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During infancy and childhood, multiple developmental changes occur in the epiphysis. Initially the epiphysis is composed entirely of hyaline cartilage. As skeletal maturation progresses, one or several secondary ossification centers (SOCs) develop within the epiphyseal cartilage. The SOCs enlarge by endochondral ossification and undergo marrow transformation in a process analogous to that of the primary physis and metaphysis. Magnetic resonance (MR) imaging can be used to evaluate vascularity, marrow, and cartilage and plays a critical role in the assessment of epiphyseal disorders in children. In cases of shoulder and hip dysplasia, MR imaging demonstrates unossified structures and helps guide treatment. In cases of trauma, the intracartilaginous pathway of fractures, the degree of physeal involvement, and early bridge formation can be assessed. With the use of intravenous gadolinium-based contrast material, avascular necrosis and reperfusion can be characterized. This article reviews the normal structure of the epiphysis, its appearance at MR imaging, and age-related changes to the epiphysis. Common conditions that lead to epiphyseal damage in children are reviewed, with an emphasis on the role of MR imaging in diagnosis, prognosis, and treatment., (© RSNA, 2014.)

There are a variety of conditions that manifest not only in bone but also in skin. Bone and skin structures can share common embryologic origins, and genetic defects that occur early in cell differentiation may lead to disease in both organ systems. Alternatively, diseases of bone and skin may be caused by defects in genes that participate in directing or controlling both systems. Many diseases of bone and skin can manifest with atypical radiologic findings or mimic malignant bone lesions. Upon encountering such a disease process, a radiologist who is familiar with both aspects of the disorder and consequently looks for associated skin findings can greatly benefit the patient by making a definitive diagnosis. Similarly, a clinician who encounters suggestive skin lesions should be prompted to look for concomitant skeletal lesions. By synthesizing knowledge of bone and skin manifestations, radiologists and clinicians can help correctly diagnose a number of these disease processes, thereby helping patients avoid further, often nonspecific invasive workup and advancing patient care., (© RSNA, 2014.)

An interactive Web-based learning module on the temporal bone has been developed. It shows normal temporal bone anatomy in four imaging planes: axial, coronal, and parallel and perpendicular to the long axis of the petrous bone. After reviewing the normal anatomy, users should be able to identify key imaging features of pathologic conditions of the temporal bone. Children with congenital abnormalities of the temporal bone may present with conductive or sensorineural hearing loss or both and may have a genetic syndrome. Acute otitis media is the most common infection of the temporal bone and is most prevalent among children. Although imaging is unnecessary in uncomplicated otitis media, it is important for evaluation of infectious complications. Classically, temporal bone fractures were described as longitudinal or transverse with respect to the long axis of the petrous bone. However, it is increasingly recognized that many fractures have both longitudinal and transverse components. Patients with temporal bone fractures may have conductive or sensorineural hearing loss in addition to other complications. The most common tumor of the temporal bone at the cerebellopontine angle is the vestibular schwannoma. Paraganglioma is the second most common tumor of the temporal bone and the most common tumor of the middle ear. Supplemental material available at http://uwmsk.org/temporalbone/atlas.html., (RSNA, 2012)

Musculoskeletal fibromatoses represent a wide spectrum of fibroblastic and myofibroblastic neoplasms with similar pathologic appearances and variable clinical behavior. These lesions can be categorized by location (superficial or deep) or by the age group predominantly affected. Superficial fibromatoses in adults (palmar and plantar) and children (calcifying aponeurotic fibroma, lipofibromatosis, and inclusion body fibromatosis) are often small slow-growing lesions; their diagnosis is suggested by location. Deep fibromatoses in adults (desmoid type and abdominal wall) and children (fibromatosis colli and myofibroma and myofibromatosis) are frequently large and more rapidly enlarging; location of these lesions may be nonspecific. Radiographic findings typically are nonspecific. Cross-sectional imaging (ultrasonography, computed tomography, or magnetic resonance [MR] imaging) reveals lesion location, extent, and involvement of adjacent structures for staging and evaluation of local recurrence. MR imaging findings of predominantly low to intermediate signal intensity, nonenhancing bands of low signal intensity on long repetition time MR images that represent collagenized regions, and extension along fascial planes ("fascial tail" sign) add specificity for diagnosis. Additional features that aid in diagnostic specificity include an abdominal wall location related to pregnancy (abdominal wall fibromatosis), a lower neck location in a young child (fibromatosis colli), an adipose component (lipofibromatosis), or multiple lesions in young children (myofibromatosis). Treatment may be conservative or surgical resection, depending on the specific diagnosis. Local recurrence is common after surgical resection owing to the infiltrative growth of these lesions. Recognition that the appearances of the various types of musculoskeletal fibromatoses reflect their pathologic characteristics improves radiologic assessment and helps optimize patient management.

Sickle cell disease results from the presence of abnormal beta globin chains within hemoglobin and may be manifested in anemia, vaso-occlusion, and superimposed infection. The gene that causes sickle cell disease is particularly prevalent in populations of African origin; approximately 8% of African Americans and 40% of the members of some African tribes carry the gene for hemoglobin S. Over time, the disease produces various musculoskeletal abnormalities as a result of chronic anemia; these include marrow hyperplasia, reversion of yellow marrow to red marrow, and, occasionally, extramedullary hematopoiesis. Familiarity with the imaging features of sickle cell disease is important for the diagnosis and management of complications. Ischemia and infarction are common complications that may have long-term effects on the growth of bone; these conditions have characteristic radiographic appearances. Infection may be more difficult to identify. Both infection and infarction may occur in muscle and soft tissue alone, without involving bone. However, osteomyelitis must be diagnosed early and treated immediately to prevent bone destruction and deformity; therefore, care must be taken to achieve an accurate diagnosis by identifying or excluding bone involvement. The clinical and radiographic features of acute osteomyelitis may be particularly difficult to distinguish from those of bone infarction. In that context, magnetic resonance (MR) imaging may be useful. At MR imaging, findings of cortical defects, adjacent fluid collections in soft tissue, and bone marrow enhancement are suggestive of infection., (RSNA, 2007)

Patients referred to the authors' hospital for evaluation on suspicion of a bone or soft-tissue malignancy frequently present to the Orthopaedic Oncology Clinic with magnetic resonance (MR) images that show typical features of nonmalignant or nonneoplastic entities. The purpose of this article is to review the benign entities that may be mistaken by the radiologist for a malignancy and thus lead to needless referral to an orthopedic oncologist. Normal hematopoietic marrow and marrow edema due to a stress reaction may mimic a neoplasm at MR imaging, but knowledge of the typical patterns and locations of these features allows an accurate radiologic interpretation. The MR imaging appearance of osteonecrosis, Paget disease, benign bone lesions, and rheumatologic conditions may be confusing; in such circumstances, radiographic findings may help formulate a correct diagnosis. Knowledge of the common locations and appearances of bursae and ganglia is necessary so that radiologists do not misinterpret these benign entities as soft-tissue sarcomas. Soft-tissue trauma and inflammation also may mimic tumors at MR imaging, but a familiarity with the imaging patterns of nonneoplastic change in muscle allows the avoidance of misinterpretation. The clinical history, as always, is an important component of proper diagnosis. The radiologist can be especially useful to both the clinician and the patient by recognizing entities that are highly unlikely to represent malignancy and by confidently reporting those entities as benign, thereby sparing the patient an unnecessary trip to the orthopedic oncologist., ((c) RSNA, 2007.)

Lumps and bumps of the scalp are a common presenting complaint in children and often pose a diagnostic dilemma. These lesions can be difficult to image, with evaluation confounded by their small size. However, accuracy in diagnosis is critical because the diagnostic and therapeutic implications can vary significantly. The clinical examination can be helpful in developing the differential diagnosis and the imaging strategy. Often, however, a single imaging study is insufficient, and the radiologist finds it necessary to image with more than one modality to correctly diagnose a lesion and provide adequate information for the surgeon. Radiography and ultrasonography are often the initial screening diagnostic tests, followed by magnetic resonance (MR) imaging or computed tomography (CT) for more detail. Multidetector thin-section CT and thin-section MR imaging with surface coils are beneficial in the work-up of these small lesions of the head and neck. The use of newer MR imaging sequences such as heavily T2-weighted single-shot turbo spin-echo imaging and diffusion-weighted imaging can improve the characterization of difficult lesions. Familiarity with the variety of new imaging tools and techniques that are available can help characterize pediatric head and neck lesions and guide clinical management., ((c) RSNA, 2004.)

Purpose: To compare short inversion time inversion-recovery (STIR) and T1-weighted contrast material-enhanced fat-suppressed spin-echo magnetic resonance (MR) sequences for depiction of bone marrow abnormalities of the foot and ankle., Materials and Methods: Fifty-one consecutive patients with bone marrow abnormalities depicted on turbo STIR images were examined with additional T1-weighted contrast-enhanced (0.1 mmol/kg gadopentetate dimeglumine) MR imaging with fat suppression. Volume and signal difference-to-noise ratio (SDNR) were measured. An additional qualitative analysis was performed by two experienced musculoskeletal radiologists to correlate the presence or absence of ill-defined edema-like zones, well-defined zones, and cystlike zones. Diagnoses determined with MR findings with each sequence were compared with the results of a review panel. Correlation coefficients (r(2)) and paired t tests were calculated for all measurements. Agreement percentages and kappa values were calculated for inter- and intraobserver reproducibility., Results: Regarding volume of bone marrow abnormalities, a high correlation (r(2) = 0.98) of both sequences was found. SDNR was substantially higher on T1-weighted contrast-enhanced images than on STIR images (mean, 125.9 vs 95.4; P <.001). The qualitative analysis demonstrated identical imaging patterns with both sequences in 96% (79 of 82, kappa = 0.38) of ill-defined zones, in 88% (72 of 82, kappa = 0.76) of well-defined zones, and in 98% (80 of 82, kappa = 0.84) of cystlike zones. Interobserver reproducibility of the three imaging patterns was similar for both sequences. The kappa values for these three zones with STIR sequence were 0.55, 0.68, and 0.69, and those for the T1-weighted contrast-enhanced MR sequence were 0.49, 0.73, and 0.58, respectively. Diagnoses determined with MR findings were equal with both sequences in 94% (80 of 85) of involved bones., Conclusion: STIR images and T1-weighted contrast-enhanced fat-suppressed MR images demonstrate almost identical imaging patterns, and diagnoses determined with these findings show little difference., (Copyright RSNA, 2002)

The radiologic features of giant cell tumor (GCT) and giant cell reparative granuloma (GCRG) of bone often strongly suggest the diagnosis and reflect their pathologic appearance. At radiography, GCT often demonstrates a metaepiphyseal location with extension to subchondral bone. GCRG has a similar appearance but most commonly affects the mandible, maxilla, hands, or feet. Computed tomography and magnetic resonance (MR) imaging are helpful in staging lesions, particularly in delineating soft-tissue extension. Cystic (secondary aneurysmal bone cyst) components are reported in 14% of GCTs. However, biopsy must be directed at the solid regions, which harbor diagnostic tissue. These solid components demonstrate low to intermediate signal intensity at T2-weighted MR imaging, a feature that can be helpful in diagnosis. Multiple GCTs, although rare, do occur and may be associated with Paget disease. Malignant GCT accounts for 5%-10% of all GCTs and is usually secondary to previous irradiation of benign GCT. Treatment of GCT usually consists of surgical resection. Recurrence is seen in 2%-25% of cases, and imaging is vital for early detection. Recognition of the spectrum of radiologic appearances of GCT and GCRG is important in allowing prospective diagnosis, guiding therapy, and facilitating early detection of recurrence.

Several postoperative complications associated with pain may develop in the stump of an amputated lower limb. Clinical findings are often nonspecific; however, radiologic evaluation, especially with magnetic resonance (MR) imaging, is useful in the early diagnosis of these complications, thereby helping minimize physical disability with its psychologic and socioeconomic implications. Conventional radiography can demonstrate evidence of osseous origins of pain (eg, aggressive bone edge, heterotopic ossification, osteomyelitis) and should be the first imaging study performed after clinical examination. Videofluoroscopy can help evaluate improper prosthetic fit by demonstrating abnormal residual limb motion, piston action, rolling of soft tissues, and abnormal angle between the limb axis and the prosthesis during gait. Ultrasonography can demonstrate inflammatory changes in the stump as well as soft-tissue fluid collections. However, MR imaging is the modality of choice when clinical and other imaging findings are indeterminate. Because of its high spatial and contrast resolution, MR imaging can demonstrate subtle inflammatory changes, fluid collections, cancers, neuromas, and subtle traumatic bone lesions. Knowledge of various surgical and rehabilitation techniques is required for accurate diagnosis of complications associated with stump pain. Correct diagnosis allows choice of the most appropriate therapy, which may involve treating the stump, remodeling the prosthesis, or both.

Musculoskeletal radiologists, owing to recent advances in imaging technologies and techniques, are playing an increasingly important role in documenting, diagnosing, and treating an increasing variety of bone and soft-tissue lesions. However, improved visualization of anatomic aberrations-"seeing better"-must be paired with "knowing more," on the basis of complete familiarity with all aspects of the biology, physiology, pathophysiology, and static anatomy of the musculoskeletal system. Only with foreknowledge of the latter can the musculoskeletal radiologist fully maximize the benefits of the former.

Lateral trochlear inclination (LTI) of the knee was compared on magnetic resonance (MR) images obtained in 30 patients with patellar instability (PI) and 30 patients with nonspecific internal knee derangement. Differences in LTI values between the two populations were significant (P <.001). Reproducibility of the measurement was judged excellent with an intraclass correlation superior to 0.98. Below a threshold value fixed at 11 degrees, LTI appears to be an excellent diagnostic test of PI with a sensitivity of 0.93 (28/30), a specificity of 0.87 (26/30), and an accuracy of 0.90 (54/60).

Purpose: To determine the prevalence of abnormalities of the acetabular labrum in asymptomatic hips by means of magnetic resonance (MR) imaging and to correlate such abnormalities with age and the portion of the labrum., Materials and Methods: MR imaging was performed in 71 asymptomatic hips that were radially sectioned perpendicular to the acetabular labrum at 30 degrees intervals., Results: The shape of the labrum was triangular in 80% (304 of 382) of the labral segments, round in 13% (49 of 382), irregular in 7% (27 of 382), and not identified in 1% (two of 382). A homogeneous low signal intensity was observed in 56% (212 of 382). The frequencies of labral irregularity or its absence and of high signal intensity increased both with subject age and with a more anterior anatomic labral location., Conclusion: In asymptomatic hips, abnormal findings regarding the shape and signal intensity of the acetabular labrum can be detected by means of MR imaging. The fact that the findings vary according to age and labral portion should be considered in interpreting MR images in patients suspected of having a labral lesion.

Purpose: To use sodium 23 magnetic resonance (MR) imaging to quantify noninvasively total sodium in human muscle and to apply the technique in exercise and musculoskeletal disease., Materials and Methods: Total [Na] sodium was determined from the ratio of the relaxation-corrected (23)Na signal intensities measured from short echo-time (0.4 msec) (23)Na images to those from an external saline solution reference. The method was validated with the blinded use of saline solutions of varying sodium concentrations. [Na] was measured in the calf muscles in 10 healthy volunteers. (23)Na MR imaging also was performed in two healthy subjects after exercise, two patients with myotonic dystrophy, and two patients with osteoarthritis., Results: (23)Na MR imaging yielded a total [Na] value of 28.4 mmol/kg of wet weight +/- 3.6 (SD) in normal muscle, consistent with prior biopsy data. Spatial resolution was 0.22 mL, with signal-to-noise ratio of 10-15. Mean signal intensity elevations were 16% and 22% after exercise and 47% and 70% in dystrophic muscles compared with those at normal resting levels. In osteoarthritis, mean signal intensity reductions were 36% and 15% compared with those in unaffected knee joints., Conclusion: (23)Na MR imaging can be used to quantify total [Na] in human muscle. The technique may facilitate understanding of the role of the sodium-potassium pump and perfusion in normal and diseased muscle.

Congenital tarsal coalition is a diagnosis that is often overlooked in young patients who first present with foot and ankle pain. Calcaneonavicular and talocalcaneal coalitions are encountered most frequently; fusion at other sites is much less common. Tarsal coalitions may be osseous, cartilaginous, or fibrous. Calcaneonavicular coalitions are readily detected on oblique radiographs. Radiographic confirmation of talocalcaneal coalition is more difficult than for fusion at other locations, although several secondary radiographic signs may indirectly suggest the diagnosis. Computed tomography (CT) and magnetic resonance (MR) imaging are invaluable for assessment of tarsal coalitions because they allow differentiation of osseous from nonosseous coalitions and because they depict the extent of joint involvement as well as secondary degenerative changes, features of vital importance in surgical planning. Short-inversion-time inversion recovery MR images may reveal bone marrow edema along the margins of the abnormal articulation, an important clue to the diagnosis. Moreover, CT or MR imaging may be required to confirm the diagnosis of talocalcaneal coalition when radiographic findings are equivocal. Because the diagnosis of tarsal coalition is often not entertained by the clinician ordering a CT or MR imaging examination, multiplanar imaging of the ankle and hindfoot is required.

Pediatric oncology patients are at risk for the development of numerous skeletal complications, and radiologic studies are important in the identification and evaluation of these conditions. Methotrexate osteopathy manifests as osteopenia, dense provisional zones of calcification, pathologic fractures, and sharply outlined epiphyses. Hypertrophic osteoarthropathy may occur with nasopharyngeal carcinoma or tumors of the lungs or pleura and manifests as cortical thickening, lamellar periosteal new bone formation, and soft-tissue swelling. Biomechanical abnormalities are often seen at bone scintigraphy in patients who have undergone surgery for bone tumors. Growth plate injury may manifest as marked deformity, sclerotic metaphyseal bands, metaphyseal fraying, and longitudinal striations. Radiation "osteitis" is seen as an initial decrease in bone density with subsequent development of a mixed radiolucent and sclerotic appearance. Ischemic necrosis of the femoral heads is best demonstrated at magnetic resonance (MR) imaging and has low signal intensity on T1-weighted images and a high-signal-intensity rim on T2-weighted images. Bone infarcts are seen as well-demarcated, often ring-shaped areas of decreased signal intensity on T1-weighted MR images and as areas of increased signal intensity on short-inversion-time inversion recovery images. Radiographic signs of infection include bone destruction, periosteal new bone formation, and sclerotic changes. Short-inversion-time inversion recovery MR imaging is particularly useful in evaluating posttherapy changes in bone marrow. Osteochondroma may demonstrate a cartilaginous cap at MR imaging, whereas the most important finding in radiation-induced sarcoma is a soft-tissue mass. Radiologists who work with children with cancer need to be familiar with these complications and their imaging appearances.

A surface lesion of bone may arise within the cortex, between the cortex and the periosteum, within the periosteum, or in the tissues immediately adjacent to the periosteum including tendinous and ligamentous attachments. While these lesions generally reflect the spectrum of more common intramedullary lesions and have an appearance similar to that of their intramedullary counterparts, their unusual surface origin often renders diagnosis difficult. Surface sarcomas are usually of a lower grade than that of the intramedullary tumor, and often they have a more favorable prognosis. Traumatic lesions of the bone surface are common and should be considered in the differential diagnosis of a surface lesion, especially in the young or athletic individual. An elevated peripheral white blood cell count and erythrocyte sedimentation rate may herald an infection of the bone surface.

Purpose: To elucidate the nature of a normally occurring cortical defect of the distal fibula., Materials and Methods: In patients with sprain and nonspecific ankle pain during a 2-year period, the authors reviewed ankle radiographs, computed tomographic (CT) scans, and magnetic resonance (MR) images. Cases were added from our file. Dried skeletons and cadavers were evaluated with radiography for the presence of this cortical defect., Results: Fifteen (1.8%) of 847 radiographs in 739 patients (male, 377; female, 362; age range, 15-84 years) showed a small cortical defect in the anterior aspect at the level of the distal tibiofibular joint. The age range of the subjects with the defect (male, four; female, 11) was 16-66 years. MR imaging in two patients showed a small low-signal-intensity area at the insertion site of the anterior tibiofibular ligament. Evaluation of 148 skeletons (75 subjects) revealed similar cortical defect in two cases (1.4%)., Conclusion: The cortical defect of the distal fibula, at the insertion site of the anterior tibiofibular ligament, has no clinical significance and should not be confused with neoplasm.

Magnetic resonance (MR) imaging is the most sensitive and accurate imaging technique for evaluation of musculoskeletal tumors. With increasing clinical experience, however, an overlap between the classic characteristics of benign and malignant tumors is frequently observed. In a prospective analysis of 87 consecutive cases of musculoskeletal tumors, the malignancy of skeletal lesions was correctly assessed with MR imaging in 55% of the cases. In 39% of the cases, the malignancy of skeletal lesions was overestimated with MR imaging. Correlation with plain radiography is extremely important in such cases and would have resulted in correct assessment of 73% of the skeletal lesions. For soft-tissue lesions, a large variability is found in the benign versus malignant appearances of lesions on MR images, with poor correlation between classic benign characteristics and the benignity of the lesion (17% of cases). The exceptions are hemangiomas and lipomas, which have characteristic appearances on MR images. Knowledge of potentially misleading appearances of musculoskeletal tumors on MR images allows more accurate diagnosis of such tumors.

Purpose: To assess the diagnostic value of parametric magnetic resonance images that display the first pass (FP) of gadopentetate dimeglumine., Materials and Methods: Dynamic, contrast material-enhanced, fast low-angle shot MR imaging was performed of 100 musculoskeletal lesions in 36 female and 64 male patients (aged 9-81 years [mean, 34 years]). The highest slope value of the time-intensity curve was calculated pixel by pixel and displayed on the FP image, with a gray-scale value equal to the slope value. Tissue vascularization and perfusion were evaluated at pathologic and angiographic examinations in 33 lesions., Results: A significant difference (P < .001) was found between the FP slope values of benign (mean, 36.2% per second) and malignant (mean, 67.4% per second) lesions. FP images depicted tissue vascularization and perfusion rather than benignity or malignancy, because there is an overlap in the slope values of highly vascular benign lesions and malignant lesions., Conclusion: FP images provide diagnostically useful information by depicting tissue vascularization and perfusion.

Purpose: To describe the pseudodefect of the distal humerus at the junction of the capitellum and lateral epicondyle, which may simulate an osteochondral lesion on axial and coronal magnetic resonance (MR) images., Materials and Methods: MR imaging studies of the elbow in 32 patients and 22 asymptomatic volunteers were retrospectively reviewed. Thirty-two human humeri were also examined for normal anatomy of the junction of the capitellum and distal humerus., Results: Twenty-two of the clinical MR examinations and 14 of the studies on volunteers revealed the presence of the pseudodefect. A groove at the junction and the overhanging lateral edges of the capitellum account for the appearance of this pseudolesion., Conclusion: Familiarity with the characteristic appearance and location of this pseudodefect will prevent its misinterpretation as an osteochondral fracture of the distal humerus.

The value of high spatial resolution and contrast material-enhanced magnetic resonance (MR) imaging was assessed in 69 patients with either femoral head avascular necrosis (AVN) or transient bone marrow edema lesions. An AVN lesion was typically a well-demarcated epiphyseal area of variable signal intensity. A transient bone marrow edema lesion appeared as an ill-delimited low-signal-intensity epiphyseal area on T1-weighted images that converted to a high-signal-intensity area on T2-weighted images. T1- and T2-weighted spin-echo images helped distinguish from AVN lesions some transient lesions apt to simulate the segmental pattern of AVN lesions. T2-weighted images also helped detect necrotic tissue in some unusual AVN lesions that mostly showed ill-delimited edemalike marrow changes. In some cases, contrast-enhanced MR images may increase diagnostic confidence by showing homogeneous hypervascularization in bone marrow edema lesions and by depicting hypovascular marrow areas in AVN lesions. The authors believe sequential MR imaging is valuable in the assessment of equivocal femoral head lesions.

The authors retrospectively reviewed the charts, radiographs, and other accompanying imaging studies of 45 patients with musculoskeletal abnormalities associated with human immunodeficiency virus (HIV) infection. These included 19 patients with osseous infection, including eight with osteomyelitis, seven with bacillary angiomatosis (six of whom were described in a previous report), and four with septic arthritis; 10 with bacterial myositis (six of whom were described in a previous report); seven with non-Hodgkin lymphoma; five with hypointense marrow signal intensity at magnetic resonance imaging; two with Kaposi sarcoma; one with polymyositis; and one with psoriasis. The musculoskeletal system can be affected by a variety of abnormalities in association with HIV infection. Knowledge of their existence and characteristic appearance is valuable to radiologists for diagnosis and to clinicians for detection and appropriate treatment.

After plain radiography has been performed, magnetic resonance (MR) imaging is considered the modality of choice for the evaluation of suspected musculoskeletal lesions because of its exquisite sensitivity to changes in the signal intensity of marrow and soft tissue. That sensitivity, however, may lead to an overestimation of the aggressiveness and extent of some benign bone lesions, particularly in children. Such lesions include chondroblastoma, osteoid osteoma, eosinophilic granuloma, and stress fractures. Potentially misleading MR features commonly seen include prominent marrow edema, soft-tissue edema, and apparent mass effect adjacent to the bone lesion. Features that these lesions have in common that may explain the MR findings include associated inflammatory reactions caused by the lesions and their occurrence in childhood, when the periosteum is more loosely attached. Knowledge of the potential pitfalls encountered with MR imaging may help explain the discrepancy between the radiographic and MR appearances of these benign lesions and avoid misplaced reliance on MR imaging for a diagnosis. Radiography remains the single most valuable modality in determining a differential diagnosis for bone lesions.

The ulnar collateral ligament (UCL) provides stability to the medial aspect of the elbow during valgus stress. Trauma to this ligament may result from repetitive forceful throwing. Diagnosis of UCL injury has been based on clinical findings of medial joint pain and valgus instability, as direct imaging of this structure has not been available. Eleven baseball pitchers with clinical evidence of UCL injury were evaluated with magnetic resonance (MR) imaging. Surgical correlation was obtained in six patients, four of whom underwent UCL reconstruction. MR imaging findings in UCL injury included laxity, irregularity, poor definition, and increased signal intensity within and adjacent to the UCL. These findings reflect the presence of hemorrhage and/or edema within the UCL due to repeated microtears, which eventually lead to weakening and possible disruption of the UCL. Optimization of spatial resolution, signal-to-noise ratio, and other technical factors is critical for evaluation of the UCL due to its small size. MR imaging is useful in documenting the presence and severity of injury to the UCL and in distinguishing this entity from other causes of elbow pain.

In a review of the indications and uses for magnetic resonance (MR) imaging of the pediatric musculoskeletal system, MR evaluation of conditions unique to the pediatric musculoskeletal system were emphasized. Indications for MR imaging of the pediatric musculoskeletal system include evaluation of bone marrow, neoplastic processes, and periarticular disorders.

Magnetic resonance (MR) imaging was performed in 60 patients with ankle pain who were suspected of having various soft-tissue or osseous abnormalities. Results of conventional radiographs had been normal or inconclusive. Soft-tissue disorders depicted by MR imaging included tendon and ligament tears, tendinitis, tenosynovitis, and plantar fasciitis. Osseous conditions demonstrated by MR imaging included osteochondritis dessicans, infarcts, bone bruises, stress fractures, tarsal coalition, and osteoid osteoma. The authors believe that MR imaging is useful in the assessment of a variety of painful ankle disorders.

Magnetic resonance (MR) images obtained in 18 patients with pathologically confirmed mycetoma in the body (n = 4) or lower extremity (n = 14) were retrospectively reviewed and compared with computed tomographic (CT) scans in 15 patients and surgical findings in 10. T1-weighted images showed an infiltrating mass (same signal intensity as muscle) involving skin, subcutaneous fat, muscles, tendons, and other tissues. On T2-weighted images, the mass and affected structures showed moderately increased signal intensity. Bone marrow involvement was detected in seven patients and was best visualized on T1-weighted images. CT showed moderate enhancement of the infiltrative process in all patients. Bone changes, seen in nine, included coarse trabeculation, periosteal reaction, endosteal proliferation, and patchy destruction. MR imaging and CT were comparable and correlated well with surgery in showing the extent of soft-tissue involvement. Early bone changes (important for therapy planning for pedal mycetoma) were seen only at CT. The study showed that MR imaging is sensitive for assessing the extent of mycetoma in the soft tissues. CT should be the method of choice for staging pedal lesions because it can be used to detect early bone involvement.

The radiologist must have a thorough knowledge of the normal anatomy and the pathologic spectrum of the skull base to determine the extent of abnormality and to help plan the surgical approach. The authors describe and present examples of congenital, benign, and malignant lesions that affect this region, including cephalocele, fracture, fistula, juvenile angiofibroma, meningioma, chordoma, pituitary adenoma, chondrosarcoma, nasopharyngeal carcinoma, and rhabdomyosarcoma. Metastatic, infectious, and other miscellaneous processes are also discussed. Imaging strategies with computed tomography and magnetic resonance imaging to aid in the diagnosis are suggested.

A large variety of benign and malignant fibrous lesions occur in the skeleton. Many fibrous bone lesions have characteristic features on plain radiographs and are easy to diagnose; others may pose significant difficulty. Most often, an osteolytic defect is seen associated with a fibrous lesion in the affected bone, although a mixed and sclerotic fibrous bone lesion is not unusual. Many benign fibrous bone lesions are asymptomatic; others become clinically apparent because of associated pathologic fracture or deformity of the involved bone. Malignant fibrous lesions tend to be aggressive, with focal bone destruction and adjacent soft-tissue involvement. The authors describe many fibrous bone lesions with their salient clinical and radiographic features.

Except for the detection of mineralization and early cortical bone erosion, the authors found MRI to be equal or superior to CT in the evaluation of musculoskeletal lesions.

Images of 7 patients with primary amyloidosis revealed organomegaly with regions of decreased tracer accumulation due to infiltration and replacement of normal tissue by the amyloid complex. These scintigraphic changes in the clinical setting of multisystem disease should suggest amyloidosis as a possible diagnosis.

Trephine bone biopsies were performed in 67 patients. Routine radiography, laminagraphy, and radioisotopic techniques were employed to determine areas of involvement and exact sites for biopsy. Sites were selected on the basis of accessibility, possible complications, and chances of recovering diagnostic material. The biopsy material was informative in 81% of patients. One controllable hemorrhage, one temporary sinus tract, a small pneumothorax requiring no therapy, and two benign vasovagal responses were the only complications. Widespread malignant disease and osteomyelitis, particularly disk-space infection, are the most suitable lesions for trephine biopsy.

Two cases of mastocytosis with skeletal involvement in children three and six months old are reported. Bone lesions, either sclerotic or lytic, were encountered in their skeletal surveys. Gastrointestinal lesions in children with mastocytosis are exceedingly rare; in addition to skeletal lesions, one of our patients had a large duodenal ulcer. The diagnosis of mastocytosis was established by skin biopsy in both patients. A review of the literature is also presented.

A scintigraphic pattern is described for bone scans with 99m-Tc-polyphosphate and 99m-Tc-diphosphonate in which abnormal tracer accumulation extends beyond the known limits of certain skeletal lesions. The associated pathologic entities include benign and malignant tumors, infection, and trauma. The pathogenesis of "extended patterns" has not been proved but probably relates to regional hyperemia induced by associated lesions. Increased blood flow results in more tracer delivery to otherwise normal bone in the "watershed" areas of hyperemia, producing these patterns.

The feasibility of combined magnetic resonance (MR) imaging and surface coil phosphorus-31 MR spectroscopy at 1.5 T was examined in a clinical study of 34 patients before biopsy of bone or soft-tissue lesions of the extremity and trunk. The results confirmed the inability of MR imaging alone to distinguish most benign lesions from malignant ones. Malignant lesions were distinguished from benign lesions on the basis of significantly higher mean peak ratios of phosphomonoester (PME) to beta-nucleoside triphosphate (NTP) and of phosphodiester to NTP, a significantly lower mean peak area ratio of phosphocreatine to NTP, and a higher mean pH. The diagnostic performance of the PME/NTP peak area ratio is characterized by a sensitivity (true-positive fraction) of 1.00 and a specificity (true-negative fraction) of 0.93. This study provided preliminary evidence that P-31 MR spectroscopy may be used to improve diagnostic specificity in bone and soft-tissue lesions.

Eighty-eight patients with maxillary-facial abnormalities were studied with 99mTc-labeled phosphate compounds. Straight and tilted anterior views plus oblique orbital and lateral views were correlated with 201 thallium transmission images of a dried skull. Interpretation of any single view may be hampered by various superimposed structures. Careful patient positioning with multiple views allows for parallactic correlation which is crucial if radiotherapy, biopsy, or corroborative studies are planned.

Thirty healthy subjects and 15 patients with a variety of musculoskeletal disorders were examined by conventional radiography, computed tomography (CT), and nuclear magnetic resonance (NMR). NMR proved capable of demonstrating important anatomic structures in the region of the lumbosacral spine. Lumbar disk protrusion was demonstrated in three patients with CT evidence of the disease. NMR appeared to differentiate annulus fibrosus from nucleus pulposus in intervertebral disk material. Avascular necrosis of the femoral head was demonstrated in two patients. The cruciate ligaments of the knee were well defined by NMR. Muscles, tendons and ligaments, and blood vessels could be reliably differentiated, and the excellent soft-tissue contrast of NMR proved useful in the evaluation of bony and soft-tissue tumors. NMR holds promise in the evaluation of musculoskeletal disorders.

Normal radionuclide patterns of the hand obtained with 99mTcO4 and 99mTc-Sn-EHDP are described and their validity supported by clinical, radiographic, and laboratory examinations performed to exclude articular disease in the control group. Comparison of the 99mTcO4 and 99mTc-Sn-EHDP images in patients with various articular diseases demonstrated higher sensitivity of 99mTc-Sn-EHDP in detection of involved joints; this was also true when the radionuclide images were compared with fine-detail radiographs in patients with rheumatoid arthritis.