肱骨近端三维有限元模型的建立与生物力学分析

Construction of a three-dimensional finite element model of proximal humerus and related biomechanical analyses

目的 探索一种快速建立肱骨近端三维有限元模型的方法,并模拟生理状态下肱骨近端受力情况,分析应力分布特征. 方法 对1名正常成年男性肩关节进行64排螺旋CT扫描,获得连续断层影像,使用Dicom数据和Mimics17.0软件生成肱骨近端三维几何模型,通过有限元分析软件ALGOR进行网格划分、材料属性赋值生成有限元模型,约束边界条件,模拟生理状态下肱骨近端受力情况,分析肱骨近端有限元模型上的应力分布特征. 结果 建立的有限元模型可以在三维空间内任意旋转,便于各个角度进行观察,单元类型均为4节点,其中皮质骨单元数为9 346,松质骨单元数为25 732,总单元数为35 078,总节点数为6 819.模拟肩关节外展90°生理状态条件,对肱骨近端三维有限元模型施加600 N的轴向载荷,肱骨近端的受力从近端向远端逐渐增加,至肱骨干外侧达应力的峰值,此处最大应力值为9.8 MPa.此外,肱骨近端外科颈内下侧皮质区应力分布较集中,此区域应力最大值为5.2 MPa. 结论 本实验建立肱骨近端有限元模型的方法快速、简便.通过模型的建立和生物力学分析,明确了肱骨距和肱骨干外侧为应力集中区域,提示内固定治疗肱骨近端骨折时,应注意在保证肱骨干张力侧支持的条件下,注重外科颈内下侧皮质完整的重要性,恢复肱骨距的支撑.

Objective To investigate a method of rapidly constructing a three-dimensional finite element model of the proximal humerus and to characterize the state and distribution of stresses on the model under a physiological state.Methods A normal adult male volunteer was subjected to spiral 64-row CT scanning of the shoulder joints.The DICOM data were input into the Mimics to generate a three-dimensional geometric model of the proximal humerus.The three-dimensional model was input into the ALGOR to create a finite element model following meshing and material property assignment.In the finite element model,boundary conditions were constrained and axial loads applied to simulate a physiological state.Stress distribution and strain results on the finite element model of the proximal humerus were obtained for analyses.Results The established finite element model of the proximal humerus could be rotated arbitrarily for observation from any perspective in three dimensions.All the units had 4 nodes.The units of cortical bone were 9,346,and those of cancellous bone 25,732.The total unit number was 35,078,and the total node number 6,819.When an axial load of 600 N was applied in a physiological state of shoulder abduction of 90°,the stress at the proximal humerus increased from the proximal to the distal end,peaking at lateral regions of the huneral shaft （9.8 MPa Max） and the stress was emphasized at the calcar region of the cortical area （5.2 MPa max）.Conclusions The Mimics software provides a simple and rapid method to construct a three-dimensional finite element model of proximal humerus.Biomechanical analysis on the model shows stress at the proximal humerus is emphasized at the calcar region and lateral regions of the humeral shaft.This indicates that,in internal fixation of fractures of proximal humerus,locked plating in a lateral tension-band position should be done first and mechanical support to the inferomedial region of the proximal humerus seems to be important for maintaining fracture reduction.