人体椎间盘的一个力学模型

对人体椎间盘力学性质的深入研究,牦极大地有助于对椎间盘脱出进行治疗和预防。众所周知,椎间盘表现出粘弹性性质,椎间盘中的含水量对于控制材料的松弛特性起重要作用。本文采用从人体椎间盘中得到的试件,进行应力松弛实验。试件取自髓核和两个不同方向纤维环的外层,在不同的湿度下进行实验,得到了松弛控制曲线。根据实验数据,提出了一种定性椎间盘模型。这种模型可以考虑椎间盘的粘弹性性质,并可研究年龄,材料结构变化和含水量等对其性质的影响。结果发现:髓核     

前交叉韧带粘弹性特性的实验研究

目的 探讨前交叉韧带的力学性能和粘弹性行为与时间的变化规律，为研究人工韧带提供生物力学参数。方法 对正常国人新鲜尸体膝关节前交叉韧带进行系统的拉伸、应力松驰、蠕变实验，得出最大载荷、强度极限、最大应变、弹性模量等；还得出了应力松驰、蠕变实验数据和曲线，归一化应力松驰函数、蠕变函数数据和曲线。并得到7200s时的蠕变量和应力松驰量。结果 ①前交叉韧带在实验中表现出典型的松弛、蠕变现象，说明其粘弹性性质在膝关节运动中起着重要的缓冲作用。②最初600s时应力应变的变化幅度较大，之后应力缓慢下降，应变缓慢上升，前交叉韧带7200s时应力松弛量1．05Mp，蠕变量为6．82％。结论 前交叉韧带具有良好的粘弹性力学性质。其粘弹性力学行为是为了适应其所在解剖部位的功能需要。     

拇指掌指关节侧副韧带粘弹性的实验研究

研究正常国人新鲜尸体的拇指掌指关节侧副韧带的粘弹性力学性质,为临床提供生物力学参数。对拇指掌指关节侧副韧带进行拉伸应力松弛、蠕变实验。得出了拇指掌指关节侧副韧带的应力松弛、蠕变数据。对实验数据进行归一化处理,得出了归一化应力松弛函数、蠕变函数及曲线。以回归分析的方法处理实验数据,得出了回归系数。表明拇指掌指关节侧副韧带为粘弹性生物材料。     

半限制型人工颈椎间盘置换与植骨融合术后下颈椎生物力学的有限元分析

目的 研究Discover、Prodisc-C人工椎间盘置换术与植骨融合术后下颈椎活动度（range of motion, ROM）、椎间盘应力、韧带张力的生物力学特性以及植入假体力学性能的改变。方法 建立C5~6椎间盘退变3种手术方案：Discover、Prodisc-C人工椎间盘置换和自体髂骨植骨融合有限元模型,同时建立C4~7节段下颈椎原始模型。分析术后下颈椎C4~7节段在矢状面、冠状面及横断面上椎体的生物力学特性变化。结果 术后手术节段关节ROM变化：Discover模型增加12.7%~73.1%,Prodisc-C模型增加74%~98%,植骨融合模型下降55.8%~71.8%。Discover置换后上邻近椎间盘应力无明显增加,下邻近椎间盘应力在前屈、后伸、轴向旋转工况下减少33.2%~54.2%,囊韧带张力增幅比Prodisc-C置换后减少30%~40%。Discover假体最大应力（36.72 MPa）出现在前屈工况下,小于Prodisc-C假体的最大应力（42.66 MPa）。结论 人工椎间盘置换术可以保留手术节段的运动性能,Discover作为新一代人工椎间盘假体,在减少韧带负担和维持脊柱稳定性方面有所进步。研究结果可为颈椎前路融合手术和人工颈椎间盘置换术的临床研究提供理论依据。     

腰椎间关节扭转的三维非线性有限元模型

过去有人认为腰椎间盘的轴向扭转是椎间盘脱出的可能原因。本文作者利用三维非线性有限元模型,对扭转如何引起腰椎间关节破坏进行了研究。在模型中椎体由骨密质壳和骨松质核心、软骨终板以及后部附件等构成,纤维层假设由八个薄层组成,髓核用不可压缩流体来模拟。模型同时还考虑了所有七条脊椎韧带的作用。材料的力学性质都表现为线性,但考虑了运动和变形的几何非线性。本文检验了关节面和韧带的作用以及后部附件、椎间盘、韧带和椎体中的应力分布。在扭转的生理范围中,关节面承担百分这十到四十的扭矩。盘中的纤维力应     

椎间盘高度降低及退变对腰椎生物力学影响的有限元分析

目的：分析椎间盘高度降低及退变对腰椎活动节段生物力学的影响。方法：首先采用一种新型CAD方法精确构建腰椎L4-5，活动节段正常高度椎间盘（NHD）、单纯高度降低椎间盘（PHDD）、椎间盘高度降低合并严重退变（DHDD）三种有限元模型。垂直压缩载荷下，分别对3种有限元模型的生物力学参数进行测试。结果：椎间盘高度降低及退变对腰椎活动节段轴向移位、后外侧椎间盘膨出、纤维环纤维应力最大值有明显的影响，DHDD模型的椎体一终板界面应力分布与NHD和PHDD模型明显不同。结论：高度降低后椎间盘刚度明显增加，DHDD最不易发生内层纤维环纤维破裂，关节突关节间隙与轴向移位比值是决定椎间盘承载力大小的关键因素，退变椎间盘对压缩应力有明显分散传递作用。     

半限制型人工颈椎间盘置换与植骨融合术后下颈椎生物力学特性的有限元分析

目的研究Discover、Prodisc-C人工椎间盘置换术与植骨融合术后下颈椎活动度(range of motion,ROM)、椎间盘应力、韧带张力的生物力学特性以及植入假体力学性能的改变。方法建立C5~6椎间盘退变3种手术方案:Discover、Prodisc-C人工椎间盘置换和自体髂骨植骨融合有限元模型,同时建立C4~7节段下颈椎原始模型。分析术后下颈椎C4~7节段在矢状面、冠状面及横断面上椎体的生物力学特性变化。结果术后手术节段关节ROM变化:Discover模型增加12.7%~73.1%,Prodisc-C模型增加74%~98%,植骨融合模型下降55.8%~71.8%。Discover置换后上邻近椎间盘应力无明显增加,下邻近椎间盘应力在前屈、后伸、轴向旋转工况下减少33.2%~54.2%,囊韧带张力增幅比Prodisc-C置换后减少30%~40%。Discover假体最大应力(36.72 MPa)出现在前屈工况下,小于Prodisc-C假体的最大应力(42.66 MPa)。结论人工椎间盘置换术可以保留手术节段的运动性能,Discover作为新一代人工椎间盘假体,在减少韧带负担和维持脊柱稳定性方面有所进步。研究结果可为颈椎前路融合手术和人工颈椎间盘置换术的临床研究提供理论依据。     

终板凹陷角变化对腰椎运动节段生物力学影响的有限元分析

目的:研究终板凹陷程度变化对腰椎运动节段生物力学影响。方法:在以往建立的腰椎L4～5运动节段三维非线性有限元模型基础上,采用CAD方法精确构建三种不同终板凹陷角改变的有限元模型,有限元模型的椎间盘前凸角、小关节间隙等其余形态学参数及网格划分均保持一致。垂直压缩、屈曲、伸直、前后剪力5种载荷条件下,分别对三种有限元模型生物力学参数进行测试。结果:负载条件下,终板凹陷角增加、终板凹陷程度减小可导致终板-椎间盘界面应变减小,椎间盘刚度及髓核内压增加,椎间盘膨出、纤维环纤维张应力、纤维环基质应力、腰椎后部结构应力以及关节突接触力减小。结论:终板凹陷程度的减小增强了椎间盘对椎体的保护作用;同时可通过影响终板的形变减少对椎间盘的营养传递。     

前交叉韧带及其替代物粘弹性性质的实验研究

本研究采用新鲜成人膝关节标本，对前交叉韧带及其转换替代物（髌韧带、髂胫束）进行系统的粘弹性力学性质的实验研究，通过粘弹性力学模型的建立，推导前交叉韧带及髌韧带、髂胫束的本构方程，对韧带的蠕变和松驰现象进行系统的分析。结果表明，韧带的损伤与韧带的生理力学性质有关，髌韧带的粘弹性性质更接近前交叉韧带，关节内髌韧带转换比髂胫束为佳。     

膝关节前交叉韧带与内侧副韧带粘弹性实验研究

目的　研究了新鲜成人尸体膝关节前交叉韧带和内侧副韧带的粘弹性力学性质，为临床提供生物力学参数依据。方法　对前交叉韧带和内侧副韧带进行应力松弛，蠕变实验。结果　对实验数据进行归一化处理，得出了归一化应力松弛函数，蠕变函数，以回归分析的方法处理实验数据，得出了回归系数和拟合曲线。结论　内侧副韧带7200s应力松弛、蠕变量小于前交叉韧带。对实验结果进行分析讨论。     

Three-Dimensional Finite Element Models of the Human Pubic Symphysis with Viscohyperelastic Soft Tissues

Three-dimensional finite element (FE) models of human pubic symphyses were constructed from computed tomography image data of one male and one female cadaver pelvis. The pubic bones, interpubic fibrocartilaginous disc and four pubic ligaments were segmented semi-automatically and meshed with hexahedral elements using automatic mesh generation schemes. A two-term viscoelastic Prony series, determined by curve fitting results of compressive creep experiments, was used to model the rate-dependent effects of the interpubic disc and the pubic ligaments. Three-parameter Mooney-Rivlin material coefficients were calculated for the discs using a heuristic FE approach based on average experimental joint compression data. Similarly, a transversely isotropic hyperelastic material model was applied to the ligaments to capture average tensile responses. Linear elastic isotropic properties were assigned to bone. The applicability of the resulting models was tested in bending simulations in four directions and in tensile tests of varying load rates. The model-predicted results correlated reasonably with the joint bending stiffnesses and rate-dependent tensile responses measured in experiments, supporting the validity of the estimated material coefficients and overall modeling approach. This study represents an important and necessary step in the eventual development of biofidelic pelvis models to investigate symphysis response under high-energy impact conditions, such as motor vehicle collisions.     

非线性模型在椎间盘黏弹性特性分析中的应用

目的 构建变参数非线性模型,研究人体椎间盘在循环应变状态下的应力松弛特性。方法 采用变参数非线性模型结合椎间盘应力松弛和蠕变反应的实验数据,研究循环应变状态下椎间盘的应力松弛特性,比较线性与非线性模型在循环状态下椎间盘黏弹性特性的差异。结果 采用变参数非线性模型得出的循环模量和松弛系数在0.01Hz循环状态下与实验模型非常接近,得出的循环模量在0.1和1 Hz下也与实验值相近,但是得出的松弛系数在0.1和1 Hz下失真严重。结论 在压缩应变作用下椎间盘经历的是一个非线性的应力行为,非线性变参数模型更符合研究在循环应变下椎间盘应力松弛反应的需要。     

腰椎间盘突出症力学特征的仿真计算方法

目的建立腰椎间盘突出症力学特征的数值计算分析模型,为腰椎间盘突出症的力学机理提供一种检测评估方法。方法利用健康成人L4～5腰椎运动节段CT影像,采用Mimics 10.01医学图像处理软件和Geomagic10.0逆向工程软件分别建立L4～5腰椎运动节段的椎骨和椎间盘,并在Ansys软件中附加腰椎相关韧带及通过改变椎间盘突出后对应的材料属性,建立腰椎L4～5运动节段有限元模型,构建正常模型和腰椎间盘突出模型;运用有限元方法模拟正常椎间盘和突出椎间盘在轴向压力、前弯、侧弯、旋转和后伸5种载荷下的生物力学特征参数。结果椎间盘突出后,椎间盘的应力分布及传递载荷的能力改变,应力集中于纤维环后外侧;在相同的载荷情况下,突出的椎间盘的最大形变量比正常椎间盘的大;椎间盘突出模型的小关节突接触力比正常模型的小关节突接触力大。结论椎间盘突出后,椎间盘的承载功能下降,关节突的应力水平升高,小关节的负荷增加,从而导致腰椎稳度下降。     

兔髌韧带压缩力学性能

目的 研究不同应变率下韧带的压缩应力-应变关系,并构建本构模型,为韧带的损伤预估及替代材料的研 发提供参考。 方法 通过万能拉伸试验机测试兔髌韧带在不同应变率(0. 001、0. 01、0. 1、1 s-1 )下的压缩力学性能 和压缩松弛响应,并构建相应的本构方程。 结果 单轴无侧限压缩实验表明,随着应变率增加,30% 、40% 应变下的 应力和切线模量均明显增大。 相比于 Gent 模型,Fung 和 Ogden 模型更适用于拟合韧带压缩曲线(R2 >0. 99);采用 4 项 Prony 级数更适用于拟合韧带的松弛曲线(R2>0. 99)。 结论 兔髌韧带的压缩力学性能有显著的黏弹性响应, Fung 和 Ogden 模型可用于拟合韧带的压缩响应,4 项 Prony 级数可用于拟合兔髌韧带的压缩松弛响应。     

Evaluation of the role of ligaments, facets and disc nucleus in lower cervical spine under compression and sagittal moments using finite element method.

Cervical spinal instability due to ligamentous injury, degenerated disc and facetectomy is a subject of great controversy. There is no analytical investigation reported on the biomechanical response of cervical spine in these respects. Parametric study on the roles of ligaments, facets, and disc nucleus of human lower cervical spine (C4-C6) was conducted for the very first time using noninvasive finite element method.A three-dimensional (3D) finite element (FE) model of the human lower cervical spine, consisted of 11,187 nodes and 7730 elements modeling the bony vertebrae, articulating facets, intervertebral disc, and associated ligaments, was developed and validated against the published data under three load configurations: axial compression; flexion; and extension. The FE model was further modified accordingly to investigate the role of disc, facets and ligaments in preserving cervical spine motion segment stability in these load configurations. The passive FE model predicted the nonlinear force displacement response of the human cervical spine, with increasing stiffness at higher loads. It also predicted that ligaments, facets or disc nucleus are crucial to maintain the cervical spine stability, in terms of sagittal rotational movement or redistribution of load. FE method of analysis is an invaluable application that can supplement experimental research in understanding the clinical biomechanics of the human cervical spine.     

Viscoelastic properties of the cervical spinal ligaments under fast strain-rate deformations

The mechanical response of ligaments under fast strain-rate deformations is a necessary input into computational models that are used for injury assessment. However, this information frequently is not available for the ligaments that are routinely injured in fast-rate loading scenarios. In the current study, experiments were conducted at fast strain rates for the cervical spinal ligaments: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. Bone-ligament-bone complexes at three spine levels were harvested for mechanical testing. Displacement-controlled sub-failure uniaxial tensile tests were performed in both load-relaxation and sinusoidal conditions. A nonlinear (separable) viscoelastic model was used to examine the experimental data. An unexpected result of the modeling was that the instantaneous elastic functions could be approximated as linear for these strain rates. A five-parameter model was sufficient to characterize the ligament viscoelastic responses and had good predictive capacity under different applied loading conditions.     

A Surface–Regional and Freeze–Thaw Characterization of the Porcine Temporomandibular Joint Disc

The temporomandibular joint (TMJ) disc is a central element in several TMJ disorders. Tissue-engineered TMJ disc replacements may alleviate discomfort associated with TMJ disorders; however, prior to developing a replacement, a thorough understanding of the native disc must be attained. Toward this end, we developed an unconfined compression, incremental stress relaxation viscoelastic model which simultaneously incorporates the strain increment magnitude and total deformation in the stress relaxation solution. This multiple strain step model was fit to stress relaxation data from (i) 80 test sites from eight porcine TMJ discs for the purposes of a surface–regional characterization and (ii) 30 test sites from five porcine TMJ discs for the purposes of a freeze–thaw characterization. The model estimated viscoelastic parameters accurately and surface–regional variations were detected throughout the TMJ disc. Regionally, the medial and anterior regions have the largest relaxation moduli, and the posterior and anterior regions have the largest instantaneous moduli. The inferior surface was found to have higher instantaneous modulus values than the superior surface. Furthermore, material properties were retained over five freeze–thaw cycles. The results of this study allow for the creation of design and validation criteria for future engineering efforts and shed light on the disc’s role in TMJ function and dysfunction.