Anterior impingement of the femoral head: a late phenomenon of Legg-Calvé-Perthes' disease.

A previously unrecognized late phenomenon of anterior impingement of the femoral head in Legg-Calvé-Perthes' disease is reported in four patients. After an asymptomatic period following reossification of the femoral head, the patients had pain triggered by internal rotation of their hips. Standard roentgenograms did not indicate any cause of the pain. Computed tomography (CT), arthrography, and arthroscopy demonstrated impingement of the anterior aspect of the femoral head against the anterior rim of the acetabulum on internal rotation of the leg. Three hips had femoral head articular surface damage with osteochondral projections at the area of anterior impingement. Arthroscopic debridement and proximal femoral osteotomy was successful in relieving the symptoms.