Finite Element Analysis Of Proximal Femoral Stress Changes After Biological Femoral Head Replacement

Background: In today’s society,the treatment of femoral neck fracture in the middle aged and elderly people are diversified,including femoral head replacement which is specially effective to the patients with preoperative complications,poor ability to tolerate surgery and more problems such as osteoporosis.But in the process of recovering,as time goes on,postoperative complications also show a growing tendency,especially the bone mass loss and prosthesis loosening caused by stress shielding of prosthesis,even resulting in operation failure.Therefore,the research of stress analysis will be applied to optimize prosthesis and to avoid prosthesis loosening.Objective: Application of finite element analysis for the middle aged and elderly people to simulate biological type femoral head replacement,can compare the stress of the proximal femur which is implanted prosthesis with the normal proximal femur.The result of the comparison can be used to analyze that if there is a large stress changes in the postoperative hip,whether the stress changes can cause prosthetic aseptic loosening during the process of rehabilitation.The result of the comparison can also provide the reference and guidance for the choice of the ways of femoral neck fracture surgery for middle aged and elderly people and the improvement of artificial prosthesis.Methods: Firstly,using CT(Computed Tomography)to scan the proximal femur of a middle aged and elderly person get the continuous images,then using Mimics software to establish the 3D model of normal femoral head.According to the type of the biological prosthesis,using 3D reconstruction software Mimics to refactor prosthetic model.Secondly,the reconstruction of the proximal femur model and the prosthetic model will be exported to the Solidworks software.According to the regular orthopaedic surgical procedures,prosthetic model will be assembled to the femoral model,then imported into the ANSYS software,endowed with different material properties and boundary conditions.Using ANSYS v12.1 software can analyze related data.According to the data of the normal proximal femur and the proximal femur which is implanted prosthesis,simulating the state of 61 KG normal person standing with one foot respectively load the two kinds of model.Thirdly,using ANSYS v12.1 software to analyze the stress and stress distribution,then compare the results.Results: Compared the normal proximal femur with the proximal femur which is implanted prosthesis after loaded,stress and the stress distribution have changed in the larger range.Because of the stress shielding,the prosthesis of implanted femur reduced the stress level of the surrounding bone,especially the great trochanter and lesser trochanter more obviously.In the normal proximal femur,the position of the minimum stress is at the great trochanter and lesser trochanter,and the minimum value is in the range of 0.013772MPa~0.035798 MPa.Compared with the normal femur,the scope of the minimum stress in implanted femur is becoming larger.As a result of prosthesis bearing more load,it leads to its surrounding bone loading decreased.This situation creates stress shielding.In the normal proximal femur,the value of the maximum stress ranges from 28.706 MPa to 74.617 MPa.But the stress of implanted femur at the same position is significantly lower,the value of stress is ranging from 17.389 MPa to 52.743 MPa.Conclusion:Through the finite element analysis software to reconstruct the normal proximal femur and the proximal femur which is implanted prosthesis has a high simulation.Comparing the two models,the stress of the implanted femur is changing a lot,and the proximal femur has the obvious stress shielding.It is an important cause of aseptic loosening of prosthesis.It provides theoretical guidance for the choice of prosthesis during surgical procedures,the determination of installation position and the modified scheme of prosthesis about artificial femoral head replacement.