Cushion bearings versus large diameter head metal-on-metal bearings in total hip arthroplasty: a short-term metal ion study

INTRODUCTION: Metal-on-metal total hip arthroplasty (MOM THA) has the advantage of replicating the femoral head size, but the postoperative elevation of serum metal ion levels is a cause for concern. Metal-on-polycarbonate-urethane is a new cushion bearing featuring a large diameter metal head coupled with a polycarbonate-urethane liner. AIM: The aim of this study was to assess and compare serum cobalt (Co) and chromium (Cr) levels in a group of 15 patients treated with a cushion bearing THA system (Group A) and a group of 15 patients treated with a MOM THA system (Group B) at short-term. At a mean follow-up of 27.3 months (18-35 months), in Group A the median Cr and Co serum levels were significantly lower than in Group B, measuring 0.24 μg/L (0.1-2.1 μg/L) and 0.6 μg/L (0.29-2.3 μg/L) compared to 1.3 μg/L (0.1-9 μg/L, p < 0.001) and 2.9 μg/L (0.85-13.8 μg/L, p < 0.001) respectively. RESULTS: All patients demonstrated an excellent clinical result, as shown by the Harris and Oxford hip scores. The cushion bearing THA studied in this paper showed clinical outcomes similar to the MOM THA bearing, with the advantage of no significant metal ion elevation in the serum. CONCLUSION: These findings warrant the continued clinical study of compliant bearing options.