Avascular necrosis of the femoral head in congenital dislocation of the hip.

A study of the X-rays of 450 children treated for congenital dislocation of the hip revealed 56 hips with total or partial avascular necrosis of the femoral head. These hips were classified into four groups. Group 1 consisted of 13 hips in which the femoral head was normal before treatment and avascular necrosis appeared during or after orthopedic or surgical procedures. These are the iatrogenic cases. Group 2 consisted of 22 hips in which avascular necrosis was evident before any treatment. The necrosis was considered a dystrophy arising from malposition. Group 3 included 12 hips in which the avascular necrosis might have been either iatrogenic or a dystrophy due to malposition. This could not be determined because these hips were treated early, before avascular necrosis was seen on X-ray. Group 4 consisted of nine hips in which unilateral dislocation was associated with avascular necrosis of the unaffected normal side prior to any treatment of the affected hip.