髌骨钉钩固定髌骨下极横形骨折的有限元分析

Finite element model analysis of patella nail-hook fixation device for transverse inferior patella fractures

目的采用有限元分析方法建立髌骨下极横形骨折模型,比较髌骨钉钩、克氏针张力带、镍钛聚髌器固定的有限元分析数据,评估髌骨钉钩固定髌骨下极横形骨折的生物力学性能。方法对1名志愿者进行膝关节CT扫描,将髌骨图像数据经Mimics软件拟合后导入Geomagic Studio软件中建成数字模型,使用Pro Engineer软件建立髌骨下极横形骨折模型,再建立髌骨钉钩、克氏针张力带、镍钛聚髌器固定模型。采用有限元分析方法比较这3种固定模型的抗拉伸强度、抗扭转强度,以及屈膝30°、45°、90°受力状态下内固定物的力学性能和形变情况。结果髌骨钩钉固定模型的抗拉伸及抗扭转强度明显高于镍钛聚髌器固定模型与克氏针张力带固定模型,而镍钛聚髌器固定模型与克氏针张力带固定模型强度相差不大。髌骨下极横形骨折3种固定模型中内固定物均存在应力集中,应力大致集中在中部,向两端递减,但应力均小于材料屈服强度。屈膝30°、45°、90°时髌骨钩钉固定模型的骨折端最大应力最小,骨折端最大位移最小,内固定物最大应力与最大形变量最小。结论髌骨钩钉固定髌骨下极横形骨折可获得与克氏针张力带、镍钛聚髌器相当甚至更好的稳定性,同时髌骨骨折断端位移小,内固定物疲劳断裂风险更低,抗拉伸及抗扭转能力更强。

Objective To establish a transverse fracture model of the lower pole of the patella with the finite element analysis method,compare the finite element analysis data of fixation with patella nails,Kirschner wire tension bands,and nickel-titani⁃um patella concentrators,and evaluate the biomechanical properties of patella nails and hooks for the fixation of transverse frac⁃tures of the lower pole of the patella.Methods A knee CT scan was performed on a volunteer.The patellar image data was fit⁃ted by Mimics software and imported into Geomagic Studio software to build a digital model.The Pro Engineer software was used to build a transverse fracture model of the lower pole of the patella and the needle tension band,nickel titanium patella concentrator fixation model.The finite element analysis method was used to compare the tensile strength and torsional strength of the three fixation models,as well as the mechanical properties and deformation of the internal fixation device when the knee was flexed at 30°,45°,and 90°.Results The tensile and torsional strengths of the patellar hook and nail fixation model were significantly higher than those of the nickel-titanium patellar concentrator fixation model and the K-wire tension band fixation model,while the strength of the nickel-titanium patella concentrator fixation model and the K-wire tension band fixation model were different not much.In the three fixation models of the inferior pole transverse fracture of the patella,stress concentration existed in the internal fixator.The stress was roughly concentrated in the middle and decreased to both ends,but the stress con⁃centration was smaller than the yield strength of the material.When the knee was flexed at 30°,45°and 90°,the maximum stress of the fracture end of the patella hook and nail fixation model was the smallest,the maximum displacement of the fracture end was the smallest,and the maximum stress and maximum deformation of the internal fixator were the smallest.Conclu⁃sion Patellar hook nail fixation of transverse fractures of the inferior pole of the patella can achieve equivalent or even better stability than Kirschner wire tension bands and nickel-titanium patellar concentrators.It has stronger tensile and torsion resis⁃tance,and has broad clinical application prospects.