Carcinogenicity of metal alloys in orthopedic prostheses: clinical and experimental studies.

Case reports of malignant tumors at sites of metal orthopedic implants in humans and domestic animals reviewed; results of carcinogenesis bioassays of implanted metal alloys and of nickel, chromium, cobalt, and titanium powders in rodents are summarized; mobilization of metals from implanted prostheses is discussed; and in vitro assays for morphological transformation of mammalian cells by metal compounds are surveyed. These considerations suggest that occurrence of sarcoma at the implantation site constitutes a complication, albeit rare, of implanted orthopedic prostheses. The author recommends (a) that orthopedic surgeons select prostheses with minimal susceptibility to metal corrosion and wear and, if feasible, replace implanted prostheses when there is evidence of corrosion or mechanical failure; (b) that epidemiological studies be undertaken to quantify cancer risks in patients with various types of metal implants; (c) that an international registry of implant-associated tumors be established; and (d) that research be focused on improved in vitro assays for carcinogenicity of alloys intended for use in orthopedic prostheses.