Summary

A study of 75,421 patients undergoing ACL reconstruction between 2003 and 2014 in New York State found that surgeons who perform more than 35 ACL reconstructions annually have a nearly 30% decreased risk of revision knee surgery compared to surgeons who perform fewer than 18 per year.

Abstract

Background

A large body of volume-outcomes literature has now demonstrated a strong positive relationship between increasing annual surgical volume and improved patient outcomes across a wide variety of surgical procedures, including orthopedics. Unfortunately, most previous research has been limited by the methods used to determine meaningful volume thresholds for comparison. As such, it is as yet unknown how many cases a surgeon should perform each year to maintain competence for most of these procedures. The purpose of this study was to determine that annual volume threshold for ACL reconstructions.

Methods

We identified ACL reconstructions performed in New York (NY) State hospitals between 2003 and 2014 using the NY-SPARCS hospital in-patient and ambulatory surgery database. These cases were followed until subsequent ipsilateral knee surgery (revision ACL, meniscus/cartilage surgery, or total knee replacement) or until the end of the study period, December 31, 2014. Surgeon volume was calculated as the number of ACL reconstructions performed by that surgeon in the 12 months prior to the case of interest. Volume strata were identified by applying stratum specific likelihood ratio (SSLR) analysis of a receiver operating characteristic (ROC) curve. A Cox proportional hazards model was used to measure the effect of surgeon annual ACL reconstruction volume on risk of subsequent knee surgery adjusting for patient characteristics: age, sex, race/ethnicity, and insurance type.

Results

Between 2003 and 2014, 77,899 ACL reconstructions were performed in NY State by 1,316 surgeons. Mean patient age was 30.8+/- 12.5 years, and patients were 61% male, 65% white race, and 74% covered by private insurance. SSLR analysis revealed 2 meaningful cutpoints in risk of subsequent ipsilateral knee surgery: 17 & 35 cases per year. The Cox proportional hazards model demonstrated a 29% decreased risk of ipsilateral knee surgery for those ACL reconstructions by surgeons performing >35 cases per year compared to those performing <17 (Hazard Ratio [HR] 1.29, 95% confidence interval [CI] 1.23-1.35, p<0.001). Further, those performing 18-35 ACL reconstructions per year demonstrated a 6% decreased risk of subsequent ipsilateral knee surgery (HR 1.06, 95% CI 1.01-1.11, p=0.014).

Conclusion

These findings suggest orthopedic surgeons should perform a minimum of 35 ACL reconstructions per year to maintain clinical competence with the procedure. No higher cutpoints were identified using these criteria, though it is possible that considering revision ACL reconstruction separately from other subsequent ipsilateral knee surgery (meniscus & cartilage procedures, and total knee replacements) would yield different results. We are in the process of exploring this more nuanced relationship.