Insufficiency subchondral fracture of the femoral head: report of 4 cases and review of the literature.

Insufficiency subchondral fractures are nontraumatic flattened lesions in the superolateral area of the femoral head, occurring in healthy adults. These lesions were recently described and are an infrequent cause of acute hip pain. We report on 4 patients who were diagnosed with an insufficiency subchondral fracture. All the patients showed radiographic progression of the lesion after 4 months, and 3 patients required a total hip arthroplasty. The etiology and the natural history of these rare lesions remain to be elucidated. These lesions should be differentiated from osteonecrosis and transient osteoporosis, because treatment and prognosis may differ.