Musculoskeletal Imaging E-Book

Thomas Lee Pope

• Herausgeber: Thieme
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 691

Veröffentlichungsjahr: 2001

Beschreibung

Due to the multitude of bone and joint disorders and their symptomatic similarities, establishing a differential diagnosis is often problematic in daily practice. This book offers invaluable help by showing the diagnostic effectiveness of multimodality imaging across the entire spectrum of bone and joint disorders. Each clinical entity is presented as a unit, with succinct text on the left and high-quality, labeled images on the right. A consistent structure featuring pathology, clinical findings, radiology, nuclear medicine, MRI, and differential diagnosis offers quick access to the information you need for any given bone, joint, or soft tissue disease. More than 1,300 high-quality radiologic images and two-color drawings that allow you to visualize each disorder. Key information presented in just 404 pages, saving you the time and inconvenience of wading through large texts. Useful tables summarizing radiologic findings for each disorder. All-inclusive coverage, with in-depth treatment of such important areas as trauma.

Leseprobe

Library of Congress Cataloging-in-Publication Data

Bohndorf, Klaus.[Radiologische Diagnostik der Knochen und Gelenke, English]Radiologic diagnos is of the bones and joints/KlausBohndorf, Herwig Imhof, Thomas Lee Pope, jr.;with contributions by W. Fischer… [et al.];translated by Peter Winter, p.; cm.Includes bibliographical references and index.ISBN 3131274417 (GTV)–ISBN 1-58890-060-6 (TNY)1. Bones–Radiography. 2. joints–Radiography.3. Bones–Diseases–Diagnosis. 4. joints–Diseases–Diagnosis. I. Imhof, H. (Herwig).II. Pope, Thomas Lee. III. Title.[DNLM: 1. Bone Diseases-radiography2. Arthrography. 3. Bone and Bones-radiography.WE 141 B677r2001a]RC930.5.B5813 2001616.7'107572-dc21                                                     2001027188

This book is an authorized translation of the German edition published and copyrighted 1998 by Georg Thieme Verlag, Stuttgart, Germany. Title of the German edition: Radiologische Diagnostik der Knochen und Gelenke.

Translated byPeter Winter, M.D.Clinical Assistant ProfessorUniversity of IllinoisCollege of Medicine at PeoriaPeoria, IL, USA

©2001 Georg Thieme Verlag,Rüdigerstraße 14, D-70469 Stuttgart, GermanyThieme New York, 333 Seventh Avenue,New York, N.Y. 10001 U.S.A.

Cover design: Martina Berge, Erbach-ErnsbachTypesetting by Ziegler + Müller, KirchentellinsfurtPrinted in Germany by Appl, WemdingISBN 3-13-127441-7 (GTV)ISBN 1-58890-060-6 (TNY)                                         1 2 3 4 5

Important Note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book.

Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers' leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user's own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed.

Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

This book, including all parts thereof, is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

Preface

This book makes the somewhat daring claim of offering a new approach to diagnostic imaging of bones and joints by redesigning the very concept of the book, the classic vehicle of relating knowledge. The authors composed most of the pages themselves with the help of personal computers, scanners, and appropriate software. The format chosen was to present the material in units of two opposing pages, with the left-hand page for reading and the right-hand page for viewing, thereby integrating text, tables, diagrams, and carefully selected images. Like radiology, the presentation is heavily image oriented. Whenever necessary, the images have been annotated for easier comprehension of the radiologic findings. Text and figures have to be seen as a unit, so not every figure is annotated in the text.

This is not a conventional multi-authored book since every chapter was thoroughly revised and edited to harmonize style and content and to create a coherent whole. Colleagues from the disciplines of orthopedics, rheumatology, traumatology, internal medicine, and nuclear medicine have reviewed the chapters and made useful suggestions.

This book attempts to define what a board-certified radiologist should know, or at one time should have known. Looking things up is legitimate and even intended. The point is to know where to look, and finding out should be made easy by the lucid presentation and systematic outline.

According to Shakespeare, brevity is the soul of wit (“Hamlet,” Act II, Sc 2, Polonius) – but does this also apply to a textbook? The process of selecting, deleting, and emphasizing is one grounded on experience in and mastery of the subject. This book does not describe all there is, but rather, it is hoped, all that is deemed relevant. For good reason, traumatology (Chapter 1) and arthrology (Chapter 9) are the supporting pillars of the book. Conventional radiology of the bones and joints continues to take first place in describing the features that can be extracted from the images and used for interpretation. At the same time, the book follows a multi-modality approach. MRI, CT, nuclear medicine, and ultrasound are presented in depth when they supplement, replace, or add information that cannot be inferred from radiography. The modalities are integrated wherever they belong together. This takes into consideration that training in radiology generally involves working with one modality at a time, though diagnosing diseases by imaging requires a profound understanding of various modalities. This book is not meant to be used with one particular modality.

Who can benefit from this book? Above all, residents who want to learn more about musculoskeletal radiology. The structure and outline of the book make it especially suitable for review in preparation for the board examination. Furthermore, it is hoped that this book might be a useful reference text for practicing radiologists and other specialists to solve problems encountered in day-to-day practice.

The authors' text was edited into the final version by our technical editor Wolfgang Fischer, M.D., who made this project possible through his commitment, ideas, and hard work. Cliff Bergman, M.D., Gert Krueger and their team eagerly took on the last hurdle by formatting the files into printable book pages. Donna Garrison did a great job in editing the English text. Last but not least, the English version was made possible through the translation by our good friend Peter Winter, M.D.

Augsburg, Vienna, CharlestonSpring 2001

Klaus BohndorfHerwig lmhofThomas Lee Pope

Acknowledgements

With thanks to those who have contributed images:

V. Cassar-Pullicino. M.D., Oswestry

S. Ehara, M.D., Morioha

Prof. Dr. j. Freyschmidt, Bremen

G. Greenway. M.D., Dallas

Prof. Dr. M. Heller, Kiel

R. Kerr, M.D., Los Angeles

P. Kindynis, M.D., Geneva

Doz. Th. Leitha, Vienna

Dr. Mathson, Riad

Priv.-Doz. Dr. A. Prescher, Aachen

D. Resnick, M.D., San Diego

Scanco Medical, Bassersdorf

K. Tallroth, M.D., Helsinki

Yung Chan Wang, M.D., Taipeh

Contributors

Martin Breitenseher, M.D.ProfessorUniversitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Johannes Demharter, M.D.Klinik für Diagnostische Radiologieund NeuroradiologieZentralklinikum AugsburgAugsburg, Germany

Wolfgang Fischer, M.D.Klinik für Diagnostische Radiologieund NeuroradiologieZentralklinikum AugsburgAugsburg, Germany

Jörg Haller, M.D.ZentralröntgeninstitutHanusch-KrankenhausVienna, Austria

Hannes Häuser, M.D.Klinik für Diagnostische Radiologieund NeuroradiologieZentralklinikum AugsburgAugsburg, Germany

Juerg Hodler, M.D.Abteilung RadiologieKlinik BalgristZurich, Switzerland

Johannes Hofmann, M.D.ZentralröntgeninstitutHanusch-KrankenhausVienna, Austria

Franz M. Kainberger, M.D.ProfessorUniversitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Egbert Knöpfle, M.D.Klinik für Diagnostische Radiologieund NeuroradiologieZentralklinikum AugsburgAugsburg, Germany

Wolfgang Michl, M.D.Klinik für Diagnostische Radiologieund NeuroradiologieZentralklinikum AugsburgAugsburg, Germany

Thomas Rand, M.D.ProfessorUniversitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Gerald Seidl, M.D.Universitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Siegfried Trattnig, M.D.ProfessorUniversitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Karl Turetschek, M.D.Universitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Soraya Youssefzadeh, M.D.Universitätsklinik für RadiodiagnostikAllgemeines Krankenhaus der Stadt WienVienna, Austria

Contents

1 Trauma

Definitions

Fracture

Joint Injury

Muscle Injury

Tendon Injury

Role of Imaging in Trauma to the Musculoskeletal SystemK. Bohndorf

Conventional Radiology

Digital Radiology

Computed Tomography

Spiral CT, 2-D and 3-D Reconstruction

Arthrography

Sonography

Magnetic Resonance Imaging

Scintigraphy

Practical Suggestions for Imaging in the Trauma SettingK. Bohndorf

Fracture Classifications and TypesK. Bohndorf

Fracture Types

Special Considerations in the Pediatric Age Group

Fractures of the Articular Surfaces (Chondral and Osteochondral Fractures)

Stress and Insufficiency Fractures

Pathologic Fracture

Fracture HealingK. Bohndorf

Primary Fracture Healing

Secondary Fracture Healing

Radiographic Signs of Osseous Consolidation

Basic Principles of Fracture Treatment

Delayed Fracture Healing

Pseudarthrosis

Complications after FracturesM. Breitenseher

Reflex Sympathetic Dystrophy (RSD)

Trauma-Induced Soft-Tissue ChangesK. Bohndorf

Tendon Injuries

Ligamentous Injuries

Muscle Injuries

Rhabdomyolysis

Myositis Ossificans

Compartment Syndrome

Radiologic Reporting of FracturesK. Bohndorf

Special Traumatology

Skull and SpineK. Turetschek

Fractures of the Cranial Vault

Fractures of the Cranial Base

Fractures of the Temporal Bone

Fractures of the Facial Bones

Spine

PelvisJ. Demharter

Pelvic Injuries

Acetabular Fractures

Hip Dislocation without Acetabular Fracture

Hip Dislocations with Fracture of the Femoral Heads (Pipkin Fractures)

Shoulder GirdleJ. Holder

Sternoclavicular Dislocation

Clavicular Fracture

Acromioclavicular Separation

Impingement and Rotator Cuff Rupture

Shoulder Dislocation, Shoulder Instability

Upper ExtremityH. Häuser

Humeral Fractures

Dislocation of the Elbow

Subluxation of the Radial Head (Chassaignac)

Tennis Elbow

Fractures of the Proximal Forearm

Forearm Fractures

Distal Forearm Fractures

Dislocation of the Distal Forearm

Injuries of the Triangular Fibrocartilage Complex (TFCC)

Fractures of the Carpal Bones

Carpal Derangements

Carpometacarpal Injuries

Lower Extremity

Femur and Patella

S. Trattnig, W. Fischer

The Post-Surgical Hip

E. Knöpfle

Internal Lesions of the Knee

S. Trattnig

Tibia/Fibula

J. Demharter

Fractures of the Ankle

J.Demharter

Tarsal and Metatarsal Bones

J. Demharter

Ligamentous Injuries of the Ankle

M. Breitenseher

Special Problems Encountered in Children

W. Michl

The Normal Development of the Epiphyseal Growth Zone, Developmental Variations, and Transition to Pathologic Cases

Battered Child Syndrome

2 Bone and Soft-Tissue Infections

OsteomyelitisK. Bohndorf

Acute Hematogenous Osteomyelitis

Newborn Osteomyelitis

Juvenile Hematogenous Osteomyelitis

Acute Hematogenous Osteomyelitis in the Adult

Imaging Features of Acute Hematogenous Osteomyelitis (All Ages)

Evidence of Healing of Acute Osteomyelitis

Complications of Acute Hematogenous Osteomyelitis (All Age Groups)

Chronic Hematogenous Osteomyelitis

Brodie Abscess

Chronic Recurrent Multifocal Osteomyelitis

Post-traumatic Osteomyelitis

Tuberculosis

Soft-Tissue InfectionsK. Bohndorf

3 Tumors and Tumorlike Lesions of the Skeleton and Soft Tissues

General Considerations in Diagnosing Skeletal TumorsK. Bohndorf

The Role of the Radiologist in Evaluating Skeletal Lesions Suspicious for Tumors

The Role of Diagnostic Imaging

Ten Rules for Classifying Skeletal Lesions Suspicious for Tumors

Staging (Determining the Extent of the Lesion)

Relative Values of the Different Imaging Modalities for Tissue Diagnosis, Biologic Activity, and Staging

Conventional Radiography

Scintigraphy

CT

Sonography

Angiography

MRI

Staging and MRI

Therapeutic Strategies of Bone and Soft-Tissue Tumors

Primary Bone TumorsK. Bohndorf

Bone-Producing Tumors

Osteoid Osteoma

Osteoblastoma

Osteosarcoma

“Conventional” Osteosarcoma

Cartilage-Producing Tumors

Osteochondroma

Enchondroma

Chondroblastoma

Chondromyxoid Fibroma

Chondrosarcoma

Giant Cell Tumor

Tumors Arising from Bone Marrow

Ewing Sarcoma

Vascular Tumors

Hemangiomas

Tumors Arising From Connective Tissue

Lipoma

Other Tumors

Chordoma

Adamantinoma of the Long Tubular Bones

Tumorlike LesionsK. Bohndorf

Osteoma, Bone Islands, Osteopoikilosis

Fibrous Cortical Defect/Nonossifying Fibroma

Simple (Juvenile) Bone Cyst

Aneurysmal Bone Cyst

Eosinophilic Granuloma and Histiocytosis X

Fibrous Dysplasia

MetastasesK. Bohndorf

Soft-Tissue TumorsK. Bohndorf

4 Hematologic Disorders

PlasmocytomaTh. Rand

LeukemiasTh. Rand

Acute Leukemia in Children

Chronic Leukemia in Adulthood

Malignant LymphomaTh. Rand

AnemiasTh. Rand

Sickle Cell Anemia

Thalassemias

MyelofibrosisTh. Rand

LipidosesTh. Rand

5 Ischemic Bone Disease

OsteonecrosisM. Breitenseher

Osteonecrosis of the Hip

Osteonecrosis in other Locations

Osteonecrosis of the Lunate

Osteonecrosis of the Scaphoid

Osteonecrosis of the Metatarsal Heads

Osteonecrosis of the Distal Femur

Bone InfarctM. Breitenseher

Bone Marrow Edema SyndromeM. Breitenseher

Legg-Calvé-Perthes Disease

Osteochondritis Dissecans (OCD)K. Bohndorf

6 Metabolic, Hormonal, and Toxic Osteopathies

OsteoporosisG. Seidl

X-Ray Absorptiometry and Osteoporosis

Rickets and OsteomalaciaS. Youssefzadeh

HyperparathyroidismS. Youssefzadeh

Renal OsteodystrophyS. Youssefzadeh

HypoparathyroidismS. Youssefzadeh

Toxic OsteopathiesS. Youssefzadeh

Metal Poisoning (Lead, Bismuth, Phosphorus)

Aluminum Bone Disease

Fluorosis

Corticosteroids

Other Medications

AmyloidosisS. Youssefzadeh, K. Bohndorf

AcromegalyW. Fischer

7 Constitutional Disorders of Bone Growth

Skeletal DysplasiasW. Michl

Early Onset Types

Thanatophoric Dysplasia

Achondroplasia

Chondrodysplasia Punctata

Asphyxiating Thoracic Dysplasia

Dyschondrosteosis

Cleidocranial Dysplasia

Late-Onset Types

Predominantly Epiphyseal Dysplasias

Predominantly Metaphyseal Dysplasias

Predominantly Spondyloepiphyseal or Metaphyseal Dysplasias

Skeletal Dysplasia with Disorganized Development of Cartilage and Fibrous Components

Enchondromatosis

Polyostotic Fibrous Dysplasia

Congenital Generalized Fibromatosis

Skeletal Dysplasias with Abnormal Density of Osseous Structures

Increased Bone Density

Dysostosis MultiplexW. Michl

Mucopolysaccharidoses

Mucolipidoses and Gangliosidoses

DysostosesW. Michl

8 Various Bone and Soft-Tissue Disorders

Paget DiseaseW. Fischer

SarcoidosisW. Fischer

Hypertrophic OsteoarthropathyW. Fischer

MelorheostosisW. Fischer

Calcifications and Ossifications of the Soft TissuesW. Fischer, K. Bohndorf

Soft-Tissue Calcification Secondary to Imbalanced Calcium-Phosphate Metabolism

Soft-Tissue Calcifications with Normal Calcium-Phosphate Metabolism

Dystrophic Calcifications

Myositis Ossificans

Chronic Venous Stasis

Pustulotic Arthro-osteitisK. Bohndorf

Congenital Hip DysplasiaW. Fischer

9 Joints

Introduction and Synopsis

Anatomy of the Synovial JointsW. Fischer

Signs of Joint Diseases on Radiography and CTF. Kainberger, W. Fischer, K. Bohndorf

Radiographic Signs of the Peripheral Joints and Their Role in the Differential Diagnosis

Radiographic Signs at Specific Joints

SonographyF. Kainberger

ScintigraphyF. Kainberger

MRIF. Kainberger

Arthritis versus Osteoarthritis (Overview)W. Fischer

Enthesopathies (Fibro-ostosis and Fibro-ostitis)K. Bohndorf

Fibro-ostosis

Fibro-ostitis

Degenerative Joint DiseasesH. Imhof

Osteoarthritis of the Peripheral Joints

Osteoarthritis of Specific Joints

Osteoarthritis of the Hip

Osteoarthritis of the Shoulder

Osteoarthritis of the Finger and Carpal Bones

Osteoarthritis of the Toes

Disk Degeneration (Chondrosis, Osteochondrosis)

Degeneration of the Intervertebral Articulations (Facet Joint Osteoarthritis)

Advantages and Disadvantages of the Different Imaging Modalities in Degenerative Disease of the Spine with Neurologic Findings (Radiculopathy)

Comments on Interpreting MRI, CT, and CT Myelography in Disk Diseases

Diffuse Idiopathic Skeletal Hyperostosis (DISH, Forestier Disease)

Inflammatory Joint Diseases

Classification of the ArthritidesW. Fischer

Special Problems

Infectious Arthritis, Spondylitis, and SpondylodiskitisW. Fischer, K. Bohndorf

Bacterial Arthritis

Infectious Spondylitis and Spondylodiskitis

Rheumatoid ArthritisJ. Haller, J. Hofmann

Juvenile Rheumatoid Arthritis (Juvenile Chronic Arthritis)J. Haller, J. Hofmann

Ankylosing SpondylitisJ. Haller, J. Hofmann

Reactive ArthritisJ. Haller, J. Hofmann

Reiter Syndrome

Psoriatic ArthropathyJ. Haller, J. Hofmann

Enteropathic ArthropathiesJ. Haller, J. Hofmann

Articular Changes in Inflammatory Systemic Connective Tissue DiseasesJ. Haller, J. Hofmann

Systemic Lupus Erythematosus (SLE)

Progressive Systemic Scleroderma (PSS)

Polymyositis, Dermatomyositis

Polyarteritis Nodosa

Mixed Collagenosis

HIV-Associated Articular DiseaseJ. Haller, J. Hofmann

Differential Diagnosis of ArthritisW. Fischer

Neurogenic, Metabolic, and Hematologic Joint Diseases

Neurogenic Osteoarthropathy (Charcot Joint)F. Kainberger

The Diabetic Foot

Corticosteroid-Induced Neuropathic-Like Alterations (Pseudo-Charcot Joint)

Crystal-Induced Arthropathies and Periarthropathies

Gout (Gouty Arthritis)G. Seidl, W. Fischer

Pyrophosphate ArthropathyF. Kainberger

Hydroxyapatite DiseaseF. Kainberger

Arthropathy in HemophiliaF. Kainberger

Tumors and Tumorlike Lesions of the JointsK. Bohndorf

Intraosseous Ganglion

Synovial Chondromatosis

Pigmented Villonodular Synovitis (PVNS)

Index

Dedicated to Susanne, Katharina, Use, Klaus, and Andrea.

Klaus Bohndorf, Herwig Imhof

Dedicated to Lou, David, Jason, my Mom, my Dad, and my brother Robin.

Thomas Lee Pope

1    Trauma

In the broadest sense of its meaning, traumatology can be described as the medical specialty that studies damage to the human body, especially to the cell. The traumatic agent can be physical (e.g., mechanical trauma, temperature changes, radiation), chemical, or biologic (e.g., bacteria, viruses, etc.). Regardless of the etiology, the body can be expected to exhibit two effects: a local effect at the site of the trauma, and a systemic effect on the body (e.g., shock, fever, and others).

In a narrower sense, traumatology deals with mechanically induced injuries of the musculoskeletal tissue. For practical reasons, other physical etiologies, such as thermal injuries, are included in this chapter.

Definitions

Fracture

A fracture is a break in the continuity of bone. Where the bone is not completely separated, a break is called a fissure.

Etiologically, fractures can be classified as direct fractures (a fracture at the site of the causative force, Fig. 1.1) or indirect fractures (a fracture at a site remote from the causative force). Furthermore, the degree and extent of the injury differentiate complete from incomplete fractures. Typical incomplete fractures are greenstick fractures, buckle fractures, and fissures.

Joint Injury

Joint injury refers to any damage to the capsuloligamentous system, cartilaginous structures, and osseous articular surfaces following contusions, subluxations, and dislocations.

Since the ligaments that connect the joints are more or less incorporated in the joint capsule, the term ‘capsuloligamentous injury’ is frequently used. Such an injury can be an elastic strain, a plastic sprain, or a complete rupture.

Joint injuries of particular interest are fractures and avulsions of cartilage (chondral fractures) with or without attached osseous fragments (osteochondral fractures, ‘flake fractures’, Fig. 1.2).

Subluxation and dislocation result from forcefully displaced articular surfaces that have failed to return to their normal position.

Muscle Injury

Muscles can suffer closed or open tears and crush injuries. Furthermore, indirect injuries can cause elastic strains, plastic sprains, or tears (Figs. 1.3–1.5).

Tendon Injury

Direct mechanical trauma (e.g., lacerations) and indirect trauma that triggers maximum muscular contraction can tear a tendon. The tear frequently occurs where the tendon shows signs of degeneration.

Role of Imaging in Trauma to the Musculoskeletal System

Roentgen's discovery of X-rays at the end of the 19th century not only revolutionized the diagnostic evaluation of trauma, but also transformed the treatment of injuries to the skeleton, joints, and soft tissues. The dominant role of conventional radiology now must be reassessed at increasingly shorter intervals in view of the continuing emergence of new imaging modalities. Some of the recently introduced techniques use X-rays, such as digital radiography or CT, while others are based on completely different physical principles, such as sonography or MRI.

Fig. 1.1 Fractures. Subcapital fracture of the humerus with avulsion of the greater and lesser tuberosity and varus position of the humeral shaft.

Fig. 1.2 Joint injury. Osteochondral fracture of the lateral talus.

Fig. 1.3 Tendon injury. Acute hematoma at the transition of the quadriceps femoris muscle with the quadriceps tendon on sagittal T1-weighted spin echo image.

Fig. 1.4 Tendon injury. Large subacute hematoma in the femoris muscle on enhanced T1-weighted spin echo image.

Fig. 1.5 Sonographic visualization of a muscle injury. Large hematoma in the gastrocnemius muscle secondary to torn muscle fibers. The tear itself is not discernible.

Conventional Radiology

Radiographs in two projections perpendicular to each other, preceded only by the clinical assessment, are generally the first and often the only diagnostic images needed for the evaluation of trauma. Some fractures, such as fractures of the radial head or femoral condyles, are only visible on additional oblique views (Fig. 1.6). Special views designed to eliminate superimposed structures are used to display complicated anatomic structures such as those encountered in the facial and carpal bones, in the shoulder and hip joint, and in the mid foot. In general, conventional radiography promptly diagnoses fractures and provides relevant information as to whether the adjacent joint is involved and how the fracture fragments are positioned. Conventional radiographs can almost always be obtained under the difficult circumstances encountered in the acute setting of severe trauma. Even with the availability of more advanced methods, such as MRI, surgical planning is still guided primarily by the clinical and radiographic findings. Following internal or external fixation with reduction of dislocations and alignment of displaced fracture fragments, radiographs are mandatory to confirm the results of these therapeutic measures. Radiographs, however, cannot always monitor the progress of healing adequately. Complications of the healing process, such as infections, reflex osteodystrophy or inadequate internal fixation, are still diagnosed clinically, and radiographs are only confirmative. Radiographs play a limited role in skeletal regions that have complex anatomy or are superimposed by soft tissues and bowel loops, and in the evaluation of soft-tissue injuries. On the other hand, radiographically demonstrated soft-tissue changes can be used as indirect signs of osseous pathology.

Digital Radiology

Diagnostic imaging and image-guided therapy are inconceivable today without digital manipulation. Computed tomography (CT), digital subtraction angiography (DSA), and magnetic resonance imaging (MRI) rely on digital image acquisition and processing.

Two digital methods are used for projection radiography today: digital image enhancement and digital luminescence radiography. Both methods store the intensity distribution of the transmitted X-rays as a set of binary data, instead of analog data as with the film-screen system.

Digital enhancement radiography is a fluoroscopic method that can be implemented as digital cardiography, digital subtraction angiography, and digital spot films. Their numerous advantages have led to the acceptance of digital methods in diagnostic and therapeutic cardiology and angiography. Because of digital enhancement radiography's limited spatial resolution, it is rarely used as a substitute for X-rays, except for intra- and postoperative assessment of the position of fracture fragments.

Currently, digital luminescence radiography or storage phosphor radiography is the most commonly used digital method for obtaining radiographs (Figs. 1.7, 1.8), using the established projections of the film-screen technique. It can also be used with existing conventional tomographic equipment. The conventional film-screen cassette is replaced with a reusable storage phosphor imaging plate which captures the incoming X-rays as a latent image. The reader scans the plate with a laser beam and releases the stored energy as light. This stimulated light emission is measured by a photo-multiplier tube interfaced to the image processor. The quality of digital luminescence radiography is adequate for diagnosing traumatic changes in all parts of the skeleton. The inferior spatial resolution of digital luminescence radiography is compensated for by its superior contrast resolution, i.e., the superior detection of small contrast differences. The linear response curve (gradient type) of the storage phosphor and the capability of display processing give this method a high tolerance for variations in exposure, reducing the number of films that have to be repeated because of inadequate exposure and ultimately decreasing the radiation dose to the patient.

Radiography of the bones and joints with flat panel detectors, an emerging new technique, is still work in progress.

Computed Tomography

CT generates images without superimposed structures, usually along the axial plane. While the patient is in a resting supine position, even anatomically difficult body regions can readily be evaluated noninvasively. A single section can be imaged in seconds and, with the addition of spiral technique (see below), an entire body region obtained during a single breath-hold. CT provides information about the bones and soft tissues and, while the resolution is slightly inferior compared to conventional radiography, is fully adequate to evaluate skeletal trauma.

CT may often show post-traumatic changes not shown by radiography (Fig. 1.9). The established indications of CT in trauma are summarized in Table 1.1. It has been reported that up to 18% of fractures not seen on conventional radiographs may be detected by CT in the occipitocervical transition when CT is routinely performed on severely injured patients.

Fig. 1.6 Dorsal avulsion of the tibial plateau and femoral condyles. The fractures are seen only in the oblique projection (b).

Fig. 1.7 Different displays of a digital radiograph with:

a contrast scaling adjusted to that of a normal radiograph,

b frequency processing with edge enhancement.

Fig. 1.8 Further examples of various displays of digital images:

a contrast scaling adjusted to that of a normal radiograph,

b edge enhancement.

Any standard CT unit can easily demonstrate rotational anomalies, length discrepancies of the long bones of the extremities, and anteversion of the femoral neck with high accuracy and reproducibility. No complicated patient positioning or dedicated software is needed. In view of its excellent results and lower radiation dose, CT should replace the conventional methods of measuring the antetorsion angle, such as the Ripstein method.

Spiral CT, 2-D and 3-D Reconstruction

Spiral CT acquires a three-dimensional data set by continuous rotation of the X-ray tube around the moving examination table. The selected parameters for section thickness and table motion determine the volume of the body region and the resultant spatial resolution. From the three-dimensional data set, axial images are reconstructed as needed to address the clinical questions. Furthermore, the three-dimensional data set can be used to reformat images in other planes (2-D technique) and to render volume images (3-D technique) (Fig. 1.10). The tremendous improvements in processing speed over the last few years have made volume rendering feasible in daily clinical work. Reconstruction of isotropic voxels generated by the new generation of multi slice spiral CTs also has improved 3-D volume imaging.

The 2-D reformatting of sagittal and coronal images from axial images can highlight longitudinal fracture lines and can make it easier to evaluate horizontal interfaces, such as the acetabular roof or orbital floor (Fig. 1.10a).

The 3-D rendering allows different displays of the volume data. Surface rendering by thresholding is the most widely used technique. The relatively rapid surface-rendering algorithms dismiss attenuation values below the user-selected threshold of bone attenuation. The soft tissues are computationally removed and the surface of the underlying osseous structure is displayed (Fig. 1.11). The surface rendering for the display of bone has the drawback of including other high-attenuation structures, such as atheromatous plaques, contrast agents, and internal fixation devices. The osseous structures depicted can be manipulated by semiautomatic subtraction of superimposed and potentially interfering anatomic structures. For instance, acetabular fractures can be displayed without the femoral head, or calcaneal fractures without the talus, essentially enacting an ‘electronic disarticulation’. By adding a virtual light source, a shaded surface display (SSD) can be achieved, which enhances the 3-D understanding of the image.

Volume rendering requires more computer manipulation. It classifies each voxel of the volume data set and incorporates it into the displayed image. It can provide a transparent 3-D display of any apparent surface from any point of view and allows the comprehensive visualization of fractures. Powerful computers are required to achieve volume rendering at a reasonable speed in clinical applications.

All reconstruction methods offer a more effective display of complex anatomic and pathologic structures. Three-dimensional imaging improves the assessment of fractures. Location and extent of the fracture, shape and position of the fracture fragments and the condition of articular surfaces can be better appreciated, making it easier to assess comminuted fractures. Surface rendering, which, in contrast to volume rendering, incorporates only a portion of the data into the 3-D image, provides an inadequate display of undisplaced and intra-articular fragments and fails to show any soft-tissue changes. In comparison to sectional imaging, surface rendering does not increase the detection rate of fractures and should only be supplementary to plain films and axial CT sections in the evaluation of comminuted fractures.

Arthrography

The role of arthrography has declined because of the excellent visualization of the intra-articular structures by MRI. However, arthrography still has a role for certain clinical questions, such as adhesive capsulitis, and is still considered to be the ‘gold standard’ for the evaluation of ligamentous injuries of the hand (Fig. 1.12). Moreover, arthrography remains part of CT- or MRI-arthrography and is superior to imaging without intra-articular contrast medium for the evaluation of shoulder instability because of the detailed arthrographic visualization of anatomic structures and pathologic changes. This feature is especially helpful for conditions involving the glenoid labrum and joint capsule.

Table 1.1 Established indications for CT in skeletal traumatologyIndicationClinical questionFacial bone injuriesExact determination of the fracture sites and position of the fracture fragmentsVertebral injuriesStability, intraspinal fragment, paravertebral/intraspinal hemorrhage, traumatic disk extrusion, fractures of the occipitocervical transitionPelvic and hip fracturesFractures of the posterior pelvic ring, acetabular fracture, intra-articular fragment, degree and type of fragment displacementWrist injuriesUnclear extent of trauma, radioulnar/carpal dislocation, rotational deformityCalcaneal fracturesFragment displacement, articular involvementBiometric viewsDetermination of malrotation, length discrepancy, angulation (antetorsion angle of the femoral neck)

Fig. 1.9 Scaphoid fracture. a The AP radiograph is normal. b The fracture line is clearly delineated by CT.

Fig. 1.10 2-D (a) and 3-D (b) reconstruction of an acetabular fracture. The 3-D reconstruction displays the joint as seen from the patient's feet.

Fig. 1.11 3-D visualization of fractures of left iliac wing and acetabulum.

Fig. 1.12 Arthrography showing a tear of the triangular fibrocartilage complex (TFCC).

Sonography

Sonography is beginning to play an increasingly important role in trauma. Among its advantages are availability, low cost, patient acceptance, and lack of radiation exposure. Its disadvantages are operator dependence, long examination times, selective and often incomprehensible documentation, and the inability to penetrate osseous structures. Reasonable indications for sonography in trauma are outlined in Table 1.2. Ruptures of the Achilles and patellar tendons can be diagnosed instantly with great accuracy. Sonography cannot always differentiate between partial and complete rotator cuff tear, and MRI must be added in these cases.

Intrafascial hematomas in the musculature of the extremities can be visualized by sonography and, if necessary, drained under sonographic guidance. Sonography should also be the primary method for evaluation of a suspected sternal fracture. Sternal fractures, which have become a frequent seat belt injury, are seen as breaks in the normal contour of bone surrounded by a hematoma, with inducible relative motion of the fracture fragments (Fig. 1.13). Radiographic visualization of sternal fractures is often inadequate because of superimposed ribs and soft tissues and inherent low bone contrast. Finally, sonography can be superior to radiography in demonstrating rib fractures.

Magnetic Resonance Imaging

MRI can effectively visualize traumatic changes of the skeleton and peripheral soft tissues, such as intramuscular hematomas and ligamentous tears. Initially, the prevailing opinion was that the signal void of cortical bone would preclude the evaluation of skeletal injuries, but this theory has been disproved. In fact, the opposite is true; the lack of any signal from cortical bone augments the signal from adjacent tissues. In particular, visualization of bone marrow has opened entirely new perspectives (Table 1.3).

Stress and insufficiency fractures can present as radiographically unexplained pain. If radiographic changes are present, they might be mistaken for neoplasms or infection, particularly in the absence of periosteal reaction. A space-occupying process can be excluded invariably by MRI. These advantages of MRI are most valuable for evaluating skeletal regions with a complex internal architecture.

Before the availability of MRI, radiologically occult fractures often posed a diagnostic dilemma. MRI can detect not only these fractures, but also other conditions, such as osteonecrosis, degenerative subchondral cysts, and metastases, which might be the cause of the patient's symptoms (Fig. 1.16).

MRI has its major impact on diagnosing traumatic joint injury. Traumatic injury to the joints was once the domain of arthroscopy, but this has now changed with the introduction of MRI and has led to a better understanding of the immediate and delayed effects of trauma on the joints. Although hyaline cartilage, subchondral lamellar and trabecular bone can be considered separately, they are now increasingly seen as a functional unit. The most frequently encountered and characteristic constellation is the subchondral trabecular fracture with underlying marrow edema. The therapeutic ramification of the bone marrow edema, the so-called ‘bone bruise’, is still not fully understood.

Because of its complex anatomy, the wrist was one of the first anatomic regions to be investigated by MRI, and special surface coils allow high-resolution visualization of the carpal bones. For imaging with conventional MRI, patients must place their hands over their heads, putting them in a relatively uncomfortable position that is rarely tolerated for examination times exceeding 20 minutes. This has been overcome by open MRI systems, which allow the patient to sit outside the unit. The inferior spatial resolution of the open systems, however, can be a problem for those clinical questions that require the evaluation of the triangular fibrocartilage complex or ligaments. Established MRI indications in the wrist include the search for occult fractures of the carpal bones as well as the assessment of osteonecroses, especially of the navicular and lunate. Numerous publications have addressed the role of MRI in the evaluation of injuries of the triangular fibrocartilage complex (TFCC). Like arthrography, MRI visualizes a variety of changes in the TFCC in asymptomatic patients, and it is difficult to determine whether the particular change seen after trauma is traumatic or degenerative in origin.

The evaluation of knee pain undiagnosed by physical examination in the patient with normal radiographs has become the domain of MRI. This technique can demonstrate intraosseous microfractures and has increased our understanding of post-traumatic pain. These trabecular fractures, which are radiographically occult but often scintigraphically positive, can be clearly identified by location and configuration of the abnormal signal pattern. These otherwise unidentifiable microfractures must be considered the most frequent cause of acute post-traumatic pain. Generally MRI findings resolve within 5 to 15 days, although no satisfactory prospective studies have been reported.

Fig. 1.13 Sonographic visualization of a sternal fracture. The sonographically visualized hematoma makes it easy to find nondisplaced fractures, making sonography more sensitive than radiography.

Fig. 1.14 Contusion of the spinal cord and posterior subluxation of C3 on C4 in a trauma patient with neurologic findings (T2-weighted SE images).

Fig. 1.15 Full-thickness tear of the supraspinatus tendon on T2-weighted SE image.

Fig. 1.16 Occult calcaneal fracture with associated bone marrow edema following minor trauma 6 weeks previously and with persistent pain. The radiograph was normal. a T1-weighted SE sequence showing the fracture line as low signal intensity, b STIR sequence showing the fracture line as high signal intensity surrounded by bone marrow edema.

Table 1.2 Established indications for sonography in the diagnostic evaluation of osseous, articular, and soft-tissue injuriesBody regionIndicationsShoulderRotator cuff tear, biceps tendon tear and dislocation, Hill-Sachs lesion, avulsion fracture, joint effusion, AC joint separationElbow, hand, footAchilles tendon tear, joint effusion, rupture of the distal triceps and biceps tendon, avulsion fractureHipJoint effusion, avulsion fracture, slipped capital femoral epiphysis (epiphyseolysis of the femoral head)KneeRupture of quadriceps and patellar tendons, rupture of collateral ligament, joint effusion, Baker cystSoft tissuesMuscle tear, hematoma, foreign bodyRibs, sternumRadiographically occult fractures

MRI detects meniscal tears with an accuracy of 80–90%, but it is still uncertain whether degenerative and traumatic tears can be distinguished by MRI. Not every meniscal lesion identified by MRI is symptomatic, and all those identified do not need surgical intervention. Obliquely oriented horizontal tears, which are commonly found on the undersurface of the meniscus, are invariably degenerative in nature, whereas vertical tears usually are traumatic in origin.

Complete tears of the anterior cruciate ligament (ACL) are detected with an average accuracy of 90%. Partial tears or distortions of the anterior cruciate ligament, which are characterized by partially intact fibers and severe intra- and periligamentous edema, are not always distinguishable from complete tears. Injuries of the posterior cruciate ligament are less common than ACL tears but are easily detected by MRI.

Even after numerous technical refinements, evaluation of the hyaline cartilage by MRI remains inferior to direct visualization by arthroscopy. This superiority of arthroscopy applies only to chondromalacia and superficial lesions of questionable therapeutic relevance. However, in many instances, osteochondral injuries are easily identified by MRI as the cause of hemarthrosis.

MRI is the most sensitive imaging test for identifying lesions of the rotator cuff of the shoulder joint (Fig. 1.15). Evaluating shoulder instability by MRI remains a controversial issue, as CT-arthrography represents a competing imaging method for this indication. But MRI-arthrography, analogous to CT-arthrography, can be viewed as the ‘gold standard’ for evaluating complex labrocapsular and ligamentous anatomy and pathology. MRI-arthrography can visualize anterior, posterior, or inferior labral injuries and Hill-Sachs defects, as well as injuries of the superior labral-biceps tendon junction.

Scintigraphy

Bone scans are performed with Tc 99 m–labeled diphosphonate and can be obtained as a static study or a dynamic study using the three-phase technique. Other scintigraphic techniques, such as minor Tc 99 m–labeled white blood cell scans, or Tc 99 m–labeled monoclonal antibody scans do not play a significant role in the evaluation of trauma.

Bone scans are established for the detection of radiologically occult fractures, but MRI has replaced this technique in most centers.

The bone scan is well suited for surveying the patient with multiple trauma for the extent of skeletal involvement. It should be kept in mind that reparative changes in juxta-articular appendicular bone might be visible only after the third day. In the diaphyses of the long bones and in the central skeleton, the bone scan might even become positive as late as one week after the trauma. Because of the known low specificity of increased bone activity on bone scan, a positive finding should be correlated with the radiographs.

In pediatrics, bone scanning plays a major role in screening for battered child syndrome (see pp. 132 ff).

Another indication for bone scanning is the search for stress fractures, including stress-induced spondylolysis of the lower lumbar spine. Focally increased osseous activity is often seen well before radiographic changes are detected.

Stress fractures should be differentiated from traumatic or degenerative irritation of tendon insertions (enthesopathy) and traumatic periosteal reaction along diaphyseal bone. Periosteal reaction along the tibia is referred to as ‘shin splints’. In comparison to stress fractures, shin splints show no increased blood flow on the blood pool images.

Post-traumatic complications of the healing process, such as pseudarthrosis and reflex osteodystrophy, can also be demonstrated by bone scanning.

Practical Suggestions for Imaging in the Trauma Setting

Any traumatized bone must be visualized in at least two projections. It is difficult to meet this requirement for certain anatomic locations, such as the hip or shoulder. Special projections have been proposed for these anatomic regions. (Refer to other texts dedicated to radiographic positioning.)For any fracture visualized next to a joint, any articular extension must be searched for. Special views must often be added to the two standard views. If conventional imaging is inconclusive, MRI should be considered.If one of two parallel long bones (such as the ulna and radius or the tibia and fibula) is fractured, a fracture of the companion bone must be excluded.Any long bone must be visualized in its entire length. In other words, the proximal and distal joint bearing ends have to be included.In patients with multiple fractures, subtle findings may be missed if other major injuries are present. A second look at a less busy time or a second reading can be beneficial in detecting findings which might be overlooked. This is particularly applicable to films of patients with multiple trauma.Whenever possible, the referring physician should state the traumatic forces and the expected pattern of the traumatic changes. This allows a focused search with the expected injuries kept in mind.Example: The supination-adduction trauma to the ankle causes a transverse fracture of the lateral malleolus below the syndesmosis, or a rupture of the lateral collateral ligament. Furthermore, this can lead to a vertical osteochondral fracture of the medial talar articulating surface. An awareness of the mechanism of injury will help direct the search pattern. This follows the adage ‘you will find what you look for’.It is mandatory to correlate clinical and radiological findings. If no exact or reliable clinical information is supplied, the radiologist or technologist must obtain it directly from the patient.While many direct signs of fracture are easily appreciated, indirect signs such as soft-tissue changes are often overlooked. It is important for all images to include indirect signs in the diagnostic process (refer to special traumatology).Equivocal radiographic findings should be further evaluated by additional views in other projections, such as oblique views. Other imaging modalities, such as sonography and CT, should be incorporated early in the diagnostic process.Fracture lines are not invariably radiolucent. They can be radiodense if fracture fragments

a) overlap,

b) are impacted,

c) are rotated relative to each other, with the radiodense line often sharply delineated, in contrast to a) and b).

Table 1.3 Established indications for MRI in the diagnostic evaluation of osseous, articular, and soft-tissue injuriesIndicationsClinical questionSkeletal traumaTrabecular fractures, occult fractures, stress fractures, vertebral fractures, suspected spinal cord involvement, posttraumatic osteonecroses, post-traumatic chronic osteomyelitisJoint traumaOsteochondral fractures, intra-articular ligamentous lesions (cruciate ligaments, collateral ligaments), meniscus injuries (especially in the knee)Trauma of the peripheral soft tissuesTendon and muscle injuries (hematoma, rupture, ligamentous injury [e.g., shoulder]), tendosynovitis in chronic repetitive microtrauma

Fracture Classifications and Types

Classification of fractures by their causative mechanisms:

Traumatic Fractures These fractures are caused by excessive mechanical loading, which can be sustained by deforming forces that act directly on bone such as tapping, crushing, or penetration, or indirectly from a distance, as occurs with traction, angulation, shearing, or compression. If the loading of bone exceeds a certain point, the bone will fail and fracture.Stress and Insufficiency FracturesStress fractures are caused by fatigue failure of otherwise normal bone induced by repeated or cyclical stresses. Insufficiency fractures are caused by normal forces or microtrauma and occur in bones of reduced internal strength, such those bones weakened by osteoporosis.Pathologic FracturesThese fractures occur in bone weakened by a preexisting condition and are caused by a force that would not break normal bone. They can be considered a local manifestation of an insufficiency fracture. The most common preexisting conditions are bone cysts, osteolytic metastases, and plasmocytoma.

Fracture Types

The morphology of the fracture reflects the direction and level of the traumatic forces. A practical classification of fracture types is illustrated in Fig. 1.20.

A special type of fracture is the compression fracture of the spine (Fig. 1.17).

The classification can be slightly modified by determining whether the fracture is associated with a dislocation (Fig. 1.18), or whether the fracture lines extend to the articular surface (Fig. 1.19).

Fig. 1.17 Compression fracture of the T9 and T10 vertebral bodies. There is increased density in the impacted anterior components of the vertebral bodies.

Fig. 1.18 Bimalleolar fracture-dislocation of the ankle. Only the lateral view shows the full extent of the injury.

Fig. 1.19 Longitudinal fracture of the tibial plateau seen as indistinct increased density on the conventional radiograph (a). MRI (T1-weighted SE sequence) shows the full extent of the fracture and the cortical involvement (b).

Fig. 1.20 Summary of the most important fracture types.

Special Considerations in the Pediatric Age Group

Trauma to the epiphysis and growth plate: The Salter-Harris classification is the most widely used classification applied to physeal injuries (Figs. 1.21, 1.24).

Type I: The epiphysis is completely separated from the metaphysis without evidence of osseous involvement.

Type II: Fracture through the epiphysis with a metaphyseal ‘corner’ fragment.

Type III: Intra-articular extension of a fracture of the epiphysis with involvement of the growth plate. The epiphyseal fragment can be displaced.

Type IV: Vertical fracture that crosses epiphysis, growth plate and metaphysis.

Type V: Compression of the growth plate (risk of premature closure of the growth plate).

Buckle or torus fracture: This is an impaction injury of the metaphysis, causing the cortex to buckle. It is frequently asymmetric with one side of the cortex more involved than the other and might even be invisible on one side (Fig. 1.22).

Greenstick fracture: This is an incomplete fracture leaving a portion of the cortex and periosteum intact (Fig. 1.23).

Growing fracture: Skull fractures in infants can grow due to development of a ‘leptomeningeal cyst’ that protrudes into the fracture line and causes it to widen as a result of marginal erosion.

Toddler's fracture: This is an oblique or spiral fracture, primarily seen in the tibia, without displacement of the fracture fragments. It is a torsional injury found in children who are just beginning to walk.

Fig. 1.21 Classification of the fractures involving the growth plates after Salter and Harris. Aitken's classification is shown in brackets.

Fig. 1.22 Buckle fracture in a 9-year-old girl.

Fig. 1.23 Creenstick fracture in a 7-year-old girl. Only one side of the cortex is fractured.

Fig. 1.24 Unusual fracture in the pediatric age group. Fracture across the metaphysis (corresponds to the Salter-Harris type II fracture), together with a subchondral fracture of the epiphysis (cartilage intact). a Unremarkable radiograph, b sagittal T1-weighted SE sequence, c axial T2-weighted sequence at the level of the femoral metaphyses.

Fractures of the articular surfaces (chondral and osteochondral fractures)

The most important biomechanical properties of hyaline cartilage are protection against excessive strain and providing a smooth surface for the joint. These properties are determined by the chemical composition and the complex spatial interaction of the extracellular matrix of the cartilage. The matrix is primarily composed of water and macromolecules (collagen, proteoglycan, and other proteins). Hyaline cartilage consists of several layers, and the deep calcified zone and the subchondral bone are closely intertwined. An avulsion of the cartilage (traumatic separation) occurs primarily between the deep calcified and the juxta-articular noncalcified cartilage.

It is known from experimental studies that compression and trabecular fractures of the subchondral bone can occur without injury to the cartilage. This can be attributed to the greater elasticity of the cartilage in comparison to the subchondral trabecular osseous structure.

Fractures of the joints can be divided into typical skeletal fractures with articular involvement and specific fractures confined to the cartilage and subchondral bone. The latter fractures are caused primarily by pressure directly transmitted onto the cartilage by a vertical load. Concurrent shearing and rotatory load can not only increase the pressure on the articular surface but can also avulse cartilaginous fragments (with or without attached bone) from the articular surface.

Frequent causes of articular surface fractures are torsion or supination/pronation injuries and these are often associated with ligamentous injuries.

The clinical findings are nonspecific, but a hemorrhagic joint effusion is invariably present. This finding can also be associated with any trauma involving the intra-articular structures.

Dislodged chondral or osteochondral fragments must be surgically reattached, but shallow articular compression deformities can be treated conservatively.

Location: The principal sites of involvement are the ankle and knee, including the patella. Other less common locations are the femoral head and humeral head.

Chondral fractures occur primarily in children and adolescents, and osteochondral fractures occur primarily in adults.

Technical considerations: If an osteo chrondral fracture of the ankle is suspected, a radiographic examination in three projections is indicated: AP, lateral, and AP oblique in slight internal rotation. The oblique view projects the articular surface of the talar trochlea without superimposition.

Ankle: The lateral osteochondral fractures of the talus are horizontally oriented and have a thin, small fragment (Fig. 1.28). The medial fractures are generally deeper and produce a crater-like defect.

Patella: The diagnostic evaluation rests on axial views, possibly obtained at different angles. Small contour defects are seen along the articular surface (Fig. 1.27).

Femoral condyles: The fracture line is invariably parallel to the articular surface. The following specific findings can occur alone or in any combination:

linear densities in the subchondral bone (caused by superimposed fragments on the summation view),irregularity of the osseous contour (undulated, serrated; Figs. 1.25, 1.29),large avulsion with complete or partial separation of the fragments (Fig. 1.30),loose fragment in the joint capsule (Fig. 1.26).

When the epiphyses are unfused, chondral/osteochondral fractures can be mistaken for variants of the epiphyseal ossification. This will be addressed further (see pp. 128 ff).

Conventional radiography has a high rate of false negative findings. For example, up to 30% of ankle fractures are overlooked.

MRI is the imaging method of choice for the definitive evaluation of altered articular surfaces.

Technical considerations: The examination protocol offers several sequences. The recommended sequences are STIR, T1-weighted, and T2-weighted (turbo) spin echo and, for more comprehensive evaluation of cartilage, gradient echo sequences. The selection of section planes depends on the anatomy and the expected site of the injury. Images should be obtained in at least two planes.

With a properly selected examination technique, MRI should disclose the findings needed for the clinically relevant differentiation between injuries with cartilaginous defects and those with intact cartilage.

Fig. 1.25 Osteochondral fracture, seen only as irregular contour of the femoral condyle.

Fig. 1.26 Osteochondral fracture with loose fragment.

Fig. 1.27 Osteochondral fracture of the retropatellar articular surface.

Fig. 1.28 Osteochondral fracture of the lateral aspect of the talar trochlea.

Fig. 1.29 Osteochondral fracture of the lateral femoral condyle. Shell-like osseous fragment and irregular condylar contour.

Fig. 1.30 Large osseous fragment of osteochondral fracture of the femoral condyle.

Injuries with cartilage defects: The major discriminating feature distinguishing strictly chondral lesions from osteochondral fractures is contour irregularity (Figs. 1.32, 1.33).

Injuries of the articular surface with intact cartilage: The following distinctions have to be made

subchondral impaction (Fig. 1.31):This produces a subtle depression of the subchondral bone parallel to the articular surface. Occasionally, scalloped signal changes and fracture lines are observed.subchondral trabecular fracture (bone bruise):This represents bone marrow edema detectable by MRI without subchondral impaction.

Fig. 1.31 Subchondral impaction with normal overlying cartilage. a T1-weighted SE image, b CRE image.

Stress and Insufficiency Fractures

Stress can be defined as the load sustained by bone. Bone is a dynamic tissue and needs stress for its normal development. The mechanical response to stress determines the osseous texture. Absence of normal stress induces rapid osteoclastic resorption of cancellous and cortical bone as well as cessation of the osteoblastic activity, leading to disuse osteoporosis.

Stress is also placed on bone from muscular activity and body weight.

It is not entirely understood how stress shapes the mechanical function of bone, but evidence suggests that the adaptive process is mediated by microfractures. Bone subjected to more than normal stress responds with osteoclastic resorption. The osteoclastic cavities are subsequently filled with lamented bone. The formation of new bone is a slow process (weeks to months), and stress in excess of the normal levels results in an imbalance between bone resorption and bone formation for the first few weeks. Therefore, new periosteal and endosteal bone formation represents a passing reparative mechanism needed to support the transiently weakened bone, especially the critical cortex. This process is basically the same in cortical and cancellous bone.

This normal physiologic adaptive process to micro damage (stress) becomes pathologic whenever there is an imbalance between the damage and repair. Continued and repetitive imbalance causes fatigue fractures of the cortical and cancellous bone. If the excessive stress abates (e.g., joggers curtail their activity because of the pain induced by the disproportionally high stress of running), a fracture line may not become visible despite radiographically apparent periosteal reaction as an adaptation to the stress. This phenomenon is referred to as stress reaction rather than stress fracture (Fig. 1.34).

Fig. 1.32 One-year-old osteochondral fracture without intact cartilage. Enhancement of the subchondral bone indicates reactive changes.

a T1-weighted CRE sequence after intravenous injection of contrast medium (indirect arthrography),

b T1-weighted SE sequence with frequency selective fat suppression following administration of contrast medium.

Fig. 1.33 Acute osteochondral fracture with surrounding edema laterally.

a Coronal T2-weighted CRE sequence with fat suppression,

b sagittal STIR sequence.

Fig. 1.34a Stress reaction with periosteal and endosteal adaptation. The patient played volleyball for 30 years but was asymptomatic. The radiographic examination was obtained because of acute trauma. b Normal radiograph for comparison.

Fig. 1.35 Elderly female patient with pain for two years. a Remote insufficiency fracture of the right sacral ala. b The diagnosis of an insufficiency fracture is supported by a remote insufficiency fracture in the left superior ischial ramus (axial CT).

Fatigue fractures are divided into two categories, depending upon the underlying conditions of bone:

Stress fractures: The density and structure of bone are normal. Only the stressed portion of the bone is (reversibly) weakened according to the mechanism described above.

Insufficiency fractures: Normal or slightly above normal stress acts on a bone of abnormal density or structure. The pathologic fracture is a special case of insufficiency fracture. While the pathologic fracture occurs at a site of local bone loss, such as that caused by tumor destruction for instance, the insufficiency fracture generally affects bone of diffusely reduced bone mineral density (BMD) (Figs. 1.35, 1.37, 1.45).

Risk factors:

Excessive mechanical strain, especially during walking.Estrogen deficiency in women.Elderly (osteoporotic bone).Reduced bone density from other causes (e.g., steroids).

Location: The tubular bones of the appendicular skeleton as well as the axial skeleton can be affected. Insufficiency fractures primarily involve the femoral neck, distal forearm, spine, and sacrum, whereas stress fractures have a tendency to occur in the tarsal bones, tibia, and femur.

The clinical findings of insufficiency lesions consist of localized pain and soft-tissue swelling with overlying warmth. The stress fracture of the femoral neck can remain asymptomatic for a long time.

It is important to remember that conventional radiography might show no abnormality for several weeks. Within the first few weeks, the radiographic sensitivity approaches 15–50%.

A lamellated periosteal reaction is frequently the first radiographic sign.In selected cases, a subtle radiolucency and an indistinctly outlined cortex may be seen early.Endosteal thickening becomes discernible at a later stage of the process.The fracture line is usually apparent only after the periosteal reaction has appeared.An indistinctly outlined sclerotic zone is seen across the cancellous bone and the cortex (late stage, Fig. 1.38).

Bone scintigraphy with Tc 99 m diphosphonate is well suited for the detection of stress and insufficiency fractures. A false negative finding is extremely rare.

A direct correlation exists between the intensity of tracer uptake and the extent of the stress fracture. Stress fractures appear as ill-defined focal areas of increased uptake, primarily in the cortex (Fig. 1.36).

Bone scintigraphy also reveals clinically asymptomatic lesions. Though the nature of these lesions cannot always be established, they are often attributed to stress reactions that have not yet become clinically apparent and have not yet induced any radiographic abnormalities.

Above all, bone scintigraphy contributes to the evaluation of anatomically complex osseous structures. Sacral insufficiency fractures present as linear or H-shaped radionuclide accumulation (the so-called ‘Honda sign’); this latter pattern is essentially pathognomonic of stress injury and not malignancy.

Fig. 1.36 Stress fracture of the tibia in a 6-year-old boy, with only minimally increased osseous uptake.

Fig. 1.37 Insufficiency fracture in the presence of severe osteoporosis.

Fig. 1.38 Remote stress fracture in a marathon runner, seen as a subtle band of increased density.

Fig. 1.39 Bilateral insufficiency fractures of the sacrum. Enhanced T1-weighted MR sequence with fat suppression showing the ‘H’ configuration (‘Honda sign’).

Fig. 1.40 Insufficiency fracture of the tibial plateau in an overweight osteoporotic woman with pain for three weeks.

Fig. 1.41 Insufficiency fracture of the calcaneus, T1-weighted spin echo sequence before (a) and after (b) administration of contrast medium. After enhancement, the fracture line is seen as a band of decreased signal intensity.

CT is a good method for delineating fracture lines, especially those in the sacrum, tarsal bones, and tubular bones. A definitive diagnosis can usually be made if the fracture line is surrounded by reactive sclerosis (Figs. 1.35, 1.37, 1.44).

MRI is an extremely sensitive method for the detection of stress and insufficiency fractures since both conditions are associated with a bone marrow edema and can be used as an alternative to bone scintigraphy (Figs. 1.39, 1.40, 1.41, 1.43). The most helpful sequences are STIR images and T1-weighted and T2-weighted images. A fracture line is not always visualized, and in cases where the MR findings are nonspecific, osteomyelitis should be included in the differential diagnosis. In selected cases, enhancement with Gd-based contrast medium might help delineate the fracture line, which remains of low signal intensity relative to the enhancing edematous bone marrow (Fig. 1.41).

Osteoid osteoma: The radiographic findings of this lesion are a round radiolucency surrounded by an irregularly outlined sclerotic rim without evidence of a linear component perpendicular to or at an acute angle with the cortex found in stress fractures.

Chronic osteomyelitis, another cause of diffuse cortical thickening usually involves the entire cortical circumference. Linear radiolucencies are not seen in this condition.

On MRI, the differential diagnosis includes an acute bone infarct, especially after radiotherapy to the pelvic region. In this setting differentiation of infarct from stress fracture can be difficult. Bone infarcts show a diffuse enhancement of bone marrow edema, and CT can be helpful in certain cases to search for fracture lines.

Pathologic Fracture

This condition represents a special case of insufficiency fracture. It is a fracture that develops in an osseous structure weakened by tumor or tumor-like conditions. These injuries are usually caused by inadequate stress or minor trauma (Figs. 1.42, 1.46).

The commonest pathologic fracture is one occurring through a juvenile bone cyst or a nonossifying fibroma. Any osseous tumor, especially metastases, can be the underlying cause of a pathologic fracture. However, the notable exception to this rule is primary or secondary bone-forming tumors, such as osteosarcoma and osteoblastic metastases, which rarely result in a pathologic fracture.

Fig. 1.42 Pathologic fracture of the proximal humerus through an osteolytic metastasis from thyroid carcinoma.

Fig. 1.43 Insufficiency fracture (STIR sequence). The clinical findings consisted of pain and tenderness, as well as swelling. The linear decrease in signal intensity distinguishes this finding from chronic osteomyelitis.

Fig. 1.44 Pain for three months, no discernible fracture line: Stress fracture with periosteal new bone formation.

Fig. 1.45 Insufficiency fracture in osteogenesis imperfecta.

Below:Fig. 1.46 Pathologic fracture in fibrous dysplasia (a). The patient suffered minor trauma. b Control radiography after internal fixation. The fibrous dysplasia was initially overlooked and only recognized after removal of the internal fixation device. c Conventional tomography.

Fracture Healing

Primary (direct) and secondary (indirect) healing of the fractures returns osseous stability by restoring the original tissue.        

Primary Fracture Healing

Definition: Primary healing is characterized by the absence of callus formation and requires:

Contact between fragments with a maximum fracture gap of 0.5 mm. Internal compression fixation of the fragments increases the chance of a primary fracture healing.Immobilization of the fracture fragments (e.g., internal fixation).Adequate blood supply and viability of the fragments.

The fracture fragments unite by direct extension of the Haversian canals from one fragment to the other (‘contact healing’), or by the formation of lamellar bone, which is later replaced by longitudinally oriented osteons (‘gap healing’). The periosteal or endosteal mesenchymal cells are not activated in this setting.

Indistinct cortical structures,invisible or faint fracture line.

Visualized interosseous or periosteal callous formation indicates the formation of ‘restless’ callus, followed by fixation callus. Furthermore, widening of the fracture line or the appearance of a ‘new’ fracture line reflects osseous resorption of the fracture fragments and indicates an impaired primary fracture healing.

Secondary Fracture Healing

A widened fracture line or inadequate mechanical fixation of the fracture fragments results in secondary fracture healing, consisting of the formation of a ‘periosteal cuff’ around the fracture gap. This cuff arises from connective tissue and represents mesenchymal new bone formation. In addition to connective tissue proliferation, cartilage is usually formed by metaplasia and ultimately transformed into osseous tissue. Thus, the original structure is restored via a detour (lamellar osseous tissue, osteons).

Secondary osseous healing passes through characteristic stages and their corresponding radiographic findings are shown in Table 1.4.

Trabecular fractures initially show increased density. Within weeks, the increased density resolves and is replaced by normal trabecular texture. A periosteal reaction always indicates cortical involvement.

Osseous consolidation of a fracture should be assessed clinically first. The radiographic signs usually lag behind the clinical signs.

The clinical signs of an osseous consolidation (not to be equated with complete fracture healing) are:

stability on physical examination,lack of pain,ability to bear weight.

Radiographic Signs of Osseous Consolidation

The osseous bridging of the fracture is solid.The fracture callus is of homogeneous density.The density of the fracture callus equals the density of the cortex.These findings must be seen in at least two projections.

Caution: Underexposed films overestimate the degree of osseous bridging.

Basic Principles of Fracture Treatment

The conservative (closed) treatment follows three approaches:

Primary functional treatment (without cast). This requires adequate axial relationships and exercise stability; for example, a subcapital fracture of the humerus in an elderly person.Repositioning and immobilization by casting, for instance, a distal radial fracture.Repositioning and immobilization by means of traction; for instance, a femur fracture.

The goals of operative (open) therapy are to restore the normal anatomic relationship of the axial planes and articular surfaces and to stabilize fracture fragments. Several approaches are available and can be combined.

Internal fixation by screws; for example, avulsion of juxta-articular or joint-bearing fragments,Internal fixation by compression plates and screws,Internal fixation by wire fixation (cerclage); for example, the olecranon and patella,Intramedullary fixation; for example, by rod and pins,External fixation; for example, the compound fracture of the lower leg.Table 1.4 Stages of secondary osseous healing. Correlation of the pathologic and radiographic findings