Metal hypersensitivity: Reality or fiction?

Hypersensitivity to metal in total hip arthroplasty is a condition that is well described in the orthopaedic literature. Despite using nearly identical biomaterials for implant manufacturing, metal hypersensitivity is less recognized in total knee arthroplasty. Unexplained pain is common after total knee arthroplasty, and metal hypersensitivity is hypothesized to play a potential role in some cases. Metal hypersensitivity is a T-cell mediated hypersensitivity that can cause a localized inflammatory response, leading to pain and swelling at the site of the implants. By recognizing potential hypersensitivity to metal antigens in high-risk patients preoperatively, the surgeon may implement specific implant selection and postoperative therapeutic measures to decrease the likelihood of this complication and subsequent poor clinical outcome. The aim of this review is to describe the epidemiology, etiology, clinical presentation, and current treatment options for metal hypersensitivity reactions in patients undergoing total knee arthroplasty.