Hip deformity in symptomatic adult Perthes' disease.

Only a limited number of patients that suffered from Legg-Calvé-Perthes' disease (LCPD) develop pain in early adulthood. Classical hinged abduction is well known and is thought to be responsible for secondary lateral insufficiency of the acetabulum, which may become painful. Another possible explanation, which was put forward more recently, is anterior femoroacetabular impingement. We collected information about the exact morphology of the proximal femur and the acetabulum of 15 hips in 15 young adults (mean age: 25.3 years) who had hip surgery consequent to childhood Perthes' disease in our hospital between 1974 and 2001. In addition to the well known lateral bulging of the femoral head, averaging 112% of the functional radius, we found an even larger anterior bulging, averaging 115% of the functional radius. The mean torsion of the femoral head was -3.6 degrees, which in fact corresponds to a retrotorsion. Retroversion of the acetabulum was found in at least 5 of the 15 hips in which the version could be adequately assessed (33%). Since any of the above deformities favours anterior femoroacetabular impingement and thus hinged flexion, this could well be a contributor to the development of the classic sequelae of LCPD and to the later development of osteoarthritis.