Boccaccio A, Vena P, Gastaldi D, Franzoso G, Pietrabissa R, Pappalettere C
Department of Mechanical and Management Engineering, Politecnico di Bari, Bari, Italy.
Proc Inst Mech Eng H. 2008 Oct;222(7):1023-36. doi: 10.1243/09544119JEIM296.
The aim of this work is to assess the fracture risk prediction of the cancellous bone in the body of a lumbar vertebra when the mechanical parameters of the bone, i.e. stiffness, porosity, and strength anisotropy, of elderly and osteoporotic subjects are considered. For this purpose, a non-linear three-dimensional continuum-based finite element model of the lumbar functional spinal unit L4-L5 was created and strength analyses of the spongy tissue of the vertebral body were carried out. A fabric-dependent strength criterion, which accounts for the micro-architecture of the cancellous bone, based on histomorphometric analyses was used. The strength analyses have shown that the cancellous bone of none of the subject types undergoes failure under loading applied during normal daily life like axial compression; however, bone failure occurs for the osteoporotic segment, subjected to a combination of the compression preloading and moments in the sagittal or in the frontal plane, which are conditions that may not be considered to occur 'daily'. In particular, critical stress conditions are met because of the high porosity values in the horizontal direction within the cancellous bone. The computational approach presented in the paper can potentially predict the material fracture risk of the cancellous bone in the vertebral body and it may be usefully employed to draw failure maps representing, for a given micro-architecture of the spongy tissue, the critical loading conditions (forces and moments) that may lead to such a risk. This approach could be further developed in order to assess the effectiveness of biomedical devices within an engineering approach to the clinical problem of the spinal diseases.
这项工作的目的是，在考虑老年人和骨质疏松症患者骨骼的力学参数（即刚度、孔隙率和强度各向异性）时，评估腰椎椎体松质骨的骨折风险预测。为此，创建了基于非线性三维连续体的腰椎功能脊柱单元L4-L5有限元模型，并对椎体的松质组织进行了强度分析。使用了一种基于组织形态计量学分析的、考虑松质骨微观结构的织物相关强度准则。强度分析表明，在正常日常生活中施加的负荷（如轴向压缩）下，没有一种受试者类型的松质骨会发生破坏；然而，对于骨质疏松节段，在矢状面或额面的压缩预加载和弯矩组合作用下会发生骨破坏，而这些情况可能不被认为是“日常”发生的。特别是，由于松质骨水平方向的高孔隙率值，会出现临界应力条件。本文提出的计算方法有可能预测椎体松质骨的材料骨折风险，并且可有效地用于绘制失效图，该图表示对于给定的松质组织微观结构，可能导致这种风险的临界加载条件（力和弯矩）。这种方法可以进一步发展，以便在工程方法中评估生物医学装置对脊柱疾病临床问题的有效性。
