松质骨表观密度和弹性模量间关系的均匀化理论模型

本文利用理想化特征胞元模型对松质骨的刚度进行了研究,提出了松质骨的二级微结构均匀化模型,考虑了骨小梁中的微结构的影响。结果表明,松质骨的弹性模量与表观密度间接近线性关系,二级均匀化松质骨模型较各向同性骨小粱松质骨模型计算出的结果偏高。     

各向异性松质骨弹性性能有限元分析

骨质疏松会导致松质骨细化从而降低松质骨力学性能。为了评估椎体松质骨的力学特性,文中采用有限元参数化建模,利用十四面体模型模拟棒状小梁骨的微结构,对各向异性松质骨的弹性性能进行了计算分析。通过控制输入参数Tb.Th、Tb.Sp、E0模拟不同骨质疏松程度的松质骨。计算结果表明,松质骨模量与骨体积分数呈平方律关系;随着各向异性比的增加,松质骨纵、横向模量间的比值呈线性增加,而横向两个模量保持基本一致。结果说明该微结构模型较好地反映了松质骨的横观各向同性性质,并能较好地反映受载松质骨的应力分布。     

松质骨表现密度和弹性模量间关系的均匀化理论模型

本文利用理想化特征胞元模型对松质骨的刚度进行了研究，提出了松质骨的二级微结构均匀化模型，考虑了骨小梁中的微结构的影响，结果表明，松质骨的弹性模量与清观密度间接近线性关系，二级均匀化松质骨模型较各向同性骨小梁松质骨模型计算出的结果偏高。     

跟骨、月骨、头状骨松质骨粘弹性实验研究

研究了跟骨、月骨、头状骨松质骨的粘弹性力学性质。对跟骨松质骨纵向、横向、4 5°方向和月骨、头状骨松质骨进行压缩应力松弛、蠕变实验。得出了跟骨松质骨纵向、横向、4 5°方向和月骨松质骨、头状骨松质骨压缩应力松弛、蠕变数据和曲线。用回归分析的方法处理实验数据 ,得出了归一化应力松驰函数 ,蠕变函数及曲线。实验结果表明跟骨松质骨纵向压缩应力松弛、蠕变量均大于横向和 4 5°方向 ;头状骨松质骨初始蠕变量大于月骨松质骨 ,月骨与头状骨 2 h内蠕变量、松弛量差异并不显著。     

股骨颈松质骨拉伸蠕变实验研究

研究了正常国人新鲜尸体股骨颈松质骨的拉伸粘弹性力学性质.对股骨颈松质骨纵向、横向、45°方向试样进行拉伸蠕变实验.得出了股骨颈松质骨三个方向的蠕变数据和曲线.对实验数据进行归一化处理,用指数一元回归分析的方法处理数据,得出了归一化蠕变函数及曲线.实验结果表明,股骨颈松质骨纵向组蠕变量均大于横向组和45°方向组,股骨颈松质骨为各向异性材料.     

松质骨细观分析及破坏机理的实验研究

本文对人胜骨近段的松质骨的变形破坏机理进行了实验和理论分析：在对松质骨力学性能实验及对进行了拉伸扫描电镜观察实验,拍摄的松质骨在不同受力载荷级别下原位观察SEM照片和断口SEM照片,可从细观的角度探讨松质骨的变形和破坏现象。在此基础上运用细观力学模型对松质骨压缩及拉伸的力学行为进行了分析,得出了弹性模量与相对密度的关系,与实验结果基本吻合。松质骨细观分析及破坏机理的实验研究@郭玉明$太原理工大学!太原030024 @朱健$太原理工大学!太原030024 @赵兴国$太原理工大学!太原030024 @段荣$太原理工大学!太原0…     

基于超声背散射信号分析松质骨中的声阻抗

采用背散射法,研究用声阻抗评价松质骨状况.对松质骨中的超声散射特性进行了分析和讨论,并将分析结果和Faran理论模型进行比较分析;最后对理论和实验所得的牛胫骨、人离体跟骨和人在体跟骨松质骨中的声阻抗分布进行了分析讨论.结果表明松质骨中的声阻抗随入射频率的增加而非线性的增加,理论和实验结果是一致的.当患有骨质疏松时,松质骨密度将减小,因此,与健康松质骨中的声阻抗相比,患骨质疏松松质骨中的声阻抗较小.     

胞元结构形式、材料性质对松质骨力学性能的影响

将均匀化理论与有限元方法相结合 ,讨论了骨小梁的弹性模量、泊松比和构成松质骨微结构的形式对松质骨力学性质的影响。结果表明微结构的形式和固体体分比确定时 ,松质骨的弹性模量与骨小梁弹性模量之间存在着确定的数量关系 ;当微结构的固体体分比较小时 ,骨小梁的泊松比对松质骨的弹性模量几乎没有影响。讨论了微结构形式对松质骨弹性模量的影响。     

国人股骨下端松质骨力学性质实验研究

对正常国人新鲜尸体股骨下端松质骨的拉伸、压缩、扭转、剪切、弯曲、冲击等力学性能进行实验研究,得出了股骨下端松质骨纵向的拉伸、压缩破坏载荷、强度极限、弹性模量,扭转破坏扭矩、扭转剪切强度极限,扭转剪切弹性模量,剪切破坏载荷、剪切强度极限,弯曲破坏载荷、弯曲强度极限,冲击功、冲击韧性指标.对松质骨的取样方法及松质骨拉伸,扭转试样固定装夹方法进行探讨.对股骨下端松质骨的力学性质进行分析讨论.     

股骨头内松质骨空间分布和力学性能变化有限元分析

目的应用有限元方法研究不同加载强度和偏轴角对股骨头内松质骨空间分布和力学性能变化的影响。方法基于断层磨削后扫描、计算机三维重建的方法建立得到股骨近端骨结构三维模型,按照与主压力小梁方向成0°、15°、45°分别选取相同大小的松质骨试件。计算试件的三维空间结构参数,应用有限元分析方法模拟单轴压缩试验,观察松质骨试件应力、应变分布,探讨不同加载强度和离轴角度对松质骨生物力学性质的影响。结果基于建立的人股骨头内松质骨三维有限元模型,模拟了松质骨试件单轴压缩试验,发现不同加载强度和偏轴角度在松质骨试件中≥5 000με(微应变)的松质骨比例存在统计学差异(P0.05)。结论股骨头内松质骨小梁空间分布与力学适应性密切相关。结构与功能的不相适应降低了股骨头内部松质骨的生物力学性能,反复不良刺激引起的骨重塑、改建可能在股骨头坏死中起着重要的作用。     

基于混合物理论的骨组织应力松弛效应分析

目的 研究骨组织在给定位移下的应力松弛响应，为骨组织粘弹性性质实验研究提供参考。方法 引入基于混合物理论的现代多孔介质模型来研究骨组织在外界刺激下的流固耦合效应，采用Laplace变换技术求解控制方程。结果 得出了一维应力松弛解析结果，算例与实验结果进行了比较。结论 松质骨呈现的表观粘弹性行为以及能量耗散性质与松质骨中流体组分的扩散和流动之间具有很大的相关性。     

The dependence between the strength and stiffness of cancellous and cortical bone tissue for tension and compression: extension of a unifying principle

A strong positive correlation between the apparent ultimate strength and stiffness of bone tissue that can be expressed by a unified relationship has been observed for cortical bone in tension and low-density cancellous bone in compression. For practical purposes, the existence of a relationship between strength and stiffness is significant in that bone stiffness can be measured in vivo using non-invasive methods. It is generally accepted that bone strength is greater in compression than in tension whereas there is no substantial evidence that bone stiffness in compression is different from that in tension. This might suggest that compressive strength would relate to the stiffness, if at all, in a way that is different from tensile strength. In order to examine similarities and differences in the way strength is associated with stiffness between modes of loading and tissue type, we tested equine cortical bone and bovine cancellous bone in compression and examined these data together with previously reported data from compression testing of human cancellous bone as well as tensile testing of cortical bone from various sources. We have found for cortical bone that (i) the sensitivity of strength to stiffness is the same for tension and compression (p>0.75, ANCOVA), and (ii) the difference between the magnitudes of compressive and tensile strength for cortical bone is the result of an additive, rather than a multiplicative factor (52.1 MPa after adjusting to 1 microstrain/s, p<0.0001, ANOVA). High-density bovine tibial cancellous bone, on the other hand, has a steeper slope for its compressive strength-stiffness relationship than that for cortical bone and human cancellous bone, resulting in a transitional relationship between compressive strength and stiffness for a range of bone types and densities. Based on the current results and previous work, it is suggested that the offset strength in the compressive strength-stiffness relationship may be a direct manifestation of the difference between the compressive and tensile strengths of the bone material that constitutes the building blocks of the bone structure. Deviation of high-density cancellous bone compressive behavior from the other bone types and densities is attributed to stress distribution differences between the bone types.     

车-人碰撞事故中行人胫骨撞击响应的二维数值分析

目的基于两相多孔弹性胫骨模型,建立一种车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法。方法选用健康成年男性胫骨行CT分层扫描,结合数值插值方法获得胫骨的结构参数;在两相饱和多孔弹性理论的框架内,建立胫骨动力学控制方程组;采用自行开发的流-固耦合两相多孔介质有限元数值分析程序,数值模拟小汽车车头从侧向撞击行人下肢的动力学过程,并计算撞击载荷作用下0-200ms内行人胫骨的动力学响应。结果胫骨的弯曲变形主要集中在撞击载荷作用的区域;胫骨骨干上节点107处的侧向位移响应,约在75ms时刻出现峰值位移（-6mm）,对撞击载荷有明显的时间滞后;胫骨骨干上单元E77中心处的轴向应力响应,约在30ms时刻出现峰值应力（140MPa）,对撞击载荷也有明显的时间滞后。结论本研究所建立的对车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法,能够近似地模拟胫骨撞击区的弯曲变形、侧向位移响应和轴向应力响应以及胫骨中骨髓流体组分对骨架固体组分动力学特性的影响。下一步研究将在现有初步结果的基础上提高胫骨动力学模型的生物仿真性。     

基于显微CT的骨微观三维变形场测量系统的研究

目的初步构建一套集成显微CT与力学加载装置的测试系统,结合数字体相关技术(digital volume correla-tion,DVC)实现骨组织内部微观三维变形场的测量。方法选用微型力学加载装置进行单轴压缩试验,维持载荷不变的同时对试样进行CT扫描;采用DVC方法对连续CT图像序列进行相关匹配和搜索计算,测量载荷变化前后试样内部结构沿三维方向的微观位移值;通过零位移重复扫描和刚体平移评价该系统的测量精度及准确度;利用该系统测试牛松质骨块的三维位移场分布。结果零位移重复扫描结果显示该系统测量加载方向的位移准确度最高,测量精度低于CT扫描分辨率的1/10;刚体平移结果显示计算位移标准差为0.001～0.002μm;松质骨块测试区域在600 N载荷作用下沿加载方向的微观位移范围为100.35～110.25μm,位移场呈现多层逐级分布。结论该系统能够满足数字体相关法测量位移的准确度及精度要求,能够实现骨组织内部微观结构的三维变形场测量,可以作为进一步研究骨组织内部变形分布与结构成分响应关系的测量平台。     

Oscillatory Pressurization of an Animal Cell as a Poroelastic Spherical Body

The analytical solution of a spherical poroelastic body under an oscillatory hydrostatic pressurization is obtained. This solution is then parameterized and interpreted in terms of a spherical animal cell with the cytoskeleton serving as the solid phase. It is found that for a cell with free or nearly free membrane leakage (such as in the case of an osteocytic cell body), the induced pore fluid pressure amplitude near the center of the cell exceeds the amplitude of the applied pressure by 50% if the loading frequency falls near that of normal human gait (1 Hz). A parametric analysis shows that the leakage coefficient is proportional to the intrinsic permeability ratio between the boundary and the bulk matrix. The physiological implication of the solution is further interpreted and discussed through an anatomical analysis of two representative cellular entities under compression: a chondrocyte and an osteocytic cell body. Finally, through a comparison between the characteristic time of gait and the characteristic pore fluid pressure relaxation times of various fluid-saturated entities in the body (such as a tumor, the brain, the cortical bone, the trabecular bone, and the cartilage, etc.), it is found that the gait-induced pore fluid transport seems to be important only in deeply buried cells and the mineralized cartilage.     

Poroelastic Evaluation of Fluid Movement Through the Lacunocanalicular System

A poroelastic lacunocanalicular model was developed for the quantification of physiologically relevant parameters related to bone fluid flow. The canalicular and lacunar microstructures were explicitly represented by a dual-continuum poroelastic model. Effective material properties were calculated using the theory of composite materials. Porosity and permeability values were determined using capillaric and spherical-shell models for the canalicular and lacunar microstructures, respectively. Pore fluid pressure and fluid shear stress were calculated in response to simulated mechanical loading applied over a range of frequencies. Species transport was simulated with convective and diffusive flow, and osteocyte consumption of nutrients was incorporated. With the calculated parameter values, realistic pore fluid pressure and fluid shear stress responses were predicted and shown to be consistent with previous experimental and theoretical studies. Stress-induced fluid flow was highlighted as a potent means of species transport, and the importance of high-magnitude low-frequency loading on osteocyte nutrition was demonstrated. This new model can serve as the foundation for future hierarchical modeling efforts that may provide insight into the underlying mechanisms of mechanotransduction and functional adaptation of bone.     

改变力学环境后松质骨胞元结构的预测

松质骨是骨的重要组成部分,结构疏松、多孔,由针状、片状骨小梁组成多种胞体,其结构称为胞元结构。正常生理状态下,骨质的形成与吸收呈平衡态,骨结构稳定,当骨所处的力学环境发生变化时,骨的结构形态也随之变化。松质骨细观结构数值模拟变化的力学环境与骨结构的关系目前未见报道,本文是采用带有生理限定应力的自适应生理模型与有限元相结合的方法,在力学环境发生变化后用计算机预测松质骨胞元结构;定量的研究了松质骨胞元结构从一种优化平衡态到另一种平衡态与其力学环境的关系,模拟了松质骨胞元结构的变化与力学环境的适应性。把这种骨结构预测从宏观水平提高到细观水平。     

Regulation of cyclooxygenase-2 in renal medulla

AIM: Renal medulla is a major site for production and action of prostaglandins (PGs). The renal medullary functions as well as structural integrity are in part dependent on PGs under certain physiological or pathophysiological conditions. The two COX isoforms, COX-1 (constitutive form) and COX-2 (inducible form) are both abundantly expressed in renal inner medulla at basal state, raising a question of which COX isoform may mediate the known functions of PGs in the region. As in many other cell types, COX-1 expression in renal medulla is unlikely subject to robust regulation. In contrast, COX-2 expression in renal medulla is markedly stimulated by chronic salt loading, dehydration and endotoxaemia in vivo. At cellular levels, the signalling pathways responsible for the COX-2 stimulation in renal medullary cells seem to involve both the mitogen-activated protein kinases and NF-kappa B. It is likely that in response to various insults that are detrimental to renal medulla, the induction of PG synthesis may become more dependent on COX-2 than COX-1, and this phenomenon may be relevant to the cytoprotective response against the insults.     

Mechanical characterization in shear of human femoral cancellous bone: torsion and shear tests

In order to investigate and compare the mechanical behaviour of human cancellous bone during different shear loading modes, two tests were performed to characterise human femoral cancellous bone in shear: a torsion test until failure and a shear test using a sharpened stainless steel tube. Paired cylindrical samples were core drilled from 12 human femoral heads, symmetrically with respect to the coronal plane and along the primary trabecular direction. The distal part of the sample was assigned to a torsion test and the shear test was performed on the proximal part along two perpendicular anatomical directions. Apparent densities and tissue densities were measured on both torsion and shear specimens. The mean torsion properties were shear modulus G, 289 (183) MPa, ultimate stress tau(torsion), 6.1 (2.7) MPa, ultimate strain gamma(ultimate), 4.6 (1.3)%, yield stress tau(yield), 4.3 (1.9) MPa and yield strain gamma(yield), 1.8 (0.3)%. Strong correlation was obtained between G and tau(torsion) (r'=0.853, p<0.001). These torsion properties were correlated with apparent density of torsion specimens showing, respectively: r'=0.713, p=0.005 and r'=0.671, p=0. 008. Properties from the shear test were invariable with regard to the two tested directions then isotropic ultimate shear stress and isotropic elementary shear stress, which represent the mean values of the two tested directions were, respectively, tau(shear), 10.0 (4. 5) MPa and tau(elem), 18.8 (6.1) MPa. Both shear stresses were correlated with apparent density of shear specimens: tau(shear), r'=0.564, p=0.045 and tau(elem), r'=0.636, p=0.024. Apparent densities for shear specimens were superior than for torsion specimens (p=0.06) and the comparison was the opposite for tissue densities (p=0.028), showing strong density gradients of cancellous bone in the femoral head. These torsion and shear tests which permit the evaluation of cancellous bone behavior under two different types of shear loading, may be performed on different human sites and the measured shear properties may be compared to structural properties of cancellous bone.     

Modeling Deformation-Induced Fluid Flow in Cortical Bone’s Canalicular–Lacunar System

To explore the potential role that load-induced fluid flow plays as a mechano–transduction mechanism in bone adaptation, a lacunar–canalicular scale bone poroelasticity model is developed and implemented. The model uses micromechanics to homogenize the pericanalicular bone matrix, a system of straight circular cylinders in the bone matrix through which bone fluids can flow, as a locally anisotropic poroelastic medium. In this work, a simplified two-dimensional model of a periodic array of lacunae and their surrounding systems of canaliculi is used to quantify local fluid flow characteristics in the vicinity of a single lacuna. When the cortical bone model is loaded, microscale stress, and strain concentrations occur in the vicinity of individual lacunae and give rise to microscale spatial variations in the pore fluid pressure field. Furthermore, loading of the bone matrix containing canaliculi generates fluid pressures in the contained fluids. Consequently, loading of cortical bone induces fluid flow in the canaliculi and exchange of fluid between canaliculi and lacunae. For realistic bone morphology parameters, and a range of loading frequencies, fluid pressures and fluid–solid drag forces in the canalicular bone are computed and the associated energy dissipation in the models compared to that measured in physical in vitro experiments on human cortical bone. The proposed model indicates that deformation-induced fluid pressures in the lacunar–canalicular system have relaxation times on the order of milliseconds as opposed to the much shorter times (hundredths of milliseconds) associated with deformation-induced pressures in the Haversian system.