Independent Suture Tape Reinforcement of Small and Standard Diameter Grafts for Anterior Cruciate Ligament Reconstruction: A Biomechanical Full Construct Model

Abstract

To compare the dynamic elongation, stiffness behavior, and ultimate failure load of standard with small diameter soft tissue grafts for anterior cruciate ligament (ACL) reconstruction with and without high-strength suture tape reinforcement. Both a tripled "small" diameter and a "standard" quadrupled tendon graft with and without suture tape reinforcement were tested using suspensory fixation (n= 8 each group). The suture tape was passed through the suspensory fixation button on the femur and tibia to ensure independent (safety belt) fixation from the graft invitro. The testing of the constructs included position-controlled cyclic loading, force-controlled cyclic loading at 250N and 400N as well as pull to failure (50mm/min). Reinforcement of a small diameter graft significantly reduced dynamic elongation of 38% (1.46 ± 0.28mm vs 2.34 ± 0.44mm, P < .001) and 50% (2.55 ± 0.44mm vs 5.06 ± 0.67mm, P < .001) after the 250N and 400N load protocol, respectively. Reinforcement of a standard diameter tendon graft decreased dynamic elongation of 15% (1.59 ± 0.34mm vs 1.86 ± 0.17mm, P= .066) and 26% (2.62 ± 0.44mm vs 3.55 ± 0.44mm, P < .001). No significant difference was found between both reinforced models. The ultimate failure loads of small and standard diameter reinforced grafts were 1592 ± 105N and 1585 ± 265N, resulting in a 64% (P < .001) and 40% (P < .001) increase compared with their respective controls. Independent suture tape reinforcement of soft tissue grafts for ACL reconstruction leads to significantly reduced elongation and higher ultimate failure load according to invivo native ACL function data without stress-shielding the soft tissue graft. If invitro results are translational to human knees invivo, the suture tape reinforcement technique for ACL reconstruction may decrease the risk of graft tears, particularly in the case of small diameter soft tissue grafts.