Outperformance of Combined Artificial Anterolateral Ligament and ACL Reconstruction Compared With Isolated Artificial ACL Reconstruction in Knees With Anterolateral Structure and ACL Deficiency: A Biomechanical Analysis

Background: Despite the promising clinical outcomes of artificial polyethylene terephthalate (PET) ligaments in isolated anterior cruciate ligament reconstruction (ACLR), their biomechanical performance after combined anterolateral ligament reconstruction (ALLR)/ACLR in anterolateral structure (ALS)/anterior cruciate ligament (ACL)–deficient knees has not been investigated. Purpose/Hypothesis: The purpose of this study was to compare biomechanical performance in cadaveric knees between combined artificial ALLR/ACLR and isolated artificial ACLR using PET ligaments. It was hypothesized that combined artificial ALLR/ACLR would restore native knee stability and outperform isolated artificial ACLR in ALS/ACL-deficient knees. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen cadaveric knees were tested using a robotic manipulator. Each knee was tested in 4 states: (1) ALS/ACL intact, (2) ALS/ACL deficient, (3) ACLR, and (4) ALLR/ACLR. The anterior tibial translation (ATT) and tibial internal rotation (IR) in each knee condition were measured under 3 loads: (1) 89 N of anterior tibial loading, (2) 5 N·m of IR torque, and (3) simulated pivot shift (combined 5 N·m of IR torque and 7 N·m of valgus load). Results: During 89 N of anterior tibial loading, there were no significant differences in ATT between the isolated ACLR and ALLR/ACLR knees. During 5 N·m of IR torque, the mean tibial IR at 45° of flexion was significantly higher in the ACLR knees (32.49°± 7.96°) than in the ALLR/ACLR knees (21.78°± 3.03°) ( P < .05). During the simulated pivot shift, the mean ATT and tibial IR at 30° and 45° of flexion were significantly higher in the ACLR knees (ATT: 5.09 ± 2.74 mm at 30°, 5.43 ± 2.79 mm at 45°; IR: 30.08°± 7.31° at 30°, 32.55°± 6.48° at 45°) than in the ALLR/ACLR knees (ATT: 1.93 ± 2.71 mm at 30°, 1.17 ± 2.26 mm at 45°; IR: 22.12°± 4.05° at 30°, 22.18°± 3.37° at 45°) ( P < .05). Conclusion: Combined artificial ALLR/ACLR restored native knee stability across multiple flexion angles and outperformed isolated artificial ACLR in ALS/ACL-deficient knees, particularly with respect to ATT and tibial IR during the pivot-shift test. Clinical Relevance: The indications of the artificial PET ligament may be expanded to include combined ALLR/ACLR to restore knee stability better than isolated artificial ACLR in ALS/ACL-deficient knees.