[Metal on metal bearing for total hip arthroplasty]

Total hip arthroplasty has led to a breakthrough in the treatment of patients with degenerative joint diseases and provides an appropriate response to the alleviation of pain and to patient mobility. The constant increase in the rate of operations for relatively young patients, as well as older ones, has raised the necessity for enhancing longevity of implants. It is currently assumed that the main reason for implant failure of conventional joints is the biological reaction to polyethylene wear that leads to bone absorption--osteolysis. In order to avoid this, interest has been renewed on alternative bearing surfaces metal-on-metal new implants technology that reduce the volume of wear particles and improve kinematics of those implants. Current technologies include highly cross-linked polyethylene in metal-on-metal and ceramic-on-ceramic surfaces. This paper reviews and discusses the biomechanical principles of metal-on-metal total hip arthroplasties, and the clinical results of this technology.