The role of metal patch testing in evaluating for metallic prosthetic joint failure

Metal allergy is thought to be an uncommon cause of prosthetic joint failure. There exists little data on patch testing to metals in this context and its effect on the outcomes of this type of surgery in these patients. A retrospective analysis from January 2016 to April 2020 was completed on a patient cohort referred to the University of Colorado Allergy and Immunology practice by the Department of Orthopedics for evaluation of metal hypersensitivity. Charts were reviewed for age, biological sex, referring specialty, patch testing results, joint, revision status, and patient reported outcome measures. Biostatistical analysis and descriptive statistics were performed to determine patch testing performance and trends among patients with suspected allergy as a cause of prosthetic joint failure. The sensitivity and specificity of patch testing, in general, is limited when evaluating patients with metallic joint replacements. However, the predictive value of testing results appeared to improve with strongly positive patch testing results. Functional outcomes in patients when positive results were used to choose the prosthesis demonstrated objective evidence of clinical improvement. The attribution of metal allergy or hypersensitivity as a cause of failure in metal prosthetic joint replacement remains unproven. Despite this shortcoming, some patients with positive histories and patch testing in which the results were used to modify the choice of implanted prosthesis had improved functional outcomes. Consequently, these results suggest it may be worthwhile to perform patch testing in patients with prior history of metal sensitivity and prior prosthetic failure.