Metal-on-metal (MoM) total hip replacement (THR) and hip resurfacing have an advantage of low wear rate and greater stability by larger head size and different characteristics of wear mechanism, tribology, lubrication or generating wear debris compared to conventional metal-on-polyethylene THR. Although the mid- or long term clinical reports of second generation MoM THR were excellent, concerns about local and systemic effect by metal particles or metal ions were remained. Recently, reports have emerged of abnormal soft-tissue reactions to metal particles or metal ions and some hip resurfacing implants were expelled from the market due to high revision rate. This article includes the history of MoM THR, tribology, the biologic effect of metal particles and ions, the clinical results of MoM THR and the issues regarding the problems associated with hip resurfacing.

Keywords: Total hip replacement, Metal-on-metal articulation, Metal particles, Metal ions