Varying Lateral Extra-articular Tenodesis Femoral Fixation Points and Fixation Flexion Angles Do Not Affect ACL Graft Force and Tibiofemoral Motion After ACL Reconstruction

Background: The addition of lateral extra-articular tenodesis (LET) to anterior cruciate ligament (ACL) reconstruction (ACLR) has been shown to reduce rotational laxity and improve graft survivorship. Despite the increased utilization of LET with ACLR, there remains a lack of consensus on the ideal location of the femoral attachment site of LET. Purpose: To compare ACL graft force and tibiofemoral motion in cadaveric specimens undergoing ACLR with the addition of LET at varying fixation angles and fixation points. Study Design: Controlled laboratory study. Methods: A total of 10 fresh-frozen cadaveric knees were tested in 6 conditions, including LET fixation at 2 anatomic locations. Location 1 was defined as 8 mm proximal and 4 to 5 mm posterior to the lateral femoral epicondyle, at the insertion of the anterolateral ligament. Location 2 was defined as 31 mm proximal to the lateral femoral epicondyle, at the insertion of the distal Kaplan fibers. The testing conditions were as follows: (1) native; (2) ACLR; (3) ACLR + LET at location 1, fixed at 30°; (4) ACLR + LET at location 2, fixed at 30°; (5) ACLR + LET at location 1, fixed at 60°; and (6) ACLR + LET at location 2, fixed at 60°. Specimens were mounted on a 6 degrees of freedom robotic system to assess tibial internal rotation and anterior tibial translation at 0°, 30°, 60°, and 90° of knee flexion. A load cell was utilized to assess ACL graft force. Results: There were no differences between the 4 LET states in any outcome. In internal rotation, the addition of LET demonstrated reductions in ACL graft force in all 4 configurations, ranging from −14.9 N (14%) to −19.5 N (20%) at 0°, −19.7 N (51%) to −21.4 N (55%) at 30°, and −3.9 N (30%) to −4.6 N (35%) at 60° (all P < .05). The addition of LET also demonstrated reductions in internal rotation range of motion in all 4 configurations, ranging from −1.86° (15%) to −2.45° (19%) at 0°, −4.87° (18%) to −5.75° (20%) at 30°, and −4.70° (19%) to −5.92° (23%) at 60° (all P < .05). Conclusion: Variations in LET fixation location and fixation flexion angle did not alter its effect on ACL graft force reduction or tibiofemoral motion in the cadaveric knee. The addition of LET had a protective effect on the ACL graft in internal rotation while demonstrating overconstraint compared to the native knee. Clinical Relevance: The findings suggest that surgeons may have flexibility in selecting the femoral fixation location and knee flexion angle for LET without substantially altering its biomechanical effect on ACL graft loading or tibiofemoral kinematics. However, because LET reduced internal rotation beyond the native state, care should be taken to avoid excessive constraint when performing the procedure.