Finite Element Analysis Of Mechanical Effect Of Different Internal Fixation For Pauwels Type Ⅲ Femoral Neck Fractures

Purpose:(1)Establish finite-element model of femoral neck fracture with computer software using finite element simulation and verify its validity,and assemble with five clinically commonly used methods for internal fixation of femoral neck fractures(2)Study using different internal fixation methods After fixation of the fracture of the femoral neck,the biomechanical characteristics of the femoral neck were different,and the therapeutic effect of each method was judged.Methods:(1)From the selected case of a unilateral femoral neck fracture with Pauwels type Ⅲ,the contralateral side was normal without fracture,and there was no malformation and other orthopedic related diseases.The CT scanning of the lower extremities was performed preoperatively.The CT data was imported into the computer three-dimensional reconstruction software Mimics 17.0 to reconstruct the three-dimensional model.A fracture model was established by performing a 70° osteotomy on the three-dimensional model of the femoral neck of the patient according to Pauwels classification Ⅲ.Subsequently,the initial finite element model was established in the Simpleware software for the fractured model of the ipsilateral femoral neck fracture and the contralateral osteotomy.With reference to the previous literature reports,the finite element analysis software Abaqus 6.14 was used to analyze the differences in biomechanical characteristics and evaluate the rationality of the finite element model for femoral neck fractures.(2)After the evaluation of the fracture model was established,the image processing software Geomagic studio was used to perform smooth noise reduction on the established fracture model.The data was imported into the engineering software Solid Works and five different internal fixations were used to perform finite element analysis.The assembly of the model includes dynamic hip screws,locking compression plates,three hollow screws,four hollow screws,and an intramedullary nail.The assembled model portfolios were respectively imported into the finite element preprocessing software Hypermesh for meshing and assignment of material properties.Cortical bones and cancellous bones were assigned to their respective mechanical characteristics and binding processing was performed to maximize the simulation of the overall tibia.Proximal biomechanical features.(3)Finally constrain the boundary conditions in the finite element processing software Aabaqus,and according to the actual weight of the selected case and the force reference provided by the reference,apply an axial load of 4000 N to compare the postoperative stress of femoral neck fractures with different internal fixations.Distribution,stress peak,displacement size.Results:(1)Reconstruction of the proximal three-dimensional model of the patient’s healthy humerus using computer simulation and fracture modeling work can be successfully completed and maintain the proximal biomechanical characteristics of the humerus.After modeling,the same three-dimensional model of the proximal humerus was assembled with different internal fixations to simulate the overall mechanical state of the selected area after internal fixation.(2)The force distribution cloud diagram,the position of the maximum stress point,the maximum displacement of the internal fixation,and the fracture when the different internal fixation methods are used under the same axial force with the same force in the same direction and the same stress point.The maximum displacement of the model has different degrees of difference.Among them,the maximum stress values(in k MPa)in different groups are as follows: Locked Compression Plate: 4.059> Dynamic Hip Screw: 3.472> Intramedullary Nail: 2.235> Three Hollow Screws: 1.375 ≈ Four Hollow Screw: 1.353.(3)The displacements of different groups(unit: mm)are as follows: Three Hollow Srews: 1.936 ≈ Four Hollow Screws: 1.931> Dynamic Hip Screws: 1.783 ≈ Intramedullary Nails: 1.753> Locking Compression Plate: 1.266.Conclusions: The use of locking compression plate fixation has the best stability,but the pressure or shear force of the fixed object is greater;three hollow screws placed in an inverted triangle and four hollow screws placed in a diamond shape are used regardless of the force condition or the femur and the inside.The displacements of the fixtures are similar,so three screws with less bone loss and less time for surgery can be used instead of four;dynamic hip screw and intramedullary nail have similar mechanical performance and displacement,but According to the mechanical cloud image analysis,the high stress point of the dynamic hip screw is more concentrated and the intramedullary nail force is more evenly distributed.Therefore,the internal fixation of the Pauwels type Ⅲ femoral neck fracture is more stable than the intramedullary nail.