Impact of Preoperative Metal Patch Testing on Surgery Using Metal Implants

BACKGROUND: Patients scheduled for metal implant surgery in some facilities in Japan undergo preoperative metal patch testing (MPT). However, few studies have reported the impact of MPT results on scheduled surgery; therefore, the value of preoperative MPT remains unknown. MATERIAL AND METHODS: In analysis 1,the preoperative MPT results requested by orthopedic surgeons from 4 institutions from 2014 to 2018 were retrospectively analyzed. In analysis 2, the medical records of all patients who underwent total hip arthroplasty, total knee arthroplasty, or total shoulder arthroplasty/reverse shoulder arthroplasty between 2014 and 2018 were collected. The number of patients who underwent MPT and their surgical results were analyzed. RESULTS: In analysis 1, MPT was performed on 72 patients during the study period. The overall MPT positivity rate was 26.4% for the entire cohort in analysis 1. In 4 out of 19 MPT-positive cases, the results of MPT changed the treatment plan to use alternative materials or cancel the surgery. In analysis 2, 1087 patients underwent total hip arthroplasty, total knee arthroplasty, and TSA/RSA; only 16 patients underwent MPT. Aseptic loosening occurred postoperatively in 3 patients (0.3%), none of whom had a history of allergy, and none underwent preoperative MPT. CONCLUSION: Metal allergy did not appear to be directly involved in aseptic loosening to any large or meaningful degree in our patient cohort. Only 1.5% of the patients underwent preoperative MPT; therefore, our results suggest this testing had limited benefit or utility. Further studies are needed to determine whether MPT is necessary in preparation for joint replacement.