Allergy to Surgical Implants

Surgical implants are essential elements of repair procedures to correct worn out joints, damaged spinal components, heart and vascular disease, and chronic pain. However, many of the materials that provide stability, flexibility, and durability to the implants are also immunogenic. Fortunately, allergic responses to surgical implants are infrequent. When they do occur, however, the associated pain, swelling, inflammation, and decreased range of motion can significantly impair the implant function. Given the high numbers of joint replacements performed in the developed world, allergic reactions to orthopedic implants form the largest category of allergic responses. The most important allergens in this category include nickel, cobalt, chromium, and bone cement. These allergens are also the most important in reactions to spinal surgeries. Multiple cardiac and neurostimulatory devices are constructed of metals and adhesives that can be sensitizing in some individuals. Implantable pulse generators, important in cardiac pacemakers, gastric stimulators, and neurostimulators, may include components made of stainless steel, titanium alloy, platinum and iridium, epoxy resins, poly methyl methacrylates, and isocyanates, all of which are immunogenic in some patients. Cardiac stents and patches are often made of Nitinol, a composite of nickel and titanium. More surgical procedures are closed using skin glues, which are also capable of triggering a blistering contact dermatitis. Patch testing is the gold standard to determine sensitization, and this review provides a list of standard allergens to test for different implants. The patients most appropriate for testing include (1) pre-operative joint replacement patients with a prior history of skin reactions to metal jewelry, jean snaps, watch bands, metal glass frames, artificial nails, or skin glue; (2) post-operative joint replacement failure patients needing revision without an obvious cause such as infection or mechanical incompatibility; and (3) post-operative cardiac or neurological patients with localized rash, pain, swelling, or inflammation near or over the implant.