Three-dimensional finite element simulations of the long-term effects of hamstring tendon graft type and tensioning on anterior cruciate ligament reconstruction

A validated finite element model of a human knee joint (including the bone, cartilage, menisci and main ligaments) is used to compare the effects of three graft tensions (i.e., 0 N, 20 N and 40 N) as well as two hamstring tendon (HT) graft types (i.e., quadruple and double HT grafts) to study the long-term effects of graft type and tensioning on joint kinematics and ligament biomechanics of anterior cruciate ligament (ACL) reconstruction. Both the joint kinematics and ligament biomechanics are obtained for a 134 N anterior tibial load. The tibia moves posteromedially with external and valgus rotations as the graft tension increases regardless of the graft type. The forces in the grafts increase as the tension increases while the stress distributions in the grafts do not change. Both the simulated kinematics and the forces in the grafts demonstrate that the double HT graft with an initial tension of 80 N gives the closest function to the original ACL.