Osteochondritis dissecans complicating Legg-Perthes disease. A report of four cases.

Osteochondritis dissecans of the femoral head occurs as a rare complication in the late onset of Legg-Perthes disease. The etiology of this complication is uncertain. Theories include: (a) persistence of an ununited fragment and (b) fragmentation of the femoral head weakened by revascularization accompanying healing. The area of osteochondritis dissecans may not be readily apparent on routine radiographs and a high index of suspicion is necessary for diagnosis. Four cases of osteochondritis dissecans of the hip presenting 6--18 years after the diagnosis of Legg-Perthes disease are described. Three patients were studied by arthrography, and the findings correlated well with symptomatology.