Who's at risk?: Commentary on an article by Timothy Leroux, MD, MEd, et al.: "The risk of knee arthroplasty following cruciate ligament reconstruction. A population-based matched cohort study".

BACKGROUND Evidence regarding the risk of end-stage osteoarthritis following cruciate ligament reconstruction is based upon small sample sizes and radiographic, rather than clinical, criteria. The goals of this study were to determine the risk of knee arthroplasty, a surrogate for end-stage osteoarthritis, following cruciate ligament reconstruction, and to identify patient, provider, and surgical factors that influence knee arthroplasty risk. METHODS Using administrative databases, we identified all patients who were sixteen to sixty years of age and had undergone cruciate ligament reconstruction in Ontario from July 1993 to March 2008. Case patients were matched by demographic variables to five individuals without knee injury from the general population of Ontario, Canada, who had not undergone previous knee surgery, including cruciate ligament reconstruction. The main outcome was knee arthroplasty. Kaplan-Meier survival curves were generated for both cohorts. A Cox proportional hazards model determined those factors that influenced knee arthroplasty risk. RESULTS We identified 30,301 eligible patients who had undergone cruciate ligament reconstruction; of these patients, 30,277 were matched to 151,362 individuals from the general population; the median patient age was twenty-eight years and 65% of the patients were male. Primary anterior cruciate ligament reconstruction accounted for >98% of index cases. During the follow-up period, there was a significant difference (p < 0.001) between matched case and control cohorts with respect to the number of patients who underwent knee arthroplasty during the study period; in the matched case cohort, 209 patients underwent knee arthroplasty (event rate, 0.68 of 1000 person-years), and in the control cohort, 125 patients underwent knee arthroplasty (event rate, 0.10 of 1000 person-years). Moreover, fifteen years after cruciate ligament reconstruction (case cohort) or study enrollment (control cohort), there was a significant difference (p < 0.001) in the cumulative incidence of knee arthroplasty between the case cohort (1.4%) and the control cohort (0.2%). Age of fifty years or more (hazard ratio, 37.28; p < 0.001), female sex (hazard ratio, 1.58; p = 0.001), comorbidity score of ≥5 points (hazard ratio, 5.91; p = 0.002), surgeon annual volume of cruciate ligament reconstruction of twelve or fewer cases per year (hazard ratio, 2.53; p < 0.001), and cruciate ligament reconstruction undertaken in university-affiliated hospitals (hazard ratio, 1.51, p = 0.008) increased the odds of knee arthroplasty; however, male sex (hazard ratio, 0.63; p = 0.001) and patient age of less than twenty years (hazard ratio, 0.07; p = 0.009) were protective. Concurrent meniscal repair or debridement did not increase arthroscopy risk. CONCLUSIONS After fifteen years, the cumulative incidence of knee arthroplasty following cruciate ligament reconstruction was low (1.4%); however, it was seven times greater than the cumulative incidence of knee arthroplasty among matched control patients from the general population (0.2%). Older age, female sex, higher comorbidity, low surgeon annual volume of cruciate ligament reconstruction, and cruciate ligament reconstruction performed in a university-affiliated hospital were factors that increased knee arthroplasty risk.