Biomechanical considerations for graft choice in anterior cruciate ligament reconstruction.

Injury to the anterior cruciate ligament (ACL) of the knee is common and often requires surgical reconstruction. There are numerous graft options available to the operating surgeon, to each of which a growing body of dedicated literature exists. Each of these potential choices of ACL graft specimen has a distinctive set of biomechanical properties, clinical outcome profiles, and other special considerations (e.g., autograft versus allograft, harvest site factors, and operating time). The purpose of this review is to discuss the biomechanical characteristics of the native ACL alongside those of several of the most commonly used ACL graft specimens based on a current review of the biomechanical literature. In doing so, this review will also briefly discuss the biomechanical implications for allograft versus autograft usage and single-bundle versus double-bundle repair techniques. This review lists and discusses the stress, strain, stiffness, Young's modulus, and ultimate load to failure of the native ACL, several common autografts [patellar bone-tendon-bone (BTB), hamstring tendon (HT), and quadriceps tendon (QT)], and several common allografts. Given the important biomechanical role of the ACL in stabilizing the knee to translational and rotational forces, it is crucial that the operating surgeon make a decision on graft choice that is informed in the biomechanical implications of ACL graft selection.