Safe Femoral Fixation Depth and Orientation for Lateral Extra-Articular Tenodesis in Anterior Cruciate Ligament Reconstruction

Background: Patients who undergo anterior cruciate ligament (ACL) reconstruction (ACLR) can have a persistent postoperative pivot shift. Performing lateral extra-articular tenodesis (LET) concurrently has been proposed to address this; however, LET femoral fixation may interfere with the ACLR femoral tunnel, which could damage the ACL graft or its fixation. Purpose: To evaluate the safe maximum implant or tunnel depth for a modified Lemaire LET when combined with ACLR anteromedial portal femoral tunnel drilling and to validate the safe LET drilling angles to avoid conflict with the ACLR femoral tunnel. Study Design: Descriptive laboratory study. Methods: Twelve fresh-frozen cadaveric knees were used. With each knee at 120 degrees of flexion, an ACLR femoral tunnel in the anteromedial bundle position was created arthroscopically via the anteromedial portal using a 5-mm offset guide, a guide wire, and an 8-mm reamer, which was left in situ. A modified Lemaire LET was performed using a 1 cm-wide iliotibial band strip harvested with the distal attachment intact, to be fixed in the femur. The desired LET fixation point was identified with an external aperture 10 mm proximal and 5 mm posterior to the fibular collateral ligament's femoral attachment, and a 2.4-mm guide wire was drilled, aiming at 0 degrees, 10 degrees, 20 degrees, or 30 degrees anteriorly in the axial plane and at 0 degrees, 10 degrees, or 20 degrees proximally in the coronal plane (12 different drilling angle combinations). The relationship between the LET drilling guide wire and the ACLR femoral tunnel reamer was recorded for each combination. When a collision with the femoral tunnel was recorded, the LET wire depth was measured. Results: Collision with the ACLR femoral tunnel occurred at a mean LET wire depth of 23.6 mm (range, 15-33 mm). No correlation existed between LET wire depth and LET drilling orientation (r = 0.066; P = .67). Drilling angle in the axial plane was significantly associated with the occurrence of tunnel conflict (P < .001). However, no such association was detected when comparing the drilling angle in the coronal plane (P = .267). Conclusion: Conflict of LET femoral fixation with the ACLR femoral tunnel using anteromedial portal drilling occurred at a mean depth of 23.6 mm but also at a depth as little as 15 mm, which is shorter than most implants. When longer implants or tunnels are used, the orientation should be directed at least 30 degrees anteriorly in the axial plane to minimize the risk of tunnel conflict, bearing in mind the risk of joint violation.