距骨颈骨折双螺钉固定力学稳定性的三维有限元分析

Three-dimensional finite element analysis of mechanical stability of double screw internal fixation for talar neck fracture

目的对距骨颈骨折后双螺钉内固定方法进行三维有限元分析,探究不同入路放置方式的双螺钉内固定方法的力学稳定性及骨折断面最佳的生物力学环境,为临床内固定物的选用提供可靠的力学论据。方法将获取的健康成年男性踝关节CT数据导入Mimics软件进行踝关节模型的三维重建,通过Geomagic软件对模型进行拟合曲面等处理后,将模型导入Solidwork软件分别建立距骨颈骨折模型及设计相应的螺钉内固定物,分别以前向后平行双螺钉、前向后交叉双螺钉、后向前平行双螺钉及后向前交叉双螺钉四种内固定与距骨颈骨折模型进行装配,继而在前处理软件Hypermesh 13.0中对其进行网格划分,最后导入Abaqus 6.14进行分析计算,探究不同固定方式下拉力螺钉的Von Mises应力分布和骨折断端应力分布及位移。结果在四组内固定骨折断端的位移云图及应力云图中,前向后平行和交叉双螺钉固定组骨折断端位移峰值分别为0.399 3 mm、0.418 6 mm,压力峰值分别为7.721 MPa、8.124 MPa。后向前平行和交叉双螺钉组固定骨折断端位移分别为0.418 3 mm、0.418 5 mm,骨折端压力峰值分别为4.848 MPa、5.692 MPa。在四种内固定的螺钉应力云图中,前向后平行和交叉双螺钉固定组的螺钉Von Mises应力峰值分别为45.11 MPa、50.18 MPa,后向前平行和交叉双螺钉固定组的螺钉Von Mises应力峰值分别为30.65 MPa、37.68 MPa。结论后向前平行双螺钉固定时骨折断面接触应力最小,螺钉受力最分散,峰值最小。在使用螺钉内固定时,后向前置钉方式优于前向后置钉方式,平行双螺钉固定所受应力优于交叉双螺钉固定。

The three-dimensional finite element analysis was done to analyze the mechanical stability of double screw internal fixation for talus neck fracture,the methods with different approaches and different placement methods as well as the optimal biomechanical environment of fracture section were discussed so as to provide reliable mechanical arguments for the selection of clinical internal fixators.Methods The acquired male adult ankle CT data were imported into Mimics for 3D reconstruction of the ankle joint model.After the model was fitted with the surface by Geomagic software,the model was imported into Solidwork software to establish the talus neck fracture model and the corresponding screw.The fixtures were assembled with the anterior-posterior parallel double screw,the anterior-posterior cross-double screw,the posterior-anterior parallel double screw,and the posterior-anterior cross-double screw,respectively.The model data were imported to Abaqus 6.14 for analysis and calculation,followed by the meshing pretreatment using software Hypermesh 13.0.The Von Mises stress distribution of the lag screw and displacement of the fracture end were observed under different fixation modes.Results In the displacement and stress cloud diagrams of the fracture ends of the four groups,the displacement peaks of the fractures of the anterior to posterior double-screw parallel and cross-fixed groups were 0.399 3 mm and 0.418 6 mm,and the peak pressures were 7.721 MPa and 8.124 MPa,respectively.The displacement peaks of posterior to anterior double-screw parallel and cross-groups were 0.418 3 mm and 0.418 5 mm,the fracture end peak pressures were 4.848 MPa and 5.692 MPa,respectively.In the screw stress cloud diagram of the four internal fixation modes,the Von Mises stress peaks of the anterior-posterior parallel screw group and cross-screw group were 45.11 MPa and 50.18 MPa,and those of the posterior-anterior parallel screw group and cross-screw group were 30.65 MPa and 37.68 MPa,respectively.Conclusion In the posterior-anterior parallel screw fixation,the fracture end has the lowest stress,and the screw has dispersive stress and the stress peak is the lowest,which is superior to other three groups.Therefore,the posterior-anterior screw is better than anterior-posterior fixation,and the parallel fixation is better than cross fixation.