THE DISTRIBUTION OF COLLAGEN-APATITE ORIENTATION IN BONE MICROSTRUCTURES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 这项工作描述了人类骨骼微结构的一个基本方面，与骨折的启动和阻止有关。它解决了接近骨细胞陷窝的基本组件的取向是否影响次级骨组织的微观生物力学。在一个新的次级骨粒模拟中，加入了关于胶原-磷灰石取向的新数据，以及先前关于远离楔周区域的胶原取向的数据，以研究取向如何与力学测试中的应变和应力有关。我们使用DataStar上的ABAQUS软件创建了一系列所谓的次级骨的有限元模型，次级骨是人类骨骼的基本单位，长度可达0.5毫米。这些模型包括模拟骨细胞陷窝的椭球体。模拟的腔隙数量在7到70个之间。骨陷窝的位置可以由操作者选择，也可以根据实验观察到的骨小梁中的分布进行分配。椭球体附近元素的机械性能模拟了我们在共聚焦显微镜下观察到的分离的板层样品中的胶原-磷灰石取向。我们已经完成了骨标本在拉伸和压缩下的实验力学行为的模拟，该行为与弹性阶段的胶原-磷灰石取向和孔洞的存在有关。对现有的胶原蛋白取向分布算法进行改进，避免了阶跃函数，使胶原蛋白取向在三维方向上保持连续性。这是为了增加模拟与实验观测的一致性。这是一个特别重要的点，因为取向分布的不连续性可能会产生错误的应变。将在PC上使用Maple软件来准备输入文件，以便ABAQUS软件在DataStar上运行。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This work characterizes a fundamental aspect of human bone micro-structure, pertinent to fracture initiation and arrest. It addresses whether orientation of elementary components proximate to osteocyte lacunae influences secondary osteon micro-biomechanics. New data at the perilacunar region concerning orientation of collagen-apatite, and prior data on collagen orientation away from the perilacunar region, were incorporated in a novel simulation of secondary osteon to investigate how orientation relates to strains and stresses during mechanical testing. We have created a series of finite element models, using Abaqus software on Datastar, of so-called secondary osteons, basic units of human skeleton which .measure up to 0.5 mm in length. The models include ellipsoids that simulate osteocyte lacunae. The number of the simulated lacunae ranges between 7 and 70. The positions of lacunae can be chosen by the operator or assigned to follow experimentally observed distributions in the osteon. The mechanical properties of the elements adjacent to the ellipsoids simulate the collagen-apatite orientation that we have observed in isolated lamellar specimens under confocal microscopy. We have completed the simulation of the experimental mechanical behavior of osteon specimens under tension and compression in relation to collagen-apatite orientation and presence of porosity during the elastic phase. The current algorithm for collagen orientation distribution will be improved to avoid step-functions and allow continuity of collagen orientation in three-dimension. This is to increase adherence of simulation to experimental observations. This is a particular important point because discontinuities in the orientation distribution may create erroneous strains. Maple software will be used on PC's to prepare the input files for Abaqus software to run on Datastar.