Metal Allergy as a Cause of Implant Failure in Shoulder Arthroplasty

Metal allergy is an uncommon and poorly understood cause of failure of orthopedic implants. To the authors' knowledge, there have been no reports of the management of shoulder arthroplasty patients with metal allergy. The authors present their experience with the diagnosis and management of patients with metal allergy. Patients with metal allergy undergoing shoulder arthroplasty were identified through retrospective chart review from January 1, 2012, to January 31, 2015. Case characteristics collected included patient risk factors (age, sex, prior cutaneous reactions to metal), metal allergy factors (type of metal allergy, method of diagnosis), and surgery factors (implant type, primary/revision, type of shoulder arthroplasty). Outcomes measured included American Shoulder and Elbow Surgeons score, Penn Shoulder Score, and Single Assessment Numeric Evaluation score. Eleven patients were identified with metal allergy. Five were diagnosed prior to the index arthroplasty, and 6 were diagnosed after shoulder replacement. The diagnosis was made through skin patch testing, memory lymphocyte immunostimulation assay, or clinical history. Patients identified after implantation presented with progressive pain and stiffness, but none had cutaneous manifestations. Patients with metal allergy had better results undergoing primary shoulder arthroplasty than undergoing revision. Metal allergy is rare but may be a clinically significant cause of unsatisfactory shoulder arthroplasty. Given the superior results of primary shoulder arthroplasty compared with revision, screening for metal allergy by clinical history is recommended.