Three-dimensional Finite Element Analysis Of Modified Threaded Kirschner Wire In The Treatment Of Ulnar Coronoid Process Fractures

Objective: To establish two kinds of three-dimensional finite element model of the ulnar coronoid process fractures(Regan-Morrey type II)after fixation by ordinary kirschner wire and modified threaded kirschner wire,using computer software to simulate the three conditions(pull-out simulation,Anti-horizontal displacement simulation,Anti-rotation displacement simulation)and perform finite element analysis,to analyze and compare the displacement variation and stress distribution of the coronoid process fracture block.In our study,we aimed to assess the performance of the modified threaded kirschner wire,and provide theoretical support for clinical treatment.Methods: We obtained the CT data after scanning the elbow joint of healthy adult volunteers with 128-slice spiral CT,used medical image editing and processing software Mimics 21.0 to image processing,and exported the data of ulnar models by reverse engineering software Geomagic Studio to produce the ulnar coronoid process fractures(Regan-Morrey type II)model.And imported the data into the Ansys19.2 software for grid subdivision.Used Unigraphics NX 10.0 software to establish the models of ordinary kirschner wire and the modified threaded kirschner wire,and imported these data into ANSYS Workbench with the ulnar coronoid process fractures model for contact analysis.To produce two postoperative fixation model of ulnar coronoid process fractures:The fixed ways were parallel fixation with two 1.2mm kirschner wire and two 1.2mm modified threaded kirschner wire respectively.Then,the three simulation conditions were calculated for the two fracture internal fixation models,it was the pull-out internal fixator simulation test,the anti-horizontal displacement simulation test,and the anti-rotation displacement simulation test.In this three simulated conditions,the load size was gradually increased,and the displacement variation and stress distribution of the ulnar coronoid process fracture(Regan-morrey type II)blocks were recorded respectively.After mises stress nephogram were produced,we compared and evaluated the images.Results: In the first working condition(pull-out internal fixator simulation test): the loading range was 0-600 N,and the displacement of each group was without obvious fluctuation relatively.In the fixed model of 1.2mm ordinary kirschner wire,the displacement of the fracture block changes was larger,and the maximum displacement occurred in the 600 N load,which was 3.96 mm,and the maximum stress was 93.2Mpa.The maximum displacement of 1.2mm modified threaded kirschner wire group was 0.20 mm,and the maximum stress was 177.6Mpa.In the second working condition(anti-horizontal displacement simulation test): the loading range was 150-600 N,and the displacement of each group was without obvious fluctuation relatively.The displacement of 1.2mm kirschner wire group was larger,with the maximum value of 0.55mm;the 1.2mm threaded wire group was smaller,with the maximum value of 0.05 mm.In the stress change curve,when the load was constant,the stress on the fracture block of the 1.2mm threaded wire group was always kept the maximum,and the maximum stress(573.7Mpa)occurred at 600 N.The 1.2mm kirschner wire group was the smaller one,and the maximum stress(199.2Mpa)occurred at 600 N too.In the third working condition(anti-rotation displacement simulation test): the load range was 100-400 N,and the displacement of each group was without obvious fluctuation relatively.In the whole process of displacement and stress changes,the figure of the kirschner wire group were all larger than those of the modified threaded wire group.And the maximum value occurred at 400 N,when the process of displacement was 3.75 mm and the stress was 332.2Mpa.The maximum of threaded wire group was 0.25 mm and 225.6Mpa.From the Mises stress diagram by the three working conditions,we found that the stress distribution of the 1.2mm modified threaded wire group was slightly concentrated compared with that of the 1.2mm kirchner wire group.Conclusion: 1.The three-dimensional finite element model of ulnar coronoid process fractures(Regan-Morrey type?)and 1.2mm modified thread kirschner wire are established successfully.2.The 1.2mm modified kirschner wire group has better stability,better overall performance,and the stress distribution is concentrated slightly in the fixation of ulnar coronoid process fractures(Regan–Morrey type?)than the 1.2mm ordinary kirschner wire group.3.This study confirme the feasibility of modified threaded kirschner wire in the treatment of ulnar coronoid process fractures,and three-dimensional finite element analysis technology can provide strong theoretical support for the production of finished products and future clinical input research.