Coupled Valgus Collapse Due To Internal Rotation: An Important Factor In the ACL Injury Mechanism

To understand the coupling between internal rotation and valgus orientation, and their effects on ACL strain. 17 cadaveric legs (45+ or -7 yrs) potted at the mid-femur and fixed at 25[degrees] of flexion to a 6-DOF force couple testing apparatus. An unconstrained pure moment was applied to the tibia over a continuous range of + or -50 Nm abduction-adduction under 1200 N quadriceps and 800 N hamstrings loads. Joint kinematics were collected using an Optotrak 3020 system. A DVRT transducer was used to calculate ACL strain. Specimens were first tested under isolated abduction-adduction loading. 20 Nm pure internal rotation moment produced significant 6.4 + or 3[degrees] coupled valgus rotation of the tibia (P