Summary
The addition of LET to ACL rconstruction did no effect graft maturation in two-year postoperative MRI.
Abstract
Background
Previous clinical and biomechanical studies have shown that adding lateral extra-articular tenodesis (LET) to anterior cruciate ligament reconstruction (ACLR) effectively controls rotational laxity and reduces failure rates. However, the mechanism by which LET decreases risk of graft failure is not well-investigated. The additional rotational stability gained via LET may reduce demands on the ACL graft, potentially supporting graft maturation. The purpose of the present study was to assess graft maturation at 2 years following ACLR with or without LET using magnetic resonance imaging (MRI) signal-to-noise quotient (SNQ) of the ACL graft. We hypothesized that patients who had undergone ACLR+LET would have better graft maturation compared to those with ACLR alone.
Methods
A subset of patients from the STABILITY I study were included on the basis of having MRI available at 2 years follow-up. All patients underwent primary ACLR with a hamstring autograft. The patients were randomized to the ACLR group or ACLR+LET group at the time of surgery. We measured SNQ of the ACL graft at 2-years postoperative via manual segmentation of proton density-weighted images. Using 3D anatomical images from the same scan, we measured Blumensaat angle, tunnel position (femur/tibia), notch width, tibial translation (medial/lateral), and posterior tibial slope (medial/lateral). We also collected functional outcomes (hop test and isokinetic strength test) and patient reported outcomes, including Knee injury Osteoarthritis and Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, and ACL-Quality of Life (ACL-QOL) were obtained. We compared ACL SNQ between the ACLR and ACLR+LET groups using independent t-tests, and evaluated relationships between ACL SNQ and clinical, anatomical, functional, and patient-reported outcomes using Pearson and Spearman correlations across the entire sample. All analyses were adjusted for age, sex, and body mass index (BMI) using multiple linear regression.
Results
Ninety-three patients (44 patients in ACLR group, mean age (±SD) 19.2±3.2 years, 54.5% females, and 49 patients in ACLR+LET group, 18.9±3.2 years, 61.2% females) were included. Groups were prognostically balanced. We observed no significant difference in ACL SNQ between ACLR and ACLR+LET groups (mean difference [95%CI] = -1.2 units [-0.3; 2.8], p>0.1). There was a significant relationship between tibial tunnel malposition and ACL SNQ, suggesting patients with malposition had poorer graft maturity (R=0.30, p=0.004). Increased SNQ was also negatively associated with Blumensaat angle (R=-0.26, p=0.01), hamstring strength limb asymmetry (R =-0.22, p=0.04), and ACL-QoL (R=-0.25, p=0.02). We also observed significant positive relationships between ACL SNQ and lateral posterior tibial offset (R=0.22, p=0.03).
Conclusion
There was no difference in graft maturation between knees undergoing ACL reconstruction with hamstring tendon autograft with or without LET at 2 years post-operative MRI analysis. When evaluating the entire sample, tibial tunnel malposition, lateral posterior tibial offset, anatomical impingement, hamstring strength weakness, and poorer ACL-QOL scores were significantly associated with higher graft SNQ. This study suggests that while some anatomical, surgical, and functional factors influence ACL graft maturation, the rotational stability gained from LET does not compromise the ACL graft.