COBALT AND CHROMIUM CONCENTRATIONS IN PATIENTS WITH METAL ON METAL TOTAL HIP REPLACEMENTS

There has been a resurgence of interest in the use of metal on metal b earings in total hip arthroplasty, Although the use of metal on metal bearing couples would eliminate or substantially reduce particulate po lyethylene generation (depending on the presence or absence of polyeth ylene in the implant system), there is concern about the potential for increased particulate and ionic metal generation in comparison with p olyethylene on metal bearings, These metallic degradation products may be transported away from the implant site and distributed systemicall y, Chromium concentrations in the serum and urine and cobalt concentra tions in the serum were measured in subjects with cobalt chromium allo y metal on metal total hip replacements and in controls without implan ts, Eight subjects with long term (> 20 years) McKee-Farrar total hip replacements had 9-fold elevations in serum chromium, 35-fold elevatio ns in urine chromium, and at least 3-fold elevations in serum cobalt c oncentrations in comparison with controls. Six subjects with short ter m (< 2 years) metal on metal surface replacement arthroplasties had 3- fold elevations in serum chromium, 4-fold elevations in urine chromium , and 4-fold elevations in serum cobalt concentrations in comparison w ith subjects with McKee-Farrar implants. Although the toxicologic impo rtance of these trace metal elevations has not been established, serum and urine metal concentrations may be useful markers for the tribolog ic performance of metal on metal bearings.