An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 1: Secondary Role of the Anterolateral Ligament in the Setting of an Anterior Cruciate Ligament Injury

• Published in: The American journal of sports medicine 2016-03, Vol.44 (3), p.585-592
• Main Authors: Rasmussen, Matthew T., Nitri, Marco, Williams, Brady T., Moulton, Samuel G., Cruz, Raphael Serra, Dornan, Grant J., Goldsmith, Mary T., LaPrade, Robert F.
• Format: Article
• Language: English
• Subjects: Adult; Anterior Cruciate Ligament - physiology; Anterior Cruciate Ligament - surgery; Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction - methods; Biomechanical Phenomena - physiology; Cadaver; Humans; Joint Instability - physiopathology; Kinematics; Knee; Knee Injuries - physiopathology; Knee Joint - physiopathology; Ligaments; Ligaments, Articular - physiology; Middle Aged; Physical Examination - methods; Range of Motion, Articular - physiology; Robotic Surgical Procedures; Robotics; Rotation; Series & special reports; Simulation; Skin & tissue grafts; Sports injuries; Sports medicine; Tibia - physiopathology; Torque
• ISSN: 0363-5465; 1552-3365
• DOI: 10.1177/0363546515618387

Background: Recent investigations have described the structural and functional behavior of the anterolateral ligament (ALL) of the knee through pull-apart and isolated sectioning studies. However, the secondary stabilizing role of the ALL in the setting of a complete anterior cruciate ligament (ACL) tear has not been fully defined for common simulated clinical examinations, such as the pivot-shift, anterior drawer, and internal rotation tests. Hypothesis: Combined sectioning of the ALL and ACL would lead to increased internal rotation and increased axial plane translation during a pivot-shift test when compared with isolated sectioning of the ACL. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human cadaveric knees were subjected to a simulated pivot-shift test with coupled 10-N·m valgus and 5-N·m internal rotation torques from 0° to 60° of knee flexion and a 5-N·m internal rotation torque and an 88-N anterior tibial load, both from 0° to 120° of knee flexion via a 6 degrees of freedom robotic system. Kinematic changes were measured and compared with the intact state for isolated sectioning of the ACL and combined sectioning of the ACL and ALL. Results: Combined sectioning of the ACL and ALL resulted in a significant increase in axial plane tibial translation during a simulated pivot shift at 0°, 15°, 30°, and 60° of knee flexion and a significant increase in internal rotation at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120° when compared with the intact and ACL-deficient states. Based on the model results, ALL sectioning resulted in an additional 2.1 mm (95% CI, 1.4-2.9 mm; P < .001) of axial plane translation during the pivot shift when compared with ACL-only sectioning, when pooling evidence over all flexion angles. Likewise, when subjected to IR torque, the ACL+ALL-deficient state resulted in an additional 3.2° of internal rotation (95% CI, 2.4°-4.1°; P < .001) versus the intact state, and the additional sectioning of the ALL increased internal rotation by 2.7° (95% CI, 1.8°-3.6°; P < .001) versus the ACL-deficient state. Conclusion: The results of this study confirm the ALL as an important lateral knee structure that provides rotatory stability to the knee. Specifically, the ALL was a significant secondary stabilizer throughout flexion during an applied internal rotation torque and simulated pivot-shift test in the context of an ACL-deficient knee. Clinical Relevance: Residual internal rotation and a positive pivot shift after