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1.
目的采用有限元仿真和实验对比分析关节软骨的承载机理和应力松弛效应。方法考虑关节软骨基质固相、孔隙液相和胶原纤维增强相,并综合考虑软骨分层结构以及关节软骨渗透率随固体基质膨胀率变化特性,建立关节软骨纤维增强多孔弹性有限元模型。基于该模型,应用ABAQUS软件和FORTRAN语言编程嵌套,对关节软骨无约束阶梯压缩进行有限元仿真。应用自行研制的生物力学性能测试系统,通过阶梯加载实验对生猪软骨有限元分析结果进行了实测对比。结果试件以0.45%/s应变速率阶梯加载时,在试件中心,液相可维持承载80 s左右,最大可承担近90%的总应力。结论基于纤维增强多孔弹性有限元模型的无约束阶梯压缩有限元分析可定量评价关节软骨的固、液两相承载能力随应变和时间的变化特性。结合软骨无约束压缩实验的仿真分析有助于更准确地评价软骨的力学性能。  相似文献   

2.
目的通过有限元仿真探究组织工程修复软骨缺损后缺损形状对修复区力学状态的影响。方法运用Abaous6.10软件建立软骨纤维增强的多孔黏弹性模型,包括软骨的两相结构、不同层区胶原纤维的作用、方向及渗透率的特征。在压缩载荷下分析缺损截面形状(矩形、梯形、圆弧形)和缺损深度(浅表层、中间层、深层、全层)对软骨修复区应力的影响。结果对于中间层缺损,矩形截面修复界面处的Mises应力最小,梯形次之,圆弧形最大。对于不同缺损深度,当弹性模量0.3 MPa时浅表层修复界面处应力最大,其他缺损深度的应力相差不大;当0.4 MPa时,应力由小到大依次为浅表层、中间层、全层、深层缺损;而在此之间时应力与泊松比大小有关。结论软骨缺损截面形状和深度对修复区应力都有影响,临床上可制作矩形缺损截面和不同的缺损深度,并选择合适的弹性模量和泊松比的软骨植入达到较好的修复效果。  相似文献   

3.
目的通过跨尺度计算,比较表层和深层软骨细胞的周边力学环境。方法建立软骨细胞两相力学模型,将软骨两相力学模型里的结果映射到细胞模型对应边界上作为边界条件。计算细胞模型得到软骨细胞的周边力学环境并进行分析。结果深层软骨细胞及周边应力比表层细胞的小一半,但都远小于细胞外的应力。软骨细胞周围基质(pericellular matrix,PCM)承担了细胞外的高应力,显著降低了细胞内的应力。两处细胞周围的间隙流动方向完全相反。结论软骨承载能力使深层软骨细胞附近应力显著降低,保护了深层软骨细胞及软骨下骨。PCM承担了细胞外围高应力,保证了软骨细胞生存工作所需的低应力环境。两处细胞周围相反的间隙流动支持了由表层关节液渗透及软骨下骨营养泵入构成的软骨双向营养供给学说。  相似文献   

4.
目的 研究胶原纤维束对软骨力学性能的影响,为临床医生指导早期软骨损伤患者的康复运动提供参考。方法 建立一种纤维增强的多孔黏弹性二维数值模型,考虑纤维分布、弹性模量、孔隙率和渗透率随软骨深度的变化关系。研究纤维束局部断裂和从表面渐进断裂以及纤维束尺寸对软骨力学性能的影响,获得软骨基质的最大主应变。结果 基质的最大主应变出现在软骨中层靠上某个位置,此位置不受纤维断裂模式和纤维束尺寸的影响。含较粗纤维束软骨的应变降低。结论 软骨中层易发生力学损伤,纤维束增粗可以降低基质的最大主应变,一旦纤维束发生断裂,较粗纤维束的软骨的基质最大主应变更大,使软骨更易发生损伤演化情况。  相似文献   

5.
目的:研究某型部分填充多孔介质麻醉蒸发器工作原理,并对其结构进行实际测量。利用Darcy扩展方程和N-S方程及能量和组分传递方程分别对多孔介质区域和纯流体区域建立数学模型,分析不同孔隙率下的平均传热传质速率随渗透率的变化。方法:文中采用运用CFD方法分析了多孔介质材料对麻醉蒸发器蒸发效果的影响,并且论述了在蒸发器多孔介质区域内麻醉药液与载气相遇、混合、蒸发过程的变化状况。假定麻醉药物蒸发雾滴与稀释气体存在热交换和动量的相互作用,忽略重力和剪切力在雾滴运动过程当中对其的影响效果,利用湍流随机跟踪模型追踪了在多孔介质区域中的气液两相流离散项麻醉药物蒸发雾滴的运动状况。结果:通过计算得到了不同状态下蒸发器多孔介质区域内气体速度场、密度、麻醉药物质量分数、药物浓度、比热变化,药物浓度场在与稀释气体混合过程中的变化以及麻醉药物挥发等结果。结论:数值模拟结果表明多孔介质特性、渗透率、孔隙率对麻醉蒸发器腔体内传热传质存在不可忽略的影响。  相似文献   

6.
关节软骨压缩特性的实验研究   总被引:4,自引:1,他引:3  
目的 探讨正常关节软骨的压缩特性。方法 将人的股骨头软骨制成圆柱形标本,分A、B、C、D四组。应用两种不同力学实验装置分别对A、B组标本加载,测定标本在受压后1秒末的应力和应变值,作出应力-应变曲线图。C组标本在恒定压力下受载,测量标本在受压后不同时间应变值的变化。D组标本受压后并保持一定的应变值,观察关节软骨受压后不同时间压力的变化。结果(1)正常关节软骨的瞬时应力-应变曲线呈非线性关系,应力越大,弹性模量值越高;两种装置的实验结果具有明显差异性。(2)关节软骨在恒定应力作用下,应变随时间的延长而增大,  相似文献   

7.
车-人碰撞事故中行人胫骨撞击响应的二维数值分析   总被引:1,自引:0,他引:1  
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。  相似文献   

8.
目的:实验研究表明。血管在周向与轴向两种单轴向拉伸作用下表现出不同的力学特性,本文通过对血管单轴拉伸的数值计算,给出分别适用于周向和轴向荷载的模拟方法。方法:基于超弹性本构模型对轴向和周向两种单轴拉伸作用下血管的应力一应变关系进行数值计算,并结合血管组织结构特点及模型适用范围对结果进行分析,同时通过数值计算对Holzapfel.Gasser-Ogden模型中的各向异性参数对结果的影响展开讨论。结果:计算结果显示单一使用各向同性超弹性应变势函数无法准确完整的模拟两种情况下的单轴拉伸实验,周向拉伸采用各向同性超弹性本构模型的数值结果较好的吻合实验,而轴向拉伸宜采用Holzapfel-Gasser-Ogden模型。Holzapfel。Gasser-Ogden模型中各向异性参数1描述血管中两组增强纤维主方向的分散程度,y值越大即纤维平均主方向与轴向加载方向夹角越小,在外荷载作用下越容易使得纤维旋转到荷载方向;参数K描述血管中每组增强纤维主方向上纤维的分散程度。K值越大,纤维在基体中分散越广泛,材料性子越接近纤维,宏观表现越硬。结论:本文基于超弹性本构模型对轴向和周向两种单轴拉伸作用下血管的应力应变关系进行数值计算,提出分别用多项式形式的各向同性超弹性本构模型数值计算周向荷载作用下应力应变关系、Holzapfel-Gasser-Ogden各向异性超弹性本构模型数值模拟轴向荷载下力学性质,数值结果与实验吻合较好,为心血管系统的数值模拟提供指导,对血管系统的力学机制和临床研究具有重要意义。  相似文献   

9.
目的 通过有限元方法探讨不同严重程度的Cam型髋关节撞击综合征(femoroacetabular impingement,FAI)关节软骨接触力学的变化。方法 建立正常髋关节及不同α角的 Cam型FAI髋关节三维有限元模型,计算行走、坐下、起立等日常活动下的关节软骨接触压力和应力。结果 完整步态周期加载过程中,不同α角的Cam型FAI软骨接触压力分布与正常髋关节接近,无高接触压力和Von Mises应力集中区域;坐下、起立加载过程中,Cam型FAI软骨接触压力均大于正常髋关节,且随α角的增加而增大,其接触区域主要位于髋臼缘前上方,局部出现过高压力和Von Mises应力集中。结论 Cam型FAI软骨接触力学变化的关键影响因素是运动方式,关节软骨过高的接触压力和Von Mises应力,可能是其引起软骨退变并最终导致骨性关节炎的力学原因。  相似文献   

10.
目的研制一种血管张应力体外加载装置,研究弹性基底(硅胶片)上的张应力、张应变分布。方法基于基底形变加载技术,研制一种接近人体血液动力学环境的血管张应力体外加载装置。利用装置中的摄像机拍摄硅胶片拉伸前后硅胶片网格点的图像并转化为数字图像,使用Matlab软件对网格点的位置特征进行计算,从而得到硅胶片的应变分布。利用万能材料试验机对硅胶片进行实验和计算得到硅胶片的力学参数,根据力学参数建立有限元模型,并对硅胶片的张应力、张应变分布进行模拟计算。将实验结果和模拟结果进行比较。结果有限元结果和实验结果基本一致,张应力、张应变的最大值均出现在加载点处,中间区域应力、应变较为均匀。硅胶片中间60%面积区域可视为均匀应变场。结论研究结果可为后期血管壁内皮细胞的动态培养以及细胞力学研究提供实验技术。  相似文献   

11.
The equilibrium depth-dependent biomechanical properties of articular cartilage were measured using an ultrasound-compression method. Ten cylindrical bovine patella cartilage-bone specimens were tested in compression followed by a period of force-relaxation. A 50 MHz focused ultrasound beam was transmitted into the cartilage specimen through a remaining bone layer and a small hole at the centre of a specimen platform. The ultrasound echoes reflected or scattered within the articularcartilage were collected using the same transducer. The displacements of the tissues at different depths of the articular cartilage were derived from the ultrasound echo signals recorded during the compression and the subsequent force-relaxation. For two steps of 0.1 mm compression, the average strain at the superficial 0.2 mm thick layer (0.35 +/- 0.09) was significantly (p < 0.05) larger than that at the subsequent 0.2 mm thick layer (0.05 +/- 0.07) and that at deeper layers (0.01 +/- 0.02). It was demonstrated that the compressive biomechanical properties of cartilage were highly depth-dependent. The results suggested that the ultrasound-compression method could be a useful tool for the study of the depth-dependent biomechanical properties of articular cartilage.  相似文献   

12.
关节软骨结构和成分的细微变化都会导致软骨组织的退化,如骨关节炎,研究软骨的材料属性具有重要意义.本文基于瞬态超声技术实时观测关节软骨样品的渗透性膨胀过程,计算软骨在不同深度因膨胀产生的应变,并结合Narmoneva的三相模型提取其轴向弹性模量.结果显示,由于软骨组织膨胀引起的应变随深度变化而变化,深层组织的应变小,表层和中层组织的应变大.弹性模量也揭示了深层软骨的硬度(E1=12.20)明显比表层软骨硬度高(E2=0.15).研究结果显示,瞬态超声技术结合三相模型提供了一种定量研究软骨退化程度的方法.  相似文献   

13.
骨关节炎(osteoarthritis OA)是一种以关节疼痛和僵硬为特征的慢性退行性关节疾患,好发于老年人群。OA发病缓慢,病程较长,早期临床表现和组织学改变均不明显,限制了疾病的早期诊断与治疗。关节软骨微观结构决定了软骨宏观力学特性。软骨微观结构具有区域差异性,导致软骨的力学性能也具有区域依赖性,从软骨浅表区到深区软骨抗负荷、抗形变能力逐渐增加。然而,在OA病程发展过程中,软骨微观构成改变导致OA软骨抗负荷、抗形变能力降低。通过检测关节软骨的微观构成可以推测软骨的力学特性,反之检测软骨的力学指标可以了解软骨早期的微观改变,从而有助于了解OA的病程发展,便于疾病的早期诊断。综述近年来关节软骨在正常和急慢性损伤状态下力学性能的相关研究文献,阐述软骨结构与力学性能之间的关系,为OA的病程发展、早期诊断与治疗提供进一步理论依据。  相似文献   

14.
The material properties of articular cartilage are depth-dependent, i.e. they differ in the superficial, middle and deep zones. The role of this depth-dependent material inhomogeneity in the poromechanical response of the knee joint has not been investigated with patient-specific joint modeling. In the present study, the depth-dependent and site-specific material properties were incorporated in an anatomically accurate knee model that consisted of the distal femur, femoral cartilage, menisci, tibial cartilage and proximal tibia. The collagen fibers, proteoglycan matrix and fluid in articular cartilage and menisci were considered as distinct constituents. The fluid pressurization in the knee was determined with finite element analysis. The results demonstrated the influences of the depth-dependent inhomogeneity on the fluid pressurization, compressive stress, first principal stress and strain along the tissue depth. The depth-dependent inhomogeneity enhanced the fluid support to loading in the superficial zone by raising the fluid pressure and lowering the compressive effective stress at the same time. The depth-dependence also reduced the tensile stress and strain at the cartilage–bone interface. The present 3D modeling revealed a complex fluid pressurization and 3D stresses that depended on the mechanical contact and relaxation time, which could not be predicted by existing 2D models from the literature. The greatest fluid pressure was observed in the medial condyle, regardless of the depth-dependent inhomogeneity. The results indicated the roles of the tissue inhomogeneity in reducing deep tissue fractures, protecting the superficial tissue from excessive compressive stress and improving the lubrication in the joint.  相似文献   

15.
目的 获得滑动载荷作用下关节软骨不同层区的法向位移分布,探讨压缩应变、滑动速率和滑动次数对不同软骨深度法向位移的影响。方法 以新鲜猪关节软骨为研究对象,采用非接触式数字图像相关技术,对滑动载荷作用下软骨不同层区的法向位移分布进行研究。 结果 滑动载荷作用下,关节软骨表层的法向位移最大,深层的法向位移最小,中间层的位移介于二者之间;随着压缩应变的增大,沿软骨厚度方向的法向位移都增大,并且表层的法向位移增加幅度最大。滑动速率越大,软骨沿厚度方向的法向位移越小。在不同的滑动次数下,法向位移随滑动时间的进行都呈上升趋势;随着滑动次数的增加,不同滑动时间时的法向位移都增大,并且发现从第1次到第2次滑动时法向位移增大最明显。结论 滑动载荷作用下,软骨不同层区的法向变形有差异,不同层区的法向位移随着压缩应变、滑动速率和滑动次数的变化而变化。本研究可以为临床软骨疾病治疗和软骨缺损修复等方面提供依据,同时对人工软骨结构组成、人工构建、力学功能评价有重要意义。  相似文献   

16.
Collagen fiber orientations in articular cartilage are tissue depth-dependent and joint site-specific. A realistic three-dimensional (3D) fiber orientation has not been implemented in modeling fluid flow-dependent response of articular cartilage; thus the detailed mechanical role of the collagen network may have not been fully understood. In the present study, a previously developed fibril-reinforced model of articular cartilage was extended to account for the 3D fiber orientation. A numerical procedure for the material model was incorporated into the finite element code ABAQUS using the “user material” option. Unconfined compression and indentation testing was evaluated. For indentation testing, we considered a mechanical contact between a solid indenter and a medial femoral condyle, assuming fiber orientations in the surface layer to follow the split-line pattern. The numerical results from the 3D modeling for unconfined compression seemed reasonably to deviate from that of axisymmetric modeling. Significant fiber orientation dependence was observed in the displacement, fluid pressure and velocity for the cases of moderate strain-rates, or during early relaxation. The influence of fiber orientation diminished at static and instantaneous compressions.  相似文献   

17.
Micro-computed tomography can be used to analyze subchondral bone features below treated cartilage defects in animal models. However, standardized methods for generating precise three-dimensional (3D) volumes of interest (VOI) below curved articular surfaces are lacking. The aims of this study were to develop standardized 3D VOI models adapted to the curved articular surface, and to characterize the subchondral bone specifically below a cartilage defect zone in intact and defect femoral trochlea. Skeletally mature rabbit distal femurs (N?=?8 intact; N?=?6 with acute debrided and microdrilled trochlear defects) were scanned by micro-computed tomography. Bone below the defect zone (3.5 mm width, 3.6 mm length, 1 mm deep) was quantified using simple geometric rectangular VOIs, and an optimized 3D VOI model with an adapted surface curvature, the Rectangle with Adapted Surface (RAS) model. In addition, a 250-μm-thick Curved-RAS model analyzed bone at three discrete subchondral levels. Simple geometric VOIs failed to analyze ~17% of the tissue volume, mainly near the top of the curved trochlear ridges. The RAS models revealed that after debridement and drilling, only 31% of the original bone remained within the VOI and bone loss was mainly accounted for by surgical debridement. Adapted surface VOIs are better than simple geometric VOI shapes for quantifying structural features of subchondral bone below a curved articular surface. Structural differences between the bone plate and cancellous bone were best captured using the smaller, depth-dependent Curved-RAS model.  相似文献   

18.
Articular cartilage lesions, which can progress to osteoarthritis, are a particular challenge for regenerative medicine strategies, as cartilage function stems from its complex depth-dependent microstructural organization, mechanical properties, and biochemical composition. Fibrous scaffolds offer a template for cartilage extracellular matrix production; however, the success of homogeneous scaffolds is limited by their inability to mimic the cartilage's zone-specific organization and properties. We fabricated trilaminar scaffolds by sequential electrospinning and varying fiber size and orientation in a continuous construct, to create scaffolds that mimicked the structural organization and mechanical properties of cartilage's collagen fibrillar network. Trilaminar composite scaffolds were then compared to homogeneous aligned or randomly oriented fiber scaffolds to assess in vitro cartilage formation. Bovine chondrocytes proliferated and produced a type II collagen and a sulfated glycosaminoglycan-rich extracellular matrix on all scaffolds. Furthermore, all scaffolds promoted significant upregulation of aggrecan and type II collagen gene expression while downregulating that of type I collagen. Compressive testing at physiological strain levels further demonstrated that the mechanical properties of trilaminar composite scaffolds approached those of native cartilage. Our results demonstrate that trilaminar composite scaffolds mimic key organizational characteristics of native cartilage, support in vitro cartilage formation, and have superior mechanical properties to homogenous scaffolds. We propose that these scaffolds offer promise in regenerative medicine strategies to repair articular cartilage lesions.  相似文献   

19.
In this study, we present and characterize a fiber deposition technique for producing three-dimensional poly(ethylene glycol)-terephthalate-poly(butylene terephthalate) (PEGT/PBT) block co-polymer scaffolds with a 100% interconnecting pore network for engineering of articular cartilage. The technique allowed us to "design-in" desired scaffold characteristics layer by layer by accurately controlling the deposition of molten co-polymer fibers from a pressure-driven syringe onto a computer controlled x-y-z table. By varying PEGT/PBT composition, porosity and pore geometry, 3D-deposited scaffolds were produced with a range of mechanical properties. The equilibrium modulus and dynamic stiffness ranged between 0.05-2.5 and 0.16-4.33 MPa, respectively, and were similar to native articular cartilage explants (0.27 and 4.10 MPa, respectively). 3D-deposited scaffolds seeded with bovine articular chondrocytes supported a homogeneous cell distribution and subsequent cartilage-like tissue formation following in vitro culture as well as subcutaneous implantation in nude mice. This was demonstrated by the presence of articular cartilage extra cellular matrix constituents (glycosaminoglycan and type II collagen) throughout the interconnected pore volume. Similar results were achieved with respect to the attachment of expanded human articular chondrocytes, resulting in a homogeneous distribution of viable cells after 5 days dynamic seeding. The processing methods and model scaffolds developed in this study provide a useful method to further investigate the effects of scaffold composition and pore architecture on articular cartilage tissue formation.  相似文献   

20.
《Acta biomaterialia》2014,10(5):2065-2075
Articular cartilage lesions are a particular challenge for regenerative medicine strategies as cartilage function stems from a complex depth-dependent organization. Tissue engineering scaffolds that vary in morphology and function offer a template for zone-specific cartilage extracellular matrix (ECM) production and mechanical properties. We fabricated multi-zone cartilage scaffolds by the electrostatic deposition of polymer microfibres onto particulate-templated scaffolds produced with 0.03 or 1.0 mm3 porogens. The scaffolds allowed ample space for chondrocyte ECM production within the bulk while also mimicking the structural organization and functional interface of cartilage’s superficial zone. Addition of aligned fibre membranes enhanced the mechanical and surface properties of particulate-templated scaffolds. Zonal analysis of scaffolds demonstrated region-specific variations in chondrocyte number, sulfated GAG-rich ECM, and chondrocytic gene expression. Specifically, smaller porogens (0.03 mm3) yielded significantly higher sGAG accumulation and aggrecan gene expression. Our results demonstrate that bilayered scaffolds mimic some key structural characteristics of native cartilage, support in vitro cartilage formation, and have superior features to homogeneous particulate-templated scaffolds. We propose that these scaffolds offer promise for regenerative medicine strategies to repair articular cartilage lesions.  相似文献   

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