From In Vitro to Retrieval Studies of Orthopedic Implants

Three main groups of metallic materials have been used for decades for orthopedic hip implants: stainless steel, cobalt chromium, and titanium-based alloys. In the first part of this overview, these materials are briefly presented together with basic in vitro studies for the investigation of corrosion resistance in simulated physiological media. Possible adverse effects of metals including cytotoxicity and hypersensitivity, as well as possible systemic effects, are described. The importance of implant retrieval programs is stressed as a valuable tool for understanding the degradation mechanism of metal in vivo. It includes various processes of wear, corrosion, and tribocorrosion. In the second part of this overview, several examples of retrieval analysis of hip implants are presented with emphasis on analysis of wear and corrosion products of metal components.