Jennifer L. Demertzis

Imaging of Juvenile Idiopathic Arthritis: A Multimodality Approach

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases characterized by synovial inflammation and is the most common rheumatic complaint in children. To facilitate research and treatment, JIA has been further classified on the basis of the number of joints involved, additional symptoms, family history, and serologic findings. Imaging in patients with JIA has historically relied on radiography, which allows the accurate assessment of chronic changes of JIA, including growth disturbances, periostitis, and joint malalignment. However, radiographic findings of active inflammation are nonspecific, and, in the past, clinical evaluation has taken precedence over imaging of acute disease. Recent advances in disease-modifying therapeutic agents that can help prevent long-term disability in patients with JIA have led to greater emphasis on the detection of early joint-centered inflammation that cannot be accurately assessed radiographically and may not be evident clinically. Both contrast material-enhanced magnetic resonance (MR) imaging and Doppler ultrasonography (US) are well suited for this application and are playing an increasingly important role in diagnosis, risk stratification, treatment monitoring, and problem solving. Contrast-enhanced MR imaging is the most sensitive technique for the detection of synovitis and is the only modality that can help detect bone marrow edema, both of which indicate active inflammation. US is more sensitive than radiography for the detection of synovial proliferation and effusions and is particularly useful in the evaluation of small peripheral joints. The complexity of the temporomandibular and sacroiliac joints limits the usefulness of radiographic or US evaluation, and contrast-enhanced MR imaging is the preferred modality for evaluation of these structures.

Fibrodysplasia ossificans progressiva: middle-age onset of heterotopic ossification from a unique missense mutation (c.974G>C, p.G325A) in ACVR1.

Fibrodysplasia ossificans progressiva (FOP) is the rare mendelian disease characterized by congenital malformation of the great toes preceding heterotopic ossification (HO) and caused by heterozygous activating mutation of the ACVR1 gene, which encodes the ALK2 receptor for bone morphogenetic proteins. Early adult life is the latest reported presentation for the HO of FOP. The patient of our report first developed HO from FOP at 47 years of age. She had congenital hallux valgus deformity but despite various traumas was previously well. HO began several months after a brief, seemingly viral, illness. Sudden and progressive pain, redness, warmth, and swelling appeared over a scapula. Computed tomography was remarkable for asymmetrical thickening of muscles and fascial planes. At first, the significance of the great toe abnormalities went unrecognized elsewhere, and biopsy for suspected inflammatory fasciitis revealed proliferating fibroblasts with scattered inflammatory cells. Prednisone improved her symptoms but, when tapered, swellings developed on her chest, posterior thorax, and flank, and FOP was diagnosed. Methylprednisolone, methotrexate, and alendronate seemed to help her symptoms, but the lesions worsened and HO appeared and rapidly progressed. Mutation analysis of the ACVR1 gene revealed heterozygosity for a unique missense defect (c.974G > C, p.G325A) that predicted a conservative (mild) amino acid change within the kinase domain of ALK2. Hence, HO in FOP can be delayed until middle‐age, and perhaps provoked by a viral illness. Nevertheless, progression of HO can then be rapid despite bisphosphonate and high‐dose immunosuppressive therapy. Possibly, our patients late‐onset HO reflects her mild alteration of ALK2 or some protective and therapeutically useful genetic, epigenetic, or nongenetic factor. Recognition of presymptomatic individuals or late‐onset HO in FOP should have these patients avoid traumas, treatments, and maybe viral illnesses that can initiate or exacerbate the HO. If the diagnosis of FOP is unclear, ACVR1 mutation analysis is available at certified laboratories.

Diabetic Musculoskeletal Complications and Their Imaging Mimics

Diabetes mellitus is increasingly prevalent and results in various clinically important musculoskeletal disorders affecting the limbs, feet, and spine as well as in widely recognized end-organ complications such as neuropathy, nephropathy, and retinopathy. Diabetic muscle ischemia-a self-limited disorder-may be confused with infectious or inflammatory myositis, venous thrombosis, or compartment syndrome. The absence of fever and leukocytosis, combined with the presence of bilaterally distributed lesions in multiple and often noncontiguous muscles in the legs, including the thighs, is suggestive of ischemia; by contrast, the presence of well-defined intramuscular abscesses with rimlike enhancement favors a diagnosis of infectious pyomyositis. In the diabetic foot, an ulcer, sinus tract, or abscess with an adjacent region of abnormal signal intensity in bone marrow favors the diagnosis of pedal osteomyelitis over that of neuropathic arthropathy. Contrast material-enhanced magnetic resonance imaging is important when planning the treatment of foot infections in diabetic patients because it allows the differentiation of viable tissue from necrotic regions that require surgical débridement in addition to antibiotic therapy. Subtraction images are particularly useful for visualizing nonviable tissue. Dialysis-associated spondyloarthropathy characteristically occurs in diabetic patients with a long history of hemodialysis. Intervertebral disk space narrowing without T2 signal hyperintensity, extensive endplate erosions without endplate remodeling, and facet joint involvement are suggestive of spondyloarthropathy instead of infectious diskitis or degenerative disk disease. Although the clinical features of these conditions may overlap, knowledge of the patients medical history, coupled with recognition of key imaging characteristics, allows the radiologist to make a prompt and correct diagnosis that leads to appropriate management.

Traumatic Tear of the Latissimus Dorsi Myotendinous Junction: Case Report of a CrossFit-Related Injury

A case of a latissimus dorsi myotendinous junction strain in an avid CrossFit athlete is presented. The patient developed acute onset right axillary burning and swelling and subsequent palpable pop with weakness while performing a “muscle up.” Magnetic resonance imaging examination demonstrated a high-grade tear of the right latissimus dorsi myotendinous junction approximately 9 cm proximal to its intact humeral insertion. There were no other injuries to the adjacent shoulder girdle structures. Isolated strain of the latissimus dorsi myotendinous junction is a very rare injury with a scarcity of information available regarding its imaging appearance and preferred treatment. This patient was treated conservatively and was able to resume active CrossFit training within 3 months. At 6 months postinjury, he had only a mild residual functional deficit compared with his preinjury level.

Upper extremity neuromuscular injuries in athletes.

Upper extremity muscle and nerve injuries in athletes are important causes of lost playing time and suboptimal performance. Although most muscle injuries are self-limited, imaging may be indicated in select situations for diagnostic and prognostic purposes, to investigate potential complications of injury, and for instituting prompt therapy to hasten recovery. MRI is particularly sensitive to soft tissue abnormalities seen in muscle injury, and it can reliably diagnose and stage direct injuries such as contusions and lacerations, and indirect injuries such as strains, delayed-onset muscle soreness, and exertional compartment syndrome. Upper extremity peripheral nerve injuries may be compressive or noncompressive in etiology, with certain sports and activities rendering particular nerves vulnerable to characteristic injuries. Initial evaluation includes a complete history, physical examination, and electrodiagnostic studies. MRI and ultrasound assessment of the nerves, surrounding tissues, and innervated muscles can provide localizing, diagnostic, and prognostic information that complements clinical and electrodiagnostic testing.

MR Imaging Assessment of Inflammatory, Crystalline-Induced, and Infectious Arthritides

The role of magnetic resonance imaging in evaluating patients with inflammatory arthritides has evolved with the recent introduction of drugs capable of modifying disease activity and natural history. In conditions like rheumatoid arthritis, active synovitis and bone marrow inflammation precede and predict bone and cartilage erosion. These imaging findings identify patients who can be treated early and aggressively to prevent future morbidity. Similarly, in gout and other crystalline disorders, specific diagnosis aided by imaging may lead to earlier medical and surgical management. Infected joints need the most rapid identification to institute immediate therapy and prevent irreversible cartilage destruction.

Synovial hemangioma of the hip joint in a pediatric patient

Hemangiomas of the articular synovium are rare and commonly associated with recurrent joint swelling and painful limitation of motion. The knee joint is the most commonly involved site, with most patients diagnosed in the second to third decade of life [1]. Although over 200 cases have been reported in the English-language medical literature, only three have originated within the hip joint, all of which were in adult patients reported in the surgical literature [2–4]. We describe a histologically proven synovial hemangioma of the hip joint in a pediatric patient that invaded the femur, acetabulum, and adjacent soft tissues, with a detailed discussion of the differential diagnosis based on the radiographic and magnetic resonance imaging (MRI) findings.

Prepatellar Morel-Lavallée effusion

Lateral radiograph of the left knee shows prepatellar soft tissue swelling. MR images demonstrate a T2-hyperintense unilocular prepatellar fluid collection located between the subcutaneous fat and underlying fascia. The collection extends beyond the transverse and craniocaudal boundaries of the prepatellar bursa, with the medial and lateral margins reaching the level of the femoral epicondyles at the midcoronal plane, and the superior and inferior margins extending from the mid-thigh to beyond the tibial tubercle. These findings are indicative of a prepatellar Morel-Lavallee effusion and are distinguished from prepatellar bursitis by location beyond the anatomic confines of the prepatellar bursa. Quadriceps muscle signal intensity is normal, excluding muscle contusion as the cause of the patient’s pain. Other post-traumatic subcutaneous lesions in the differential diagnosis such as fat necrosis, pseudolipoma, and coagulopathy-related hematoma are unlikely given the anatomic location, imaging characteristics, and clinical history [1]. The patient was successfully treated with activity restriction, ice, and compression wraps. Maurice Morel-Lavallee first described closed degloving injuries of the hip and pelvis in 1853 [2]. Excessive shearing force or repetitive compressive trauma causes separation of the skin and subcutaneous fat from underlying deep fascia resulting in disruption of perforating vessels and formation of fluid collections containing blood, fat, and lymph [1–3]. Morel-Lavallee lesions adjacent to the greater trochanter, proximal femur, buttock, and lower back are well known [4, 5], and MR imaging has an established role in their diagnosis. The appearance of Morel-Lavallee effusions on MRI depends on lesion acuity and the amount of blood product, fat, and lymph tissue within it [1]. Mellado et al. described six types of Morel-Lavallee effusions ranging from seroma to infected collections, with a unilocular T2 hyperintense fluid collection being the most common finding of the basic subtypes [1]. Neither blood product, fat, nor a fibrous pseudocapsule was identified in this particular case. Of these findings, the presence of an enhancing pseudocapsule has prognostic value, suggesting possible benefit of therapeutic aspiration or debridement to facilitate resolution of the lesion [1, 2]. Despite the established diagnosis of Morel-Lavallee effusion in the pelvis and hips, its occurrence in the prepatellar region has only recently been described in the orthopedic [6, 7] and radiology literature [8, 9]. A recent case series of 24 The case presentation can be found at doi:10.1007/s00256-012-1399-0.

Appropriate Use Criteria in Musculoskeletal Imaging

In the United States, health care costs are spiraling upward at an unsustainable rate. Concurrently, medical specialties, legislatures, and the population each recognize the need to prove that current medical practices are effective, measured by outcomes. These forces necessitate a change in radiologys role, from emphasizing interpretation and reporting to maintaining and demonstrating quality and value. An important part of this task involves establishing the appropriateness of imaging tests by application of objective data and expert opinion in an effort to optimize resource utilization and modality selection. We explore the justifications for establishing appropriateness use criteria, various paradigms that have been applied to their creation, inherent limitations of appropriateness rules based on imperfect data, and challenges associated with their widespread implementation and utilization. An appendix of key terms that may be unfamiliar to radiologists is included for future reference.

Impact of Shoulder Sonography on Clinical Decision Making

To assess the impact of musculoskeletal shoulder sonography (US) on clinical decision making.