Risk factors for Recurrent Anterior Cruciate Ligament Reconstruction: A Population Study in Ontario, Canada with 5-year Follow-up

OBJECTIVES: Anterior cruciate ligament reconstruction (ACLR) is routinely performed to treat symptomatic instability. Despite being a common procedure, significant variation persists in technique and graft choice. How patient, provider and surgical factors influence the risk of revision or contralateral primary ACLR has not been investigated using administrative data. The goal of our study was to define the rate and risk factors for ACL re-operation in Ontario. METHODS: All primary elective ACLR performed in Ontario, Canada from July 2003 to March 2008 in patients aged 15 to 60 years were identified via billing, diagnosis and procedural databases. The main outcomes were revision and contralateral ACLR, sought until January 2012. Patient factors (age, gender, co-morbidity, income quintile, and length of index hospital admission), provider factors (surgeon volume, academic hospital status) and surgical factors (allograft vs. autograft; fixation: screw, button, staple; concomitant operative procedures) were used as covariates in a Cox Proportional Hazards survivorship model to generate Hazard Ratios (HR) with confidence intervals (alpha 0.05). Kaplan-Meier survivorship curves to revision were generated. RESULTS: A total of 12,967 ACLR with a mean follow-up of 5.2 years were identified. The revision rate was 2.6% [after a median 2.72 years (interquartile range 1.38, 4.11)]. The rate of primary contralateral ACLR was 4.6% [after a median 2.71 years (interquartile range 1.49, 4.22)]. In the Cox model, younger age [15-19 years; HR=2.1 (95% CI: 1.5-2.9), p<0.001], ACLR performed at an academic hospital [HR=1.6 (95% CI: 1.2-2.1), p<0.001] and the use of allograft [HR=1.7 (95% CI: 1.1-2.6), p=0.02] significantly increased the risk of revision ACLR. The K-M curves to revision ACLR for allograft and autograft demonstrated equivalent survivorship for approximately 3 years, after which allograft ACLR were more commonly revised (Figure 1). Only younger age [15-19 years; HR=2.1, (95% CI: 1.6-2.7), p<0.001] was associated with an increased risk of contralateral ACLR. CONCLUSION: Contralateral ACLR was more frequent than revision ACLR in this population, while both re-operations were significantly more common in patients <20 years old. Academic hospital status but not surgeon volume, and the use of allograft also increased the risk of revision ACLR. Late failure of allograft ACLR is a novel finding.