Summary
Medial and lateral tibial slopes were not independently predictive of ACL graft failure or subsequent surgery when utilizing hamstring autograft
Abstract
Background
The understanding of anterior cruciate ligament (ACL) reconstruction patient and surgical factors has led to continued improvements in techniques, graft selection, and concomitant procedural strategies. Recent literature has demonstrated an increased risk of graft rerupture following ACL reconstruction with a hamstring autograft in young, high-demand athletes. An increasing interest among orthopaedic sports medicine surgeons is emerging with regards to evaluating tibial slope as a risk factor for ACL reconstruction failure, with several studies reporting that posterior tibial slope greater than 8-12 degrees may require corrective osteotomies during revision surgeries. Some studies advocate for consideration of slope-reducing osteotomies in select populations during a primary ACL reconstruction. This study investigates the effect of posterior medial tibial slope (mTS) and lateral tibial slope (lTS) on subsequent ipsilateral or contralateral ACL rupture following primary reconstruction with hamstring autograft.
Hypothesis/Purpose: The purpose of this study is to investigate the effect of posterior mTS and lTS on the risk of hamstring autograft failure and subsequent ipsilateral revision ACL reconstruction or primary contralateral ACL reconstruction in a prospective cohort.
Study Design: Level 2: Prospective longitudinal cohort study.
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. The contribution of age, sex, BMI, MARX activity score, hamstring diameter, and tibial slope on graft failure was studied via mixed effect modeling. The effect of posterior mTS and lTS on risk of subsequent surgery was analyzed using multivariable linear regression modeling that controlled for patient and surgery characteristics. Two-year outcomes were collected for incidence of subsequent surgery to either knee, including ipsilateral revision ACLR and contralateral primary ACLR. Tibial slope was measured by three independent authors utilizing the two-circle technique published by Hudek et al in 2009 in JBJS. A novel computer software was created to allow tibial slope measurement to be calculated with respect to the true rotational and sagittal axis of the tibia.
Results
There was 90.4% follow up at minimum of 2 years for the patients undergoing ACLR with hamstring autograft who met inclusion criteria, resulting in 376 patients. After exclusion of patients with inadequate MRI for measurement, 332 independent knees were evaluated. The median age was 23, 41% were females, median BMI was 25.5, and 31% had a baseline Marx activity score of 12 or greater. A total of 58 patients (15.4%) had subsequent ipsilateral surgery and 27 patients (7.2%) 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. Inter-rater reliability was calculated between three different raters for a total of 35 measurements utilizing intraclass correlation, demonstrating good correlation for medial slope measurements (ICC = 0.79 [ 0.66, 0.88]) and moderate correlation for lateral slope measurements (ICC = 0.6 [0.41, 0.76]). Multivariable model for ipsilateral ACL revision surgery within 2 years demonstrated that when controlling for age, sex, sports, autograft diameter and mTS and lTS, only age was a significant predictor of failure. Likewise, for all ipsilateral surgeries within 2 years, only baseline MARX score was predictive of failure. The correlation of mTS and lTS was 0.96, and the large majority of patients with graft failure in the present cohort had tibial slopes less than 12 degrees.
Conclusion
In patients with two-year follow-up after ACL reconstruction using hamstring autograft, age and baseline activity score were the only predictive factors of graft failure. Medial and lateral tibial slopes were not independently predictive of ACL graft failure or subsequent surgery.