Metal Hypersensitivity Is Associated With Inferior Implant Survivorship in Total Knee Arthroplasty, but Not Total Hip Arthroplasty: A Large-Database Matched-Cohort Analysis

Background: The purpose of this study was to determine if a preoperative diagnosis of metal hypersensitivity (MHS) is a risk factor for worse implant survivorship following total hip arthroplasty (THA) or total knee arthroplasty (TKA). Methods: A retrospective cohort study was performed using United States national claims data from January 2010 to October 2022, sourced from a large national database. A cohort of 524 patients undergoing THA and 1,559 patients undergoing TKA who had an MHS diagnosis were 1:4 propensity score-matched to 2,075 THA and 6,189 TKA controls on age, sex, and Charlson comorbidity index (CCI). All patients were ≥18 years old at the time of surgery, underwent primary procedures, and had a minimum 2-year follow-up. Time to revision surgery at up to 5-year follow-up for all causes, for periprosthetic joint infection (PJI), and for mechanical loosening were compared between groups using the Cox proportional hazards model. Hazard ratios (HRs) with 95% confidence intervals were calculated. Results: For the THA analysis, the 5-year cumulative incidence of revision was low in both groups (MHS 4.8 versus control 3.0%) and there was no significant difference in risk of all-cause revision between groups (P > 0.05). For the TKA analysis, the 5-year cumulative incidence of all-cause revision was high in the MHS group (MHS 13.1 versus control 3.8%), and the MHS group also had a higher risk of all-cause revisions (HR 3.63 [3.00 to 4.39], P < 0.001), revision for PJI (HR 4.11 [2.81 to 6.02], P < 0.001), and revision for mechanical loosening (HR 4.96 [3.82 to 6.46], P < 0.001). Conclusions: Preoperative MHS was associated with a higher risk of all-cause revision by 5-year follow-up following TKA, but not THA, though the present study could not establish a causal relationship between MHS and the need for revision surgery. Level of Evidence: III, retrospective cohort study.