Orthopedic Anterior Cruciate Ligament Evaluator (OR.A.C.L.E): A Preliminary Design

An anterior cruciate ligament (ACL) tear is one of the most prominent, and debilitating injuries currently to athletes. Physical therapist students need to be able to practice common physical examination techniques regularly and repeatedly in order to gain the skills necessary to accurately diagnose an ACL tear. A cost effective, adjustable knee apparatus that could mimic the behavior of both a healthy and an injured knee joint may mitigate this problem. We built an apparatus mimicking the geometry and function of a knee joint, including the effect of forces and stiffness proper of knee ligaments. SimWise 4D was used to dynamically simulate an anatomically approximated model of the knee joint during physical examination conditions. The numerical simulation tested the displacement between the femur and the tibia with and without an ACL ligament. The SimWise 4D simulation gave an increase in displacement of 1.58 mm or 30% after removing the ACL, which is comparable with known displacements in human test subjects. Finally, a design for a 3D rapid prototype is proposed and fabricated with fusion deposition modeling (FDM).