Graft selection and biomechanical considerations in ACL reconstruction (isometry, stress, preload)

This article discusses graft selection and important biomechanical principles in anterior cruciate ligament (ACL) reconstruction. Presently, there is no place for synthetics. Bone-patellar tendon-bone (BPTB) or multiple-strand hamstring grafts have been equally successful. Allograft is an alternative, but outcomes may not be as good. When carrying out the reconstruction, the surgeon must have sufficient knowledge of the effect of tunnel placement within the femur and tibia, the effect of flexion angle at the time of fixation, the effect of pretension and the effect of posterior load on tibia. These variables all affect the maximum unloaded length of the graft, which, in turn, will determine the loads imposed on the graft.