McNamara B P, Cristofolini L, Toni A, Taylor D
Mechanical Engineering Department, Trinity College, Dublin, Ireland.
Clin Mater. 1994;17(3):131-40. doi: 10.1016/0267-6605(94)90136-8.
The aim of this study was to determine the validity with which the finite element method could model synthetic bone and thereby determine the appropriateness of such femur analogues for application in pre-clinical tests. The performance of these synthetic femora was compared with cadaveric bone when employing the same geometric and material definition protocols. A four-point bend loading configuration was selected for this analysis. Four synthetic femurs and an embalmed cadaveric bone were tested experimentally to determine the structural bending stiffness (k) for the diaphysis of these bones. A finite element (FE) model was generated and an analysis performed for each bone type to estimate the Young's modulus (E) required to obtain a model stiffness equivalent to that obtained experimentally. The estimated material elastic modulus in the FE model for the synthetic femur was found to be very similar to available data for this bone analogue. The estimated cadaveric bone modulus however was found to differ significantly from documented values for cortical bone. A theoretical analysis demonstrated the great sensitivity of the estimated modulus value to the accuracy of the geometric definition. The very low variability found in the experimental test on the synthetic bones together with their more regular geometry and the possibility of achieving greater accuracy in geometric definition was shown to enable the production of a valid FE model of this bone for an isotropic homogeneous material description. Conversely, the greater irregularity of geometry, together with the less obvious differentiation between the cortical and cancellous bone in the cadaveric specimen makes accurate geometric description of this bone very difficult. This fact, together with the uncertainty concerning the quality of the cadaveric bone and its viscoelastic response during mechanical testing, makes reproduction of its behaviour in a FE model a much more demanding task. It is suggested that this greater capability of reproducing the experimental behaviour of the synthetic bone makes them a very useful model for both experimental and numerical studies which involve in-vitro pre-clinical testing of implant design and stem-bone behaviour.
本研究的目的是确定有限元方法对合成骨进行建模的有效性，从而确定这种股骨类似物在临床前测试中应用的适用性。在采用相同的几何和材料定义方案时，将这些合成股骨的性能与尸体骨进行了比较。为此分析选择了四点弯曲加载配置。对四个合成股骨和一块防腐处理的尸体骨进行了实验测试，以确定这些骨头骨干的结构弯曲刚度（k）。生成了一个有限元（FE）模型，并对每种骨类型进行了分析，以估计获得与实验获得的刚度等效的模型所需的杨氏模量（E）。发现FE模型中合成股骨的估计材料弹性模量与该骨类似物的现有数据非常相似。然而，发现尸体骨模量的估计值与皮质骨的记录值有显著差异。理论分析表明，估计模量值对几何定义的准确性非常敏感。合成骨实验测试中发现的极低变异性，连同其更规则的几何形状以及在几何定义中实现更高精度的可能性，表明能够为各向同性均匀材料描述生成该骨的有效FE模型。相反，尸体标本中几何形状的更大不规则性，以及皮质骨和松质骨之间不太明显的区分，使得对该骨进行准确的几何描述非常困难。这一事实，连同尸体骨质量及其在机械测试过程中的粘弹性响应的不确定性，使得在FE模型中再现其行为成为一项要求更高的任务。建议合成骨在再现实验行为方面的这种更大能力使其成为实验和数值研究的非常有用的模型，这些研究涉及植入物设计和骨干行为的体外临床前测试。
