Reinforced Screw Fixation of Severe Osteoporotic Intertrochanteric Femur Evans II Fracture Biomechanics Biomechanical Finite Element Analysis 

Abstract

Objective: To compare the biomechanical differences between cement- reinforced intramedullary nailing with reinforced screws (a new patented invention), plain PFNA, and cemented nail tract reinforced PFNA for severe osteoporotic Evans II intertrochanteric fractures of the femur. Methods: The CT data of one patient with intertrochanteric femoral fracture with severe osteoporosis (signed and informed) were selected in Mimics 20 software and Geomagic Wrap 2017 software for medium-sized femoral model assembly, assembly standard reference standard of surgical technique. The assembled model was then subjected to osteotomy in the 3-Matic software according to the type Evans II femoral intertrochanteric fracture criteria to obtain the corresponding fracture model, And set the cancellous bone around the spiral blade of the common PFNA screw and around the proximal end of the reinforcing screw in the corresponding fracture model, Save as A (ordinary PFNA), B (nail reinforced PFNA) and C (reinforced screw), Corresponding parameters and conditions according to the CT data and the material standard of internal fixation, according to the force of human mechanics in the femur and the weight of the patient, They were stored separately and analyzed using the Explicit Dynamics module in the ansys2019 software. Observations: The degree of cutting of the screw at the proximal end of the femur, the angle of the femoral neck turning inward, the angle of rotation, the distribution of stress in the femur, and the distance where the femoral fracture part is displaced.Results:The cutting of the screw at the proximal femur, the inward turning angle of the femoral neck(0.32°), the distribution of stress in the bone of the femur and the displacement of the femoral fracture part(0.58 mm) are superior over PFNA and nail reinforcement. Conclusion Reinforced screws have better biomechanical results than common bone PFNA and nail-track reinforced PFNA for severe osteoporotic intertrochanteric Evans II femur fractures.