Finite Element Analysis of Fretting Wear between the Cortical Suspension Device and the Cortical Bone

Anterior cruciate ligament (ACL) requires ACL reconstruction after rupture because of its inability to regenerate. Cortical suspension device is one of the most common fixation devices for ACL reconstruction at the femoral. The purpose of this paper was to study the fretting wear behavior of the cortical suspension device. Considering the fretting behavior of contact surfaces between the titanium plate in the cortical suspension device and the cortical bone of the femur due to the alternating load, the finite element method for the fretting wear of titanium/cortical bone was proposed, and the fretting wear behavior between the cortical suspension device and the femoral surface was predicted by this method. Firstly, the ALE adaptive mesh and the UMESHMOTION subroutine in the ABAQUS finite element software and the Archard model were used to establish a ball/plane fretting wear model of titanium/cortical bone material. And the correctness of the finite element method had been verified by comparing with results of Hertz contact theory and experiment. The effects of displacement amplitude, friction coefficient and normal force on the fretting wear were researched. Finally, a titanium plate/cortical bone fretting wear model was established using validated models and methods to study the fretting wear behavior between the cortical suspension device and the femur. By studying the fretting wear behavior of the ball/plane fretting wear model, it was found that with the increase of fretting displacement amplitude from 2 μm to 10 μm, the wear state gradually changed from partial slip to complete slip; the wear depth increased from 0.195 μm to 14.13 μm and the wear volume increased from 5.69×10⁴ μm³ to 1.4×10⁶ μm³. The wear depth decreased from 8.38 μm to 2.17 μm and the wear state changed from complete slip to partial slip with the increase of the friction coefficient from 0.3 to 0.7 when the displacement amplitude was 5 μm; the wear depth decreased from 15.25 μm to 10.96 μm and the wear state was in complete slip when the displacement amplitude was 10 μm. With the increase of the normal force from 40 N to 120 N, the wear depth decreased from 6.06 μm to 2.71 μm and the wear state changed from complete slip to partial slip when the displacement amplitude was 5 μm. However, the wear depth increased from 10.9 μm to 15.2 μm and the wear state was in complete slip when the displacement amplitude was 10 μm. By studying the fretting wear behavior of the titanium/cortical bone fretting wear model under alternating load, it was found that the wear was at the edge of cortical bone tunnel hole and the maximum CPRESS stress was. As the friction coefficient increases from 0.3 to 0.7, the wear depth gradually decreased from 12.6 μm to 4.4 μm, which was the same as the prediction trend of ball/plane fretting wear model. By increasing the friction coefficient between the cortical suspension device/cortical bone tunnel hole edge contact surface, the anti-fretting capacities of cortical bone could be improved, which could improve the success rate of ACL reconstruction.