The biological and biomechanical effect of different graft tensioning in anterior cruciate ligament reconstruction: an experimental study

The objective of the present animal experimental study was to determine the effect of initial graft tension (1 N, 7.5 N, 17.5 N) on the biomechanical and histological behavior of the anterior cruciate ligament (ACL) graft using a rabbit model. After 2, 8, and 32 weeks, the femur-ACL-tibia complex was removed, and biomechanical and histomorphometrical studies were performed. The morphometric parameters cellularity, cell nucleus volume, and vascularity increased up to the 8th postoperative week and showed significant differences between the study groups. The values obtained demonstrated that higher pretension had increased the pull-out force and stiffness. However, at 32 weeks postoperatively, the pull-out force was significantly below the values of the normal ACL (40.5% at 1 N, 45.1% at 7.5 N, and 50.8% at 17.5 N). In the present study, it was demonstrated that an intraoperatively selected initial tension of 17.5 N induces histomorphometric changes in the graft, which result in a higher biomechanical loading capacity. The results showed that higher initial graft tension resulted in improved histological and biomechanical parameters. Pathological changes in the graft such as an increased central necrosis rate or cartilage damage due to 'overconstraining' of the knee were not observed at the selected initial tensions.