Release of hexavalent chromium from corrosion of stainless steel and cobalt-chromium alloys.

Experiments were undertaken to determine whether hexavalent chromium was released during corrosion of orthopedic implants. Uptake of chromium (Cr) by cells and separation using amberlite resin were the methods used to determine that hexavalent Cr was present. We used salts of chromium as trivalent chromium (chromic chloride) and hexavalent chromium (potassium dichromate) to verify that the amberlite separation technique separates hexavalent Cr into the upper phase and trivalent Cr into the lower phase. The use of the salts also verified that only the hexavalent Cr became red blood cell-associated and that most of this was intracellular rather than membrane bound. The use of the amberlite separation technique demonstrated that the hexavalent Cr in the red blood cells was rapidly reduced to trivalent Cr. Cellular uptake of chromium was documented in red blood cells following corrosion of stainless-steel and cobalt-chromium implants in vivo, in the red blood cells of patients undergoing total joint revisions, and in fibroblasts subjected to products of fretting corrosion of stainless-steel and cobalt-chromium implants. Thus, corrosion of implants can lead to the release of the biologically active hexavalent chromium into the body. This chromium is rapidly reduced to trivalent chromium in cells.