Do ion concentrations after metal-on-metal hip resurfacing increase over time? A prospective study.

Thirteen male and five female patients received a Conserve Plus hip resurfacing and prospectively provided blood samples to measure cobalt and chromium levels for up to 11 years. Trends in metal levels over time in unilateral and bilateral patients were studied. A multi-variate regression model was used to account for potential covariates. For unilaterals over all time intervals, the median Serum Cobalt level (CoS) was 1.06 μg/L, while the median Serum Chromium level (CrS) was 1.58 μg/L. For bilaterals, the median post operative CoS was 2.80 μg/L, while the median CrS was 5.80 μg/L. Metal levels increased within the first year then decreased and stabilized. These results show that serum metal levels in well-functioning implants can be low and do not increase with time.