Anterolateral Ligament and Iliotibial Band Control of Rotational Stability in the Anterior Cruciate Ligament–Intact Knee: Defined by Tibiofemoral Compartment Translations and Rotations

Abstract

To determine the stabilizing effect of the anterolateral ligament (ALL) and iliotibial band (ITB) in resisting internal tibial rotation limits and anterior subluxations of the tibiofemoral compartments in anterior cruciate ligament (ACL)-intact knees during anterior drawer, internal rotation, and under 2 different 4-degree-of-freedom pivot-shift conditions. A 6-degree-of-freedom robotic simulator tested 19 fresh-frozen cadaver specimens with 3 testing conditions: intact, ALL- or ITB-sectioned (random), and both ALL and ITB sectioned. Anterior translation of the medial and lateral compartments and internal tibial rotation were measured under 100N anterior drawer, 5 Nm internal rotation, and 2 pivot-shift conditions. Statistical equivalence was defined as P < .05. Sectioning the ALL alone had no effect on lateral compartment translation or internal rotation under any loading condition (equivalent P < .05). After ITB sectioning alone, small increases in internal rotation were found under 5 Nm internal rotation at 60° (3.0° [90% confidence interval 1.9-4.1]; P= .99) and 90° (2.2° [90% confidence interval 1.5-2.9]; P= .84) flexion. After both ALL and ITB were sectioned, increases in internal rotation of 1.7°, 4.5°, and 3.9° occurred at 25°, 60°, and 90° flexion, respectively (P > .05). Small increases in pivot-shift internal rotation (Group 1: 2.0° [90% confidence interval 1.4-2.6]; P= .52) and lateral compartment translation occurred (Group 1: 0.9mm [90% confidence interval 0.7-1.1]; P < .001). Sectioning the ALL does not lead to an increase in tibiofemoral compartment subluxations in the pivot-shift test with an intact ACL. Accordingly the ALL would not represent a primary restraint to pivot-shift subluxations. ALL sectioning alone does not lead to an increase in internal rotation motion limits, however sectioning both the ALL and ITB did produce small increases in rotation limits at higher flexion angles which would likely not be clinically detectable. A deficiency to both the ALL and ITB during invitro-simulated pivot-shift tests and internal rotation tests results in small, clinically undetectable changes in knee kinematics in the majority of knees assuming intact ACL function.