Release of corrosion products by F‐75 cobalt base alloy in the rat. I: Acute serum elevations

The release of corrosion products by implants has become a matter of concern. Using a microsphere model, the release of chromium, cobalt, and nickel, secondary to implantation of various surface area exposures of F-75, a cast cobalt-chromium alloy, was studied over a 30 day period in the rat. Dose related elevations were observed in the serum concentration of chromium and cobalt but not of nickel, with the maxima being achieved at 3 days after metal implantation followed by declines in concentration. The chromium elevation, approximately twelvefold for a surface area to body weight (SA/BW) ratio of 300 X is similar to that previously reported in patients receiving total hip replacement arthoplasties . However, the cobalt elevation, twentyfold for a SA/BW ratio of 300 X, has not been previously observed. These serum concentration changes are as yet unexplained, but are probably not due to fibrous capsule maturation or alloy repassivation .