Metal-on-Metal Hip Resurfacing

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Introduction

Metal-on-metal hip resurfacing improves health related quality of life (1), post-operative function (2-5) and activity (6). Increasing number of hip resurfacing arthroplasties is being undertaken with good to excellent outcomes (4). Published reports show significant advantages of hip resurfacing as compared to total hip arthroplasty. Studies have shown improved gait parameters (7) and increased range of motion (8), but others have reported no difference when compared with standard hip arthroplasty (9, 10).

Despite these advantages there are concerns which affect patient’s and surgeon’s decision to undertake metal-on-metal hip resurfacing arthroplasty. These issues range from being technically demanding, stringent patient selection criteria (11), high early incidence of femoral neck fractures(12, 13) and reported risk of high circulating metal ions(14-17). There are theoretical concerns about cancers following exposure to high levels of cobalt and chromium ions (18).

With improvement in post-operative quality of life, activity level and function, hip resurfacing may influence mortality. Secondly, studies suggest that high levels of cobalt and chromium in circulation contribute to increased risk of cancers (19). Mortality and cause of death following total hip arthroplasty has been reported low as compared to general population. In a study by the Finnish joint registry (20), the overall SMR was 0.69(CI 0.67 -0.70) in a cohort of 24,638 patients undergoing total hip arthroplasty. The cancer mortality was also low with SMR of 0.54(CI 0.50 – 0.57).

Published literature lacks evidence regarding mortality and cause of death after metal-on-metal hip resurfacing. We present an epidemiological analysis of cause of death...

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... disparity. Our study reports epidemiological results from a single cohort. The clinical significance of these results can be improved by a prospective study comparing total hip arthroplasty and metal-on-metal hip resurfacing. The present project was limited to hip resurfacing arthroplasty but we emphasis that future studies should include a control group.

Our results provide a preliminary insight in to the effects of hip resurfacing on mortality and cause of death with special reference to death from cancers and cardiovascular diseases. This study has shown a low risk of mortality following metal-on-metal hip resurfacing in multicenter cohort. We emphasize that above results must be viewed with caution and suggest increasing participation of operating surgeons and centers towards longer follow-up of a larger cohort so that more conclusive results can be obtained.

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