Summary
In a matched cohort study, patients with LET showed significantly less femoral and tibial tunnel widening than those without LET, possibly indicating improved ACL graft healing secondary to the protective effect of the LET.
Abstract
Introduction
Lateral extra-articular tenodesis (LET) is a well-established technique that has enjoyed increased interest recently as a supplementary procedure to reduce re-injury after anterior cruciate ligament reconstruction (ACLR). The rationale behind LET was to reduce anterolateral rotatory instability (ALRI) and protect the anterior cruciate ligament (ACL) graft. Biomechanical studies have revealed LET significantly reduces the intra-articular forces across the ACL graft and affects the overall biomechanics of the knee joint. We hypothesized that this protection of the graft could improve graft healing, or conversely possibly stress shield the graft and impair healing. This study aimed to assess graft healing in patients who underwent ACLR alone versus those who underwent ACLR+LET using a previously standardized MRI protocol at one-year post-surgery.
Methods
A matched cohort comparison was performed on patients who underwent ACLR with and without the addition of the LET. Patients were matched by age, sex, body mass index, and initial tunnel diameter and graft size. A total of 80 patients who underwent ACLR were enrolled in the study. 40 patients underwent ACL reconstruction alone, while 40 underwent ACLR in addition to LET. All ACLRs performed were single bundle quadrupled hamstring grafts with suspensory fixation on both the femur and tibia. All ACLR+LET surgeries were performed by the senior author and a modified deep Lemaire technique was used for the LET using PEEK screw fixation to the lateral femoral condyle. No revision ACLR surgeries or patients who underwent meniscectomies were included. 12 months post-surgery, patients underwent a standardized 3T magnetic resonance imaging (MRI) scan utilizing a validated protocol which included volumetric and near isotropic (0.5mm x0.5mm x 0.65mm) turbo spin echo sequences optimized for graft assessment. Two observers performed the MRI analysis on 3 x20-mm2 regions of interest (ROI) on the intra-articular graft (proximal, middle, and distal) using oblique reconstructions both parallel and perpendicular to the graft. The Signal Noise Quotient (SNQ) was calculated with the formula SNQ= graft signal-posterior cruciate ligament signal/background signal. Tunnel aperture signal and areas were also measured using multi planar reformation. Tunnel widening was evaluated by determining the difference between the initial intra-operative drilled tunnel diameter and the MRI measured tunnel diameters.
Clinical evaluations were performed using International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC), Tegner Activity Scale (Tegner) and Lysholm Knee Score (Lysholm) both pre-injury and at 12 months post-surgery. Post operative side to side laxity was determined using GNRB arthrometer.
Results
80 patients were included in the study, 40 in each group. The mean age was 18.6±3.74 in the ACLR+LET group and 18.6±3.95 in the ACLR group (P>0.05). The average preoperative BMI was 21.95±8.15 in the ACLR+LET group and 23.89±3.23 in the ACLR group (P>0.05). The mean femoral tunnel widening in the ACLR +LET group was 3.38±1.23 mm2 and 4.66±1.2 in the ACLR group (P=<0.05). The mean tibial tunnel widening in the ACLR +LET group was 2.60±1.13 mm2 and 3.89±1.03 in the ACLR group (P=<0.05). The mean adjusted graft SNQ was 8.93±14.54 in the ACLR+LET group and 9.58±12.84 in the ACLR group (P>0.05). No significant findings were found between both groups when comparing clinical outcome scores and anterior laxity testing.
Discussion
At one year post-operatively we noted significantly less femoral and tibial tunnel widening in the ACLR+LET group, but otherwise no difference in clinical outcome. This could be explained by the protective effects of the LET on the ACL graft during healing and ligamentisation. Further studies are needed to determine whether this significant effect imparts any clinical benefit to ACLR patients.