Biomechanical evaluation of an inverted fixation for ACL reconstruction with nonmetallic hardware and tibial subcortical support to increase strength at the tibial site

Abstract

In this paper, we evaluate the initial biomechanical properties of an anterior cruciate ligament (ACL) reconstruction technique that inverts the anatomical location of the commonly used hardware and relies the tibial fixation on the subcortical bone to increase tibial site strength. Four 7-specimen groups were tested in a porcine model: for the control ACL reconstruction technique, the femur with a cross-pin fixation supported in the trabecular bone and the tibia with a biodegradable interference screw (BIS); for the new proposed technique, the femur with a BIS and the tibia with a cross-pin fixation leaned on the tibial subcortical bone. The specimens were subjected to cyclic and load-to-failure tests to compute their biomechanical performance. At the tibia, the cross-pin fixation revealed higher resistance than the BIS ( p=0.000 for ultimate load and p=0.006 for yield load), additionally cyclic and total displacement at representative loads showed extremely high values with BIS fixation (in two specimens greater than 9mm for 250 N and greater than 10mm for 450N). At the femur, no differences between fixations were observed. The inverted ACL reconstruction improves resistance at the tibial site with respect to the control technique, with similar resistance at the femoral site and no differences in total displacement at representative loads. It offers a useful and robust solution when greater tibial resistance is required.