Effects of femoral tunnels on mechanical properties of human femur

Firstly in this paper, a three dimensional model of human femur was built based on spiral CT images utilizing the software Mimics 8.1. Based on this femur model and according to the demand of the ligament reconstruction surgery, three approximately 3D finite element models corresponding to intact femur model, the femur model with a signal tunnel and femur model with double tunnels are built. Then, the loads received by the femur in joint movement are decomposed into three forces: namely compress, bend and torsion forces and are applied to the three finite element femur models to carry out the finite element simulation. This paper introduces the sectional stress comparison method, which extract the max virtual stress and max primary stress from stress nephogram of femur sections to evaluate the tunnels' effects on femur's mechanical properties. The results show that, the femoral tunnels affect the distribution of femur section stress insignificantly after ACL reconstruction, with the max virtual stress and max primary stress change less than 5.06% and 6.85% respectively. Therefore, surgeons can only concentrate their attentions on considering the precise sites of the femoral tunnels in the surgery. Also, the section stress comparison method proposed in this work suggests a new way to evaluate femur's mechanical properties after ACL reconstruction.