Metal Hypersensitivity Reactions to Orthopedic Implants

Total hip and knee replacement surgery using metal alloy devices is common. Type IV allergic reactions to these implants occur, though infrequently. While uncommon, peri-implant metal allergic reactions may cause significant morbidity for the affected individual-including aseptic loosening, pseudotumor formation and frank device failure. It is challenging to predict who will have these reactions, even in those with established pre-implant metal allergy. At this time, the scientific literature clearly supports few conclusions. Despite this, we believe several conclusions can be made: routine pre-implant testing in asymptomatic individuals is not indicated; listen to patient's concerns about metal allergy if the concern arises; patch testing is probably the best pre- and post-implant screening test; post-implantation testing is controversial and even positive LTT or patch test does not definitively diagnose morbidity from a metal allergy; and complete recovery following revision placement of an immunologically inert device is diagnostic. More research is needed to scientifically approach this issue.