Use of an alumina-on-alumina bearing system in total hip arthroplasty for osteonecrosis of the hip

Background: The results of total hip arthroplasty in patients with osteonecrosis of the femoral head are not always optimal. The use of alumina-on-alumina interfaces in young and active patients may decrease wear and lower the rate of aseptic loosening of the implant and appears to be an attractive alternative to the use of conventional cobalt-chromium-on-polyethylene bearings. The purpose of this study was to evaluate the safety and efficacy of the alumina-on-alumina bearing in patients with osteonecrosis and to compare this group of patients to a group of similarly treated patients with osteoarthritis and a group of patients who received conventional cobalt-chromium-on-polyethylene bearings. Methods: Patients were selected from a United States Investigational Device Exemption multicenter prospective randomized clinical study that was initiated in 1996. Seventy patients with osteonecrosis of the femoral head (seventy-nine hips) received a cementless alumina-on-alumina bearing system and were directly matched to seventy-six patients with osteoarthritis of the hip (seventy-nine hips) who were managed with the same implant. Both groups were compared with twenty-five patients (twenty-six hips) with osteonecrosis and twenty-five patients (twenty-six hips) with osteoarthritis who were managed with a cementless cobalt-chromium-on-polyethylene bearing system. All patients received a cementless hydroxyapatite-coated femoral stem and were followed both clinically and radiographically. Results: The clinical outcomes for alumina-on-alumina bearings were similar for both osteonecrotic and osteoarthritic hips. The seven-year survival probability was 95.5% for the osteonecrotic hips and 89.4% for the osteoarthritic hips in the alumina-on-alumina bearing group and 92.3% for the osteonecrotic hips and 92.9% for the osteoarthritic hips in the cobalt-chromium-on-polyethylene bearing group. At the time of the most recent follow-up, the mean Harris hip score was 96 points for both the osteonecrotic and the osteoarthritic hips in the alumina-on-alumina group and 96 points for the osteonecrotic hips and 97 points for the osteoarthritic hips in the cobalt-chromium-on-polyethylene bearing group. Conclusions: The results of the use of alumina-on-alumina and cobalt-chromium-on-polyethylene bearings in cementless standard total hip implants in patients with osteonecrosis and osteoarthritis were comparable. The low revision rate for the alumina-on-alumina bearing is encouraging and offers a promising option for younger, more active patients who have this challenging disease. Level of Evidence: Therapeutic Level Ill. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.