release of metal ions Metal bearings corrode at a rate determined by their surface area and cause a release of metal ions. When wear particles are being formed, the total surface area of metal is increased considerably. These ions may attach to proteins and cause allergic reactions (1,19-21). Hypersensitivity reactions of surrounding tissues were described. (22-25). High blood levels of chrome and cobalt were found in patients with metal-on-metal prostheses and changes in red and white blood cells have been reported (24,26-43). High metal ion levels are important, knowing the fact that chrome and cobalt may cause cancer and may be mutagenic although investigations are not conclusive about the relation with orthopedic implants (43,44).