Tribology of metal-on-metal artificial hip joints

Natural hip joints are briefly introduced, followed by artificial hip replacements. The main problem of osteolysis and loosening of prosthetic components in current polyethylene hip joints is briefly discussed, and alternative bearings, such as metal-on-metal, are introduced. A brief account of the historical development of metal-on-metal hip joint replacements is presented. An overview is given to tribology and its scope, as well as associated techniques. Detailed discussion of results and important findings for metal-onmetal hip implants are presented for contact mechanics, friction, lubrication, and wear. The importance of integrated studies of friction, wear, and lubrication is demonstrated in order to understand the complex tribology mechanism in metal-on-metal hip implants. Concerns about the long-term potential adverse biological reactions due to metallic ions and debris are discussed, and the importance of coupled tribological-biological studies of metal-on-metal hip implants is emphasized. Finally, future developments of both tribological techniques and new hip joint implants are summarized.