A Prospective Metal Ion Study of Large-Head Metal-on-Metal Bearing: A Matched-Pair Analysis of Hip Resurfacing Versus Total Hip Replacement

s. co m Recent improvements in metal-on-metal bearing technology have further led to the development of a total hip arthroplasty (THA) system that makes use of large-diameter femoral heads in both stem type and resurfacing hip arthroplasties. Metal ion release remains a concernwith using thesebearings because of possible adverse tissue reactions and subsequent prosthetic loosening. Recent reports have shown that metal ion release can be affected by bearing design, acetabular component orientation, as well as modularity due to fretting corrosion. Although several clinical trials have shown relatively low metal ion levels after metal-on-metal hip resurfacing (HR) as well as 28-mm diameter Metasul (Zimmer, Warsaw, IN, USA) and 36-mm metal-on-metal total hip replacements, it is unclear if these studies can be applied to other implant designs as well as even larger-diameter metal-on-metal total hip replacements. Initial in vitro laboratory tribological wear testing have shown lower wear rates with the larger-diameter metalon-metal bearings, with further reduction in bearingwearbeingproposedusingdifferential hardness bearings, which are intended to limit abrasive, adhesive, and surface fatigue damages.