Three-Dimensinal Finite Element Analysis For LISS-DF In Treating Distal Femoral Fractrue

Objective To investigate the effects of stress changes by using proximal LISS-DF screw different unilateral or bilateral cortical fixation in distal femoral fracture using finite element simulation in order to find out the most optimal fixation methods. Methods Sheep femoral and LISS were used as specimen. A series of pictures with the interval of 1mm were taken by CT scanning. After extracting the coordinates of key pionts of some pictures by the procedure, we used a C program to process the useful data. Then by applying Ansys software of finite element analysis, We determined property parameter of materials and meshing. According to the model-building principle from point to line to area to volume, we constructed a three-dimensional finite element model of the sheep distal femoral fracture AO/33-A3 fixed by LISS. The stress of the model detected were to simulate the 20kg sheep the axial load and pressure torque with the average of middle digital of 40 sheep-femoral twisting moment accomplished biomechanical test. By altering proximal LISS-DF screw different unilateral or bilateral cortical fixation in distal femoral fracture, we analysised the stress distribution and strain changes of femoral, LISS-femoral fracture, and the distortion of fracture position. We found out the best fixation methods with sound biomechanical principle. Results In all kinds of fixation metheds, the fixation manner of 2, 4 hole fixed with bilateral cortical screw is better in extracting and torsion resistance, better stability, which suggested the optimal fixation methods. When other fixation methods were used, all evaluated parametes more or less greatened, and the stability were worse than the 2, 4 hole fixed with bilateral cortical screw. Conclusions We can conclude that using 2, 4 bicortical screws in the proximal end of the LISS is the best way treating distal femoral fractures AO/33-A3, which can provide reasonable fixtion effects and reach the best balance with the distal end, which can creat the biggest force to resist torsional force, eliminate the shearing force, torsional force, and can prevent hardware failure.