Ion Production and Excretion in a Patient with a Metal-on-Metal Bearing Hip Prosthesis

Metal-on-metal bearings have been associated with the generation of metal particles and ions1,2 and, in comparison with that seen in other bearing surfaces, a measurable increase in the concentration of cobalt and chromium ions in blood and urine3-7. The risks of higher ion levels include delayed-type hypersensitivity, organ toxicity, and carcinogenesis8-10. Studies of cobalt and chromium ion levels have demonstrated variability from patient to patient4,7. Levels tend to be highest in the short-term and, with a well-functioning prosthesis, decrease with time4.