Biomechanics of synthetic augmentation of ligament reconstructions

Synthetic augmentation of an anterior cruciate ligament reconstruction is intended to provide stress protection to the biological graft during the early healing period when the graft tissue is weak. It is hypothesized that the ligament augmentation device carries the majority of the load during the early post-operative period, and as the graft tissue heals the load is gradually transferred from the ligament augmentation device to the biological graft. This transfer of load to the biological graft occurs as the stiffness of the remodeling graft tissue increases. Cadaver studies of biological grafts augmented with the Kennedy LAD¿ demonstrated that the LAD carried 28% of the load with a high-stiffness bone-patellar tendon-bone graft and 45% of the load with a lower-stiffness semitendinosus/gracilis graft, which supports the hypothesis that load sharing is dependent on the stiffness of the graft tissue. Cadaver studies have also demonstrated high fixation strength with the Kennedy LAD¿. A new bioabsorbable LAD with long-term strength retention has been developed to avoid potential complications caused by the implant material.