METAL-ON-METAL HYBRID TWIN CUPS FOR TREATMENT OF FEMORAL HEAD NECROSIS

Abstract

Purpose: Treatment of Ficat stage III and IV femoral head necrosis is a major problem and a subject of debate because of the young age of the patients and the disappointing results obtained with total hip arthroplasty (THA). We present our experience with hybrid twin cups cemented on the femoral side and not cemented on the acetabular side using a metal-on-metal bearing to determine the mechanisms leading to revision and to assess mid-term outcomes.

Material and methods: Fifty-four hips with osteonecrosis were treated with the twin cup and studied at minimum two years follow-up. Mean patient age was 40.4 years (16–56), 13% of the patients were women and 87% men. The Ficat score (13% stage III, and 87% stage IV) was used. A prior operation had been performed in 33% of the hips.

Results: Mean follow-up was 4.4 years (2.1–6.8). Four hips required revision, three for femoral loosening after mean 46.3 months, and one for fracture of the acetabular wall immediately after the operation. The mean UCLA scores showed improvement: 3.3 to 9.3 for pain, 5.5 to 9.7 for walking, 5.0 to 9.4 for physical functioning, and 4.2 to 7.2 for activity. Physical and mental items on the SF-12 showed that normal quality-of-life was restored (compared with the general population in the United States).

Discussion: Although it is too early to speculate concerning the long-term outcome of these twin cups implanted in young patients with hip osteonecrosis, the clinical results have been encouraging. This prosthesis is an interesting alternative to the adjusted cup in the event of acetabular cartilage damage. If necessary, the acetabular component can be saved during conversion to THA without any deleterious clinical effects.