胸腰段骨质疏松三维有限元模型的建立及临床应用

Establishment and analysis of thoracicolumbar spine three-dimensional finite element models in normal people and osteoporotic patients

目的:探讨利用螺旋CT建立骨质疏松腰椎三维有限元模型的高度数字化方法,为腰椎骨质疏松的生物力学试验提供标准模型。方法:一个有代表性的健康成年男性志愿者,范围从T11～L2,先行X线检查以排除可见的脊椎病变及损害。经螺旋CT沿横断面0.699mm层厚扫描,以jpg格式输出其断面图像并转入微机保存。利用三维重建软件Mimics建立T11～L2段正常脊柱骨性结构的三维模型,再经过自由造型系统进行表面光滑化处理及对0.699mm层厚引起的数据丢失予以修补。利用有限元软件Patran的前处理功能,在脊柱模型骨性结构的基础上,补充建立终板、椎间盘、髓核、前纵韧带、后纵韧带、黄韧带、棘间韧带、棘上韧带等结构。采用合适的材料性质和实体单元类型对模型进行智能有限元网格划分。结果:①正常腰段脊柱三维模型有限元网格划分结果:利用三维重建软件Mimics和有限元软件Patran成功进行正常腰段脊柱三维模型有限元网格划分。完整的脊柱胸腰段三维有限元模型包括共276580个四面体单元,8532个六面体单元,673个杆单元,总计共95219个结点。建立的模型负荷正常椎体的几何特性;②骨质疏松腰椎三维有限元模型的建立:利用有限元软件Patran的前处理功能,对不同组织的物理特性进行定义,皮质骨、终板、后部结构模量减少33%,松质骨减少66%,同时考虑髓核脱水,弹性模量增加1倍,符合真实的生物力学要求,真实模拟了骨质疏松椎体的材料特性,成功建立骨质疏松腰椎三维有限元模型。结论:建立的骨质疏松腰椎三维有限元模型接近真实的生物力学标本,是理想的研究骨质疏松腰椎生物力学的数字化模型,可应用于骨质疏松腰椎后凸成形术的评估。

Objective Established by spiral CT of lumbar spine osteoporosis highly three-dimensional finite element model of the digital approach for lumbar Biomechanical osteoporosis provides a standard model.Methods A sample of normal vertebral column T11～L2 from senile male was chosen and X-ray examination was made to eliminate the visible pathological changes and injury;CT scanning was made at 0.699 mm intervals and the slices were preserved in computer.Mimics graphics digital technique were used to obtain 3 D coordinates of the thoracicolumbar spine,and the 3 D finite element model was developed by using Patron finite element software.Results Finite element mesh division of three-dimensional model of vertebral column at normal lumbar segment：3-dimensional reconstructed software Mimics and finite software Patron were used successfully to perform finite element mesh division of three-dimensional model of vertebral column at normal thoracolumbar segment. There were 285 785 units and 95 219 nodes.Constructed three-dimensional finite element model and entity tissue were well similar in geometry. Construction of three-dimensional finite element model of osteoporosis：With the pretreatment function of finite element software Patrons,physical features of different tissues were defined.Elastic modulus of cortical bone,lamina terminals ,and back both reduced by 33%,And the cancellous bone reduced by 66%,which satisfied the real demand of biomechanics and simulated the material features of osteoporosis vertebral body.Three- dimensional finite element model of osteoporosis occurred at lumbar vertebra were constructed successfully.Conclusion The model is approximate to the natural biomechanical specimen and an ideal digital model for biomechanical research on biomechanical experiment of kyphoplasty.