Biological response to common surface bearings used in orthopaedics.

Wear particles are the most important cause of aseptic loosening of orthopaedic devices. To reduce the amount of particles generated from the conventional metal-on-polyethylene system, alternative bearings have been introduced. However, there are some concerns about so-called "adverse reactions" to these bearing surfaces. Despite an apparent longevity, metal particles and metal ions released from the prosthesis can induce a series of adverse reactions. The purpose of this review is to provide the readers an up-to-date overview of the literature on the biological responses to different bearing surfaces with particular reference to metal-on-metal bearings and the local and systemic effect of metal ions.