Results of the long-term follow-up study after the metasul metal-on-metal cementless total hip arthroplasty

Abstract

The objectives of this study are to investigate the long-term results after the second-generation metal-on-metal cementless total hip arthroplasty (THA) and to validate continued use for metal-on-metal bearing couples. Between 1997 and 2002, 87 patients (97 hips) underwent the Metasul metal-on-metal cementless total hip arthroplasty. Seven patients died, and 12 patients were lost before 10-year follow-up. Seventeen patients (18 hips) underwent reoperation. The remaining 51 patients (60 hips) with more than 10-year follow-up without reoperation were reviewed clinically. The average age was 59.9 years, and the average follow-up period was 12.3 years. The average Merle D'Aubigné and Postel hip scores were improved from 8.5 preoperatively to 16.3 at the latest follow-up. All of the femoral components and acetabular components without reoperation were well fixed at the latest follow-up. Osteolysis was seen for seven hips and three of them were revised. The main reasons for reoperation were pseudotumor formation in three hips, pelvic osteolysis in three hips, and pain due to impingement in three hips. Five reoperations were associated with the liner dissociation of the APR cup. Survival rates at 15 years were 71.2 % defined with the endpoint as reoperation and 94.9 % defined with the endpoint as revision for aseptic loosening. The problems of the second-generation metal-on-metal cementless THA in the long-term follow-up were the locking mechanism failure of the early type of the cup and the relatively small-diameter head prone to prosthetic impingement. There is little benefit for continued use of metal-on-metal bearings in THA.