Evaluation and management of metal hypersensitivity in total joint arthroplasty: a systematic review

Metal hypersensitivity has been an identified problem in orthopedics for nearly half a century, but its implications remain unclear. Establishing which total joint arthroplasty (TJA) candidates may do poorly with conventional implants and which patients would benefit from revision to an allergen-free implant remains challenging. Our systematic search of the MEDLINE database identified 52 articles for inclusion in our review. Case reports revealed that half of patients presented with pain and swelling, while only one-third presented with cutaneous symptoms. All patients were symptomatic within the first post-operative year; 90% were symptomatic within 3 months. Reports of patch testing revealed that patients with TJAs were positive for metal sensitivity more often than patients without TJAs (OR 1.3). Those with poorly functioning arthroplasties and those who had already had revisions tested positive more often than those with well-functioning TJAs (OR 1.7) and those without TJAs (OR 3.1). Lymphocyte transformation testing (LTT) shows promise in diagnosing metal allergy, and components of bone cement are also being recognized as potential allergens. Further work is necessary to delineate which patients should be tested for metal allergy and which patients would benefit from allergen-free implants.