Myositis ossificans is a relatively rare, well-defined entity. The 23 cases sent for consultation to two of us (L.V.A. and A.N.) were reviewed. Clinical, radiologic, and microscopic information was reexamined, and special attention was given to features infrequently seen in typical myositis ossificans. Average age at presentation was 23 years, but 1 patient was younger than 2 years, and 2 were younger than 10 years. Due to the uncommon location of 15 lesions and an unusual presentation in 5, the correct diagnosis was not obvious in these cases. A history of trauma was elicited in 8 patients, denied by 7, and was not queried in the remainder. Radiologic studies raised the possibility of a malignant bone-forming tumor in at least three instances; myositis ossificans was originally diagnosed in 6 cases radiologically. In 8 cases, histologic evidence suggested malignancy, including osteosarcoma, either parosteal or extraosseous, in 6. Other diagnoses included epithelioid sarcoma and callus formation. Presentation of these variations from the norm highlights the importance of recognizing the evolution of a nonneoplastic fibro-osseous and cartilaginous entity in which conservative treatment is curative.

Twenty-seven cases of an unusual, poorly recognized destructive hip arthropathy with radiographic findings of rapid severe joint destruction are presented. Radiographic findings mimicked those of other disorders such as septic arthritis, rheumatoid and seronegative arthritis, primary osteonecrosis with secondary osteoarthritis, or neuropathic osteoarthropathy, but none of the patients had clinical, pathologic, or laboratory evidence of these entities. All patients underwent hip arthroplasty, and osteoarthritis was confirmed at pathologic examination. Rapid progression of hip pain and disability was a consistent clinical feature. The average duration of symptoms was 1.4 years. Radiographs obtained at various intervals before surgery (average, 18 months) in nine patients documented rapid hip destruction. Involvement was unilateral in 89% (24 of 27 cases). Twenty patients (83%) were elderly women. The authors postulate that these cases represent an uncommon, rapidly destructive subset of osteoarthritis.

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Several factors may play a role in the etiology of "spontaneous" osteonecrosis of the medial femoral condyle. Corticosteroids are known to induce osteonecrosis, and 45% of the patients in this study received steroids parenterally or by intra-articular injection. Another factor, heretofore given little attention, is the association of medial meniscal tears and "spontaneous" osteonecrosis. Twenty-one (78%) of 27 knees examined by arthrography demonstrated meniscal tears. Stress concentration over the edge of the meniscal fragment may result in ischemic necrosis of the femoral condyle. Early detection of a medial meniscal tear by arthrography in older patients and prompt treatment may be important in avoiding the late changes of "spontaneous" osteonecrosis.

Isolated fractures of the hamulus, formerly considered rare, are being seen more frequently. Many of these injuries are sports related, particularly in golf, tennis, racquetball and baseball players. Failure to make an early diagnosis can result in severe pain and sometimes incapacitating disability. We studied the clinical and radiological findings in 12 patients who had fracture of the hook of the hamate. We propose three radiographic signs of fracture that are readily seen on routine PA projections: "absence" of the hook of the hamate; "sclerosis" of the hook; and lack of cortical density, i.e., a barely visible outline, of the hamulus.