Finite Element Analysis Of Comminuted Fractures Of The Mid-shaft Clavicle Fixed With Elastic Intramedullary Nail And Reconstruction Plate

Objective:To provide theoretical reference for clinical applications by analyzing the biomechanical properties of comminuted mid-shaft clavicular fractures fixed with elastic intramedullary nail and reconstruction plate through finite element analysis(FES).Methods:Based on the CT image of the clavicle,the three-dimensional model of the clavicle was established by using Mimics software and Geomagic Studio software.Two models of internal fixation including elastic intramedullary nail and reconstruction plate were established by using SolidWorks 2017 software.Then the finite element model of normal clavicle was established and compared with the data of previous in vitro experiments to verify the effectiveness of the model.Based on the clavicle model,four models of comminuted fractures of the mid-shaft clavicle were generated(butterfly fracture model with 5mm bottom and height,multi-segment fracture model with 5mm width,butterfly fracture model with 10 mm bottom and height and multi-segment fracture model with 10 mm width),then,8 models of comminuted fractures of the mid-shaft clavicle fixed with elastic intramedullary nail and reconstruction plate was simulated,the above 8 models were applied to the finite element analysis software Abaqus under the same boundary and load conditions,respectively,to simulate the stress distribution and comprehensive displacement of human body under axial load,vertical load and clockwise torsional load.Results:(1)Under the same loading condition,the maximum comprehensive displacement of the same fracture model is: fracture model fixed with elastic intramedullary nailing > fracture model fixed with reconstruction plate > non-invasive claviclar model.Under the two conditions of 200 N axial load and 200N·mm torsional load,the maximum comprehensive displacement of the elastic intramedullary nail group was similar to that of the reconstruction plate group,and was not significantly larger than that of the non-invasive model;but under the two vertical load conditions of 100 N and 200 N,the largest comprehensive displacement of the the same fracture model fixed with two kinds of internal fixation were significantly larger than that of the non-invasive model,especially in the elastic intramedullary nail group,and with the increases of vertical load(100N to 200N)or comminuted bone mass(5mm to 10mm),all showed significant increases,accordingly,the maximum stress of internal fixation also increased.(2)In the reconstruction plate fixation group,except for the 10 mm comminuted bone mass groups under 200 N axial load,the maximum comprehensive displacement of the butterfly comminuted fracture models is greater than that of the same width multi-segment fracture model under the other conditions;the maximum stress of butterfly comminuted fracture model was greater than that of the same width multi-segment comminuted fracture model except for 10 mm comminuted bone mass group under 200N·mm torsional load.(3)Under the three different loading conditions,stress concentration appeared at the fracture ends of the models fixed with elastic intramedullary nail,but the stress distribution was similar to that of the normal nondestructive clavicle model;In the models fixed with reconstruction plate,the stress distribution of clavicle under axial load is similar to that of the non-invasive claviclar model,while the stress distribution of the clavicle under vertical load and torsional load is obviously different with that of the non-invasive claviclar model,resulting in stress shielding of the reconstruction plate.Conclusion:(1)If the impact of vertical load can be reduced(such as the affected limb suspension),elastic intramedullary nail can meet the biomechanical needs of the mid-shaft clavicular comminuted fracture fixation,also can meet the biomechanical needs of moderate passive functional exercise in the early postoperative period.(2)When the elastic intramedullary nail was used to fix the comminuted fracture of the mid-shaft clavicle,the applied load can increase the stress between the fracture ends,correspondingly,the displacement of the fracture ends increases obviously due to the weak stability.(3)When the reconstruction plate is used to fix the comminuted fracture of the mid-shaft clavicle,its mechanical stability is weaker than that of the normal clavicle,however,the quality of reduction and fixation of the comminuted fragment is beneft to increase the postoperative mechanical stability of the fracture.