Department of Mechanical Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA, USA.
Department of Mechanical Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA, USA.
J Mech Behav Biomed Mater. 2018 Jun;82:18-26. doi: 10.1016/j.jmbbm.2018.03.013. Epub 2018 Mar 11.
A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales.
评估骨抗骨折能力的一个重要长度尺度是亚微观尺度，它由矿化胶原纤维（MCF）和纤维外基质（EFM）组成。尽管已经确定了亚微观尺度骨成分对骨抗骨折能力的贡献过程，但由于 MCF 和 EFM 个体性质的变化对亚微观机械响应的改变程度尚未确定。因此，本研究旨在使用一种新的有限元建模方法，定量研究单个 MCF 和 EFM 材料性能改变对亚微观尺度骨力学性能（弹性模量、极限强度和破坏阻力）的影响，该方法结合了具有三种不同取向的 MCF 三维网络以及 EFM 的显式表示。模型在横向（代表 MCF 分离）和纵向（代表 MCF 断裂）加载下进行评估。结果表明，所有取向在两种加载方向下亚微观尺度的表观弹性模量仅受 MCF 弹性模量变化的影响。MCF 分离和断裂强度主要取决于 EFM 和 MCF 的极限强度，而其他材料性能的影响较小。MCF 分离过程中的损伤程度随 EFM 的极限强度的增加而增加，随 EFM 的断裂能的增加而减小，而 MCF 的弹性模量的贡献最小。对于 MCF 断裂， MCF 断裂能的变化百分比与 MCF 弹性模量的变化百分比之间几乎呈线性关系。 MCF 的极限强度和弹性模量对 MCF 断裂能有中等至有限的影响。本研究的结果量化了在 MCF 断裂和分离过程中能量耗散过程可能发生的变化程度，相对于组织中单个成分的变化。这一新知识极大地有助于提高对亚微观尺度材料性能改变如何影响较大长度尺度的骨折过程的理解，这些改变可能是由于疾病、与年龄相关的变化和治疗引起的。
