Cobalt and Chromium Ion Levels in Patients With Metal-On-Metal Hip Resurfacing Prostheses

Sixty patients with a metal-on-metal hip resurfacing were enrolled in a prospective trial to assess serum, erythrocyte, and urine cobalt and chromium ion levels. At 1 year, median serum cobalt levels were 1.2 μg/L and median serum chromium levels were 2.3 μg/L. The median levels at 2 years were 1.3 μg/L for cobalt and 3.3 μg/L for chromium. At 1 year, median erythrocyte cobalt levels were 1.0 μg/L and median erythrocyte chromium levels were 1.3 μg/L. The median erythrocyte levels at 2 years were 0.9 μg/L for cobalt and 0.9 μg/L for chromium. Resurfacing arthroplasty is associated with an elevation of cobalt and chromium ions. There is a strong correlation between serum and erythrocyte cobalt levels but a poor correlation between serum and erythrocyte chromium levels. This emphasizes the need for a standardized method of ion assessment and reporting after any metal-on-metal hip arthroplasty.