Sectioning of the Anterolateral Ligaments in Anterior Cruciate Ligament Sectioned Knees Increases Internal Rotation of the Knee Joint: A Systematic Review and Meta-analysis of Cadaveric Studies

Purpose: To investigate whether anterolateral ligament (ALL) sectioning (sALL) in the anterior cruciate ligament (ACL)sectioned (sACL) knee increases the anterior tibial translation (ATT) or internal rotation (IR) of the knee from previous cadaveric biomechanical studies. Methods: Multiple comprehensive literature databases, including PubMed (MEDLINE), EMBASE, and Cochrane Library, were searched for studies evaluating the in vitro biomechanical function of ALL. This meta-analysis compared the increased ATT and IR between the sACL and sACL + sALL knees at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Thresholds of 2 mm for the difference in ATT and 2 degrees for the difference in IR were considered to be clinically significant. Results: Thirteen cadaveric biomechanical studies were included. All 13 studies satisfied the threshold for a satisfactory methodological quality (Quality Appraisal for Cadaveric Studies score >75%). At 30 degrees of knee flexion, the meta-analysis showed a greater increase in ATT in the sACL + sALL knees than in the sACL knees by 1.23 mm (95% confidence interval [CI], 0.62-1.84; P < .0001). However, the mean difference was less than the minimal clinically significant difference (<2 mm). The meta-analysis also showed a greater increase in IR in the sACL + sALL knees than in the sACL knees at 30 degrees (mean difference [MD]: 2.24 degrees; 95% CI: 1.39-3.09; P < .00001), 60 degrees (MD: 2.77 degrees; 95% CI: 1.88-3.67; P < .00001), and 90 degrees (MD: 2.29 degrees; 95% CI: 1.42-3.15; P < .00001) of knee flexion. The differences in IR at 30 degrees, 60 degrees, and 90 degrees of knee flexion were clinically relevant (>2 degrees). Conclusions: Despite the different experimental setups and protocols between studies, the meta-analysis of biomechanical cadaveric studies showed that sectioning of the ALL in sACL knees increased IR at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Clinical Relevance: The results of this systematic review and meta-analysis suggest that ALL contributes to IR in ACL-deficient knees at 30 degrees, 60 degrees, and 90 degrees of flexion.