Outcomes of hip and knee replacement surgery in private and public hospitals in Australia.

Background: This study determined the contributing factors of hospital sector (private versus public) variation in revision rates after elective total hip replacement (THR) for hip fracture, and elective total knee replacement (TKR).

Methods: Using data from a large national arthroplasty registry, funnel plots for hospitals were generated, displaying the proportion of revised primary procedures. The proportion of outliers for each distribution was defined as the proportion outside the upper 99.7% confidence limit. Survival analyses determined differences between hospital sector revision rates separately for implants with the lowest revision rate, and for all other implants. Multivariate Cox regression determined the role of hospital sector in revision, adjusting for possible confounders.

Results: For THR performed for osteoarthritis, 17.4% of private and 4.4% of public hospitals were outliers. For TKR performed for osteoarthritis, 19.6% of private and 10.0% of public hospitals were outliers. For THR for fractured neck of femur, 8.1% of private and 0.0% of public hospitals were outliers. Adjusted and unadjusted Kaplan-Meier analyses showed higher THR revision rates in private hospitals for osteoarthritis and fractured neck of femur, but no difference when restricted to the 10 prostheses with the lowest revision rate. The Kaplan-Meier analysis of TKR showed higher revision rates for private hospitals, with the association reversing when restricted to prostheses with the lowest revision rate.

Conclusions: Considerable variation was seen in the revision rate after THR and TKR between hospital sectors in Australia. The variation was largely due to differences in prosthesis selection.