2001). As detailed in Chapters 3 and 11, US demonstrates giant cell tumor as a painless solid hypoechoic nodule with a hypervascular pattern located adjacent to or enveloping a tendon (Fig. 17.59c). Especially in lesions with marked hemosiderin content, low T2-signal intensity areas are typical at MR imaging (Fig. 17.59d–f). Among primary malignant soft-tissue neoplasm of the foot, synovial sarcoma and the clear cell sarcoma should be mentioned. Synovial sarcoma is

883

Foot

a

b Fig. 17.57a–c. Submetatarsal bursitis. Longitudinal 12–5 MHz US images obtained from a lateral to c medial over the plantar aspect of the first metatarsophalangeal joint show a flattened compressible mass (arrowheads) characterized by mixed internal echotexture reflecting an adventitial bursa distended by hypertrophied synovium. The bursa is located in close relationship with the lateral sesamoid (LS), the flexor hallucis longus tendon (fhl), and the bipartite medial sesamoid (MS1 and MS2)

M2

c

∗ M3

a

c

b

d

e

Fig. 17.58a–e. Plantar foreign bodies: spectrum of US findings. a,b Radiolucent wood splinter. a Transverse 12–5 MHz US image over the sole in the forefoot region of a patient presenting with painful soft-tissue swelling following a penetrating wound reveals a linear hyperechoic structure (arrows) transversely oriented under the second (M2) and third (M3) metatarsals consistent with a foreign body, surrounded by a hypoechoic halo (asterisk). b Plain film was negative. Removal of the fragment revealed a wood splinter. c,d Radiopaque metallic needle. c Longitudinal and d transverse 12–5 MHz US images over the heel fat pad demonstrate a thin linear bright hyperechoic structure (arrows) with posterior reverberation artifact (white arrowheads) overlying the calcaneus. e Plain film and subsequent surgical removal confirmed the presence of a metallic needle (arrow) infixed in the heel fat pad

885

Foot

Nav

b

a

d

c

e

Fig. 17.60a–e. Synovial sarcoma in a 15-year-old boy presenting with a soft-tissue mass growing in the medial midfoot. a Anteroposterior radiograph show a soft-tissue mass that contains stippled amorphous calcifications (arrows) located superficial to the navicular bone. b,c Transverse b gray-scale and c color Doppler 12–5 MHz US images with d sagittal T2-weighted MR imaging correlation demonstrate a relatively well defined mass (arrows) with small calcific deposits (arrowhead) and a hypervascular pattern. The tumor has a multilobular shape and appears slightly heterogeneous on the T2-weighted sequence. Nav, navicular. e At the time of the diagnosis, the chest radiograph already revealed lung metastases (arrow)

a

Fig. 17.61a–c. Clear cell sarcoma of the forefoot in an 18-year-old girl with pain and swelling over the lateral forefoot. a Anteroposterior radiograph shows a softtissue mass causing pressure erosion of the fifth metatarsal bone (arrowhead). b,c Transverse color Doppler 12–5 MHz US image with c post-contrast fat-suppressed T1-weighted MR imaging correlation reveals a hypoechoic heterogeneous mass (arrows) characterized by hypervascular pattern and marked contrast uptake. The mass is attached to the lateral aspect of the fifth metatarsal and develops in the lateral plantar compartment of the foot causing invasion of the muscles, subcutaneous fat, and deep layer of the dermis

b

c

886


References Akfirat M, Sen C, Gunes T (2003). Ultrasonographic appearance of the plantar fasciitis. Clin Imaging 27:353–357 Ashman CJ, Klecker RJ, Yu JS (2001) Forefoot pain involving the metatarsal region: differential diagnosis with MR imaging. RadioGraphics 21:1425–1440 Bedi DG, Davidson DM (2001) Plantar fibromatosis: most common sonographic appearance and variations. J Clin Ultrasound 29:499–505 Bernathova M, Bein E, Bendix et al (2005) Sonographic diagnosis of plantar vein thrombosis: report of 3 cases. J Ultrasound Med 24:101–103 Bianchi S, Abdelwahab IF, Tegaldo G (1991) Fracture and posterior dislocation of the os peroneum associated with rupture of the peroneus longus tendon. Can Assoc Radiol J 42:340–344 Blitz NM, Christensen JC, Ford LA (2002) Plantar plate ruptures of the second metatarsophalangeal joint. J Foot Ankle Surg 41:138–139 Blitz NM, Ford LA, Christensen JC (2004) Plantar plate repair of the second metatarsophalangeal joint: technique and tips. J Foot Ankle Surg 43:266–270 Bodner G, Stockl B, Fierlinger A et al (2005) Sonographic findings in stress fractures of the lower limb: preliminary findings. Eur Radiol 15:356–359 Boles MA, Lomasney LM, Demos TC et al (1997) Enlarged peroneal process with peroneus longus tendon entrapment. Skeletal Radiol 26:313–315 Borman P, Koparal S, Babaoglu S et al (2005) Ultrasound detection of entheseal insertions in the foot of patients with spondyloarthropathy. Clin Rheumatol 1:1–5 Boutry N, Larde A, Lapegue F et al (2003) Magnetic resonance imaging appearance of the hands and feet in patients with early rheumatoid arthritis. J Rheumatol 30:671–679 Boutry N, Flipo RM, Cotten A (2005) MR imaging appearance of rheumatoid arthritis in the foot. Semin Musculoskelet Radiol 9:199–209 Boutry N, Vanderhofstadt A, Peetrons P (2006) Ultrasonography of anterosuperior calcaneal process fracture: report of 2 cases. J Ultrasound Med 25:381–385 Brigido MK, Fessell DP, Jacobson JA et al (2005) Radiography and US of os peroneum fractures and associated peroneal tendon injuries: initial experience. Radiology 237:235–241 Brock JG, Meredith HC (1979) Case report 102. Osteomyelitis of hallux sesamoid. Skeletal Radiol 4:236–239 Brook A, Corbet M (1977) Radiographic changes in early rheumatoid arthritis. Ann Rheum Dis 36:71–73 Bruce WD, Christofersen MR, Phillips DL (1999) Stenosing tenosynovitis and impingement of the peroneal tendons associated with hypertrophy of the peroneal tubercle. Foot Ankle Int 20:464–467 Cardinal E, Chhem RK, Beauregard CG et al (1996) Plantar fasciitis: sonographic evaluation. Radiology 201:257–259 Clifford LJ, Mauer A, Mizel MS (1998) Congenital absence of the hallux fibular sesamoid: a case report and review of the literature. Foot Ankle Int 19:329–331 Cole C, Seto C, Gazewood J (2005) Plantar fasciitis: evidencebased review of diagnosis and therapy. Am Fam Physician 72:2237–2242 D’Agostino MA, Said-Nahal R, Hacquard-Bouder C et al (2003) Assessment of peripheral enthesitis in spondyloarthropa-

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Foot injection of recalcitrant plantar fasciitis. Ann Rheum Dis 57:383–384 Kane D, Greaney T, Shanahan M et al (2001) The role of ultrasonography in the diagnosis and management of idiopathic plantar fasciitis. Rheumatology 40:1002–1008 Karasick D, Schweitzer ME (1998) Disorders of the hallux sesamoid complex: MR features. Skeletal Radiol 27:411–418 Koski JM (1993) Ultrasonography of the subtalar and midtarsal joints. J Rheumatol 20:1753–1755 Koski JM (2000) Ultrasound guided injections in rheumatology. J Rheumatol 27:2131–2138 Kruse RW, Chen J (1995). Accessory bones of the foot: clinical significance. Mil Med 160:464–467 Le Minor JM (1987) Comparative anatomy and significance of the sesamoid bone of the peroneus longus muscle (os peroneum). J Anat 151:85–99 Le Minor JM (1999) Congenital absence of the lateral metatarso-phalangeal sesamoid bone of the human hallux: a case report. Surg Radiol Anat 21:225–227 Ledderhose G (1897) Zur Pathologie der Aponeurose des Fusses und der Hand. Langenbecks Arch Klin Chir 55:694–712 Lee T, Wapner KL, Hecht PJ (1993) Current concepts review: plantar fibromatosis. J Bone Joint Surg Am 75:1080–1084 Lehtinen A, Taavitsainen M, Leirisalo-Repo M (1994) Sonographic analysis of enthesopathy in the lower extremities of patients with spondyloarthropathy. Clin Exp Rheumatol 12:143–148 Levine SE, Myerson MS, Shapiro PP et al (1998) Ultrasonographic diagnosis of recurrence after excision of an interdigital neuroma. Foot Ankle Int 19:79–84 Levitsky KA, Alman BA, Jevsevar DS et al (1993) Digital nerves of the foot: anatomic variations and implications regarding the pathogenesis of interdigital neuroma. Foot Ankle 14:208–214 Lindenbaum BL (1979) Ski-boot compression syndrome. Clin Orthop Rel Res 140:109–110 Marcus CD, Ladam-Marcus VJ, Leone J et al (1996) MR imaging of osteomyelitis and neuropathic osteoarthropathy in the feet of diabetics. RadioGraphics 16:1337–1348 Martin MA, Garcia L, Hijazi H et al (1995) Osteochondroma of the peroneal tubercle: a report of two cases. Int Orthop 19:405–407 Mengiardi B, Pfirrmann CW, Vienne P et al (2005) Anterior tibial tendon abnormalities: MR imaging findings. Radiology 235:977–984 Meyer JM, Hoffmeyer P, Savoy X (1988) High resolution computed tomography in the chronically painful ankle sprain. Foot Ankle 8:291–296 Mohana-Borges AVR, Theumann NH, Pfirmann CWA et al (2003) Lesser metatarsophalangeal joints: standard MR imaging, MR arthrography and MR bursography: initial results in 48 cadaveric joints. Radiology 227:175–182 Morel M. Boutry N, Demondion X et al (2005) Normal anatomy of the heel entheses: anatomical and ultrasonographic study of their blood supply. Surg Radiol Anat 27:176–183 Morton TG (1876) A peculiar painful affection of the fourth metatarsophalangeal articulation. Am J Med Sci 71:37–45 Mulder JD (1951) The causative mechanisms in Morton’s metatarsalgia. J Bone Joint Surg Br 33:94–95 Okazaki K, Nakashima S, Nomura S (2003) Stress fracture of an os peroneum. J Orthop Trauma 17:654–656 Oliver TB, Beggs I (1998) Ultrasound in the assessment of metatarsalgia: a surgical and histological correlation. Clin Radiol 53:287–289

Ostendorf B, Scherer A, Modder U et al (2004) Diagnostic value of magnetic resonance imaging of the forefeet in early rheumatoid arthritis with findings on imaging of the metacarpophalangeal joints of the hands remain normal. Arthitis Rheum 50:2094–2102 Peacock KC, Resnick EJ, Thoder JJ (1986) Fracture of the os peroneum with rupture of the peroneus longus tendon: a case report and review of the literature. Clin Orthop Rel Res 202:223–226 Pierson JL, Inglis AE (1992) Stenosing tenosynovitis of the peroneus longus tendon associated with hypertrophy of the peroneal tubercle and an os peroneum: a case report. J Bone Joint Surg Am 74:440–442 Pollak RA, Bellacosa RA, Dornbluth NC et al (1992) Sonographic analysis of Morton‘s neuroma. J Foot Surg 31:534– 537 Prieskorn D, Graves SC, Smith RA (1993) Morphometric analysis of the plantar plate apparatus of the first metatarsophalangeal joint. Foot Ankle 14:204–207 Quinn TJ, Jacobson JA, Craig JG et al (2000) Sonography of Morton‘s neuromas. AJR Am J Roentgenol 174:1723–1728 Rawool NM, Nazarian LN (2000) Ultrasound of the ankle and foot. Semin Ultrasound CT MR 21:275–284 Read JW, Noakes JB, Kerr D et al (1999) Morton‘s metatarsalgia: sonographic findings and correlated histopathology. Foot Ankle Int 20:153–161 Redd RA, Peters VJ, Emery SF et al (1989) Morton neuroma: sonographic evaluation. Radiology 171:415–417 Reed M, Gooding GA, Kerley SM et al (1991) Sonography of plantar fibromatosis. J Clin Ultrasound 19:578–582 Robbins MI, Wilson MG, Sella EJ (1999) MR imaging of anterosuperior calcaneal process fractures. AJR Am J Roentgenol 172:475–479 Rockett MS (1999) The use of ultrasound in the foot and ankle. J Am Podiatr Med Assoc 89:331–338 Rozbruch SR, Chang V, Bohne WH et al (1998) Ganglion cysts of the lower extremity: an analysis of 54 cases and review of the literature. Orthopedics 21:141–148 Sabir N, Demirlenk S, Yagci B et al (2005) Clinical utility of sonography in diagnosing plantar fasciitis. J Ultrasound Med 24:1041–1048 Schon LC (1994) Nerve entrapment, neuropathy and nerve dysfunction in athletes. Orthop Clin North Am 25:47–59 Schweitzer ME, Maheshwari S, Shabshin N (1999) Hallux valgus and hallux rigidus: MRI findings. Clin Imaging 23:397–402 Sellman JR (1994) Plantar fascia rupture associated with corticosteroid injection. Foot Ankle 15:376–381 Shapiro PP, Shapiro SL (1995) Sonographic evaluation of interdigital neuromas. Foot Ankle Int 16:604–606 Smyth CJ, Janson RW (1997) Rheumatologic view of the rheumatoid foot. Clin Orthop. 340:7–17 Sobel M, Pavlov H, Geppert MJ (1994) Painful os peroneum syndrome: a spectrum of conditions responsible for plantar lateral foot pain. Foot Ankle Int 3:112–124 Sobiesk GA, Wertheimer SJ, Schulz R et al (1997) Sonographic evaluation of interdigital neuromas. J Foot Ankle Surg 36:364–366 Tehranzadeh J, Stoll DA, Gabriele OM (1984) Case report 271. Posterior migration of the os peroneum of the left foot, indicating a tear of the peroneal tendon. Skeletal Radiol 12:44–47 Theodorou DJ, Theodorou SJ, Kakitsubata Y et al (2000) Plan-

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Weinfeld SB, Haddad SL, Myerson MS (1997) Metatarsal stress fractures. Clin Sports Med 16:319–338 Weishaupt D, Schweitzer ME, Alam F et al (1999) MR imaging of inflammatory joint diseases of the foot and ankle. Skeletal Radiol 28:663–669 Weishaupt D, Schweitzer ME, Morrison WB et al (2001) MRI of the foot and ankle: prevalence and distribution of occult and palpable ganglia. J Magn Reson Imaging 14:464–471 Woertler K (2005) Soft-tissue masses in the foot and ankle: characteristics on MR Imaging. Semin Musculoskelet Radiol. 9:227–242 Wong SM, Griffith JF, Tang A et al (2002) The role of ultrasonography in the diagnosis and management of idiopathic plantar fasciitis. Rheumatology 41:835–836 Wu KK (1996) Morton’s interdigital neuroma: a clinical review of its etiology, treatment, and results. J Foot Ankle Surg 35:112–119 Wu KK (2000) Morton neuroma and metatarsalgia. Curr Opin Rheumatol 12:131–142 Yang PY, Wang CL, Wu CT et al (1998) Sonography of pigmented villonodular synovitis in the ankle joint. J Clin Ultrasound 26:166–170 Yao L, Cracchiolo A, Farahani K et al (1996) Magnetic resonance imaging of plantar plate rupture. Foot Ankle Int 17:33–36 Yu JS (2000) Pathologic and postoperative conditions of the plantar fascia: review of MR imaging appearances. Skeletal Radiol 29:491–501 Yu JS, Smith G, Ashman C et al (1999) The plantar fasciotomy: MR imaging findings in asymptomatic volunteers. Skeletal Radiol 28:447–452 Zanetti M, Weishaupt D (2005) MR imaging of the forefoot: Morton neuroma and differential diagnoses. Semin Musculoskelet Radiol 9:175–186 Zanetti M, Strehle JK, Zollinger H et al (1997) Morton neuroma and fluid in the intermetatarsal bursae on MR images of 70 asymptomatic volunteers. Radiology 203:516–520

US-Guided Interventional Procedures

Interventional Procedures

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US-Guided Interventional Procedures Stefano Bianchi and Maria Pia Zamorani

CONTENTS 18.1 General Considerations 891 18.1.1 US-guided Needle Placement 891 18.1.2 Arthrocentesis and Drainage of Soft-Tissue Collections 894 18.1.3 Steroid Injection Procedures 895 18.1.4 Tumor Biopsy 896 18.1.5 Removal of Foreign Bodies 897 18.1.6 US-Guided Regional Anesthesia 898 18.1.7 Treatment of Painful Neuromas 899 18.2 Specific Applications 900 18.2.1 Shoulder 900 18.2.1.1 Glenohumeral Joint Aspiration and Injection 900 18.2.1.2 Subacromial Bursa Steroid Injection 900 18.2.1.3 Percutaneous Treatment of Calcifying Tendinitis 901 18.2.1.4 Percutaneous Aspiration of Paralabral Ganglia 904 18.2.1.5 Acromioclavicular Joint Aspiration and Injection 905 18.2.2 Elbow 906 18.2.3 Wrist and Hand 907 18.2.4 Adult Hip 908 18.2.5 Knee 909 18.2.6 Ankle and Hindfoot 910 18.2.7 Forefoot 913 References

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S. Bianchi, MD Privat-docent, Université de Genève, Consultant Radiologist, Fondation et Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland M. P. Zamorani, MD Unité de Recherche et Dévelopement, Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland

18.1 General Considerations The term “interventional US” refers to a wide and heterogeneous range of invasive procedures performed percutaneously using US guidance. In practice, most of these procedures consist of aspiration of fluid collections and injection of steroids either into joint cavities and tendon sheaths or into the para-articular soft tissues (Adler and Sofka 2003; Cardinal et al. 1997, 1998; Sofka et al. 2001). More complex US-guided procedures, such as biopsies of space-occupying masses and removal of foreign bodies, are usually performed in specialized centers. This chapter describes the basic technique (and the tricks of the trade) to localize the needle under US guidance and to aspirate joint and soft-tissue collections. Specific techniques for intra- and paraarticular injection of corticosteroids are illustrated in specific joints. Finally, some new applications of interventional musculoskeletal US are reported.

18.1.1 US-guided Needle Placement Before starting any interventional procedure, an accurate US examination of the affected body area should be repeated, not only to confirm the expected findings but also to identify the most adequate path of approach. Then, efforts should be made to find the most appropriate and comfortable position for the patient and the examiner. The patient should be kept informed as to why and how the procedure will be conducted. Although the risk is remote, the possibility of complications (e.g., septic arthritis) has always to be taken into consideration and a preliminary disinfection of patient’s skin and instruments is necessary before starting the procedure. In our experience, sterile envelopes for the probe are

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not necessary to maintain the procedure aseptic. When joint aspiration is followed by intra-articular injection of long-acting corticosteroids, the patient should be warned of the possibility of secondary crystalline synovitis, which usually leads to the onset of postprocedural local pain. Local ice and a course of nonsteroidal anti-inflammatory drugs are usually sufficient to treat this mild, self-limiting complication. Regardless of the procedure type, the patient is always required to inform the examiner about the onset of fever or any disturbance persisting for more than 2 or 3 days after the procedure, because these symptoms might be indirect signs of infection. Arthrocentesis of the affected joint and appropriate synovial fluid sampling for culture must be performed immediately when septic arthritis is suspected. After written informed consent has been obtained (O’Dwyer et al. 2003), the patient is invited to remain as relaxed as possible while the procedure is performed: a cooperative patient makes needle placement easier in most cases. Once the patient is seated or has lain down, the puncture site should be accurately disinfected according to established protocols (Baffroy-Fayard et al. 2002). When possible, the skin should be covered with sterile sheath with a hole revealing only the region of interest, to minimize the risk of contamination of the sterile field. After that, the examiner prepares the material using sterile gloves and a surgical mask. It is important to handle syringes and needles out of the patient’s view in order to prevent vagal reactions. Note that these reactions happen more frequently in young sportsmen than in older ladies! In children, the use of a combination of topical anesthetic creams and ethyl chloride spray may be helpful to reduce the discomfort of the injection. Selection of the type and size of the needle basically depends on the expected nature of the fluid to be aspirated and the depth of the target. Highly echogenic infectious collections and sterile mucoid fluid, like that of ganglion cysts, usually require large-bore needles, in some cases even larger than 18 gauge. Remember that needle thickness is measured using the gauge scale: with this scale, the lower the gauge the thicker the needle (e.g., 22 gauge = 0.8 mm diameter; 19 gauge =0.9 mm diameter; 18 gauge = 1.0 mm diameter). For arthrocentesis of deep-seated joints, an adequate length of the needle is an essential requirement. Aspiration and injection of the adult hip, for instance, should be performed using 7–10 cm long spinal needles due to the considerable depth of this joint.

There are two main ways to insert the needle under US-guidance: the indirect technique and the real-time technique. In the former, US is used to establish the puncture site and the depth of the target but not to guide advancement of the needle (Fig. 18.1). For large-sized targets, two perpendicular scans are performed over the lesion: the outer boundaries of the target are marked on the skin with a skin-marking pen; then, the depth of the target is measured with the calipers of the equipment software and annotated. After removal of the probe and rigorous local disinfection, the needle is inserted in the center of the mark and advanced blindly perpendicular to the skin surface up to the distance noted earlier. When the lesion is small, a “paperclip technique” can be helpful (Fig. 18.2). With this technique, an extended paperclip is placed between the probe and the skin. The clip is shifted along the long axis of the probe until its posterior artifact matches up with the center of the target. Then, it is gradually retracted away from the short axis of the probe until it disappears from the field-of-view of the US image. The probe is then removed and the site for needle insertion identified as the point just distal to the extremity of the paperclip still resting on the skin. A needle could be used instead of the paperclip but we noticed that patients are more confident and less anxious when a paperclip is used. The insertion path of the needle is vertical. Using a real-time technique, the probe is placed in close proximity to the puncture site and the needle is advanced under direct US control. Depending on the experience of the examiner, the needle can be aligned with the small side of the transducer during insertion (lateral approach) or may be inserted while keeping the needle shaft and the probe shaft parallel (coaxial approach). In the first case, the examiner may be able to follow the entire shaft of the needle (Fig. 18.3a,b). In the latter case, which requires more experience, the transducer needs to be tilted continuously to view the tip of the needle (Fig. 18.3c,d). One of the essential prerequisites for performing a safe and successful needle insertion under US guidance is an adequate technique for visualization of the needle tip (Saker et al. 1997). In its long axis, the metallic needle appears at US as a bright straight echo with posterior reverberation or a comet-tail artifact. Needle detection essentially depends on the needle size and the angle of incidence of the US beam (Fig. 18.4). One should attempt to maintain the needle axis as perpendicular as possible to the US beam. In fact, similar to other specular reflectors, needle visualization progressively improves as the

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incidence of US beam approaches 90° and worsens rapidly as the angle increases from 90° toward 180° or decreases from 90° toward 0° (Fig. 18.5). When the needle cannot be identified with certainty on static images, real-time scanning moving it quickly into and out of the puncture site may enhance the confidence of the examiner in following the needle’s progress. Injection of a small amount of lidocaine or air bubbles can be useful to confirm the position of the needle tip. For aspiration purposes, special handle devices can increase the traction force on the syringe plunger. The indirect technique is easier to perform as it does not require coordination between needle insertion and probe handling. On the other hand, though real-time guidance requires more experience it allows a more precise assessment of the destination of the needle in the intended target. Biopsy guides can be installed on the probe to help guide the procedure. However, these guides make the procedure less flexible compared with the freehand technique, require more time for disinfection and limit the needle path available. Whatever the technique used, it is essential to accurately examine the soft-tissue structures along the needle path in order to avoid incidental damage to nerves, tendons or vessels. In general, the shortest path to the lesion is the most adequate. The patient will complain of little or no discomfort if the correct technique is used.

18.1.2 Arthrocentesis and Drainage of Soft-Tissue Collections When substantial fluid is found within a symptomatic joint, the role of arthrocentesis is twofold: diagnostic and therapeutic (Moskowitz 1982). Synovial fluid analysis can lead to a definite diagnosis in infectious conditions, gout and chondrocalcinosis. In these instances, Gram stain, leucocyte count, fluid culture and microcrystal analysis give specific information and should be routinely performed in patients with monoarthritis. Initial inspection of the synovial fluid can be performed soon after the procedure. The appearance of fluid is variable depending on the underlying disease. In normal conditions, it is markedly viscous and light yellow in color. Inflammatory fluid tends to be less thick and more watery. On the other hand, fluid present in degenerative conditions, such as osteoarthritis, demonstrates only a minimal decrease in viscosity. Detection of intra-articular blood suggests trauma, pigmented villonodular synovitis or coagulation disorders. Fat droplets contained in a bloody effusion indicate lipohemarthrosis, which is consistent with an intra-articular fracture. Compared with the blind technique, US guidance is particularly useful in obese patients or in the case of poorly accessible joints, such as the hip. Because fluid is expected

30°

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90°

a

b

c

d

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Fig. 18.5a–f. US detection of metallic needles inserted with different angles relative to the US beam. In vitro experimental setting using a turkey breast. a–c Schematic drawing and d–f corresponding 15–7 MHz US images obtained at a,d 90°, b,e 45° and c,f 30° incidence. The best visualization of both shaft (arrows) and tip (arrowhead) of the needle is reached at 90°. With increasing obliquity, the needle becomes less evident and detection of its tip uncertain


to be dense, relatively thick (18–20 gauge) needles should be considered for aspiration. From the clinical point of view, drainage of large effusions allows decompression of the joint cavity and subsequent relief of local pain. Symptomatic cysts can also be drained. In Baker cysts, the one-way mechanism that allows fluid to migrate from the knee cavity into the cyst can be responsible for increased intracystic pressure and pain. In these instances, fluid evacuation is best performed using a posterior approach. Para-articular collections are most often secondary to trauma and blood accumulation either inside or among muscles, in the fascial planes and in the subcutaneous tissue. The usefulness of evacuating hematomas is still debated. Some clinicians believe they should be aspirated to obtain prompt recovery and reduce the risk of fibrous adhesions; others consider these lesions as self-healing conditions and believe that aspiration is an unnecessary procedure leading to an increased risk of secondary infections. In this regard we believe sonologists should act in close cooperation with their referring clinicians without performing invasive procedures unless specifically asked.

18.1.3 Steroid Injection Procedures Injections of mixtures of lidocaine and steroid within articular cavities and para-articular tissues are routinely performed to treat a variety of joint, tendon, bursal and nerve disorders. Cautious and thoughtfully used local therapy is a valuable adjunct to systemic therapeutic programs for treatment of arthritis and often allows reduction of the overall dose of systemic drugs. The efficacy of local therapy depends not only on the amount and type of injected drugs but also on the appropriate space or structure into which the solution is injected. A small dose of steroids instilled within an inflamed bursa is far more effective than a larger dose injected in the adjacent tissues and has fewer side-effects. In many cases, intra-articular injections can be guided by palpation of the bony landmarks and do not require imaging guidance. When injecting large synovial joints, such as the knee, an expert clinician does not usually have difficulties placing the needle appropriately. Small or deep joints and tendon sheaths are more difficult to inject blindly. This is particularly relevant when aggressive drugs, such as immunosuppressive agents or radioactive

materials, are administered. In these cases, definite proof of the correct positioning of the needle tip is critical to avoid incidental para-articular injections resulting in necrosis and resorption of subcutaneous tissue. US allows precise needle positioning within these small spaces with millimeter accuracy, thus reducing injuries to the adjacent structures and side-effects related to the extra-articular instillation of medicaments, and shortens the overall time of the procedure. While injecting tendon sheath and para-articular bursae, care should be taken not to instil corticosteroids within the tendon substance as these drugs may lead to tendon necrosis and rupture. Although fluoroscopy, CT and MR imaging can be used as an alternative to US, these techniques are time-consuming, less handy, and involve radiation exposure or require special needles. In general, the injection within bursae, tendon sheaths and joint cavities consists of a mixture of corticosteroid and local anesthetic. Because of the greater risk of infection than with the aspiration procedure, injection of steroids into a sterile joint should be done extremely carefully. Long-acting steroids are the most commonly used because of their slow local release and prolonged activity. Anesthetics are usually added to obtain relief of local pain during the procedure and to treat reactions to steroid crystals. They can be omitted in elderly patients to avoid the risk of side-reactions. Multi-dose vials must be avoided because they can be contaminated. We prefer to use a combination of 30-40 mg triamcinolone esacetonide (Kenalog) or triamcinolone acetonide (Kenacort Retard) mixed with 1% lidocaine hydrochloride (Xylocaine). For superficial injections, where the risk of subcutaneous leak is not negligible, depomedrone (Depomedrol) should replace triamcinolone as the corticosteroid of choice. Using this latter drug, the risk of inducing necrosis of the subcutaneous tissue and subsequent permanent deformities of the skin surface seems to be less. In those instances in which the examiner is less certain about the correct needle placement, a preliminary injection of a small amount of local anesthetic can be helpful to distend the cavity and confirm the adequate location of the needle tip. In general, the injection should be stopped when unexpected resistance is encountered. This often occurs when the needle pushes against the bone or is infixed within dense structures, such as tendons or aponeurotic tissue. In our experience, aspiration before injection may not be so useful to ensure adequate placement of the needle inside a synovial joint because dense

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fluid or synovial proliferation may obstruct the needle cavity. In most cases, diffusion of the drug into the joint can be appreciated with US as a hyperechoic filling similar to the effect of US contrast agents (Fig. 18.6). At least in part, this effect may be explained by the presence of air bubbles created by cavitation of the fluid injected through the needle. In an experimental setting, some authors have found this effect related to differences in acoustic impedance and immiscibility of the mixture of steroid and anesthetic (Luchs et al. 2004). After steroid injection, the syringe should be flushed with anesthetics or saline to avoid spreading of steroid along the needle path when retracting the needle. Relief can be immediate and a remarkable improvement in joint motion can also be appreciated. At the end of the procedure, however, the examiner should recommend the patient to keep the joint relatively immobile to maximize the therapeutic effect of the injected drugs and reduce their possible diffusion into the adjacent tissues. In cases of prolonged manipulations or repeated punctures, a 7 day course of a broad spectrum oral antibiotic can be given to reduce the possible risk of infection. Generally speaking, US-guided procedures for the musculoskeletal system are quite simple to carry out but – like other percutaneous procedures – they include a definite, although minimal, risk of infection and should not be performed in the active phases of an infection or in patients affected

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by coagulopathy. Relative contraindications to the use of corticosteroid are diabetes mellitus, arterial hypertension and glaucoma. Allergy to lidocaine is very rare and can be ruled out by asking the patient about possible side-effects of dental anesthesia. Worsening of local symptoms may be secondary to the administration of long-acting steroids and can be related to needle trauma and microcrystalline synovitis. Flushing can be experienced by the patient if multiple injections are performed in a short time interval, as a result of systemic effects of the injected steroids. Patches of depigmented skin at the injection site and local resorption of fat are frequent complications when steroid are incidentally injected within the subcutaneous tissue. More severe problems are rare. They include devastating infections following steroid administration and tendon tears related to intratendinous steroid injection (e.g., preinsertional Achilles tendon tear caused by unsuccessful steroid injection in the retrocalcaneal bursa). Injection of long acting steroids into joints affected by osteonecrosis should be avoided as they can worsen the healing process.

18.1.4 Tumor Biopsy US-guided percutaneous biopsies of soft-tissue masses should be performed in specialized centers by skilled sonologists working in close cooperation

Fig. 18.6a–d. US-guided injection of anesthetic/steroid solution inside the subacromial subdeltoid bursa. Sagittal 12–5 MHz US images obtained over the dependent lateral pouch of the bursa. a The bursa is distended by anechoic effusion (asterisks). b The needle (arrow) is advanced under US control until its tip (void arrowhead) penetrates the bursal cavity. c During injection, the steroid/anesthetic mixture appears as a cloud-like hyperechoic area (white arrowhead) filling the bursal cavity. d Afterwards, the hyperechoic solution (arrowhead) migrates upward for gravity. Hs, humeral shaft


with tumor surgeons (Rubens et al. 1997). Before performing a biopsy, careful scanning of the area of interest should be performed in order to plan the best access route and select those areas of the lesion which are more suitable for sampling. In particular, accurate assessment of space compartments traversed by the needle are the mainstays for obtaining diagnostic material and avoiding unnecessary destructive surgery. In sarcomas, the risk of seeding the tumor along the needle tract is high. An incorrect approach may require more aggressive surgery, including the en-bloc removal of the tumor along with the needle path of the biopsy. The choice between large-core biopsy needles (14–18 gauge), such as Tru-cut types or automated biopsy guns, or fine needles (18–22 gauge) mainly depends on the clinical data and availability of an experienced cytologist (Saifuddin et al. 2000; Torriani et al. 2002). Color Doppler imaging may be useful to avoid large vessels or highly vascularized areas within the tumor tissue (high-velocity flow), thereby reducing the risk or bleeding. It can also identify regions of tumor neovasculature (lowvelocity flow), which are areas of viable tissue as opposed to those of necrotic tissue. These areas are the best target for the biopsy. Because central areas of liquefaction often reflect necrosis, they should be avoided. US has also been used as a guidance technique for performing biopsies of bone tumors (GilSanchez et al. 2001). We believe the main indications of US over CT to guide bone biopsies are related to destructive lytic lesions with an associated soft-tissue mass or lytic lesions with a broken cortex where the tumor tissue can be visualized through the cortical defect. When the lesion is subperiosteal or cortical in location, it may be identified with US even if it does not destroy the bony cortex. Such lesions can be considered for US-guided biopsy too. Combined fine needle aspiration cytology (22 gauge) and core biopsy (14–18 gauge) obtained with a Tru-cut type automatic device is recommended to achieve better diagnostic yield. Preliminary sedation of the patient and local anesthesia of the periosteum are needed in lesions with an intact cortical shell due to the exquisite sensitivity of the bone envelope. The coaxial approach using a free-hand technique seems the most appropriate to penetrate small lesions or when the needle has to be screwed into the bone. As regards the needle type, one should remember that the results of cytologic samples are, in general, less specific than those of core biopsy. In addition,

biopsies from metastatic bone tumors more often allow adequate material to be obtained than do biopsies from primary bone tumors (Civardi et al. 1994). In a recent series based on a wide range of bone lesions, a successful biopsy diagnosis guided by US was achieved in 92% of cases (Gil-Sanchez et al. 2001). The main difficulties in performing skeletal biopsies with US guidance are represented by deep-seated lesions (i.e., pelvis bones, vertebral bodies), sclerotic tumors and those that do not alter the hyperechoic bony cortex (Gil-Sanchez et al. 2001).

18.1.5 Removal of Foreign Bodies US is able to detect and assess a variety of foreign bodies of different shapes and material composition in an in vitro and in vivo setting (Turner et al. 1997). US-assisted removal of superficial foreign bodies has been described by several authors (Shiels et al. 1990; Bradley et al. 1992; Turner et al. 1997). Because of the composition of the fragment, metallic splinters and gravel are easily removed under US guidance (Fig. 18.7). On the other hand, removal of pieces of glass and wood require patience and meticulous technique, especially when these foreign bodies are embedded in hypoechoic granulation tissue. The procedure may be difficult to perform in some body areas, such as the web spaces. A sterilized set of surgical instruments, including Mosquito, Kelly, Kocker and Splinter forceps, is needed. The position of the most superficial end of the foreign body is marked and a skin incision is made to allow the instrument to enter the soft tissues and proceed toward the foreign body. Care should be taken to ensure an adequate incision width to allow extraction of the fragment without significant injury to adjacent soft tissues. The procedure is easily and quickly accomplished if the examiner handles the probe and the grasping instrument simultaneously (Shiels et al. 1990). Like any other skill, it is operator-dependent and requires appropriate training. For this reason, we recommend sonologists to acquire practice by inserting foreign bodies into chicken thighs or turkey breasts in an attempt to simulate the tissue interfaces present in human tissues. Recently, the use of US for localization and removal of nonpalpable subcutaneous contraceptive implants has also been reported (Nelson and Sinow 1998; Amann et al. 2003).

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Fig. 18.7a–f. US-guided foreign body removal. A 4 mm metallic fragment was retained in the subcutaneous tissue of the middle third of the forearm in an ironmonger. a 12–5 MHz US identifies the fragment (arrow) based on its hyperechoic appearance and posterior acoustic shadowing. b,c Following a small skin incision, a forceps is inserted in the soft tissues and guided toward the fragment in real time under US control. After catching hold of the foreign body, the forceps rotates it (curved arrows) before extraction to make the fragment free from adhesions. d Photograph shows the small skin incision required for extracting the foreign body. e Photograph of the removed metallic fragment (arrow). Note its small size in relation to a millimeter scale. f Mosquito forceps used in this case

18.1.6 US-Guided Regional Anesthesia The use of US guidance for regional anesthesia is gaining increasing popularity among anesthetists not only for performing procedures in locations with complex anatomy or that are difficult to reach blindly, but also for carrying out anesthetic blocks at common sites to better ensure that the needle is advanced as close as possible to the nerve bundles and to avoid unintended complications, such as the inadvertent puncture of organs or vessels. In the upper limb, brachial plexus anesthesia can be performed in the interscalenic, supraclavicular, infraclavicular and axillary regions depending on the level of the block required. With the same scanning technique described for imaging brachial plexus nerves (see Chapter 6), US can guide the procedure successfully in each of these locations with significant advantages over the blind technique. A detailed description of the individual techniques to induce complete and subtotal blocks of brachial plexus nerves is beyond the scope of this chapter. It should be pointed out, however, that US has proved to be a very efficient tool in this field. In the interscalenic region, for instance, US has a reported success

rate of 98% compared with 77% for the nonguided technique (Jandrasits et al. 1998); in the supraclavicular region, where the nerves course adjacent to the subclavian artery, the success rate of US-guided technique is 95% versus 72% for the nonguided technique (Kapral et al. 1994; Moorthy et al. 1991); in the infraclavicular and axillary regions, the overall success of the procedure was estimated at approximately 95% (Kapral et al. 1994; Ootaki et al. 2000). In the lower limb, US guidance is described for psoas compartment block (Kirchmair et al. 2002), pudendal nerve block in the gluteal region (Kovacs et al. 2001) and three-in-one block of the inguinal region, involving the femoral, the lateral femoral cutaneous and the obturator nerves (Marhofer et al. 1998, 2000). Psoas puncture is obtained with a posterior approach at the L2–L3 and L4–L5 levels. The main role of US guidance is to avoid the inadvertent puncture of the kidney. To obtain pudendal nerve block, the patient is placed prone and the needle is advanced in the area of the ischiatic spine and the sacrospinous ligament. The pudendal artery is the main landmark to identify the nerve, which courses lateral to it. For three-in-one block, the needle is inserted distal to the inguinal ligament and advanced as close as possible to the femoral


nerve within the lacuna musculorum. The lateral spreading of the anesthetic indirectly reaches the lateral femoral cutaneous (lateral) and the obturator (medial) nerve.

18.1.7 Treatment of Painful Neuromas Amputation stump neuromas are a frequent cause of debilitating pain. They derive from transection of the nerve fascicles with disorganized proliferation of Schwann cells and axons at the lesion site in an attempt to restore the continuity of the nerve. Neuromas can be painless or can lead to pain that may not respond to conservative management. In painful cases, treatment may be problematic due to the high recurrence rates and long-term relapse of refractory local pain. In this field, the range of therapeutic options is wide, including surgical resection, implantation into muscle or bone, capping with inert material, cauterization, cryosurgery, steroids, phenol and alcohol injections (Wu and Chiu 1999). US-guided injection of steroids has been used to treat amputation stump neuromas (Fig. 18.8) (Ernberg et al. 2003). Steroids act by promoting reduction of local inflammatory response and loosening of the scarring tissue around the neuroma. Very thin (25 gauge) needles and a mixture of long-acting steroids and anesthetics (like those used to inject joints) enable the procedure to be carried out successfully (Ernberg et al. 2003). Before administration of steroids, it is advisable to minimize pain by anesthetizing the needle path and the tissues surrounding the neuroma. The

amount of steroid-anesthetic solution should be very small to avoid drug leakage into the proximity of the neuroma with subsequent abnormal pigmentation and thinning of the skin and subcutaneous fatty atrophy. Repeated injections may be required with time. The response to steroid therapy may assume biphasic characteristics, with immediate relief of symptoms related to the short-term action of anesthetics, recurrence of pain after a few days and late (3–4 months) subsidence of symptoms due to the long-term action of the steroids. Recently, US-guided phenol injection has been used as an alternative to steroid therapy in the treatment of painful stump neuromas (Gruber et al. 2004). This drug induces intraneural chemical axonotmesis, with severe demyelination, axonal degeneration, edema and hemorrhage leading to complete derangement of the nerve structure (Westerlund et al. 2001). Phenol injection is performed by means of a 21 gauge needle advanced to the involved nerve, slightly proximal to the stump neuroma. First, 15 ml of lidocaine is administered around the nerve proximal to the neuroma. Then, the needle is advanced into the nerve proximal to the neuroma under real-time control and used to inject 0.3–1 ml of 80% phenol solution consisting of 8.0 g of crystalline phenol in 2.0 mg of distilled water (Gruber et al. 2004). Only a minority of patients with recurrent neuroma pain require a second treatment (Gruber et al. 2004). Using this technique, relief of pain seems to be long-lasting. Both steroid and phenol injection need, however, further experience on larger series of patients to observe long-term results and monitor them for success rates and possible complications.

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b Fig. 18.8a,b. US-guided steroid injection for treatment of painful stump neuroma of the tibial nerve. The patient had surgical amputation of the lower extremity. a Sagittal 12–5 MHz US image showing the swollen sciatic nerve (arrowheads) and the needle (arrows) positioned within it. b After infiltration, transverse a 12–5 MHz US image reveals foci of increased echogenicity (asterisk) within the nerve (arrowheads), representing bubbles and the steroid/anesthetic mixture. The patient remained free of pain at 1 year follow-up

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18.2 Specific Applications A series of procedures which are safe and reasonably simple to perform in the radiology room will be briefly described for each individual body area, including the shoulder, the elbow, the wrist and hand, the hip, the knee, the ankle and hindfoot and the forefoot.

18.2.1 Shoulder A variety of interventional procedures in the shoulder region can be performed percutaneously under US guidance. The purpose of these procedures is twofold: to inject contrast medium into the glenohumeral joint and to drain fluid collections or inject therapeutic agents.

18.2.1.1 Glenohumeral Joint Aspiration and Injection A variety of imaging-guided methods are described to support the injection of contrast material into the glenohumeral joint (DeMouy et al. 1997; Trattnig et al. 1997). Traditional fluoroscopy allows real-time visualization of the needle and the acquisition of image frames during the early phases of injection (particularly useful to display subtle pathologic changes) and at different degrees of arm rotation (Farmer and Hughes 2002). The main limitation of fluoroscopic guidance is related to the use of ionizing radiations (both patient and examiner are exposed). Although the anterior access is most often used with the patient supine on the examination bed, the posterior approach has advantages in cases of suspected anterior instability to avoid leakage of contrast material that can interfere with image interpretation (Farmer and Hughes 2002). Injection under real-time US control offers several advantages over fluoroscopy (Cicak et al. 1992; Valls and Melloni 1997; Vireola 2002; Zwar et al. 2004). The posterior approach is preferred with this modality. The injection technique should be tailored for each individual case. A semiprone position of the patient with the affected shoulder uppermost (to keep the needle away from the patient’s view) is used to puncture the posterior glenohumeral recess (Zwar et al. 2004). The probe is aligned in the long axis of the

myotendinous junction of the infraspinatus and the needle (20–22 spinal needle) is inserted and directed toward the joint space with an oblique course from lateral to medial (Fig. 18.9). The path of the needle is adjusted to reach the recess deep to the free margin of the glenoid labrum and tangential to the curvature of the humeral head (Zwar et al. 2004). In shoulder joint injection performed with the patient seated, external rotation of the arm relieves pressure of the infraspinatus and teres minor against the posterior capsule, thus leading to a secondary increase in the amount of fluid located inside the posterior recess. In routine clinical practice, US-guided arthrocentesis is performed if sampling of fluid is required to demonstrate crystals or bacteria as well as to obtain correct needle placement before steroid injection. Initially, a systematic US examination of the shoulder should be performed to assess the overall state of the joint and the para-articular structures. The technique for US-guided aspiration of effusions in the posterior recess is similar to that described for injection. Because the sheath of the long head of the biceps tendon communicates with the glenohumeral joint, a sample of joint fluid can also be obtained from it (Fig. 18.10). An anterolateral approach can be used with the needle advanced in the transverse plane, while keeping the patient supine with the head rotated toward the opposite side. The advisability of corticosteroid injection into the glenohumeral joint of patients with rotator cuff pathology is debated. Some authors prefer not to inject the drug in patients with partial-thickness tears of the rotator cuff to prevent progression of tendon damage. Others believe that injection inside the subacromial bursa can be rather safe in these circumstances.

18.2.1.2 Subacromial Bursa Steroid Injection

As described in Chapter 6, anterosuperior impingement derives from chronic friction of the bursal aspect of the supraspinatus tendon against the undersurface of the acromion. The subacromial subdeltoid bursa reduces local attrition and improves gliding of this tendon during arm abduction. In subacromial impingement, the bursa has thickened walls and may contain fluid as a result of chronic inflammation. Intrabursal injection can be performed for both diagnostic and therapeutic purposes. When clinical findings are inconclusive and the diagnosis of anterolateral impingement is uncer-

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more closely correlates with the site of shoulder pain (Aina et al. 2001). Intrabursal calcific deposits must not be treated as they undergo spontaneous resolution. The procedure can be performed with the patient seated, keeping the arm extended or in a neutral position, or supine. This latter position has the advantage of treating calcified deposits in the subscapularis tendon and must be used in patients with previous vagal reaction during steroid injections. After identifying and localizing the calcified deposit at US, three main techniques can be used to puncture the calcifications. The first derives from the fluoroscopic technique as it makes use of two large-bore (16–18 gauge) needles (Fig. 18.13a) (Farin et al. 1995, 1996). Under US guidance, local anesthesia is administered by injecting lidocaine within the subacromial subdeltoid bursa and along the bursal surface of the affected tendon (Figs. 18.14a, 18.15a). The same needle used for anesthesia is then advanced within the core of the calcification (Figs. 18.14b, 18.15b). With a second, usually thinner needle (18–20 gauge), puncture of

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the calcification is achieved, again under real-time observation, in an attempt to fragment the calcific deposit (Figs. 18.14c, 18.15c). Then, a solution containing saline and 1% lidocaine is injected through one needle and aspirated by the other needle in turn – the so-called aspiration irrigation technique – until most of the calcium is evacuated (Fig. 18.14d). It is important not to attempt to aspirate the calcium when the needle is fixed within the calcification because, in this instance, the bore of the needle will be blocked by the fragments. Rotation of the needle to grind the calcification may be helpful. A sequence of short repeated pressures and releases with the syringe plunger gives better results, leading the lidocaine solution to flow back into the syringe dragging the calcium with it. During this procedure, a cloudy whitish fluid is extracted and tends to deposit in the dependent portion of the syringe by gravity (Fig. 18.13b–d). At the same time, a fluid-filled hypoechoic cavity appears in the calcification, expanding when the fluid is pushed forward and reducing in size when the pressure ceases (Fig. 18.13c–e). The

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Fig. 18.10a–d. US-guided shoulder arthrocentesis obtained by an anterior approach. a Schematic drawing of a transverse view through the shoulder demonstrates the needle access to reach the biceps tendon sheath. This approach is less invasive than the posterior, because the needle path is not required to perforate the rotator cuff. b Transverse 12–5 MHz US image obtained over the anterior aspect of the shoulder, just caudal to the bicipital groove, demonstrates the sheath of the biceps tendon (Bt) distended by anechoic fluid (asterisk). c Under real-time US guidance, a 22 gauge needle (arrows) is inserted within the biceps sheath by a lateral approach. Observe the needle tip (arrowhead) placed in the most superficial part of the recess. d After USguided injection of steroid/anesthetic mixture, the recess becomes diffusely hyperechoic (arrowheads)

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caused by widespread local diffusion of the calcific material. Whatever the technique, US-guided percutaneous treatment of calcifying tendinitis provides longstanding clinical success rates varying from 60% to 74% of patients in terms of shoulder pain and disability (Farin et al. 1996; Aina et al. 2001). Some general considerations merit attention. First, only painful calcifications must be treated: finding calcification within a rotator cuff tendon does not automatically mean that shoulder pain is related to it. A typical mistake is to treat calcifying tendinitis in patients with shoulder pain derived from other causes, including cervical spine disease. Remember that most calcifications are asymptomatic. Second, the best results are achieved on large calcifications. Treatment of clusters of smaller calcifications is almost invariably unsuccessful. Third, the goal of the procedure is to disrupt the calcification and to remove some but not all calcific material (Fig. 18.14f). Too many needle insertions to remove as much as possible of the calcification should be avoided to prevent tendon tears. Once ruptured, calcification almost invariably evolves toward resorption, and shoulder pain and disability improve in most cases (Fig. 18.16).

“lavage” should be suspended when no further calcium is extracted. Some syringe exchanges are necessary to keep the solution clear during the procedure. The second technique is a single-needle procedure which has been developed with the aim of minimizing potential damage to the tendon by multiple tracks of large-bore needles (Aina et al. 2001). After local anesthesia (by the same procedure described previously), one 22–25 gauge needle (depending on the size of calcification) is inserted with a horizontal course inside the calcification during real-time US scanning in the sagittal plane. Once positioned, gentle rotational movements of the needle followed by repetitive injection and aspiration of lidocaine are performed to disrupt the bulk of the calcification and aspirate part of the calcific material. The aspiration of semiliquid (“toothpaste”) deposits is the most successful as the puncture of the high-pressure calcium-containing cavity promotes passage of fluid and microcrystals within the syringe. In other cases, part of the calcification may persist in tendons at the end of the procedure. This does not represent a failure of the treatment because residual calcium tends to undergo spontaneous resorption over the months following the procedure. The third technique consists of multiple fine-needle punctures of the calcification without aspiration, and injection of a mixture of steroid and lidocaine in the subacromial subdeltoid bursa. Regardless of the technique used, at the end of the procedure a mixture of corticosteroids and lidocaine is injected into the subacromial bursa (Figs. 18.14e, 18.15f). Steroid injection helps to treat and prevent crystal-induced inflammation

18.2.1.4 Percutaneous Aspiration of Paralabral Ganglia

Paralabral ganglia derive from tears of the glenoid labrum and appear at US as multilobulated cystic masses with thin echogenic walls (Leitschuh et al.

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Fig. 18.13a–d. US-guided treatment of calcifying tendinitis: aspiration irrigation technique. a Photograph showing double needle insertion for treatment of a calcification in the supraspinatus tendon. b–d Photographs demonstrate the results of aspiration in three different patients. Note calcium fragments collected in a syringe (b) and over a gauze (c). In d, whitish calcium powder accumulates in the dependent portion of the syringe. (Courtesy of Dr. Giovanni Serafini, Pietra Ligure, Italy)

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Fig. 18.15a–f. US-guided treatment of calcifying tendinitis: aspiration irrigation technique. Series of transverse 12–5 MHz US images obtained over the anterior aspect of the shoulder illustrate the two-needle procedure to treat a large type III calcification in the subscapularis tendon. a A first needle (arrowheads) is directed toward the subacromial subdeltoid bursa. Note the relationship of the calcific deposit (star) with the lesser tuberosity (LT) and the coracoid (C). b After injection of lidocaine, the bursa appears distended by fluid (curved arrow) and the needle is redirected toward the calcification. c–e The first (white arrowheads) and the second (open arrowheads) needle are activated in turn to inject and aspirate the solution of saline and lidocaine. During this process, a fluid-filled hypoechoic cavity (asterisk) appears in the calcification (straight arrows), expanding when the fluid is pushed forward (c,d) and reducing in size when the pressure ceases (e). In d, note the bursa (curved arow) partially distended with fluid. f At the end of the procedure, lidocaine is injected into the bursa by the first needle (white arrowheads). Note the residual calcium in the tendon. (Courtesy of Dr. Giovanni Serafini, Pietra Ligure, Italy)

focal collections of fluid around the joint. Using a superior approach, an indirect method is usually preferred. The joint space is first localized by means of coronal and sagittal planes and the intersection of the two lines representing the position of the probe is marked on the skin. After local anesthesia and accurate asepsis, the needle is then inserted into the joint blindly (Widman et al. 2001). Alternatively, when the examiner wants to follow the needle insertion under real-time control, the probe should be placed in the sagittal plane over the joint. Using this plane, the acromioclavicular joint can be easily identified by shifting the probe from the head of the clavicle toward lateral. When the clavicle disappears, the transducer is positioned just over the joint. Further lateral movement brings the acromion into view and may be helpful to confirm the correct position of the transducer. In this position, the needle is inserted at 90° to the transducer from the anterior aspect of the joint. Due to the small size of the acromioclavicular joint cavity, no more than 0.5–1 ml of anesthetic/steroid solution can be injected.

18.2.2 Elbow The best path to puncture the elbow joint is the lateral approach through the radiocapitellar joint, which is somewhat similar to that selected for routine arthrography. When an effusion is present, a posterior injection path can also be used by inserting the needle at the medial or lateral side of the triceps tendon keeping the elbow flexed at 90°. The main landmark for lateral access is the groove between the humerus and the olecranon. Medial access requires careful technique to avoid incidental damage to the ulnar nerve that courses along the internal aspect of the medial head of the triceps. We prefer to use an indirect technique to inject the elbow joint by localizing the site for injection at US and then inserting the needle blindly. For this purpose, a 21–22 gauge needle is suitable. When injecting the elbow joint, remember it can accept approximately 10 ml of anesthetic/steroid solution. In cases of suspected intra-articular loose bodies, US can be used to distend the joint with


saline (US arthrography) or gadolinium (preceding MR arthrography). Tendinopathy or enthesopathy at the insertions of the common extensor tendon into the lateral epicondyle (lateral epicondylitis) and the common flexor tendon into the medial epicondyle (epitrochleitis) are common causes of elbow pain. In cases of “recalcitrant” symptoms that have failed to respond to physiotherapy and anti-inflammatory drugs, these conditions can be treated by steroid injections. Due to their superficial position, these tendons are easily palpable and real-time US guidance is rarely required for needle placement. US is an accurate means of locating the exact site of pathologic changes and marking the skin for the injection. Special care should be taken not to inject steroids into the tendon substance and to avoid steroid leakage into the subcutaneous tissue that may result in depigmented skin patches and subcutaneous fatty atrophy. The elbow position is the same as used for imaging (i.e., halfway between supination and pronation for the extensor tendon; hypersupinated for the common flexor tendon). A 21–22 gauge needle is used to inject approximately 1–2 ml of 30% depomedrone and 1% lidocaine. The needle should be inserted at the proximal edge of the probe and advanced beyond the deep surface of the tendon insertion, in proximity to the radiocapitellar joint. An alternative procedure that may avoid the use of corticosteroids is so-called “dry needling”; this consists of multiple passages with the needle in the tendon substance (needle tenotomy) to accelerate healing by combining re-injury with a rehabilitation program (McShane et al. 2006). Intratendinous autologous blood injection has also been proposed with the same aim (Connell et al. 2006; Suresh et al. 2006). In the anterior elbow, cubital bursitis and ganglion cysts are definite indications for US-guided injections (Fig. 18.18). Because the brachial vessels

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and the median and radial nerves cross the anterior aspect of the joint, these procedures may benefit from real-time imaging guidance. Depending on the relationship of the target with the surrounding structures, transverse or sagittal planes are the most useful to direct the needle. Although olecranon bursitis is evident on clinical grounds, US can identify the nature of its content when a diagnostic or therapeutic puncture is planned. In fact, distinguishing a bursa filled with hypertrophied synovium from a bursa containing fluid may be difficult at physical examination. In the former case, US can direct the needle into the small amounts of fluid intervening between the synovium to increase the success rate of the procedure.

18.2.3 Wrist and Hand Arthrocentesis of the small joints of the wrist and hand is almost invariably performed by means of a dorsal approach. Before the procedure, US is performed to identify which joint is involved. Owing to the small size of the wrist and hand joints and their close proximity to the carpal joints, physical examination is, for the most part, unable to assess the exact location of the involved joint. Once localized, the effusion is aspirated using an indirect technique after skin marking. Small-footprint transducers may allow real-time puncture. Physical examination of the dorsal wrist is often unable to distinguish effusion in the joint recesses from hypertrophied synovium distending the extensor tendon sheaths. Such differentiation is essential because lack of fluid makes the procedure unnecessary, and carries with it the risk of infection. In larger joints, such as the distal radioulnar and radiocarpal joints, the amount of injected solution is approximately 1–2 ml. Small joints of the hand and fingers accept only 0.5–1 ml.

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Fig. 18.16a–c. US-guided treatment of calcifying tendinitis: radiographic results. Series of anteroposterior standard radiographs of the shoulder obtained a before, b soon after the procedure and c 2 months later in a patient with a painful calcification (arrow) in the supraspinatus tendon. Although partial removal of the calcification is observed initially, most of the calcification then dissolves with time. (Courtesy of Dr. Giovanni Serafini, Pietra Ligure, Italy)

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In the wrist, US is accurate for guiding the injection of steroids within the compartments of the extensor tendons in cases of tendinitis, such as de Quervain disease. Thin needles (25 gauge) can make the procedure painless and the subsequent steroid injection safe. The needle should be inserted using a shallow angle according to the long axis of the tendon. Before needle insertion, attention should be directed at orienting the bevel of the needle toward the tendon in order to reduce the risk of tendon puncture. In de Quervain disease, the examiner should always check whether an accessory vertical septum separating the abductor pollicis longus from the extensor pollicis brevis is present. If it is, the inflammatory process may selectively involve one half of the compartment only (see Chapter 10). In this case, the injection should be directed to the involved part of the tunnel to obtain successful treatment. Similar to ganglia at other sites, symptomatic ganglia of the wrist and hand can be aspirated and injected under US guidance (Breidahl and Adler 1996). The real mechanism by which long-acting steroids provide benefit in the treatment of ganglion cysts is still debated; interference with chronic inflammation seems to be the most likely. The main advantages of US guidance are in the treatment of small nonpalpable ganglia (e.g., cysts arising from the dorsal wrist in the area around the scapholunate ligament), and in its ability to estimate the volume of therapeutic agent to inject (Breidahl and Adler 1996). Following corticosteroid injection, ganglia may resolve completely or may undergo a reduction in size with relief of symptoms (Breidahl and Adler 1996). The carpal tunnel is almost invariably injected blindly after palpation of the flexor carpi radialis tendon, which is a good landmark to assess the position of the median nerve. Transverse and longitudinal planes may be helpful to confirm the adequate location of the needle tip relative to the flexor tendon. Because the median nerve is usually displaced from its location after release of the transverse carpal ligament, local injections to treat postsurgical recurrences are difficult without imaging guidance. In these cases, US may help to determine the position of the nerve and to mark the skin in order to ensure a safe local injection.

18.2.4 Adult Hip Coxofemoral joint arthrocentesis and aspiration of synovial fluid for laboratory analysis is a mainstay for differentiating septic arthritis from other

joint diseases, such as seropositive and seronegative arthritides, crystal deposition disease and other disorders. Because of the nonspecific appearance of septic effusion at US, aspiration followed by Gram stain and culture should always be obtained if the clinical picture suggests local infection. If the joint is distended, it can be punctured under real-time guidance, placing the transducer on the anterior femoral neck in the sagittal plane with the patient supine keeping the hip in external rotation. The best point for needle insertion is lateral to the transducer. Care should be taken to avoid the neurovascular bundle of the groin, such as the femoral artery and the femoral nerve, which are located more medially. The needle is advanced oblique to the probe toward the anterior synovial recess. The psoas muscle needs to be traversed by the needle. Alternatively, the indirect modality can be used by locating the site of maximal distension of the anterior recess, marking the skin over it with the technique described previously and inserting the needle until bone contact. A 21–22 gauge spinal needle is used to inject approximately 4–5 ml of anesthetic/steroid solution. The sacroiliac joints can be examined with US using a posterior access. Color Doppler imaging has proved able to diagnose active sacroiliitis by depicting hyperemia inside and around the joint (Arslan et al. 1999). Intra-articular steroid injection is an effective therapy in patients with ankylosing spondylitis or degenerative joint disease, providing substantial clinical improvement. To avoid the radiation exposure given by fluoroscopy and CT, US has recently been proposed as an alternative means to guide sacroiliac joint injections (Pekkafali et al. 2003). The procedure, which requires a definite learning curve, is performed with the patient prone on the fluoroscopic table. At US, the sacroiliac joint appears as a 4–5 mm wide hypoechoic cleft between the continuous bright echoes of the sacrum and the iliac bone, approximately 5 cm from the midline (Arslan et al. 1999; Pekkafali et al. 2003). The needle (20 gauge) should be inserted from medial to lateral and directed to the lower third (synovial part) of the joint. Pushing the needle further the posterior ligament, a “pop” sensation indicates that the joint has been entered. A mixture of triamcinolone and lidocaine is then administered. Iliopsoas bursitis is usually punctured under real-time guidance because of its proximity to the femoral vessels and nerve. For this purpose, transverse US planes are the most adequate because they allow concomitant detection of the distended bursa and the adjacent anatomic structures. In total


hip replacement, anterior impingement between the acetabular portion of the prosthesis and the undersurface of the psoas muscle and tendon can occur (see Chapt. 12). Like CT, US can accurately direct anesthetic/steroid injection between these two structures. This injection has diagnostic and therapeutic implications. Peritrochanteric bursitis, affecting the superficial trochanteric bursa and the subgluteus medius and minimus bursae, and tendinopathy of the abductor muscles are leading causes of pain around the hip in subjects performing competitive or recreational sport activities. If the trochanteric bursa is distended, a US-guided local injection can be performed by placing the needle tip within the distended bursa (see Figs. 12.49, 12.50). A posterolateral approach with the patient supine keeping the affected side upward is used. A 21–22 gauge spinal needle works well to inject approximately 2–4 ml of anesthetic/steroid solution. To inject the trochanteric bursa, the needle traverses the gluteus maximus muscle, whereas the injection of the subgluteus bursae also requires passage through the gluteus medius tendon. If the abductor tendons (gluteus medius and minimus) are thickened and hypoechoic for tendinopathy, US allows the needle to be directed close to their surface to obtain a peritendinous area of infiltration, thus increasing the efficacy of the injected steroid (see Fig. 12.43). Intratendinous injections must be avoided. Similarly, patients with chronic groin pain secondary to strains of the adductor origin can be injected. Careful technique is needed to infiltrate the soft tissues around the insertion of the adductor longus muscle. For this purpose, the patient is placed with the leg abducted and externally rotated.

18.2.5 Knee Puncturing the knee joint with a lateral approach is common clinical practice. The needle is inserted blindly at the level of the upper pole of the patella to reach the suprapatellar synovial recess. In general, US guidance is not requested to direct the needle within the joint space. However, in patients presenting with small effusion or knee prosthesis or when the puncture has to be performed quickly (pediatric patients), US guidance may be helpful. Both indirect and direct techniques can be used. We prefer to recognize the site of maximal fluid accumulation within the suprapatellar pouch on transverse images.

In small effusions, the patient is asked to rotate the leg externally to increase filling of the lateral portion of the pouch so it can be easily punctured. For this purpose, a 21 gauge spinal needle is adequate. The knee being a large synovial joint, up to 50 ml can be aspirated from it and/or injected within it. Baker cysts can be aspirated for both diagnostic purposes (to analyze the internal fluid) and to reduce patient discomfort by decreasing the intracystic pressure. Under real-time US guidance, the probe is placed along the long axis of the cyst and the needle (18–20 gauge) is advanced up to reach its center (Fig. 18.19a–d). Guiding the needle in transverse planes is less useful because the local anatomy of the popliteal fossa does not allow the needle to advance perpendicular to the US beam. Then, aspiration can be performed followed by steroid injection in order to reduce the risk of recurrence and to treat chronic symptoms (Fig. 18.19e). Popliteal ganglia or ganglia arising from the posterior cruciate ligament are more difficult to puncture than Baker cysts because of their deeper position and proximity to the popliteal vessels (see Fig. 14.109). In difficult cases, CT guidance offers a more confident procedure. On the other hand, Hoffa ganglia can be successfully aspirated using an anterior approach on the lateral or medial side of the patellar tendon. Because of their superficial position, prepatellar and pretibial bursitis can be punctured without the need of imaging guidance. US has a secondary role in demonstrating the nature and amount of intrabursal fluid before the insertion of the needle. Intramuscular ganglia derive from the superior tibiofibular joint and extend caudally within the muscles of the anterolateral compartment of the leg. They can cause entrapment of the peroneal nerve leading to a characteristic foot-drop. US is able to identify intramuscular ganglia and to assess their size, internal structure and relationship with the peroneal nerve and its divisional branches. Similar to other ganglia, aspiration of the yellowish viscid content of the cyst can confirm the US diagnosis and may have a therapeutic implication as it may reduce the intracystic pressure and the subsequent compression on the nerve (see Chapter 14). Once the path of insertion is selected, the needle is advanced under US guidance (Fig. 18.20). For aspiration, large-bore needles (18 gauge) and strong traction on the piston of the syringe are required for a successful procedure. Multiple to-and-fro passages through the cystic wall with the needle and steroid injection can facilitate leakage and resorption of fluid in the adjacent soft tissues.

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Fig. 18.18a–c. US-guided aspiration of a ganglion cyst arising at the anterior aspect of the elbow. a Sagittal 12–5 MHz US image of the anterior elbow obtained over the radial head (RH). The ganglion (open arrows) appears as a well-defined multilobulated anechoic mass superficial to the anterior capsule. Hum, humeral capitellum. b Under real-time guidance, an 18 gauge needle (white arrow) is advanced within the ganglion. Note the correct placement of the needle tip (arrowhead). c After aspiration, note the significant reduction in size of the ganglion

assessed either using an anterior approach by placing the probe just below and anterior to the anterior talofibular ligament to examine the groove between talus and calcaneus, or using a posterior approach by placing the probe behind the lateral malleolus or scanning caudal to the posterior recess of the tibiotalar joint. Once the presence of subtalar joint synovitis has been established, US can guide aspiration and makes the injection therapy easier and more reliable, because this joint is small and difficult to reach blindly. A 21 gauge needle is required. Other midtarsal joints, including the Chopart and Lisfranc joints, can also be injected after localizing the appropriate joint space with US. In the appropriate clinical setting, US-guided injection of ankle tendon sheaths can be performed for diagnostic (contrast material injection for conventional, CT or MR tenography) or therapeutic (steroid injection) purposes. The tibialis posterior, the flexor hallucis longus and the peroneals are the ankle tendons on which interventional procedures are most often focused (Figs. 18.21, 18.22). Smallfootprint transducers and epidermal thin (23–25 gauge) needles greatly facilitate tendon sheath cannulation (Sofka and Adler 2002). Under realtime guidance, the needle should be inserted at the point where the sheath is distended by effusion: this allows a more reliable procedure. In general, the puncture site is located just cranial to the malleolar tip for both tibialis posterior and peroneal tendons. As in other applications, preliminary injection of small amounts of lidocaine is useful to cause hyperechoic bubble distension of the sheath and make the examiner confident that the needle is correctly placed. Due to the limited space of tendon sheaths, the injection of corticosteroids should be followed in real time with US to reduce the risk of any leakage into the subcutaneous tissue. In fact, even small

movements or muscle contraction may cause displacement of the needle tip out of the sheath. Tarsal tunnel injections are performed for treatment of either tarsal tunnel syndrome or reflex sympathetic dystrophy. In this application, US guidance is not necessary to identify the site of injection, but it can be useful in selected cases. For treatment of painful insertional Achilles tendinopathy, steroid injection in the retrocalcaneal bursa can be performed with a medial approach inserting the needle just cranial to the calcaneus while keeping the foot dorsiflexed as for the Achilles tendon examination. The needle is inserted from the medial side to minimize the risk of contact with the sural nerve. Its progression must be checked in real time by placing the probe in the transverse plane over the posterior aspect of the Achilles tendon (Fig. 18.23). Preliminary injection of lidocaine may be helpful to confirm the intrabursal positioning of the needle in cases of mild effusion. Depomedrone is the steroid of choice. An interesting US-related application to treat painful chronic mid-portion Achilles tendinosis that has the potential to have a major health impact is the intratendinous injection of polidocanol (Thesit) using color Doppler imaging guidance (Öhberg and Alfredson 2002). Polidocanol (aethoxyskerol) is a surface anesthetic used as a venous sclerotic agent in patients with bleeding peptic ulcer and skin varicosities. In Achilles tendinosis, neovasculature is a prominent feature on color Doppler imaging in cases of painful tendinopathy, but not in those who are pain-free. Although it is not clear cause and effect, it appears that neovasculature may be part of the pain mechanism. Accordingly, the procedure is based on injection of small amounts (2–4 ml) of the drug (5 mg/ml) in areas of neovasculature of the Achilles tendon, as depicted on color Doppler imaging, until all intra-

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Fig. 18.19a–e. US-guided percutaneous treatment of symptomatic Baker cyst. a Schematic drawing of a sagittal view through the posteromedial knee shows the landmarks for real-time intracystic needle placement. The relationship of the superficial part of the Baker cyst (asterisk) with the medial head of the gastrocnemius (GMH) is depicted. b Sagittal 12–5 MHz US image obtained at the medial aspect of the popliteal space shows the Baker cyst (asterisk) demonstrated in its long axis. c Under real-time US guidance, the needle (arrow) is introduced within the cyst and advanced until its tip (arrowhead) reaches the cystic center. d After aspiration of approximately 10 ml of clear synovial fluid, there is complete collapse of the superficial part of the cyst. e Steroid injection (white arrowheads) inside the lumen of the cyst is checked in real time

TA

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d Fig. 18.20a–d. US-guided aspiration of an intramuscular ganglion arising from the superior tibiofibular joint. a Photograph of the aspiration procedure. b Sagittal 12–5 MHz US image obtained over the upper third of the anterolateral compartment of the leg reveals the intramuscular ganglion as an anechoic rounded mass (arrowheads) with internal septa located within the tibialis anterior muscle (TA). The needle (arrow) is placed in the center of the ganglion. During needle insertion, care should be taken to avoid incidental damage to the peroneal nerve and the anterior tibial artery. c After aspiration, the ganglion (arrowheads) contains only a small amount of residual fluid. d Steroid injection is checked in real time to avoid leakage in the adjacent soft tissues


a

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Fig. 18.24a–f. US-guided treatment of intermetatarsal bursitis: dorsal approach with plantar US guidance. a Schematic drawing of a sagittal view though the forefoot illustrates the dorsal approach for imaging the intermetatarsal spaces. Plantar compression exerted by the examiner’s thumb (black arrow) on the opposite side of the probe may help to reduce the soft-tissue thickness, thus making findings more evident. b Schematic drawing shows the technique used for dorsal injection. Plantar positioning of the transducer, away from the needle, reduces the risk of secondary infection. c Longitudinal 12–5 MHz US image of the third intermetatarsal space obtained from a dorsal approach reveals a distended intermetatarsal bursa (arrow). d Same US image as shown in c obtained with a plantar approach. Correct needle (arrowhead) placement in the bursa is achieved from the dorsal foot. e,f After injection, longitudinal 12–5 MHz US images confirm adequate filling of the bursa (arrow) by hyperechoic material (white arrowheads) and absence of steroid leakage into the surrounding soft tissues

*

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Fig. 18.25a–d. US-guided treatment of intermetatarsal bursitis: dorsal approach with dorsal US guidance. a Schematic drawing of a sagittal view through the forefoot illustrates transducer and needle positioning. b Corresponding sagittal 12–5 MHz US image shows a fluid-filled bursa (arrow) located just dorsal and proximal to a Morton neuroma (asterisk). c Same US image as shown in b demonstrates correct positioning of the needle (arrowheads) inside the bursal cavity. d The injected steroids appear as hyperechoic spots (white arrowhead) in the bursa

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going sclerosing treatment, Morton neuromas tend to become more echogenic and may exhibit volume reduction with time (Fanucci et al. 2004). From the echotextural point of view, neuromas presenting as hypoechoic masses with discrete posterior acoustic attenuation before the procedure seem characterized by less likelihood of success compared with those free of posterior attenuation. In a recent series of 40 consecutive patients, long-term results indicated a high rate of clinical success, comparable to or better than those related to other surgical procedures (Fanucci et al. 2004).

References Adler RS, Sofka CM (2003) Percutaneous ultrasound-guided injections in the musculoskeletal system. Ultrasound Quart 19:3–12 Aina R, Cardinal E, Bureau N et al (2001) Calcific shoulder tendinitis: treatment with modified US-guided fine-needle technique. Radiology 221:455–461 Amann P, Botta U, Montet X et al (2003) Ultrasonographic detection and localisation of a clinically non detectable subcutaneous contraceptive implant. J Ultrasound Med 22:855–859 Arslan H, Sakarya ME, Adak B et al (1999) Duplex and color Doppler sonographic findings in active sacroiliitis. AJR Am J Roentgenol 173:677–680 Baffroy-Fayard N; Groupe de travail du CCLIN Paris-Nord (2002) Infection control in interventional radiology: good practice guideline. J Radiol 83:351–359 Bradley M, Kadzombe E, Simms P et al (1992) Percutaneous ultrasound guided extraction of non-palpable soft tissue foreign bodies. Arch Emerg Med 9:181–184 Breidahl WH, Adler RS (1996) Ultrasound-guided injection of ganglia with corticosteroids. Skeletal Radiol 25:635–638 Cardinal E, Beauregard CG, Chhem RK (1997) Interventional musculoskeletal ultrasound. Semin Musculoskeletal Radiol 1:311–318 Cardinal E, Chhem RK, Beauregard CG (1998) Ultrasoundguided interventional procedures in the musculoskeletal system. Radiol Clin North Am 36:597–604 Chaudhry HJ (1999) Ultrasound therapy for calcific tendinitis of the shoulder. N Engl J Med 341:1237 Chiou HJ et al (1999) Alternative and effective treatment of shoulder ganglion cyst: ultrasonographically guided aspiration. J Ultrasound Med 18:531–535 Cicak N, Matasovic T et al (1992) Ultrasonographic guidance of needle placement for shoulder arthrography. J Ultrasound Med 11:135–137 Civardi G, Livraghi T, Colombo P et al (1994) Lytic bone lesions suspected for metastasis: ultrasonically guided fine-needle aspiration biopsy. J Clin Ultrasound 22:307–311 Comfort TH, Arafiles RP (1978) Barbotage of the shoulder with image-intensified fluoroscopic control of needle placement for calcific tendinitis. Clin Orthop 135:171–178 Connell DA, Ali KE, Ahmad M et al (2006) Ultrasound-guided autologous blood injection for tennis elbow. Skeletal Radiol 35:371-377

De Smet AA (2004) Ultrasound-guided injections and aspirations of the extremities. Semin Roentgenol 39:145–154 DeMouy EH, Menendez CV Jr, Bodin CJ (1997) Palpationdirected (non-fluoroscopically guided) saline-enhanced MR-arthrography of the shoulder. AJR Am J Roentgenol 169:229–231 Dockery GL (1999) The treatment of intermetatarsal neuromas with 4% alcohol sclerosing injections. J Foot Ankle Surg 38:403–408 Ebenbichler GR, Erdogmus CB, Resch KL et al (1999) Ultrasound therapy for calcific tendinitis of the shoulder. N Engl J Med 340:1533–1538 Ernberg LA, Adler RS, Lane J (2003) Ultrasound in the diagnosis and treatment of a painful stump neuroma. Skeletal Radiol 32:306–309 Fanucci E, Masala S, Fabiano S et al (2004) Treatment of intermetatarsal Morton’s neuroma with alcohol injection under US guide: 10-month follow-up. Eur Radiol 14:514–518 Farin PU, Jaroma H, Soimakallio S (1995) Rotator cuff calcifications: treatment with US-guided technique. Radiology 195:841–843 Farin PU, Rasanen H, Jaroma H et al (1996) Rotator cuff calcifications: treatment with ultrasound-guided percutaneous needle aspiration and lavage. Skeletal Radiol 25:551–554 Farmer KD, Hughes PM (2002) MR arthrography of the shoulder: fluoroscopically guided technique using a posterior approach. AJR Am J Roentgenol 178:433–434 Gil-Sanchez S, Marco-Domenech SF, Irurzun-Lopez J et al (2001) Ultrasound-guided skeletal biopsies. Skeletal Radiol 30:615–619 Gimblett PA, Saville J, Ebrall P (1999) A conservative management protocol for calcific tendinitis of the shoulder. J Manipulative Physiol Ther 22:622–627 Gruber H, Kovacs P, Peer S et al (2004) Sonographically guided phenol injection in painful stump neuroma. AJR Am J Roentgenol 182:952–954 Jandrasits O, Likar R, Marhofer P et al (1998) The use of ultrasonography for regional anesthetic techniques: upper extremity blockades. Acta Anaesthesiol Scand 24:48–51 Kapral S, Krafft P, Eibenberger K et al (1994) Ultrasoundguided supraclavicular approach for regional anesthesia of the brachial plexus. Anesth Analg 78:507–513 Kirchmair L, Entner T, Kapral S et al (2002) Ultrasound guidance for the psoas compartment block: an imaging study. Anesth Analg 93:477–481 Kovacs P, Gruber H, Piegger J et al (2001) New simple, ultrasound-guided infiltration of the pudendal nerve: ultrasonographic technique. Dis Colon Rectum 44:1381–1385 Leitschuh PH, Bone CM, Bouska WM (1999) Magnetic resonance imaging diagnosis, sonographically directed percutaneous aspiration, and arthroscopic treatment of a painful shoulder ganglion cyst associated with a SLAP lesion. Arthroscopy 15:85–87 Lind B, Öhberg L, Alfredson H (2006) Sclerosing polidocanol injections in mid-portion Achilles tendinosis: remaining good clinical results and decreased tendon thickness at 2year follow-up. Knee Surg Traumatol Arthrosc 14:1327-1332 Luchs JS, Adler RS, Sofka CM (2004) In vitro analysis of the sonographic contrast effect of therapeutic steroid and anesthetic injections. AJR Am J Roentgenol 182 [Suppl]:42–43 Marhofer P, Schrögendorfer K, Koinig H et al (1997) Ultrasonographic guidance improves sensory block and onset time of three-in-one blocks. Anesth Analg 85:854–857

US-Guided Interventional Procedures Marhofer P, Schrögendorfer K, Walner T et al (1998) Ultrasonographic guidance reduces the amount of local anesthetic for 3-in-1 blocks. Reg Anesth Pain Med 23:584– 588 McShane JM, Nazarian LN, Harwood MI (2006) Sonographically guided percutaneous needle tenotomy for treatment of common extensor tendinosis in the elbow. J Ultrasound Med 25:1281-1289 Moorthy SS, Schmidt SI, Dierdorf SF et al (1991) A supraclavicular lateral approach for brachial plexus regional anesthesia. Anesth Analg 72:241–244 Moskowitz RW (1982) Synovial fluid analysis. In: Moskowitz RW (ed) Clinical rheumatology. A problem-oriented approach. Lea and Febiger, Philadelphia, p 421 Nelson AL, Sinow RM (1998) Real-time ultrasonographically guided removal of nonpalpable and intramuscular Norplant capsules. Am J Obstet Gynecol 178:1185–1193 O’Dwyer HM, Lyon SM, Fotheringham T, Lee MJ (2003) Informed consent for interventional radiology procedures: a survey detailing current European practice. Cardiovasc Intervent Radiol 26:428–433 Öhberg L, Alfredson H (2002) Ultrasound guided sclerosis of neovessels in painful chronic Achilles tendinosis: pilot study of a new treatment. Br J Sports Med 36:173–177 Ootaki C, Hayashi H, Amano M (2000) Ultrasound-guided infraclavicular brachial plexus block: an alternative technique to landmark-guided approaches. Reg Anesth Pain Med 25:600–604 Pekkafali MZ, Kiralp MZ, Basekim CC et al (2003) Sacroiliac joint injections performed with sonographic guidance. J Ultrasound Med 22:553–559 Rasmussen MR, Kitaoka HB, Patzer GL (1996) Nonoperative treatment of plantar interdigital neuroma with a single corticosteroid injection. Clin Orthop 326:188–193 Rubens DJ, Fultz PJ, Gottlieb RH, Rubin SJ (1997) Effective ultrasonographically guided intervention for diagnosis of musculoskeletal lesions. J Ultrasound Med 16:831–842 Saifuddin A, Mitchell R, Burnett SJ et al (2000) Ultrasoundguided needle biopsy of primary bone tumours. J Bone Joint Surg Br 82:50–54

Saker MB, Kane RA, Matalon TAS (1997) Factors affecting and techniques to improve needle visualization. Semin Interv Radiol 14:471–475 Shiels WE II, Babcock DS, Wilson JL et al (1990) Localization and guided removal of soft-tissue foreign bodies with sonography. AJR Am J Roentgenol 155:1277–1281 Sofka CM, Adler RS (2002) Ultrasound-guided interventions in the foot and ankle. Semin Musculoskeletal Radiol 6:163–168 Sofka CM, Collins AJ, Adler RS (2001) Use of ultrasonographic guidance in interventional musculoskeletal procedures: a review from a single institution. J Ultrasound Med 20:21–26 Suresh SP, Ali KE, Jones H et al (2006) Medial epicondylitis: is ultrasound guided autologous blood injection an effective treatment? Br J Sports Med 40:935-939 Torriani M, Etchebehere M, Amstalden E (2002) Sonographically guided core needle biopsy of bone and soft tissue tumors. J Ultrasound Med 21:275–281 Trattnig S, Breitenseher M, Pretterklieber M et al (1997) MRguided joint puncture and real-time MR-assisted contrast media application. Acta Radiol 38:1047–1049 Turner J, Wilde CH, Hughes KC et al (1997) Ultrasound-guided retrieval of small foreign objects in subcutaneous tissue. Ann Emerg Med 29:731–734 Valls R, Melloni P (1997) Sonographic guidance of needle positioning for MR arthrography of the shoulder. AJR Am J Roentgenol 169:845–847 Vierola H (2004) Ultrasonography-guided contrast media injection to shoulder joint using a posterior approach: a technique worth trying. Acta Radiol 45:616–617 Westerlund T, Vuorinen V, Röyttä M (2001) Same axonal regeneration rate after different endoneurial response to intraneural glycerol and phenol injection. Acta Neuropathol (Berl) 102:41–54 Widman DS, Craig JG, van Holsbeeck MT (2001) Sonographic detection, evaluation and aspiration of infected acromioclavicular joints. Skeletal Radiol 30:388–392 Wu J, Chiu DTW (1999) Painful neuromas: a review of treatment modalities. Ann Plast Surg 43:661–667 Zwar RB, Read JW, Noakes JB (2004) Sonographically guided glenohumeral joint injection. AJR Am J Roentgenol 183:48–50

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Pediatric Musculoskeletal Ultrasound

Pediatric Applications

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Pediatric Musculoskeletal Ultrasound Carlo Martinoli and Maura Valle

CONTENTS 19.1

Introduction 921

19.2 Hip Disorders 921 19.2.1 Developmental Dysplasia of the Hip 921 19.2.1.1 Graf ’s Technique 923 19.2.1.2 Harcke’s Technique 926 19.2.1.3 Femoral Head Coverage Technique 928 19.2.1.4 Screening Programs and Follow-up 928 19.2.2 Painful Hip 929 19.2.2.1 Transient Synovitis and Hip Infection 929 19.2.2.2 Perthes Disease 931 19.2.2.3 Slipped Upper Femoral Epiphysis 935 19.3 Disorders Beyond the Hip 935 19.3.1 Bone 935 19.3.1.1 Congenital Clubfoot 935 19.3.1.2 Congenital Tarsal Coalition 939 19.3.1.3 Occult Fractures 940 19.3.1.4 Pulled Elbow 941 19.3.1.5 Acute and Chronic Recurrent Multifocal Osteomyelitis 941 19.3.2 Tendons and Ligaments 943 19.3.2.1 Traction Apophysitis 945 19.3.2.2 Apophyseal Separation 946 19.3.2.3 Ligament Injuries 949 19.3.3 Joints 952 19.3.3.1 Juvenile Idiopathic Arthritis 952 19.3.3.2 Hemophilic Arthropathy 954 19.3.4 Muscles 954 19.3.4.1 Fibromatosis Colli 955 References

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19.1 Introduction US is particularly well suited to examination of the pediatric musculoskeletal system, as an exquisite depiction of the immature skeleton with large amounts of cartilaginous bone can be obtained in a well-tolerated and noninvasive way without using ionizing radiation or sedation. Although US has been widely used in the diagnosis of hip disorders in children, many other applications for US in the pediatric musculoskeletal system have been developed (Keller 2005). More than other imaging techniques, US is ideally suited to the evaluation of the soft-tissue structures, including tendons and ligaments, joints and muscles. In this chapter, we will review the use of US in developmental dysplasia and painful hip and will also describe its use in a variety of other musculoskeletal applications, including congenital, inflammatory and traumatic abnormalities. Spine disorders are not included in this chapter.

19.2 Hip Disorders 19.2.1 Developmental Dysplasia of the Hip

C. Martinoli, MD Associate Professor of Radiology, Cattedra “R” di Radiologia – DICMI, Università di Genova, Largo Rosanna Benzi 8, 16132 Genova, Italy M. Valle, MD Staff Radiologist, Reparto di Radiologia, Istituto Scientifico “Giannina Gaslini”, Largo Gaslini 5, 16148 Genova, Italy

Developmental dysplasia of the hip, formerly referred to by the less appropriate term “congenital dysplasia of the hip,” can be defined as a deformity of the acetabulum to various extents, in which the femoral head may lie in its proper position, sublux or dislocate (Gerscovich 1997a). Based on physical findings, the reported incidence of this condition varies widely throughout the world, accounting for approximately 2–6/1000 live newborns (Gerscovich 1997a). The cause of hip dysplasia is multifactorial and seems to be related to late alteration during

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b Fig. 19.3a–d. US examination of the infant hip. a Patient positioning. The infant lies in the lateral decubitus position with the knees slightly flexed. The transducer is placed on a coronal plane over the hip joint. b Positioning device. These devices serve to better restrain the patient during scanning for measurements and to provide a support against which the stress maneuvers can be performed. In general, the infant’s mother cooperates by restraining and entertaining the infant. The use of this device is, however, not essential. Most pediatric radiologists prefer to scan the patient freely. c Standard coronal 12–5 MHz US image of the normal infant hip with d schematic drawing correlation shows the relevant anatomic structures for evaluation of hip dysplasia. They are: the hypoechoic rounded femoral head (FH) centered over the hypoechoic triradiate cartilage (2); the promontory (arrow), represented by the junction between the iliac wing (a) and the bony acetabular roof (b); the fibrocartilaginous labrum (c) in continuity with the acetabular hyaline cartilage (1); and the ischium (3). More superficially, the gluteus medius (Gme) and the gluteus minimus (Gmi) muscles are seen inserting into the greater trochanter (gt). As a rule, the iliac bone must be always kept parallel to the probe, otherwise measurements will be inaccurate

laterally; when scanning too posteriorly, it becomes concave (gluteal fossa). As a rule, the sharper the promontory, the more mature the hip. Based on the standard coronal plane, Graf described two angles formed by the intersection of three lines: the iliac line (baseline), tangential to the iliac wing; the acetabular roof line, which joins the promontory with the deepest edge of the acetabulum; and the labral line, drawn from the

promontory to the middle of the fibrocartilaginous labrum (Fig. 19.4) (Graf 1980, 1984a). The intersection of the first two lines forms the α angle (acetabular inclination angle), which reflects the depth of the bony acetabular roof and the coverage of the femoral head (Fig. 19.5a,b). This angle is relevant as it correlates with hip maturity: the wider the angle, the more mature the hip; the smaller the angle, the greater the degree of dysplasia. In normal mature

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α

2 3 b

a Fig. 19.4a,b. Lines and angles used to evaluate hip dysplasia using Graf ’s method. a Schematic drawing of a standard coronal plane of the hip with b corresponding 12–5 MHz US image demonstrates the baseline (1), the labral line (2) and the acetabular roof line (3) relative to the anatomic structures as shown in Fig. 19.3c. The α angle is formed by the intersection of the baseline and the acetabular roof line: it is an expression of the depth of the bony acetabular roof. The β angle is formed by the intersection of the baseline and the labral line: it reflects the cartilaginous coverage of the femoral head. In normal conditions, the α-angle is ⱖ60° and the β angle is

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