USE OF AN ALUMINA-ON-ALUMINA BEARING SYSTEM FOR TOTAL HIP ARTHROPLASTY FOR AVASCULAR NECROSIS OF THE HIP

Abstract

Introduction: The results of total hip arthroplasty in patients with avascular necrosis of the hip have been variable. This study analyzed the clinical and radiographic outcome of young patients treated with Four different cementless systems, three with alumina-on-alumina bearings in comparison to a control metal-on-poly couple in young patients with avascular necrosis of the femoral head.

Materials and Methods: This was a US IDE multicenter prospective randomized clinical trial begun in 1996 to evaluate safety and effectiveness of alumina-alumina bearings in young patients. Four cementless systems were compared in 95 patients (105 hips), three alumina-on-alumina bearing systems: ABC System I, porous coated cup; ABC System II, hydroxyapatite coated cup; Trident system, hydroxyapatite coated cup with metal sleeve backing on ceramic cup liner. The control group was the ABC System III, porous coated cup with polyethylene and cobalt chromium bearing system. All patients received a cementless Omnifit HA femoral stem. Patients were randomized to receive ABC System I, II, or III. Trident patients (Study arm begun in 1999) were not randomized. Examinations were performed at 7 weeks, 6 months, 1 year, and yearly thereafter including x-rays, clinical exam and modified Harris Hip Scores (HHS).

Results: For the alumina-alumina hips patients had a mean age of 45 years (21–67) with 18 women (23%) and 61 men (77%) at a mean follow up of 4.2 years (range, 2–7). The mean HHS at latest evaluation was 96 points. There were three revisions: one revision of all components for hip pain (sepsis suspected but not confirmed); one stem and head for traumatic postoperative periprosthetic femoral fracture; and one insert and head for subluxation in a patient implanted with the Trident insert and head. For the metal-poly hips, there were similar demographics, follow-up, and clinical scores. There were two revisions; one stem and head for traumatic postoperative periprosthetic femoral fracture, and one insert only 2 days after index surgery for dislocation.

Discussion: Both bearing couples (alumina-alumina and metal-poly) did well in theses cementless hip arthroplasties performed in young patients with avascular necrosis of the femoral head. The low revision rate is encouraging for these previously difficult to treat patients.