Femoral offset found not to affect metal ion levels in metal-on-metal total hip arthroplasty

BackgroundFailure to restore femoral offset in metal on polyethylene total hip arthroplasty (THA) causes polyethylene wear and aseptic loosening. To our knowledge, no study to date has investigated the relationship between femoral offset and wear in metal-on-metal (MOM) THA.AimsIn this study, we investigated the relationship between femoral offset and wear by measuring circulating metal ion levels in MOM THA.MethodsIn this retrospective study, we identified patients who had undergone MOM THA with the ASR XL system (DePuy International Ltd., Leeds, UK). Femoral offset was measured using anteroposterior radiographs, and circulating metal ion levels (cobalt and chromium) were recorded.ResultsIn total, 95 patients were included (68 males and 27 females). The mean age at the time of surgery was 64.9. Mean time from surgery to blood sampling was 15.4months. No statistically significant relationship was found between femoral offset and cobalt (p=0.313) or chromium (p=0.401) ions.ConclusionIt is known that failure to restore femoral offset during THA can lead to high rates of wear in metal-on-polyethylene articulations. In our study, no statistically significant relationship was found between femoral offset and serum cobalt or chromium ions. This study adds to the information available to surgeons regarding factors that increase wear in metal-on-metal total hip arthroplasty.