New Zealand Joint Registry data underestimates the rate of prosthetic joint infection

Background and purpose — Recent studies have revealed defi - ciencies in the accuracy of data from joint registries when reop- erations for prosthetic joint infections (PJIs) are reported, par- ticularly when no components are changed. We compared the accuracy of data from the New Zealand Joint Registry (NZJR) to a multicenter audit of hospital records to establish the rate of capture for PJI reoperations. Methods — 4,009 cases undergoing total knee or hip arthro- plasty performed at 3 tertiary referral hospitals over a 3-year period were audited using multiple hospital datasets and the NZJR. The number of reoperations for PJI that were performed within 2 years of the primary arthroplasty was obtained using both methods and the data were compared. Results — The NZJR reported a 2-year reoperation rate for PJI of 0.67%, as compared to 1.1% from the audit of hospital records, giving the NZJR a sensitivity of 63%. Only 4 of 11 debridement- in-situ-only procedures and 7 of 12 modular exchange procedures were captured in the NZJR. Interpretation — The national joint registry underestimated the rate of reoperation for PJI by one third. Strategies for improv- ing the accuracy of data might include revising and clarifying the registry forms to include all reoperations for PJI and frequent validation of the registry data against other databases.