正常人与骨质疏松患者胸腰椎三维有限元模型的建立及分析

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

目的:基于CT医学图像,建立骨质疏松患者的T11～L3的三维有限元模型,对其生物力学特性进行分析。方法:实验于2003-09/2004-02在上海大学生物力学研究所完成。选取骨质疏松症患者1例,女,65岁,骨密度值与正常人相比,T值=-2.68<-2.5。CT扫描证实无脊柱畸形或破坏。应用CT扫描技术、图形数字化方法获取胸腰段的三维坐标,利用ANSYS5.0有限元分析软件等工具建立骨质疏松患者胸腰段的三维有限元模型。结果:①L1椎体在轴向载存800N作用下的应力场分布表明,正常椎体皮质骨、松质骨、终板、纤维环、后部结构的平均应力值高于骨质疏松椎体(分别为1.786,1.542MPa;0.742,0.601MPa;0.839,0.608MPa;0.862,0.554MPa;0.424,0.308MPa)。②从椎体的剖面上观察,外面皮质骨应力较大,里面松质骨应力较小。椎体骨密质的应力集中在近椎弓根附近,松质骨的应力集中在与终板临近的中央部分,后部结构的应力分布不均匀,应力集中在椎弓根、峡部和小关节部分,而横突和棘的应力水平很低。胸腰椎的应力分布规律和人体正常椎体相似。骨质疏松椎体的应力分布规律与正常椎体应力分布相似,相同承载,不过应力比较低,负载规律相一致。两者的应力分布相似,就是数值不同而已。结论:应用三维有限元法分析骨质疏松椎体的力学特性是切实可行的并能获得独特的信息,结果可信。

AIM： To set up the three-dimensional（3D） finite element model of T11-L3 of osteoporotic patients on the basis of CT medical images, and analyze the biomechanical characteristics. METHODS： The experiment was conducted at Institute of Biomechanics, Shanghai University from September 2003 to February 2004. One patient aged 65 years with osteoporosis was selected, whose bone density value compared with normal people, T value=-2.68〈-2.5. The patient had no spinal deformity or demolish after CT scan. CT scan and graphics digital technique were used to obtain 3D coordinates of the thoracolumber spine, and the 3D finite element model was developed by using ANSYS5.0 finite element software and other tools. RESULTS： The stress distribution of L1 vertebral body under axial direction 800 N showed that the mean stress value of cortical bone, cancellated bone, end-flake, annular fibrosus and posterior Structure of normal vertebra was higher than the osteoporotic vertebral body （1.786, 1.542 MPa; 0.742, 0.601 MPa; 0.839, 0.608 MPa; 0.862; 0.554 MPa; 0.424, 0.308 MPa）. Observed from the cross section of vertebral body, the stress of outer cortical bone was greater compared with the inner bone. The stress of vertebral bone density focused on the nearly of lateral mass of vertebrae, while the stress of cancellated bone focused on the central part near the end-flake, the posterior structure distributed unevenly, which localized at lateral mass of vertebrae, isthmus and small joints and was low in processus transversus and spine. The stress distribution rules of thoracicolumber were similar to normal people. The stress distribution rules of osteoporotic vertebral body were similar to normal ones bearing the same weight, but lower than normal ones. The stress distribution had similar appearance, but the values were different. CONCLUSION： Using 3D finite element models method to analyze the mechanical trait of osteoporotic centrum is feasible, and can gain some unique information Moreover, the conclusions are credible.