Biomechanical Effect of Tunnel Positions and Pre-tension Forces on Implanted Graft Stress and Strain During Outside-in ACL Reconstruction Surgery: A Simulation Study

The selection of surgical site for the femoral tunnel during anterior cruciate ligament (ACL) reconstruction surgery remains controversial. However, it is not only surgical site that lacks scientific consensus but also the level of pre-tension force applied during implanted graft fixation. This study aims to propose the optimal femoral tunnel position considering appropriate pre-tension in ACL reconstruction surgery. To select the optimal position, the stress and strain on the implanted graft in 40 cases was calculated by testing combinations of 10 recommended tunnel positions on the femoral epicondyle and four pre-tension forces (0, 10, 20, and 30 N) using multi-flexible body dynamics. The lowest implanted graft stress and strain was found in a posterior proximal site at 15 mm from the lateral femoral epicondyle; the pre-tension force here showed no significance. In conclusion, changes in stress on the implanted graft were affected more by tunnel position than by pre-tension.