Anterior Cruciate Ligament Tear Initiation Locus: A 3D Finite Element Analysis

Abstract

Understanding the mechanism for anterior cruciate ligament (ACL) injury is important. 250,000 ACL injuries annually (U.S.) creates an annual billion dollar expenditure. This investigation shows which lower extremities movement combinations initiate anterior cruciate ligament (ACL) tears. A 3-dimensional (3D) knee joint model was developed to create a tear initiation locus for the ACL with respect to the relative movements between the tibia and femur. Bones and ligaments were digitized from magnetic resonance images (MRI). Bone was modeled as rigid; ligaments were modeled as transversely isotropic hyperelastic based on the Weiss modified Mooney-Rivlin material model and bundle specific prestrain was incorporated within 3D ligaments. An ACL tear initiation locus was created from a series of parametric finite element simulations considering various knee joint motions. These motions included knee flexion, femoral internal/external rotation and valgus/varus angle. The relationship between knee-joint orientation and ligament bundle tear initiation was plotted providing a bundle specific susceptibility spectrum for ACL tear initiation. The posterolateral bundle shows higher rupture susceptibility than the anteromedial bundle. Varus angle simulations required 23% less angle for failure compared to valgus angle simulations. Femoral external rotation decreases valgus/varus failure angle by 43.05% compared to internal rotation. The data from these studies can improve athletic training programs by adapting current methods to address harmful knee orientation avoidance. The model provides improved accuracy for clinically determining bundle specific ruptures. Monitoring knee orientations during bundle rupture improves knowledge of injury mechanisms, aiding clinical professionals with injury diagnoses.