Poster 314: Hamstring Autograft Diameter Effect on Surgical Outcome in a Prospective ACL Reconstruction Patient Cohort

OBJECTIVES: The purpose was to investigate the effect of hamstring autograft diameter on risk of graft failure and subsequent either knee surgery following ACLR in a prospective cohort. Background: Optimization of graft selection and incorporation in anterior cruciate ligament (ACL) reconstruction (ACLR) is an evolving science. Recent studies suggest hamstring tendon autograft diameter may influence outcomes in primary ACLR, with a larger diameter acting as a protective factor against ACL graft rupture. Further evidence using a prospective patient database is valuable in corroborating the association between ACL autograft diameter and patient outcomes. METHODS: Prospective data was collected for a cohort of patients undergoing primary ACLR from February 2015 to February 2018. Exclusion criteria included non-hamstring graft selection, allograft augmentation, skeletally immature patients, revision ACLR, prior contralateral ACLR, and multiligament injuries. Cases from 10 fellowship-trained surgeons within a single institution were included. Recorded tunnel size was utilized as a surrogate for autograft diameter. The contribution of age, sex, BMI and operating surgeon on autograft diameter was studied via mixed effect modeling. The effect of hamstring tendon autograft diameter on risk of subsequent surgery was measured using multivariable linear regression modeling that controlled for patient and surgery characteristics including age, sex, BMI, Marx activity score, and graft diameter. Two-year outcomes were collected for incidence of subsequent surgery to either knee, including ipsilateral revision ACLR and contralateral primary ACLR. RESULTS: Of the patients undergoing ACLR with hamstring autograft who met inclusion criteria, there was 90.5% follow up for subsequent surgery outcomes at minimum of 2 years, resulting in 381 patients. Female sex and lower BMI was associated with smaller autograft diameter and operating surgeon had a significant effect on autograft diameter. 59 patients (15.5%) had subsequent ipsilateral surgery and 27 patients (7.09%) had revision ACLR within 2 years. 29 patients (7.61%) had contralateral subsequent knee surgery and 20 patients (5.25%) had primary contralateral ACLR within 2 years. After controlling for age, sex, BMI, and baseline Marx activity score, hamstring autograft diameter was not associated with risk of all ipsilateral subsequent knee surgery (odds ratio (OR) 0.87, 95% confidence interval (CI) 0.56 - 1.36, p = 0.536). Baseline Marx score greater than or equal to 12 was associated with risk of all ipsilateral subsequent knee surgery with OR 2.55 (CI 1.41 – 4.59, p = 0.002). After controlling for age, sex and BMI, hamstring autograft diameter was not associated with risk of revision ACLR (OR 0.71, CI 0.38 - 1.33, p = 0.286). Age was associated with risk of ipsilateral revision ACLR with OR 0.16 (CI 0.05 – 0.51, p = 0.002). After controlling for age, sex and BMI, hamstring autograft diameter was not associated with risk of all contralateral subsequent knee surgery (OR 0.89, CI 0.50 - 1.59, p = 0.703) including contralateral ACLR (OR 0.78, CI 0.39 - 1.59, p = 0.501). Age was found to be a significant prognostic variable of contralateral ACLR with OR 0.30 (CI 0.10 – 0.93, p = 0.037). No variables within the model were associated with risk of all contralateral subsequent surgery events. CONCLUSIONS: Hamstring autograft diameter greater than 8mm was not associated with risk of revision ACLR or other subsequent surgery in the ipsilateral or contralateral knee in a multivariable logistic regression analysis of a prospective patient cohort. Lower age was associated with risk of ipsilateral revision ACLR and contralateral ACLR. Baseline Marx activity score greater than or equal to 12 was associated with risk of all subsequent ipsilateral knee surgery.