Rationale for metal-on-metal total hip replacement.

Traditional metal-on-polyethylene total hip replacements are prone to wear with secondary osteolysis and aseptic loosening, especially in younger, more active patients. Metal-on-metal represents an alternative bearing surface that offers much lower wear rates with the aim of improving longevity and the use of larger femoral heads that confer increased inherent stability, resulting in fewer patient restrictions and improved patient satisfaction. This article discusses the science and clinical evidence in support of choosing metal-on-metal as a bearing as well as its limitations.