Long-term results of metal-on-metal total hip replacement after a minimum of seventeen years' follow-up

Abstract

Background: Second-generation metal-on-metal bearings were introduced in 1988, as an alternative to reduce wear and avoid polyethylene particle-induced osteolysis in total hip arthroplasty. In 2007, we reported the long-term results of 105 cementless primary total hip prostheses with high-carbide-concentration metal-on-metal articulating surfaces, implanted in 98 patients between November 1992 and May 1994. This study gives an update on this patient cohort. Methods: At a minimum of 17 years postoperatively, 49 patients, who had had a total of 52 implants, were available for follow-up examination. We retrospectively evaluated the clinical and radiographic results, as well as the serum metal concentration. The mean age of the patients at the time of the index arthroplasty was 56 years. Results: Three cups (2.8 %) and one stem (0.9 %) were revised because of aseptic loosening of the implants. At the time of final follow-up, the result of the Harris hip score was 88.8, of the UCLA score 6.7 on average. The cumulative rate of survival of the prostheses with aseptic failure as the end point was 93.0 % at 18.8 years. The median serum cobalt concentration of the patients with their hip replacement as the only source of cobalt was 0.70 μg/L (range 0.4-5.1 μg/L), showing no increase compared to the values of our previous study after a minimum of 10 years' follow-up. Conclusions: The clinical and radiological results of the longest follow-up of a series of cementless total hip arthroplasties with a 28-mm metal-on-metal bearing continue to be comparable to other hard-on-hard bearings at a minimum of 17 years postoperatively. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.