A Biomechanical Study of the Role of the Anterolateral Ligament and the Deep Iliotibial Band for Control of a Simulated Pivot Shift With Comparison of Minimally Invasive Extra-articular Anterolateral Tendon Graft Reconstruction Versus Modified Lemaire Reconstruction After Anterior Cruciate Ligament Reconstruction

Abstract

To determine whether the deep fibers of the iliotibial band (dITB) or the anterolateral ligament (ALL) provides more control of a simulated pivot shift and whether a minimally invasive anterolateral reconstruction (ALR) designed to functionally restore the ALL and dITB is mechanically equivalent to a modified Lemaire reconstruction (MLR). Six matched pairs of cadaveric knees (N= 12) were subjected to a simulated pivot shift to evaluate anteroposterior translation; internal rotation; and valgus laxity at 0°, 30°, and 90° of flexion. The anterior cruciate ligament (ACL) was sectioned in all specimens, and retesting was performed. Within each pair, sequential sectioning of the ALL and dITB was performed, followed by testing; the contralateral knee was sectioned in reverse order. Knees underwent ACL reconstruction (ACLR) and repeat testing. Then, MLR (n= 6) or ALR (n= 6) was performed on matched pairs for final testing. Sectioning of the dITB versus ALL (after ACL sectioning) produced significantly more anterior translation at all flexion angles (P= .004, P= .012, and P= .011 for 0°, 30°, and 90°, respectively). The ACL-plus-dITB sectioned state had significantly more internal rotation at 0° versus ACL plus ALL (P= .03). ACLR plus ALR restored native anterior translation at all flexion angles. ACLR plus MLR restored anterior translation to native values only at 0° (P= .34). We found no statistically significant differences between ACLR plus ALR and ACLR plus MLR at any flexion angle for internal rotation or valgus laxity compared with the native state. ALR of the knee in conjunction with ACLR can return the knee to its native biomechanical state without causing overconstraint. The dITB plays a more critical role in controlling anterior translation and internal rotation at 0° than the ALL. The minimally invasive ALR was functionally equivalent to MLR for restoration of knee kinematics after ACLR. The dITB is more important than the ALL for control of the pivot shift. A minimally invasive extra-articular tendon allograft reconstruction was biomechanically equivalent to a modified Lemaire procedure for control of a simulated pivot shift.