Toxicology of wear particles of cobalt-chromium alloy metal-on-metal hip implants Part II: Importance of physicochemical properties and dose in animal and in vitro studies as a basis for risk assessment

Part II of this analysis evaluated animal and in vitro toxicology studies of CoCr particles with respect to their physicochemistry and dose relevance to metal-on-metal (MoM) implant patients. Particle characteristics were infrequently considered, and administered doses were orders of magnitude higher than what has occurred in patients. Animal studies indicated that CoCr micron sized particles were more biopersistent and resulted in inflammatory responses that were not seen with nano sized particles. Future studies should focus on physicochemical characteristics of nano and micron sized particles, and on doses relevant to those generated in patients or in properly conducted hip simulator studies.98