The radiological features of avascular necrosis of the femoral head in homozygous sickle cell disease.

Out of a total of 1031 patients with homozygous sickle cell (SS) disease attending a sickle cell clinic in Jamaica, 52 patients were found to have changes of avascular necrosis of the femoral head in 76 hips. Hip involvement was unilateral in 28 patients (31 males and 21 females). The age of onset varied from nine to 45 years in the 40 patients in whom data appeared reasonably reliable and 82% developed this lesion between 10 and 29 years. Radiological change occurred, by definition, in the femoral head in all hips, in the acetabulum in 55 (72%) hips, femoral head migration occurred in 37 (49%) hips, and periosteal new bone formation in 24 (32%) hips. Two broad patterns of involvement were discernible according to the age at which avascular necrosis had occurred. Involvement of the immature femoral head epiphysis resulted in a flattened femoral head, epiphysio-metaphyseal overlap, a wide femoral neck and a mushroom deformity of the mature femoral head. In these lesions the articular surface and joint space was generally well preserved and little or no disability resulted in adult patients. Involvement of the mature femoral head was typical segmental, most commonly antero-superior, and with continued weight bearing resulted in collapse of the head and disruption of the articular surface. These lesions caused pain, limitation of movement, and commonly changes of osteo-arthrosis.