The Finite Element Analysis Of Proximal Femoral Anti-rotation Intramedullary Nail Combined With Plate Wire Reconstruction Of The Lateral Wall And Posterior Medial Bone Block For Complex Intertrochanteric Fracture

Objective: For intertrochanteric fracture,the blood flow is rich in fracture end and the local stable mechanical environment is the main factor that affects fracture healing process.Considering that intramedullary nail system has a certain failure rate in the treatment of unstable intertrochanteric fractures,this research intended to use computer software and finite element analysis(FEA)to simulate unstable intertrochanteric fractures with medial and lateral defects in order to compare the stresses and displacements of the intramedullary nails with different fixation methods: dependently intramedullary nail and intramedullary nail combined with fixation plate and wire.The significance and application of fixation plate and wire to assist reconstruction for intertrochanteric fractures with medial and lateral defects was comprehensively investigated.Methods:A healthy 75-years-old male volunteer was enrolled in this research.Based on the CT scan data of his proximal femur,an accurate 3D model of the proximal femur was established by applying Mimicsl 7.0 software and Geomagic Studio software.This femoral model was osteotomized using Solidworks 2019 software to simulate intertrochanteric fractures,including intertrochanteric fractures combined with medial defects,lateral defects,and medial-lateral defects.Each fractures was internally fixed with proximal femoral intramedullary nail anti-rotation(PFNA)and PFNA plus fixation plate or wire to obtain 10 internal fixation models of intertrochanteric fractures.The above internal fixation models were imported into the finite element analysis software Abaqus,and constraints and loads were applied.The stresses and displacements at the union of the intramedullary nail and screw blade were observed under three conditions of simulated horizontal neutral bipedal standing still,slow walking and fast walking.Results: The stress distribution was calculated by finite element software.In condition of the medial defect model and neutral bipedal standing still,stress of PFNA,PFNA+wire was 176 Mpa,121 Mpa respectively;In the lateral defect model,stress of PFNA,PFNA+wire,PFNA+plate,PFNA+wire+plate was 92 MPa,85 MPa,89 MPa,67 MPa respectively;In the mediallateral defect model,stress of PFNA,PFNA+wire,PFNA+plate,PFNA+wire + plate was 239 MPa,141 MPa,213 MPa,107 MPa respectively.Similar results were observed in condition of slow walking and fast walking groups with greater overall stress and less stress after reconstruction.Conclusion: The FEA method simulates that the medial defect of PFNA internal fixation for intertrochanteric fracture is more stressful than the lateral defect;in the case of lateral defect or medial and lateral defects wire is more stable compared with plate,and plate reconstruction alone is not recommended;in the case of both medial and lateral defects,the simultaneous application of plate plus wire reconstruction is recommended.