Medial And Lateral Wall Injuries And Small Trochanteric Fractures Mode On Intertrochanteric Fractures By Finite Element Analysis Of The Biomechanical Effects

PART ONE:Three-dimensional finite element analysis of medial and lateral wall damage of intertrochanteric fractureObjective: To study the stress and displacement of proximal femur and PFNA after fixation of intertrochanteric fractures involving medial or lateral wall by finite element analysis.Methods: The proximal femoral model bone was selected and CT scan was performed,and the software such as Mimics19.0;Geomagic Studio 2015;solidwork2018;Ansys Workbench 17.2 was used to establish the proximal femoral three-dimensional finite element model and then simulated the type I fracture of Evans,and then the model of intertrochanteric fracture to remove the medial or lateral wall.Apply 600 N axial pressure to the proximal femur after PFNA implantation,observe the stress value and displacement value of each part of the model during the defect of the medial or lateral wall,analyze the data and further analyze the clinical significance of the medial and lateral walls.Results: The finite element model of proximal femur bone and intramedullary nail was established.The femoral stress and displacement of the model of intertrochanteric fracture of femur in the whole group were 14.764 Mpa,22.000 Mpa,47.924 Mpa,1.147 mm,1.226 mm,1.403 mm,respectively.The stresses of intramedullary nails in the complete group,the lateral wall defect group and the medial wall defect group were 135.42 Mpa,166.73 Mpa,296.92 Mpa,and the displacement was 1.0265 mm,1.0808 mm,1.2040 mm,respectively.The model of the lateral wall and the medial wall has a significant increase in the stress and displacement of the complete group model,and the increase of the model value of the medial wall defect group is greater than that of the outer wall lateral group model.Conclusion: In the treatment of intertrochanteric fractures involving medial wall and lateral wall,the stress displacement of PFNA and femur will be increased obviously,and the model stress and displacement of medial wall defect group will increase most significantly,that is,the importance of medial wall is greater than that of lateral wall from biomechanical point of view.PART TWO:Finite element analysis of the effect of the small rotor fracture pattern on the biomechanics of intertrochanteric fracturesObjective: Based on the complete model of intertrochanteric fracture in the first part,seven different models of trochanteric fracture were established to explore the stress and displacement values of proximal femur and PFNA.Methods: The complete model of intertrochanteric fracture was selected in the first part,and seven different models of intertrochanteric fracture with trochanteric fracture were designed by using mechanical design automation software solidwork2018: group A(complete group),group B(simple trochanteric missing),group C(small trochanteric involved partial medial cortex),group D(bone block involved half of femoral coronal surface),group E(bone block larger than half of femoral coronal surface),group F(bone block involved anterior side of medial wall)and Group G(all medial wall missing).Apply 600 N axial pressure to the proximal femur after PFNA implantation,observe the stress value and displacement value of each part of the seven groups of models,analyze the data,and further analyze the clinical significance of the small rotor fracture pattern on the stability of intertrochanteric fracture.Results: The finite element model of different fracture patterns of small trochanter was established,and the internal plant and femoral stress cloud map and displacement cloud map were calculated by finite element software.The femoral stresses and displacements from Group A to Group G were 14.764 Mpa,15.659 Mpa,20.947 Mpa,29.300 Mpa,47.036 Mpa,65.597 Mpa,60.790Mpa;1.147 mm,1.138 mm,1.155 mm,1.231 mm,1.216 mm,1.235 mm,1.400 mm,respectively.The stress values and displacements of intramedullary nails from group A to group G were 135.4Mpa,138.5Mpa,149.7Mpa,162.4Mpa,191.3Mpa,254.7Mpa,296.9Mpa,and1.0265 mm,1.0170 mm,1.0271 mm,1.0865 mm,1.0677 mm,1.0764 mm,1.2045 mm,respectively.The stability of fracture was similar between group A and group B,and the stress and displacement of group D and group E increased obviously.Conclusion: There is no effect on fracture stability due to the avulsion of small trochanteric.When the small trochanteric fracture is involved in the lower than half of the coronal surface of the femur,it has little effect on the fracture stability.When it comes to more than half of the coronal surface of the femur,it has a great effect on the stability of the fracture.It is recommended to fix the small trochanteric fracture block at this time.