Summary

T1rho and T2 relaxation times are similar between patients undergoing ACLR and ACLR + LET at two-years post-operative.

Abstract

Introduction

The addition of a lateral extra-articular tenodesis (LET) to hamstring tendon autograft anterior cruciate ligament reconstruction (ACLR) has been demonstrated to reduce failure rates in the first two years post-operative. However, concern over lateral compartment over constraint and the subsequent potential risk of post-traumatic osteoarthritis (OA) development remains due to the historic experience of LET being performed in isolation in ACL deficient knees.

Purpose

The purpose of this study was to evaluate whether augmentation of ACLR with a LET affects articular cartilage quality on magnetic resonance imaging (MRI) two years post-operatively in a young, active population.

Methods

Patients included in this analysis were participants in the Stability 1 Study, a multi-center, international, pragmatic randomized controlled trial comparing hamstring tendon autograft ACLR alone to ACLR + LET. A consecutive sub-group of patients at the Fowler Kennedy Sports Medicine Clinic with healthy contralateral knees underwent bilateral 3T MRI at two-years post-surgery. The primary outcome was T1rho and T2 relaxation times, determined using quantitative MRI (qMRI) pulse sequences consisting of a Sagittal Multi-Echo Spin Echo T2 Mapping sequence, and a 16-shot Gradient Echo T1rho Mapping sequence. Articular cartilage was manually segmented on three consecutive load-bearing slices, and values were averaged for three regions on the tibia and five regions on the femur in both the medial and lateral compartments. Independent t-tests were used to compare relaxation times between groups for each compartment. An effect size (Cohen’s d) was calculated to estimate the magnitude of the standardized difference between groups for each compartment =(<0.2 = trivial, 0.2 to 0.5 = small, 0.5 to 0.8 = moderate, >0.8 = large).

Results

Ninety-seven participants (47 ACLR, 50 ACLR+LET) with a mean age of 18.9 years (59.8% female, 58/97) underwent MRI 2-years post-operative (range = 20 to 36 months). Eighty-seven scans were available for analysis however, two were excluded due to significant movement artefact. Means and standard errors (SE) were calculated for T1rho and T2 relaxation times (ms) for each compartment. There was no difference in relaxation times for any of the regions in the medial compartment. T1rho relaxation times were significantly lower for the ACLR+LET group in the PL tibia (ACLR+LET = 39.7 ± 0.7, ACLR = 42.0 ± 0.6, p = 0.02). T2 relaxation times were significantly higher for the ACLR + LET group in the central (CL) tibia (ACLR+LET = 39.0 ± 0.3, ACL = 37.9 ± 0.4, p =0.04) and posterolateral (PL) femur (ACLR+LET = 46.3 ± 0.7, ACLR = 44.0 ± 0.6, p = 0.01). Effect sizes ranged from trivial (0.0) to moderate (0.56) for each compartment.

Conclusions

T1rho and T2 relaxation times were relatively similar between groups. T1rho favoured ACLR + LET in the PL tibia and T2 favoured ACLR alone in the CL tibia and PL femur. Differences were small to moderate in magnitude indicating that further research, including long-term follow-up, is required to better understand the clinical significance of these findings.