颈椎椎间盘退变对终板结构生物力学特性的影响

目的研究颈椎椎间盘对终板结构生物力学特性的影响。方法50节颈椎标本,采用Nachemson椎间盘分级标准将标本分为4组,正常组(n=22)、Ⅰ度退变组(n=10)、Ⅱ度退变组(n=9)、Ⅲ度退变组(n=9),对每一终板平面上20个特定的测试点进行压缩实验,直径2mm的半球形压头以003mm/s的速度垂直于终板平面下压2mm,由所得的力─位移曲线计算出最大压缩力及刚度,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果颈椎椎间盘退变可导致颈椎终板最大压缩力及刚度的显著性减小(P<001),且存在负相关关系(分别为rs=-0429,P<0001;rs=-0244,P<0001);上终板随着椎间盘退变的加重终板平面中央承力逐渐变弱,外周承力逐渐增强,下终板的力学分布无明显改变。结论颈椎椎间盘退变是影响终板结构生物力学特性的重要因素,在进行颈椎前路融合术时应警惕由于椎间盘退变引起的“植入物沉陷”。     

生物力学对椎间盘营养及其退变的影响

椎间盘退变的因素众多,生物力学和椎间盘营养是目前研究的热点。长期过高和过低的压力负荷均为椎间盘退变的病因之一,生物力可影响椎间盘营养途径,近年研究证实生物力学改变导致的椎间盘营养供应减少可能是启动椎间盘退变的关键因素。     

椎间盘退变生物力学的研究现状

在日常活动中腰椎间盘常常承受力学负荷。腰椎椎间盘内静水压平卧休息位最低(202．650～303．925KPa)，弯腰前屈抬重物时增高(接近3039．75KPa)。搬运重物的体力劳动者、长时间坐位工作者在病理学上椎间盘退行性改变显著；从事机床、卡车司机及搬运重物的职业是下腰痛及椎间盘突出的危险因素，且患椎间盘突出症的几率是一般成人3倍。     

颈椎前融合对颈椎退变的影响

本文探讨颈椎等合术退变加重的根本原因,以提高颈椎病患者的手相治疗效果。     

退变性椎间盘应力分布变化的有限元分析

【摘要】 目的：分析退变性腰椎间盘在不同生理载荷下应力分布的变化情况。方法：建立正常人体L3~S1三维有限元模型及L4/5椎间盘退变模型,导入Ansys软件进行分析,在L3椎体上表面施加500N压力模拟轴向压缩,施加10Nm的力矩模拟腰椎前屈、后伸、侧屈和旋转等各种生理载荷,测量不同载荷下正常与退变椎间盘不同部位的应力,分析退变椎间盘应力分布变化的情况。结果：正常椎间盘垂直载荷时椎间盘应力集中于椎弓根附近,应力最大的分区中压力为29.649N;各种屈曲位时,屈曲侧应力较高,分区中压力最高为59.514N,向对侧逐渐减少,拉力最高为32.686N。相同载荷下,退变椎间盘应力分布发生了变化,髓核压力由45.170~55.308N降至5.471~8.046N;纤维环压力增加,内层纤维环由80.379~95.923N增加至98.898~120.557N,中层纤维环由107.160~140.983N增加至118.549~156.827N,外层纤维环由160.872~204.867N增加至169.302N~216.298N。结论：椎间盘退变后其髓核和纤维环的应力分布会发生变化,在总应力变化不大的前提下,髓核所受应力明显减小,而纤维环所受应力则相应增加,尤以内层和中层纤维环为主。这可能是椎间盘突出和椎间盘源性腰痛的原因之一。     

有限元分析在颈椎生物力学研究中的应用

随着计算机技术的不断发展,骨科虚拟建模也越来越先进。有限元分析是研究颈椎功能、发病机制及选择颈椎疾病治疗方法的重要方法。该方法具有操作简便、模型获取方便、实验可靠性强等优点,近年来在脊柱外科基础和临床研究中获得较大关注。该文就有限元方法在颈椎椎体、颈椎间盘、颈椎韧带、颈椎中医按摩手法、颈椎手术（包括颈前路手术、颈后路手术）等研究中的应用进行综述。     

颈椎终板生物力学与终板形态学及椎间盘退变的关系

颈椎终板解剖学及生物力学特点在脊柱外科融合治疗中扮演极其重要角色.终板几何形态、大小以及厚度、骨密度均与终板受力情况密切相关,特别是后两者在一定程度上与终板力学分布呈正相关.随着终板受力情况改变,终板形态也随之发生适应性改变.解剖形态异常和受力异常可导致终板及椎间盘退变,退变反过来导致终板解剖形态及力学特性进一步改变.临床上对退变性颈椎病进行手术治疗时需要妥善处理终板,平衡好力学支持与血管长入椎间融合器之间的关系.植入物设计的理想状态应该是与终板表面契合,避免点状受力,以降低术后融合器沉降,最终达到骨性愈合.     

人工颈椎间盘置换术对邻近节段生物力学影响的三维有限元分析

[目的]建立人工颈椎间盘置换术前、术后(C4～7)的三维有限元模型,分析颈椎间盘置换术的特点,并探讨术后对邻近节段生物力学的影响.[方法]选取1名行人工颈椎间盘置换的男性病人的术前、术后CT片,范围为C4～7,(包括椎体、邻近椎体和邻近椎间盘)分别建立术前、术后的三维脊柱功能单元的有限元模型.对模型加载2 N*m的力矩和10 N*m的转矩,分析其在垂直载荷、前屈、后伸、侧屈及旋转的情况下,手术前后的椎体的变化以及椎体皮质骨、松质骨、椎间盘、终板的应力改变,以及活动度的变化.[结果]手术后轴向负荷力线后移,人工间盘邻近椎体上下终板所受应力,以及邻近椎间盘所受应力有所增加,但所受压力、张力不明显.节段活动度的变化减小不明显.[结论]人工颈椎间盘置换术有效的改善了脊柱功能单位的生物力学性能,但需谨慎选择人工椎间盘的大小,并且最大限度保留终板骨性组织,以避免出现术后假体下沉、移位、脱出、节段后凸等不良影响.     

有限元方法在颈椎生物力学研究中的应用进展

有限元方法作为一种新的生物力学研究方法,属于数学物理方法范畴.有限元方法在人体的生物力学分析中已经得到广泛的应用,脊柱的有限元分析是热点之一,有限元模型不仅能逼真地模拟椎体、椎间盘、脊髓、韧带,甚至肌肉,还能分析模型内部各种组织的应力和张力.近些年,随着计算机辅助技术的发展,颈椎有限元模型的不断完善,有限元方法在颈椎损伤机制,颈椎手术方式以及内固定器械等方面的生物力学分析起着越来越大的作用.现将近年来有限元方法在颈椎生物力学研究中的应用进展作如下综述.     

颈椎前融合对颈椎退变的影响

本文探讨颈椎融合术导致颈椎退变加重的根本原因,以提高颈椎病患者的手术治疗效果。对实施颈椎融合术的76例颈椎间盘突出症患者和64例颈椎骨折脱位患者进行回顾性对比分析,归纳出影响颈椎融合术治疗效果的根本原因。结果显示:76例颈椎间盘突出症患者术后有33例发生颈椎退变明显加重,其中4例再次发生颈椎间盘突出症;64例颈椎骨折脱位患者术后有8例出现颈椎退变加重。作者认为:融合术前,融合节段上下端颈椎已有的退变是导致术后退变加重的根本原因,手术治疗时应给予特别的关注。     

应用三维有限元模型研究颈椎不同工况下的生物力学变化

目的 研究颈椎前屈、后伸、侧屈、旋转等多种工况下，钩椎关节、小关节应力规律，从应力角度探讨钩椎关节、小关节退变的生物力学机制。方法 测量尸体颈段脊柱各节点三维坐标，利用SUPER—SAP软件建立机内模型，模拟完整的颈段脊柱力学模型。通过测量求得力矩值，直接或根据力矩等价公式间接将肌力值加载于模型体表各点。运用颈椎周围不同肌肉对颈椎作用力的变化，模拟正常活动范围内颈椎前屈、后伸、侧屈、旋转等多种工况。分别计算并得出相应载荷下钩椎关节、小关节应力值。结果钩椎关节在各种工况下的受力总体上集中于颈椎中下段。前屈时，由上至下呈现逐渐增大趋势；后伸时，在C4-5，C5-6出现应力集中现象。小关节各种工况下的受力状况总体趋势与钩椎关节相同，前屈时z轴上受到拉应力，后伸时受到压应力，且后伸时承受的拉应力是前屈时承受压应力的2倍多。这说明小关节在后伸时起到承受和传导载荷的作用。结论 不同运动状态下，中下段颈椎的钩椎关节、小关节出现应力集中。     

MRI evaluation of spontaneous intervertebral disc degeneration in the alpaca cervical spine

Animal models have historically provided an appropriate benchmark for understanding human pathology, treatment, and healing, but few animals are known to naturally develop intervertebral disc degeneration. The study of degenerative disc disease and its treatment would greatly benefit from a more comprehensive, and comparable animal model. Alpacas have recently been presented as a potential large animal model of intervertebral disc degeneration due to similarities in spinal posture, disc size, biomechanical flexibility, and natural disc pathology. This research further investigated alpacas by determining the prevalence of intervertebral disc degeneration among an aging alpaca population. Twenty healthy female alpacas comprised two age subgroups (5 young: 2–6 years; and 15 older: 10+ years) and were rated according to the Pfirrmann‐grade for degeneration of the cervical intervertebral discs. Incidence rates of degeneration showed strong correlations with age and spinal level: younger alpacas were nearly immune to developing disc degeneration, and in older animals, disc degeneration had an increased incidence rate and severity at lower cervical levels. Advanced disc degeneration was present in at least one of the cervical intervertebral discs of 47% of the older alpacas, and it was most common at the two lowest cervical intervertebral discs. The prevalence of intervertebral disc degeneration encourages further investigation and application of the lower cervical spine of alpacas and similar camelids as a large animal model of intervertebral disc degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1776–1783, 2015.     

Disc degeneration in the cervical spine

One hundred and twenty-eight cervical discs obtained from 30 autopsied subjects were examined morphologically. The cervical degenerative process was divided into five stages: (i) The initial stage—characterized by the disappearance and calcification of cells of the cartilagenous plate; (ii) the early stage—characterized by vessel invasion and formation of a calcification front; (iii) the progressive stage—characterized by progressive degenerative changes in all disc components; (iv) the late stage—characterized by destruction of the cartilagenous plates; and (v) the terminal stage—c characterized by eburnation of the bony end-plate. The cervical spine has three main differences from other regions of the spine: a large range of motion, the capacity for frequent and rapid movements, and the presence of Luschka's joint. Each of these three features is related to cervical disc degeneration. A preliminary report of this paper was presented at the 2nd Annual Orthopaedic Research Meeting of the Japanese Orthopaedic Association (Kyoto, Japan, September, 1987) and at the 22nd Annual Meeting of the Japan Spine Research Society (Toyama, Japan, June, 1993).     

Effect of disc degeneration on the mechanical behavior of the human lumbar spine: a probabilistic finite element study

BACKGROUND CONTEXT

Intervertebral disc degeneration has been subject to numerous in vivo and in vitro investigations and numerical studies during recent decades, reporting partially contradictory findings. However, most of the previous studies were limited in the number of specimens investigated and, therefore, could not consider the vast variety of the specimen geometries, which are likely to strongly influence the mechanical behavior of the spine.

利用MIMICS和ABAQUS建立正常人颈椎的三维有限元模型

[目的]建立符合人体解剖结构的颈椎三维有限元模型,并验证其有效性,以用于后续的颈椎生物力学分析.[方法]选择1名健康男性志愿者,采集其颈椎数据,利用MIMICS软件进行数据处理,建立实体模型,然后导入有限元分析软件Abaqus进行网格划分,并添加椎间盘及主要韧带肌肉等结构,建立人体颈椎有限元模型.在此模型上施加2.0N·M的作用力,模拟颈椎在前屈、侧屈和旋转工况下的反应,与其他颈椎有限元模型和体外生物力学实验数据进行对比验证.[结果]整个模型包括C2 ～76个椎体、C2、3 ～ C6、75个椎间盘及后部结构与主要韧带,共有472 065个单元和98 708个节点.在模拟外力作用下,在前屈、侧屈和旋转工况条件下的活动度与之前的实验结果高度吻合.[结论]建立的颈椎三维有限元模型具有良好的生物逼真度,可以用于颈椎临床生物力学分析.     

Intervertebral disc degeneration in a naturally occurring primate model: Radiographic and biomechanical evidence

Classic degenerative disc disease is a serious health problem worldwide, whose etiological basis—mechanical stimulus, biochemical changes, or natural aging—is poorly understood. Animal models are critical to the study of degenerative disc disease initiation and progression and for attempts to regulate, ameliorate, or eliminate it. The macaque represents a primate model with natural disc degeneration that might serve to advance the field; we aimed to provide radiographic (morphologic) and biomechanical evidence of natural disc degeneration in this model. A factorial study design was used to examine the relationship between the radiographic appearance of disc degeneration and its biomechanical consequences. Eighteen macaques of advanced age (22.3 ± 0.9 years) had radiographs taken to assess the degree of thoracolumbar intervertebral disc degeneration using a standard atlas method. Each spine was harvested and dynamic biomechanical tests were performed. Advancing disc degeneration (degree of disc space narrowing and osteophytosis) was associated with increased stiffness, decreased energy absorption, and increased natural frequency of the intervertebral disc. These associations linking the dynamics of the intervertebral disc and its degree of degeneration are similar to those found in humans. Our results indicate the macaque model with morphologic and biomechanical efficacy could aid in understanding the progression of disc degeneration and in developing therapeutic strategies to prevent or inhibit its course. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1283–1288, 2008     

上颈椎三维非线性有限元模型的建立及其有效性验证

目的建立具有详细解剖结构的上颈椎三维非线性有限元模型并验证其有效性。方法对健康成年男性志愿者进行CT扫描,获得枕骨底(C0)到C3的体层图像,将数据导入Mimics软件进行上颈椎骨质的三维模型重建,用Freeform软件进行模型修改,导入有限元软件Ansys9.0进行分析计算。模型中韧带以非线性的弹性元素建模,分为弹性区和中性区,分别定义元素性质,韧带的起止点及横截面积根据文献确定,寰椎横韧带坚韧、弹性低,定义为固体元素性质,同时便于对齿状突横韧带关节进行受力分析。寰枕关节、寰枢关节、C2,3关节突关节、寰椎齿状突关节、齿状突横韧带关节均定为有摩擦系数的表面滑动接触关节。使模型C3椎体下缘固定,在枕骨底施加40N的预载荷和1.5N·m的力矩作用下使其产生前屈、后伸、旋转、侧屈运动,将模型的活动度(ROM)与Panjabi测得正常上颈椎的实验数据对比进行验证。结果建立了具有详细解剖结构的上颈椎三维非线性有限元模型,整个模型有229047个节点和152475个单元,模型运动范围与Panjabi的数据相符合。结论建立的上颈椎模型具有较高的真实性,可以用于生物力学分析实验。     

Effects of aging and degeneration on the human intervertebral disc during the diurnal cycle: A finite element study

A significant biochemical change that takes place in intervertebral disc degeneration is the loss of proteoglycans in the nucleus pulposus. Proteoglycans attract fluid, which works to reduce mechanical stresses in the solid matrix of the nucleus and provide a hydrostatic pressure to the annulus fibrosus, whose fibrous nature accommodates this stress. Our goals are to develop an osmo‐poroelastic finite element model to study the relationship between proteoglycan content and the stress distribution within the disc and to analyze the effects of degeneration on the disc's diurnal mechanical response. Stress in the annulus increased with degeneration from ～0.2 to 0.4 MPa, and an increase occurred in the center of the nucleus from 1.2 to 1.6 MPa. The osmotic pressure in the central nucleus region decreased the most with degeneration, from ～0.42 to ～0.1 MPa in a severely dehydrated disc. A 3% decrease in diurnal fluid lost with degeneration equated to ～21% decrease in fluid exchange, and hence a decrease in nutrients that require convection to enter the disc. We quantified the increases in internal stresses in the nucleus and annulus throughout the various stages of degeneration, suggesting that these changes lead to further remodeling of the tissue. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:122–128, 2012     

The effect of disc degeneration on anterior shear translation in the lumbar spine

Many pathologies involving disc degeneration are treated with surgery and spinal implants. It is important to understand how the spine behaves mechanically as a function of disc degeneration. Shear loading is especially relevant in the natural and surgically stabilized lumbar spine. The objective of our study was to determine the effect of disc degeneration on anterior translation of the lumbar spine under shear loading. We tested 30 human cadaveric functional spinal units (L3–4 and L4–5) in anterior shear loading. First, the specimens were imaged in a 1.5 T magnetic resonance scanner. The discs were graded according to the Pfirrmann classification. The specimens were then loaded up to 250 N in anterior shear with an axial compression force of 300 N. Motion of the vertebrae was captured with an optoelectronic camera system. Inter‐ and intra‐observer reliability for disc grading was determined (Cohen's and Fleiss' Kappa), and a non‐parametric test was performed on the translation data to characterize the effect of disc degeneration on this parameter. We found fair to moderate agreement between and within observers for the disc grading. We found no significant effect of disc degeneration on anterior shear translation (Kruskal‐Wallis ANOVA). Our results indicate that disc degeneration, as classified with the Pfirrmann scale, does not predict lumbar spinal motion in shear. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:450–457, 2015.