Finite Element Analysis Of Different Intramedullary Fixation Methods For Femoral Intertrochanteric Fractures

Objective:To compare the biomechanical efficacy of proximal femoral anti-spin intramedullary nail(PFNA),proximal femoral combined compression interlocking intramedullary nail(Intertan),and proximal femoral bionic intramedullary nail(PFBN)under vertical loading as well as internal and external reactive force finite element model analysis.To provide a theoretical reference for selecting intramedullary fixation modality for clinical work.Materials and methods:Volunteers with no previous history of femoral disease were selected,320 CT of the full length of the femur was taken bilaterally,and the femoral CT data were imported into Mimics in DICOM format,grayscale values were set,3D femoral model data were extracted,3D femoral model data were curved to generate solids,and fracture models were established.The 3D models of the proximal femur anti-rotation intramedullary nail,proximal femur joint compression interlocking intramedullary nail,and proximal femur bionic intramedullary claw were also set and assembled with the fracture models respectively,and the three groups of models were tested under vertical load,inversion stress,and out version stress states respectively,and the displacement clouds,maximum stress clouds and equivalent force clouds of the femur and internal fixation device in the three groups of models were obtained under the three conditions.Results:From the displacement clouds,it can be seen that the maximum deformation location of all femurs was located in the femoral head,and the femur deformation in the PFBN group under vertical load was smaller than that in the PFNA and Intertan groups(1.3339 mm in the PFNA group,0.36152 mm in the Intertan group,and 0.26855 mm in the PFBN group),and the femur deformation in the PFBN group under internal and external overturning stress was the smallest,and the femur deformation in the Intertan group was the smallest.Deformation was the smallest in the PFBN group,followed by the Intertan group,and the largest in the PFNA group(0.25464 mm for PFNA,0.088086 mm for Intertan,and 0.057034 mm for PFBN).For the internal fixation system,the deformation of PFBN under vertical load was less than that of the PFNA and Intertan groups(1.3298 mm for the PFNA group,0.34347 mm for the Intertan group,and0.23726 mm for the PFBN group),and the deformation of PFBN under internal and external overturning stress was also less than that of the PFNA and Intertan groups(0.21145 mm for the PFNA group,0.075255 mm for the Intertan group,and 0.047671 mm for the PFBN group).That means PFBN has better stability against vertical stress and inward and outward turning stress than PFNA and Intertan.From the stress cloud,the peak femoral stress in the PFBN group was the smallest under vertical load and the largest in the PFNA group(11.655 MPa in the PFBN group,12.083 MPa in the Intertan group,and 15.859 MPa in the PFNA group);the peak femoral stress in the PFNA group was the smallest under external rotation stress,and the peak femoral stress in the Intertan group was The peak femoral stress in the PFNA group was0.8661 Mpa,0.87122 Mpa in the PFBN group and 0.97562 Mpa in the Intertan group,and the peak femoral stress in the PFBN group was 0.81421 Mpa,which was smaller than that in the PFNA and Intertan groups.In other words,there was no significant stress concentration in the femur in the PFBN group compared with the PFNA group and the Intertan group.Conclusion:Under vertical loading,PFNA,Intertan,and PFBN can provide effective support,but PFBN has more biomechanical advantages compared with PFNA and Intertan.Due to the unique design structure of PFBN,it has a stronger ability to resist internal and external rotation stress.