Abstract
Purpose: To compare the kinematics of anterolateral structure (ALS) reconstruction (ALSR) and lateral extra-articular tenodesis (LET) in ACL-ALS-deficient knees with anterior cruciate ligament (ACL) reconstruction. Methods: Ten fresh-frozen cadaveric knees with the following conditions were tested: (1) intact, (2) ACL-ALS deficiency, (3) ACL reconstruction (ACLR), (4) ACLR combined with ALSR (ACL-ALSR) or LET (ACLR+LET). Anterior translation and tibial internal rotation were measured with 90-N anterior load and 5 N·m internal torque at 0°, 30°, 60°, and 90°. The anterolateral translation and internal rotation were also measured during a simulated pivot-shift test at 0°, 15°, 30°, and 45°. The knee kinematic changes in all reconstructions were compared with each other, with intact knees as the baseline. Results: Isolated ACLR failed to restore native knee kinematics in ACL-ALS-deficient knees. Both ACL-ALSR and ACLR+LET procedures decreased the anterior instability of the ACLR. However, ACLR+LET caused overconstraints in internal rotation at 30° (−3.73° ± 2.60°, P =.023), 60° (−4.96° ± 2.22°, P =.001) and 90° (−6.14° ± 1.60°, P <.001). ACL-ALSR also overconstrained the knee at 60° (−3.65° ± 1.90°, P <.001) and 90° (−3.18° ± 2.53°, P <.001). For a simulated pivot-shift test, both combined procedures significantly reduced the ACLR instability, with anterolateral translation and internal rotation being overconstrained in ACLR+LET at 30° (−3.32 mm ± 3.89 mm, P =.005; −2.58° ± 1.61°, P <.001) and 45° (−3.02 mm ± 3.95 mm, P =.012; −3.44° ± 2.86°, P <.001). However, the ACL-ALSR overconstrained only the anterolateral translation at 30° (−1.51 mm ± 2.39 mm, P =.046) and internal rotation at 45° (−2.09° ± 1.70°, P <.001). There were no significant differences between the two combined procedures at most testing degrees in each testing state, except for the internal rotation at 30° (P =.007) and 90° (P =.032) in internal rotation torque. Conclusion: ACL reconstruction alone did not restore intact knee kinematics in knees with concurrent ACL tears and severe ALS injury (ACL-ALS-deficient status). Both ACL-ALSR and ACLR+LET procedures restored knee stability at some flexion degrees, with less overconstraints in internal rotation resulting from ACL-ALSR. Clinical Relevance: For patients with combined ACL tears and severe ALS deficiency, isolated ACLR probably results in residual rotational and pivot-shift instability. Both ACL-ALSR and ACLR+LET show promise for the improvement of knee stability, whereas ACL-ALSR has less propensity for knee overconstraint. © 2021 Arthroscopy Association of North America