HP12: THE EFFECT OF OPERATIVE VOLUME ON THE OUTCOME OF HIP RESURFACING

Abstract

Introduction: Although Hip Resurfacing Arthroplasty (HRA) has become a popular alternative to THR, the outcome of these procedures varies extensively between centres. This has been attributed to variations in patient selection, surgical experience, and patient volume. In this study we examine the effect of hospital volume on the outcome of hip resurfacing using a national database.

Methods: We examined data collected by the Australian Joint Registry between September 1999 and December 2006 relating to 8945 hip resurfacing procedures performed in 196 hospitals. Survivorship of the implanted components was calculated with revision as the end-point. The cumulative rate of revision at 4 years was compared between hospitals as a function of the number of cases performed during the study period (< 25, 25–49, 50–100, > 100 procedures). Using the log-rank test, differences in the risk of revision, corrected for age and sex of patients, were compared for low (< 25 cases) vs. higher volume centres (> 25 cases). We also estimated the number of cases/year of each centre and examined its apparent impact on revision rate.

Results: The majority (74%) of hospitals reporting performed less than 30 resurfacing procedures over the 7 year study period, with 64% of procedures performed at 16 “high volume” hospitals (> 100 cases), Overall, 249 of the 8945 resurfacing procedures (2.9%) were performed for revision of the original components. At 4 years, the cumulative revision rate dropped from 5.8% for hospitals performing less than 50 cases to 4.7% (50–99 cases) and 2.7% (> 100 cases) for larger volume centres. When adjusted for differences in patient age and sex, the risk of revision was 66% higher in hospitals performing < 25 cases. Based on the available data, the gap in revision rate between high and low volume centres is reduced by 50% once a surgeon’s operative volume exceeds 6 cases per year. On average, this corresponds to a learning curve of approximately 5 cases.

Conclusions: In this study, hospital volume is primarily a reflection of the operative experience of individual surgeons. Our results show that the outcome of hip resurfacing is strongly dependent on the experience of the surgeon and hospital performing the procedure. Even when adjusted for age and sex of the patients, the risk of revision increased by 66% when cases were performed at low volume centres. This supports the need for increased training of surgeons before undertaking hip resurfacing.