| Objective:The three-dimensional finite element model of distal humerus type A fracture was established by finite element analysis,and the fracture model was fixed by locking compression plate and modular external fixation scaffold respectively.From the perspective of biomechanics,the mechanical stability of the two fixation methods was compared,providing theoretical basis for clinical treatment of open and closed distal humerus type A fracture.Methods:1.Reconstruction image and finite element modeling.Spiral CT scan was performed on the left humerus of healthy male volunteers,CT data were extracted using Mimics 21.0 software,and reverse processing function of Geomagic Studio 2014 was applied to establish the left normal humerus model and distal humerus type A fracture model.The internal fixation model of the locking compression plate and the external fixation model of the assembled external fixation bracket were established and assembled.The finite element pre-processing and post-processing were carried out by Hypermesh2021 software,MSC.Patran2019 software and MSC.Nastran2019 software,respectively.Including finite element grid attribute setting,material parameter definition,load application,boundary condition constraint,and various calculation conditions analysis.2.Three-dimensional finite element analysis of locking compression plate for internal fixation of distal humerus Type A fracture.The finite element simulation analysis was carried out on the bone plate internal fixation group of distal humerus type A fracture by finite element method.Von Mises equivalent stress nephogram and Displacement nephogram of humerus and plate fixation under three common postoperative actions(axial compression,internal rotation and three-point bending)that have the greatest effect on bone stress were obtained.3.Three-dimensional finite element analysis of external fixation scaffold for Type A fracture of distal humerus.The Von Mises equivalent stress nephogram and the Displacement nephogram of the whole structure of the humerus were obtained by using the finite element method to simulate and analyze the combined external fixation stent group of the distal humerus type A fracture under the effects of axial compression,internal rotation and three-point bending.Results:1.The three-dimensional geometric models of the left intact humerus and distal type A humerus fractures established in this study are highly realistic,providing a model basis for subsequent finite element analysis of this study and other related studies.2.Biomechanical studies were conducted on locking compression plate internal fixation(internal fixation group)and modular external fixation scaffold external fixation(external fixation group)of the three-dimensional finite element model of distal humerus type A fracture by finite element analysis.Three different biomechanical experiments were applied.Von Mises equivalent stress intensity,displacement value and stiffness value of humerus were observed and analyzed respectively under axial compression,internal torsion and three-point bending tests.The results are as follows:(1)Under the axial compression test,the peak value of the equivalent stress of the humerus in the internal fixation group is 9.041 MPa,the overall displacement is 0.041 mm,and the overall stiffness is 4878N/mm;In the external fixation group,the peak value of humerus equivalent stress was 8.871 MPa,the total displacement was0.047 mm,and the total stiffness was 4255N/mm.(2)Under the three-point bending test,the peak equivalent stress of the humerus in the internal fixation group was 4.796 MPa,the overall displacement was 0.008 mm,and the overall stiffness was 4038 N.m /°.In the external fixation group,the peak value of equivalent stress of humerus was 3.009 MPa,the overall displacement was 0.011 mm,and the overall stiffness was 2988 N.mm/°.(3)Under the internal rotation and torsion test,the peak value of equivalent stress of humerus in the internal fixation group was47.85 MPa,the overall displacement was 3.78 mm,and the overall stiffness was 3750N/mm.In the external fixation group,the peak value of equivalent stress of humerus was 29.664 MPa,the overall displacement was 5.132 mm,and the overall stiffness was 2727 N/mm.Conclusion:1.In this study,the three-dimensional finite element model of intact humerus and distal humerus type A fracture was successfully established,which has the advantages of high efficiency,flexibility and repeatability compared with traditional mechanical experimental methods.In addition,the complete humerus model can be repeatedly applied to other studies related to three-dimensional finite element analysis,and has the advantages of strong independence and high utilization.2.Von Mises equivalent stress intensity,displacement degree and structural stiffness of humerus,internal fixation and external fixation were observed and analyzed under three different biomechanical tests(axial compression,internal torsion and three-point bending).It was found that the humerus structures in the internal fixation group and the external fixation group were subjected to different stresses.The stress concentration occurred in the humerus nail hole,the joint between the plate and the screw,the joint between the Schanz needle and the clamp,and the joint between the connecting rod and the clamp.The humerus displacement under internal rotation and torsion test is more sensitive than that under axial compression and three-point bending test.The overall stiffness of the humerus in the external fixation group was lower than that in the internal fixation group.Compared with the internal fixation group,the overall stiffness of the humerus in the external fixation group was reduced by about 12.77%,26.00% and 27.28% under axial compression,internal torsion and three-point bending tests,respectively.From the perspective of structural stability,the structural stability of the internal fixation group is better than that of the external fixation group,but the theoretical calculation results show that the structural stability of the external fixation group can meet the external fixation needs of the distal humerus type A fracture during the rehabilitation period without weight-bearing state,and provide theoretical guidance for the clinical application of the installation and simplification of the modular external fixation scaffold for open fractures. |
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