The Anterolateral Structure of the Knee Does Not Affect Anterior and Dynamic Rotatory Stability in Anterior Cruciate Ligament Injury: Quantitative Evaluation With the Electromagnetic Measurement System

Abstract

Background: The biomechanical function of the anterolateral structure (ALS), which includes the anterolateral joint capsule and anterolateral ligament (ALL), remains a topic of debate. Hypothesis: The ALS contributes to knee joint stability during the Lachman test and the pivot-shift test in anterior cruciate ligament (ACL)–deficient knees. Study Design: Controlled laboratory study. Methods: Fourteen fresh-frozen hemipelvis lower limbs were used. For 7 specimens, the anterior one-third of the ALS and the residual ALS were cut intra-articularly with a radiofrequency device. Subsequently, the ACL was cut arthroscopically. For the other 7 specimens, the ACL was cut first, followed by the anterior one-third of the ALS and the residual ALS intra-articularly. During the procedures, the iliotibial band (ITB) was kept intact. At each condition, the anterior tibial translation (ATT) during the manual Lachman test and the acceleration of posterior tibial translation (APT) and the posterior tibial translation (PTT) during the manual pivot-shift test were measured quantitatively with an electromagnetic measurement system. The mean values of those parameters were compared among 6 groups (ACL intact, one-third ALS cut, all ALS cut, ACL cut, ACL/one-third ALS cut, and ACL/all ALS cut). Results: The mean ATTs during the Lachman test and the mean APTs and PTTs in the ACL-cut conditions (ACL cut, ACL/one-third ALS cut, and ACL/all ALS cut) were significantly larger than those under the ACL-intact conditions (ACL intact, one-third ALS cut, all ALS cut) ( P < .01). However, no statistically significant differences were observed among the intact, one-third ALS–cut, and all ALS–cut conditions, within the ACL-intact or ACL-cut conditions. Conclusion: Intra-articular dissection of the ALS did not increase the ATT during the Lachman test or the APT and PTT during the pivot-shift test under the intact condition of the ITB, regardless of the integrity of the ACL. When the ITB is intact, the ALS does not have a significant role in either anterior or dynamic rotatory knee stability, while the ACL does. Clinical Relevance: Recent growing interest about ALL reconstruction or ALS augmentation may not have a large role in controlling either anterior or dynamic rotatory knee instability in isolated ACL-deficient knees.