颈椎前路椎间盘切除融合术与人工颈椎椎间盘置换术治疗跳跃型颈椎椎间盘突出症的生物力学效应有限元分析

目的 探讨颈椎前路椎间盘切除融合术(ACDF)和人工颈椎椎间盘置换术(CDA)治疗跳跃型颈椎椎间盘突出症的生物力学改变情况.方法 建立正常人颈椎(C2～7)三维有限元模型,并与既往研究数据进行对比,验证模型的有效性.选择C3/C4和C5/C6建立节段跳跃ACDF(Zero-P系统)、跳跃CDA(Prestige-LP假...     

颈椎前路分节段减压融合术三维有限元分析

目的应用三维有限元模型分析颈椎前路分节段减压融合术的生物力学特点。方法建立C2～7三维有限元模型,在此基础上根据临床实际建立手术模型,观察不同手术方式的颈椎活动范围和邻近节段椎间盘应力。结果建立的颈椎三维有限元模型有效,分节段减压融合术比传统椎体次全切除术术后邻近节段椎间盘应力小,二者颈椎活动范围相同。结论颈椎前路分节段减压融合术比传统椎体次全切除术更符合人体生物力学要求。     

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.     

双节段颈前路椎间盘切除融合术应用零切迹系统或钢板联合融合器固定后颈椎生物力学变化的三维有限元研究

目的：通过三维有限元分析法比较双节段颈椎前路椎间盘切除融合术（anterior cervical discectomy and fusion,ACDF）应用零切迹（zero-profile,ZP）系统与钢板联合融合器（cage-and-plate,CP）固定后颈椎的生物力学变化。方法：采集1例正常成年女性志愿者颈椎C3～C7节段CT扫描数据,建立C3～C7颈椎有限元模型并通过对比前期研究验证模型有效性。ZP固定模型与CP固定模型的手术节段均设定为C4/5与C5/6节段。在C3椎体上方施加轴向压缩负荷73.6N的模拟重力,并逐步施加1.8N·m的转矩,进而模拟屈伸、侧屈及轴向旋转等颈椎运动。测定并比较手术模型融合节段活动度（range of motion,ROM）、邻近节段椎间盘内应力、C5椎体及融合器装置应力。结果：CP固定模型融合节段的ROM在屈伸、侧屈、旋转位均明显小于ZP固定模型;CP固定模型相邻节段（C3/4、C6/7）的椎间盘内应力均远远高于ZP固定模型,两种模型融合节段上方的椎间盘内应力均高于融合节段下方;各工况下,ZP固定模型的C5椎体应力均明显高于CP固定模型,在前屈位...     

带肌肉组织全颈椎三维有限元模型的建立及分析

目的 :建立带肌肉组织的全颈椎三维有限元模型并验证该模型的有效性,为进一步分析颈椎疾患的生物力学作用机制建立良好的工作平台。方法:选取一名34岁健康男性志愿者进行颈椎薄层CT扫描,将CT原始数据以Dicom格式存贮。用Mimics 17软件将CT图像逆向重建出颈椎三维点云模型,利用Geomagic Studio 2012软件把点云模型拟合成NURBS曲面模型,然后导入Hypermesh12软件中进行网格划分、赋予材料属性、定义接触及边界条件等操作,最后提交至ABAQUS 6.12软件进行有限元分析,将各个工况(前屈、后伸、侧弯和轴向旋转)下各节段活动度与文献数据进行比较,验证该模型有效性。结果:建立的带有肌肉组织的全颈椎三维有限元模型共包含789024单元,285045节点,外观与人体颈椎具有非常好的几何相似性。该模型在屈伸、侧弯及旋转工况下的活动度与文献数据进行了80次对比,共计24次(占30%)超出部分参考范围,其中,仅C5-6左右侧弯活动度8.4°、C0-C1左右旋转活动度24.2°超出所有参考范围(P0.05)。结论:本研究建立的带有肌肉组织的全颈椎三维有限元模型符合有限元分析几何相似性和力学相似性要求,可用于颈椎生物力学分析。     

利用Mimics和Freeform建立下颈椎三维非线性有限元模型

目的建立具有详细解剖结构的下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C4-7,节段的断层图片,将数据保存为Dicom格式,导入Mimics9．1软件进行三维几何模型重建,形成三维图像,利用Freeform软件进行模型修改和表面划分,以IGES格式转入有限元软件Ansys9．0完成有限元模型建模。下颈椎韧带以非线性的弹性元素建模,韧带的起止点及横截面积根据文献确定,关节突关节定义为有摩擦系数、表面滑动接触关系。在C4施加40N的预载荷,在1．8N·m的力矩作用下使模型产生前屈、后伸、侧屈、旋转运动,将实验结果与Moroney等实验结果对比进行验证。结果建立了具有详细解剖结构的下颈椎三维非线性有限元模型。整个模型共有145570个节点,96645个单元,模型在各种工况下的平均刚度与Moroney等的结果基本吻合。结论利用Mimics和Freeform建立的下颈椎模型在一定条件下是有效的,可以进行临床和实验研究。     

颈椎间盘退变对颈椎生物力学影响的有限元研究

目的建立人体颈椎C4-C5-C6节段颈椎间盘退变三维有限元模型,分析椎间盘退变对颈椎运动节段生物力学的影响。方法通过改变椎间盘材料特性和高度等参数,建立椎间盘轻度退变模型(LD)、中度退变模型(MD)和重度退变模型(SD)。在45 N垂直载荷下,分别对正常、轻、中、重度4种有限元模型进行生物力学测试,比较4种模型之间各项生物力学参数的差异。结果建立了C4-C5-C6节段颈椎间盘逐级退变三维有限元模型。45 N垂直载荷条件下,正常模型(ND)、MD、SD椎间盘轴向位移及向外膨出位移逐渐变小,LD椎间盘轴向位移及膨出位移比ND增大,四组模型纤维环轴向压缩应力逐渐增大,髓核内压力逐渐减小。ND、MD、SD关节突关节接触力逐渐减小,LD关节突关节接触力较ND轻度增大。结论椎间盘轻度退变时,颈椎稳定性下降。中、重度退变时,颈椎稳定性重新获得。从生物力学方面证明退变的椎间盘对维持颈椎的稳定性有一定的代偿作用。     

带有颅底的全颈椎三维有限元模型的建立及分析

【摘要】 目的：建立带有颅底的全颈椎三维有限元模型并验证模型有效性,为分析颈椎疾患的生物力学机制提供帮助。方法：选取一31岁健康男性志愿者进行颈椎（包括颅底）薄层CT扫描,并将CT原始数据以Dicom格式存贮。运用建模软件Simpleware3.0把CT数据转化为STL格式数据,通过Geomagic 8.0对数据中的图像进行修补、去噪、铺面并转化为NURB曲面模型,得到带有颅底的全颈椎（C0-C7）三维有限元实体模型。应用软件Hypermesh 9.0进行前处理,包括接触定义、网格划分、材料属性设定及载荷与边界条件设定。应用Abaqus 6-9-1大型有限元计算软件进行计算,将屈曲、伸展、左右侧弯和左右旋转工况下的活动范围（ROM）与Panjabi的实验数据进行比较,对模型进行验证。结果：建立的正常全颈椎三维有限元模型共包含664026单元,228557节点,具有逼真的几何外观。通过与Panjabi的实验数据进行对比验证,发现该模型在屈伸、侧弯及旋转工况下的ROM与Panjabi的数据基本一致,只有在C2-C3旋转活动度方面存在差异（6.03° vs 3°±2.5°,P＜0.05）。结论：所建立的带有颅底的正常全颈椎三维有限元模型满足有限元分析的几何相似性和力学相似性,可用于颈椎的生物力学分析。     

下颈椎全椎板切除后生物力学特性改变机制的有限元分析

目的:探讨下颈椎全椎板切除后生物力学特性改变的机制。方法:采集1例成年健康男性志愿者下颈椎(C3～C7)的CT数据集,应用Mimics 10.01、Geomagic studio 10.0、HyperMesh 10.0、Abaqus 6.9.1等软件建立下颈椎(C3～C7)完整有限元模型、完整保留双侧关节突关节三节段(C4～C6)全椎板切除后有限元模型。模拟施加74N头颅预载荷和1.8Nm运动附加力矩,使模型产生前屈、后伸、侧屈和旋转运动,测试颈椎全椎板切除前后的运动范围和关节囊韧带、后纵韧带在各种加载方式下的拉力。结果:C4～C6全椎板切除后即刻颈椎屈伸、侧弯和旋转的运动范围与完整状态下比较均没有增加,但C4～C6节段之间的关节囊韧带和后纵韧带在各种加载方式下受到的拉力均增大。结论:完整保留双侧关节突关节的全椎板切除术不会对下颈椎即时稳定性造成影响,但关节囊韧带和后纵韧带承受着超正常生理负荷。     

齿状突Ⅱ型骨折三维有限元模型的建立

目的 建立具有详细解剖结构的上颈椎齿状突Ⅱ型骨折(C0-3)三维非线性有限元模型.方法 将CT体层扫描图像导入Mimics软件进行上颈椎三维模型重建,横行去除齿状突基底部骨质,模拟齿状突Ⅱ型骨折.导入有限元软件Ansys 9.0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.在枕骨底施加40N的预载荷和1.5 Nm的力矩使其产生前屈、后伸、旋转、侧屈运动,将模型的活动度(ROM)与齿状突Ⅱ型骨折的体外实验结果对比进行验证.结果 模型有229 047个节点和152 475个单元,寰枢节段运动范围:屈伸38.3度,侧屈20.4度,旋转74.2度,与体外实验结果相符合.结论 建立的上颈椎齿状突Ⅱ型模型具有较高的真实性,可以用于生物力学分析实验.     

The efficacy of using an image-guided Kerrison punch in performing an anterior cervical foraminotomy. An anatomic analysis.

STUDY DESIGN: This study comprised two parts: first, a feasibility study to determine the efficacy of using an image-guided Kerrison punch while performing a foraminotomy during an anterior cervical decompression and, second, an anatomic analysis using vector measurement to determine the distance from the entrance of the neuroforamen to the medial margin of the vertebral artery in the subaxial cervical spine. OBJECTIVE: To assess the feasibility of using an image-guided Kerrison punch when performing an anterior foraminotomy and to obtain data regarding the distance from the vertebral artery to the entrance of the neuroforamen. SUMMARY OF BACKGROUND DATA: The documented incidence of catastrophic iatrogenic vertebral artery injury in anterior cervical decompression is low. The use of a real-time image-guidance surgical system should reduce the risk of this complication. METHODS: Twelve cadaveric cervical spines were harvested. Standard anterior cervical discectomies with bilateral foraminotomies were performed in the subaxial cervical spine using an image-guided Kerrison. Surgically significant morphometric data were measured using a computer-assisted image-guided surgical system. RESULTS: Successful navigation into all neuroforamina in the subaxial cervical spine was attained using the image-guided Kerrison punch. The vector measurement from the neuroforamen to the vertebral artery averaged 5.8 +/- 1.2 mm at C3-C4, 6.5 +/- 1.6 mm at C4-C5, 7.9 +/- 1.4 mm at C5-C6, and 9.1 +/- 1.8 mm at C6-C7. Statistically significant differences (P < 0.05) were found between all cervical levels except C3-C4 and C4-C5. CONCLUSION: An image-guided Kerrison punch may be used successfully when performing cervical foraminotomies during an anterior cervical discectomy, thus eliminating the risk of potential vertebral artery injury. These data confirm previous findings by other authors. Knowledge of these data may aid the spine surgeon in performing a foraminotomy during anterior cervical decompression.     

The cortical shell architecture of human cervical vertebral bodies.

STUDY DESIGN: An anatomic study of cervical vertebral bodies. OBJECTIVES: To provide quantitative information on the cortical shell architecture of the middle and lower cervical vertebral bodies. SUMMARY OF BACKGROUND DATA: Some external dimensions have been measured, but little quantitative data exists for the cortical shell architecture of the vertebral bodies of the cervical spine. METHODS: Twenty-one human cervical vertebral bodies (C3-C7) were sectioned along parasagittal planes into five 1.7-mm thin slices for each vertebra. Radiographs of each slice were digitized, and external and internal dimensions were measured. Averages and standard deviations were computed. Single factor analysis of variance was used to determine significant (P < 0.05) differences between the vertebral levels. RESULTS: The superior endplate was thickest in the posterior region (range 0.74-0.89 mm) and thinnest in the anterior region (range 0.44-0.56 mm). The inferior endplate was thickest in the anterior region (range 0.61-0.81 mm) and thinnest in the posterior region (range 0.49-0.62 mm). In the central region, the superior endplate (range 0.42-0.58 mm) was thinner than the inferior endplate (range 0.53-0.64 mm). Variation with vertebral level was dependent on the dimension studied. CONCLUSIONS: Comprehensive quantitative anatomic data of the middle and lower cervical vertebral bodies have been obtained. This may be useful in improving the understanding of the three-column and other vertebral-fracture theories, the fidelity of the finite element models of cervical spine, and the designs of surgical instrumentation.     

寰椎侧块-枢椎椎板螺钉固定的有限元分析

目的:建立寰椎侧块-枢椎椎板螺钉固定的三维有限元模型并进行有限元分析,探讨其生物力学特性。方法:通过CT扫描获取1例健康成年男性寰枢椎图像信息,应用VTK软件及ABAQUS软件构建寰椎侧块-枢椎椎板螺钉固定的三维有限元模型,观察中立、前屈/后伸、侧弯、旋转、前后平移等载荷下固定系统的应力变化,分析寰枢侧块-枢椎椎板螺钉固定系统的生物力学特性。结果:所建立的有限元模型逼真地描绘了寰椎侧块-枢椎椎板螺钉固定系统的结构特点,共包含183363个节点(椎骨130982个,螺钉52381个),116082个单元(椎骨83776个,螺钉32306个)。在不同运动状态下,螺钉应力分布主要集中在螺钉置入骨质部分的根部周围和钉棒连接处。前屈载荷时,连接棒从头端至尾端的应力逐步减小,在寰椎侧块螺钉的钉棒连接处应力最大;其他载荷下连接棒应力分布从头端至尾端逐步增大,至枢椎椎板螺钉的钉棒连接处达到最大。后伸和旋转载荷下,螺钉存在明显的高应力区,各螺钉的应力最大值大于其他运动状态。结论:寰椎侧块-枢椎椎板螺钉固定系统固定时各螺钉在颈椎旋转及后伸时所受应力明显增加,术后应避免颈椎过度旋转及后伸,以减少螺钉松动和断裂的发生。     

Comparison between sheep and human cervical spines: an anatomic, radiographic, bone mineral density, and biomechanical study

STUDY DESIGN: The quantitative anatomic, radiographic, computerized tomographic, and biomechanical data of sheep and human cervical spines were evaluated. OBJECTIVES: To compare the anatomic, radiographic, computerized tomographic, and biomechanical data of human and sheep cervical spines to determine whether the sheep spine is a suitable model for human spine research. SUMMARY OF BACKGROUND DATA: Sheep spines have been used in several in vivo and in vitro experiments. Quantitative data of the normal sheep cervical spine are lacking, yet these data are crucial to discussion about the results of such animal studies. METHODS: In this study, 20 fresh adult female Merino sheep cervical spines and 20 fresh human cadaver cervical spines were evaluated anatomically, radiographically, computerized tomographically, and biomechanically. Three linear and two angular parameters were evaluated on four digital radiographic views: anteroposterior, right lateral in neutral position, flexion, and extension. Quantitative computed tomography scans at the center of each vertebral body and 3 mm below both endplates were analyzed for bone mineral density measurements. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending by a nondestructive stiffness method using a nonconstrained testing apparatus. Range of motion and stiffness of each motion segment were calculated. Additionally, 10 linear anatomic parameters of each vertebra were measured using a digital ruler. RESULTS: Anterior and mean disc space height in the sheep cervical spine increased constantly from C2-C3 to C6-C7, whereas middle disc space height decreased and posterior disc space height remained unchanged. Anterior and mean disc space height were significantly higher in sheep. In both sheep and human cervical spines, intervertebral angles were not significantly different. Standard deviations of bone mineral density in the human cervical spine were fourfold higher than in the sheep cervical spine, yet no significant differences were found in bone mineral density values between the two species. Range of motion differed significantly between the two species except in flexion-extension of C3-C4, C5-C6, axial rotation of C2-C3, and lateral bending of C2-C3, C3-C4, and C4-C5. Stiffness also was significantly different except in flexion-extension of C2-C3, C4-C5, C5-C6, and lateral bending of C2-C3, C3-C4, and C4-C5. Anatomic evaluation showed no difference in upper endplate parameters for C4 and C5. CONCLUSIONS: Although several differences were found between human and sheep cervical spines, the small intergroup standard deviations and the good comparability with the human spine encourage the use of the sheep cervical spine as a model for cervical spine research. On the basis of the quantitative data obtained in this study, the sheep motion segment C3-C4 seemed to be the most reliable model for the corresponding human motion segment.     

前路经寰枢关节螺钉内固定生物力学性能的有限元分析

目的:通过有限元分析的方法评估前路经寰枢关节螺钉内固定的生物力学性能。方法:选择一名21岁健康男性志愿者,采用螺旋CT对枕骨底到C3椎体进行层厚1mm的薄层扫描,利用MIMICS 13.0软件、Freeform Plus软件及ANSYS 9.0软件,建立正常上颈椎有限元模型。去除模型中横韧带的所有单元模拟寰枢关节不稳,以枢椎前弓下缘与枢椎椎体侧缘交界点上方4mm处为进钉点,经寰枢关节分别向两寰椎侧块外上角中部置钉,最终建立前路经寰枢关节螺钉内固定治疗寰枢关节不稳的有限元模型。给予模型分别施加前屈、后伸、侧屈、旋转四种生理载荷,观察不同载荷下螺钉的三维运动范围与应力变化,分析前路经寰枢关节螺钉内固定的生物力学性能。结果:前路经寰枢关节螺钉内固定在不同载荷下三维运动范围均较小,但前屈、后伸状态下三维运动范围(0.72°,1.08°)明显大于侧屈、旋转状态(0.39°,0.32°)。不同状态下应力集中区域均为螺钉经寰枢关节部位,最大应力值为10.58×107Pa,出现在后伸状态。结论:前路经寰枢关节螺钉内固定具有可靠的生物力学性能,在侧屈、旋转状态下的力学性能优于前屈后伸状态,螺钉经寰枢关节部位易产生应力集中,为可能的断钉部位,临床应用时应采取有效预防措施。     

A finite element investigation of upper cervical instrumentation.

STUDY DESIGN: The finite element technique was used to predict changes in biomechanics that accompany the application of a novel instrumentation system designed for use in the upper cervical spine. OBJECTIVE: To determine alterations in joint loading, kinematics, and instrumentation stresses in the craniovertebral junction after application of a novel instrumentation system. Specifically, this design was used to assess the changes in these parameters brought about by two different cervical anchor types: C2 pedicle versus C2-C1 transarticular screws, and unilateral versus bilateral instrumentation. SUMMARY OF BACKGROUND DATA: Arthrodesis procedures can be difficult to obtain in the highly mobile craniovertebral junction. Solid fusion is most likely achieved when motion is eliminated. Biomechanical studies have shown that C1-C2 transarticular screws provide good stability in craniovertebral constructs; however, implantation of these screws is accompanied by risk of vertebral artery injury. A novel instrumentation system that can be used with transarticular screws or with C2 pedicle screws has been developed. This design also allows for unilateral or bilateral implantation. However, the authors are unaware of any reports to date on the changes in joint loading or instrumentation stresses that are associated with the choice of C2 anchor or unilateral/bilateral use. METHODS: A ligamentous, nonlinear, sliding contact, three-dimensional finite element model of the C0-C1-C2 complex and a novel instrumentation system was developed. Validation of the model has been previously reported. Finite element models representing combinations of cervical anchor type (C1-C2 transarticular screws vs. C2 pedicle screws) and unilateral versus bilateral instrumentation were evaluated. All models were subjected to compression with pure moments in either flexion, extension, or lateral bending. Kinematic reductions with respect to the intact (uninjured and without instrumentation) case caused by instrumentation use were reported. Changes in loading profiles through the right and left C0-C1 and C1-C2 facets, transverse ligament-dens, and dens-anterior ring of C1 articulations were calculated by the finite element model. Maximum von Mises stresses within the instrumentation were predicted for each model variant and loading scenario. RESULTS: Bilateral instrumentation provided greater motion reductions than the unilateral instrumentation. When used bilaterally, C2 pedicle screws approximate the kinematic reductions and instrumentation stresses (except in lateral bending) that are seen with C1-C2 transarticular screws. The finite element model predicted that the maximum stress was always in the region in which the plate transformed into the rod. CONCLUSIONS: To the best of the authors' knowledge, this is the first report of predicting changes in loading in the upper cervical spine caused by instrumentation. The most significant conclusion that can be drawn from the finite element model predictions is that C2 pedicle screw fixation provides the same relative stability and instrumentation stresses as C1-C2 transarticular screw use. C2 pedicle screws can be a good alternative to C2-C1 transarticular screws when bilateral instrumentation is applied.     

Possible complications of anterior perforation of the vertebral body using cervical pedicle screws

No previous studies have analyzed the possible complications of anterior perforation of the cervical vertebral body with pedicle screws. The objective of this study was to identify the possible implications of an anterior vertebral body perforation. Ten consecutive Euro-American cadavers (C2-C7) were used. The male-to-female ratio was 3:7. The average specimen age was 79.6 years (range: 65-97 years), and average height was 159 cm (range: 155-175 cm). Axial computed tomography scans through the isthmus of pedicles were taken. Five millimeter and 10 mm margins anterior to the vertebral bodies were defined. Within 5 mm anterior to the anterior cortex of the vertebral body, we found mostly muscles (at C2: m. longus colli and pharyngeal constrictors; at C3 and C4: m. scalenus medius, longus colli, pharyngopalatinus and pharyngeal constrictors; at C5 and C6: m. longus colli and longus capitis; and at C7: m. longus colli), except at C3, C4, and C7, where the pharynx and esophagus were within the margin. Between 6 and 10 mm, we found mostly hollow organs (at C2: pharynx and small veins; at C3 and C4: the same muscles as within the 5 mm margin, with addition of the pharynx and some small veins; at C5 and C6: pharynx, pharyngeal constrictors and the thyroid cartilage; and at C7: the esophagus). Except C2, there is no safe zone anterior to the cervical vertebral bodies in the cervical spine, which would allow bicortical purchase of pedicle screws without being close to important surrounding structures.     

Influence of preload magnitudes and orientation angles on the cervical biomechanics: a finite element study

OBJECTIVE: Although a number of in vivo, in vitro, and finite element studies have attempted to delineate the natural biomechanics, injury mechanisms, and surgical techniques of the cervical spine, none has explored the influence of various preload magnitudes and orientations on the biomechanical responses. METHODS: A nonlinear three-dimensional finite element model of the lower cervical spine (C5-C6) was used for this study. The model was tested under four preload magnitudes and three orientations. For every preload, magnitude, and orientation, pure moments of 1.8 Nm were applied to the superior surface of the moving vertebra (C5) in flexion, extension, lateral bending, and torsion. The resulting rotational motions were obtained and compared against literature data. RESULTS: The predicted biomechanical responses under the same loading directions varied, depending on the preload magnitudes and orientations. With flexion and extension, increasing the preload magnitudes and varying the C5-C6 orientation in the sagittal plane changed the rotational motions by 1% and 18%, respectively. Under normal orientation and with increasing preload magnitudes, flexion and extension increased, whereas lateral bending and torsion decreased. These changes were found to be influenced by several spinal components: posterior facets, passive ligaments, and stiffening of the intervertebral disc. The predicted responses under the direction of loading varied significantly, depending on the preload magnitudes and orientations. Under fixed preload magnitudes and varying the three types of orientations, rotational motions were not affected under flexion but changed under extension, lateral bending, and axial rotations. Under normal orientation and increasing preload magnitudes, biomechanical responses under flexion and extension increased, whereas lateral bending and torsion decreased. Changes in the predicted responses were found to be influenced by several spinal components: posterior facets, passive ligaments, and stiffening of the intervertebral disc. CONCLUSION: The findings of the current study were important for the further understanding of the cervical biomechanics during in vitro testing.     

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。