Ali Davar, Sen Sadri
Ataturk University, Faculty of Engineering, Department of Mechanical Engineering, Erzurum, Turkey.
Ataturk University, Faculty of Engineering, Department of Mechanical Engineering, Erzurum, Turkey.
J Mech Behav Biomed Mater. 2017 Nov;75:262-270. doi: 10.1016/j.jmbbm.2017.07.035. Epub 2017 Jul 25.
Scaffold design necessitates the consideration of mechanical properties and fluid flow dynamics as the main factors in the development of such materials. The mechanical behavior of bone scaffolds is characterized by properties such as elastic modulus and compressive strength. In terms of fluid flow dynamics, within bone scaffolds, permeability is an important parameter that affects cells' biological activities, and flow-induced shear stress is used as a mechanical stimulant of cell growth. In this study, two scaffold architectures with gyroid and lattice-based rectangular unit cells were designed to analysis the effective elastic moduli, compressive strength, permeability and fluid flow-induced wall shear stress as functions of porosity. Six levels of porosity (65%, 70%, 75%, 80%, 85% and 90%) were assigned to the scaffold architectures, and 12 models were developed. Scaffold deformation under static loading, compressive strength based on von Mises criteria, pressure drop, and fluid flow-induced wall shear stress in the scaffolds were then determined by finite element analysis. In both the scaffold types, models with higher porosity exhibited lower mechanical properties. Under the same porosity, the lattice-based scaffolds exhibited a Young's modulus and a compressive strength higher than those achieved by the gyroid scaffolds. With reference to geometrical parameters and the derived pressure drop from the computational fluid dynamics (CFD) analysis, scaffolds permeability was calculated using Darcy's law. In both the scaffold architectures, high porosity increased permeability and decreased wall shear stress. In the same porosity, the lattice-based models exhibited higher permeability and lower wall shear stress than did the gyroid models. On the basis of the results on elastic modulus and permeability, the models that most effectively mimic the properties of cancellous bones were identified.
支架设计需要将机械性能和流体流动动力学作为此类材料开发中的主要因素加以考虑。骨支架的力学行为由诸如弹性模量和抗压强度等特性来表征。就流体流动动力学而言，在骨支架内部，渗透率是影响细胞生物学活性的一个重要参数，而流动诱导剪切应力则被用作细胞生长的一种机械刺激因素。在本研究中，设计了两种具有螺旋状和基于晶格的矩形单位晶格结构的支架，以分析有效弹性模量、抗压强度、渗透率以及作为孔隙率函数的流体流动诱导壁面剪切应力。为这两种支架结构设定了六个孔隙率水平（65%、70%、75%、80%、85%和90%），并建立了12个模型。然后通过有限元分析确定支架在静态载荷下的变形、基于冯·米塞斯准则的抗压强度、压力降以及支架中的流体流动诱导壁面剪切应力。在这两种支架类型中，孔隙率较高的模型表现出较低的力学性能。在相同孔隙率下，基于晶格的支架的杨氏模量和抗压强度高于螺旋状支架。参照几何参数以及从计算流体动力学（CFD）分析得出的压力降，使用达西定律计算支架渗透率。在这两种支架结构中，高孔隙率增加了渗透率并降低了壁面剪切应力。在相同孔隙率下，基于晶格的模型比螺旋状模型表现出更高的渗透率和更低的壁面剪切应力。基于弹性模量和渗透率的结果，确定了最有效地模拟松质骨特性的模型。
