Does a Surgeon Outlier Policy Improve Surgical Performance? Results From the New Zealand National Joint Registry, January 2018 to December 2024

Introduction In December 2018, the NZ Joint Registry introduced a “Surgeon Outlier” policy, whereby each year, if an individual surgeons’ lower 95% confidence interval of their revision rate was above the NZ mean, that surgeon was required to audit their results with a nominated peer. Materials & Methods De-identified data was obtained from the NZ Joint Registry on all surgeons identified as outliers between January 2018 (one year of results before notification) and 31st Dec 2024. Results Thirty-four surgeons performing total hip arthroplasty were notified they were outliers. As of December 2024, 21 surgeons had improved their results such they were no longer considered outliers. Four surgeons were outliers for 1 year, eight for 2 years, 2 for three years, and 7 surgeons were outliers for 4 years. At the time of first notification, the mean revision rate of this group was 7.28% (NZ registry revision rate 5.14%). Thirteen surgeons continue to be outliers (notified Dec 2024 with at least one previous notification). The mean revision rate for this group was 5.99%, unchanged between first and last notification. Two of these surgeons have been identified as outliers for seven consecutive years (mean revision rate 6.4%). The other 11 are more recently trained surgeons, with a mean revision rate of 5.89%, and with relatively lower numbers on the registry (mean 270, range 184 – 501). Conclusion The NZ revision rate for THJR between 2013 and 2018 was stable at 0.72 revisions per 100 component years. Since 2019 it has fallen steadily to 0.58 in 2024. Twenty-one of 34 surgeons notified as an being an outlier have improved their surgical results. All 267 surgeons performing 11,078 primary hip replacements in 2024 are aware of this outlier policy, likely also contributing to lowering of the revision rate since 2019.