AVASCULAR OSTEONECROSIS OF THE ACETABULUM

Objective. To investigate the possible occurrence of osteonecrosis in the acetabulum in patients with non-traumatic necrosis of the femoral head. Design and patients. One hundred and seventy-nine patients with nontraumatic femoral head necrosis were assessed by MRI and radiograph y for the presence of acetabular necrosis. Three criteria were establi shed to differentiate between osteonecrosis and osteoarthritic changes : (1) heterogeneous morphology and irregular contours of the lesion; ( 2) typical demarcation lines of osteonecrosis; (3) deficient accumulat ion of intravenous gadolinium in the affected regions.Results. In four patients histological confirmation of acetabular necrosis was obtaine d. The MR analysis of 22 acetabula (9.5% of those examined) showed cha nges which suggested osteonecrosis. No cystic lesions were demonstrate d in the subchondral bone of any patient, Two cases of acetabular necr osis were found without an ipsilateral femoral head necrosis. In two p atients of the 14 who had undergone total hip replacement following ne crosis of the femoral head, aseptic loosening of the acetabular compon ent was found. Conclusion. The study suggests that acetabular necrosis may be an accompaniment to aseptic necrosis of the femoral head, Furt her work is required to assess its importance in premature loosening o f the acetabular element of total hip arthroplasty.