The changing effect of surgeon volume on revision rates in shoulder arthroplasty with time in Australia.

Abstract

Background: The concept that surgical volume effects rates of total primary shoulder arthroplasty (TSA) revision is widely accepted. The aim of this study was to determine if surgical volume is confounded by patient, implant, institutional factors and time from TSA.

Methods: Using data from a large national arthroplasty registry for the period 1 January 2008 to 31 December 2022, all interactions with orthopedic surgeon volume (SV) undertaking primary TSA procedures for all diagnoses were examined. A sub-analysis from 1 January 2017 provided a contemporary analysis with additional patient demographics. The primary outcome measure was the cumulative percentage revision (CPR) which was defined using Kaplan-Meier estimates of survivorship and hazard ratios from Cox proportional hazard models with a multivariable adjustment.

Results: The incidence of orthopedic surgeons completing TSA nationally increased from 0.9 per 100,000 population in 2008 to 1.8 in 2022. Of 55,605 TSA procedures, the CPR at 11 years varied from 8.8% (95% confidence interval (CI) 8.0, 9.6) and 5.6% (95%CI 4.0, 7.7) for implants by SV < 10 per annum surgeons and SV >35 prostheses, respectively. Instability/dislocation was the most common reason for revision. SV had a significant effect on the revision rate for all diagnoses (p= 0.001), instability/dislocation (p=0.018) and revision within 5 years of primary arthroplasty (p=0.011). In contrast, at sub analysis (last 5 years) there was no interaction both with main effects (SV effect adjusted by age and gender) and with an extended adjustment for both instability/dislocation and all cause revision.

Conclusions: Nationally there is an increasing incidence of primary TSA procedures and surgeons performing them. The association between SV and revision rate is complex. While there is an association with main effects, there was no association in the last five years. Reduction in instability/dislocation revision rates contributed to this change. Patient, implant or institutional factors did not confound analysis of surgeon volume on primary TSA revision rates, but recency did.