National joint registry data underestimates the burden of prosthetic joint infection

OBJECTIVE: Joint registries are powerful tools for tracking outcomes following joint arthroplasty. However recent literature has exposed deficiencies in data accuracy when reporting re-operations for prosthetic joint infections (PJI), particularly when no components are changed. The aim of this study was to compare accuracy of data from the New Zealand Joint Registry (NZJR) to a multi-centre audit of hospital records to establish the rate of capture for PJI reoperations. METHODS: We followed 4009 patients undergoing total knee or hip arthroplasty performed at the three tertiary referral hospitals from January 2006 to December 2008 for two years. The reoperation rate for PJIs was extracted from the NZJR. In addition, an audit of hospital records for the same patients was carried out to identify reoperations for PJI. The audit data was then compared to the NZJR data. RESULTS: The NZJR reported a reoperation rate of 0.67% for PJI within two years of the primary arthroplasty compared to 1.1% from the audit of hospital records, giving the NZJR a sensitivity of 63%. Only 36% of washout only procedures and 58% of modular exchange procedures were captured. Surgeons were more likely to report PJIs to NZJR if they performed the primary procedure. CONCLUSION: National joint registry data significantly underestimates the rate of reoperation for PJI. Strategies for improving data accuracy may include revising the registry forms to include reoperation without change of components and frequent validation of national data with other databases.