Abstract
Objectives:
The addition of the lateral extra-articular tenodesis (LET) procedure with anterior cruciate ligament reconstruction (ACLR) has shown to improve graft survivorship. Its primary indication has been in the revision setting or those patients at higher risk for graft failure in the primary setting. However, there remains a lack of consensus on the ideal location of the femoral attachment site of the LET procedure and radiographic assessment fixation location has demonstrated significant variability. The purpose of this study was to compare ACL graft forces and tibiofemoral motion in cadaveric specimens with the addition of LET at varying fixation angles and fixation points on the distal lateral femur. We hypothesize that fixation of the LET at the insertion of the antero-lateral ligament (ALL) will lead to a greater reduction of ACL graft force compared to insertion at the distal Kaplan fibers (DKF).
Methods:
Ten fresh-frozen cadaveric knees (mean donor age, 55.1 years (range 38-62); 6 female; 5 right knees) were tested in 6 conditions: 1) Native, 2) ACLR, 3) ACLR + LET at location 1, fixed at 30 degrees 4) ACLR + LET at location 2, fixed at 30 degrees, 3) ACLR + LET at location 1, fixed at 60 degrees 4) ACLR + LET at location 2, fixed at 60 degrees. Location 1 was defined as 8 mm proximal and 4 mm posterior to the lateral femoral epicondyle (LFE), at the insertion of the antero lateral ligament (ALL). Location 2 was defined as 31 mm proximal to the LFE, at the insertion of the distal Kaplan fibers (DKF). The order of states 2-6 was randomized. LET fixation location was confirmed with radiographic assessment. Specimens were mounted on a 6 degrees-of-freedom robotic system that was used to assess tibial internal rotation (IR, 5 Nm) and anterior tibial translation (ATT, 88 N) at 0, 30, 60 and 90 degrees of knee flexion. A load cell was utilized to assess ACL graft force at during all testing states and flexion angles.
Results:
The results at 30° flexion are shown on figures 1-4. There was no statistically significant difference between the 4 LET states in any outcome. In internal rotation, the addition of all four LETs demonstrated significant reduction in ACL graft force at 0° (-14.9 to -19.5 N, all p<0.05), 30° (-19.7 to -21.4 N, all p<0.05) and 60° (-3.5 to -4.6 N, all p<0.05), and significant reduction in range of motion compared to native at 0° (-1.86° to -2.45°, all p<0.05), 30° (-4.87° to -5.75°, all p<0.05), and 60° (-4.70° to -5.92°, all p<0.001). In anterior drawer testing, there was no statistically significant decrease in ACL graft force or anterior tibial translation with the LETs.
Conclusions:
Variation in LET fixation location and fixation flexion angle did not alter its effect on ACL graft force reduction or tibiofemoral motion in this study. The addition of LET had no effect on the biomechanics of anterior translation. In internal rotation, LET had a protective effect on ACL graft force, but showed consistent over-constraint of internal rotation range of motion.
