Cobalt and Chromium Levels in Blood and Urine Following Hip Resurfacing Arthroplasty with the Conserve Plus Implant

Background: The purpose of the present study was to determine cobalt and chromium ion levels in the blood and urine of patients in whom a modern-generation metal-on-metal hip resurfacing device had been implanted. Methods: A total of ninety-seven patients with a Conserve Plus metal-on-metal hip resurfacing implant were followed prospectively for two years. Cobalt and chromium levels in erythrocytes, serum, and urine were measured preoperatively as well as three, six, twelve, and twenty-four months postoperatively. Results: The median serum cobalt and chromium ion levels were 1.04 mu g/L (range, 0.31 to 7.42 mu g/L) and 2.00 mu g/L (range, 0.28 to 10.49 mu g/L), respectively, at one year after surgery and 1.08 mu g/L (range, 0.44 to 7.13 mu g/L) and 1.64 mu g/L (range, 0.47 to 10.95 mu g/L), respectively, at two years after surgery. The corresponding mean levels (and standard deviations) of serum cobalt and chromium were 1.68 +/- 1.66 mu g/L and 2.70 +/- 2.22 mu g/L, respectively, at one year after surgery and 1.79 +/- 1.66 mu g/L and 2.70 +/- 2.37 mu g/L, respectively, at two years after surgery. Conclusions: These levels compare favorably with other published ion results for metal-on-metal hip resurfacing and replacement implants. No pseudotumors or other adverse soft-tissue reactions were encountered in our study population. Further research is needed to determine the clinical importance of increased cobalt and chromium ion levels in serum and urine following metal-on-metal hip resurfacing.