The effect of collagen organization on tensile strength loss in anterior cruciate ligament grafts post-reconstruction surgery

Abstract

Grafts used for anterior cruciate ligament (ACL) reconstructions fall short of restoring native mechanics. This study investigated a morphological cause for tension loss by comparing native ACL and two common grafts, bone-patellar tendonbone (BPTB) and semitendinosus/gracilis hamstring tendon (ST/G), in a cadaveric system. Tension loss during continuous passive motion was quantified via force transducer. Microstructural changes were assessed by measuring collagen crimp angles. No significant differences were found for rates of percent tension loss relative to total tension loss among grafts. However, all groups displayed exponential decay, implying rapid tension loss. The crimp angles for the unstressed grafts were significantly different from each other, suggesting innate differences. The percent change experienced by stressed grafts, normalized to their unstressed baselines, showed that ST’s crimp behavior was significantly different from that of ACL and BPTB, implying the BPTB graft is superior for ACL reconstruction because it better mimics the ACL’s morphological behavior.