上颈椎有限元模型的建立及分析,以10岁儿童为例

本研究以一名10岁龄男童颈椎CT DICOM数据包为例,将数据导入MIMICS进行图像分割处理,得到优化的硬组织表面模型,再导入有限元前处理软件Hypermesh行颈椎C_0~C_2各部分网格的划分、建立颈椎韧带模型并对各部分赋材质、单元属性,建立了颈椎C_0~C_2有限元整体模型,最后导入有限元软件ANSYS14.0中行载荷计算和结论分析。进一步在模拟生理载荷下(颅底垂直加载30 N预压力,1.0 Nm力矩)测定上颈椎模型各节段(C_0~C_1,C_1~C_2)的前屈、后伸、侧屈、旋转的三维运动范围,将所得结论与文献结论进行对比,验证所建模型的有效性。研究表明,本研究成功建立了一个外观逼真的儿童上颈椎有限元模型,模拟生理载荷并测量出上颈椎各节段角位移量,较好的通过了有效性的验证,我们所建立的儿童上颈椎有限元模型几何相似性较好,对进一步用来进行生物力学研究具有重要的参考价值。     

肱骨有限元模型建立及生物力学分析

目的:以成人肱骨为例,将医学图像三维重建技术和有限元方法结合应用于正骨手法研究,建立正常肱骨有限元模型,验证模型的有效性并进行生物力学分析。方法:选择一位青年男性志愿者,对其上肢自尺桡骨上端至肱骨头进行连续断层扫描,得到CT图像,将CT数据导入MIMICS软件中,通过图像分割、三维重建和材料属性赋值,构建正常肱骨有限元模型,利用ANSYS软件进行力学分析,与文献中肱骨的生物力学数据相比较,以此验证模型的有效性。结果:建立了正常肱骨三维几何模型和有限元模型。利用ANSYS软件,对模型进行了有效性验证。所建模型物理特性与真实骨骼相近,能很好地反映骨骼的力学变化,实现手法的定量分析。结论:所建立的肱骨模型外形逼真、在不同载荷下的应力值与相关文献一致,可用作中医仿真系统中的虚拟骨折模型。     

力学环境对软骨基质代谢的影响

正常关节软骨所受压力是由动态压力与静态压力交替完成。压力引起软骨一系列生理变化包括细胞及细胞外基质成分变形、组织内液体流动、水流电位和生理生化变化。这些变化直接调控细胞外基质代谢。体外构建有良好功能的组织工程化软骨是目前软骨病变、缺损理想的修复方法。研究力学环境对软骨基质代谢的影响,对构建组织工程化软骨有深远意义。     

青少年颈椎病X线征象分析及病因与防治探讨

目的:探讨青少年颈椎病的X线征象、针对青少年颈椎病的病因进行分析,并提出相关干预对策.方法:选取本院87例经临床确诊的青少年颈椎病患者的临床及X线资料,对其病因和X线改变进行分析对比.结果:青少年颈椎病是由于长时间低头伏案工作、学习或某些不良习惯使椎间盘长时间处于异常负荷环境下,造成椎间盘提前退变所致,其X线表现主要为颈椎生理曲度改变和颈椎失稳.结论:青少年颈椎病X线平片上具有其特征性,良好的工作、学习、生活习惯可以有效避免青少年颈椎病的发生.     

基于有限元法的下颈椎弓根螺钉人工椎体系统研究

本实验利用有限元法对下颈椎前路椎弓根螺钉人工椎体系统进行研究,采用有限元法对构建下颈椎的生物力学稳定性及应力情况进行分析,进而对椎弓根螺钉进行优化设计,为临床医用提供进一步的理论。通过对患者的下颈椎处进行CT扫描,获得DICOM数据导入Mimics中,根据不同HU值范围构建下颈椎参数,并运用蒙板编辑、阈值选取、三维增长等工具建立颈椎结构区域的三维模型。采用ANSYS对建立构建的三维下颈椎模型进行有限元分析。构建人体下颈椎有限元模型,对皮质骨、软骨终板等椎间韧带结构进行模拟,设计的下颈椎模型单元有276 382个,节点有413 522个。研究表明,下颈椎在侧弯、屈伸、旋转等六个工况下的ROM椎间值与Panjabi及Kallemeyn等实验研究进行对比,实验数值与Panjabi的实验很近似,且都处于有效区间内,进而证实了实验模型的可行性与有效性。对设计的模型进行网格划分,AVB组设置273 347个单元,378 746个节点,AP组设置265 634个单元,374 593个节点。AP组相较于AVB组的应力峰值明显有增大趋势,但是AVB组的应力情况呈现均匀分布,最大应力主要分布在螺钉尾部及L形钛板与人工椎体接触部位;AP组的最大应力分布在前路钛板的钛网、中上部、螺钉钉杆尾端以及上下椎体接触部位,在钉板连接部位AP组出现应力集中现象。     

中国始新世纹齿兽科多瘤齿兽对掘土的适应

<正> 本文记述了内蒙古沙拉木伦地区下始新统巴彦乌兰层(脑木根组)内采集到的多瘤齿兽类(鼓泡斜剪齿兽)部分颅后骨骼。这些材料包括:愈合的第2-3颈椎(C2-C3),第4颈椎(C4)的部分神经弧,完整的第5-7颈椎(C5-C7),第1-2胸椎(T1-T3),以及两块首次报道的肱骨。第2和第3颈椎的愈合,具十分粗大三角肌脊的肱骨的强壮结构及其具有突出的桡     

浮针埋线联合推拿疗法对神经根型颈椎病疗效及对颈椎活动度、生理曲度变化的影响

摘要 目的：探讨与分析浮针埋线联合推拿疗法对神经根型颈椎病疗效及对颈椎活动度、生理曲度变化的影响。方法：2019年2月到2021年6月选择在本院诊治的神经根型颈椎病患者105例作为研究对象,根据1：1简单分配原则把患者分为浮针组53例与对照组52例。对照组给予推拿治疗,浮针组在对照组治疗的基础上给予浮针埋线治疗,两组都治疗观察21 d,记录患者颈椎活动度、生理曲度变化情况。结果：治疗后浮针组的总有效率为98.1 %,与对照组的86.5 %相比有明显提高（P<0.05）。浮针组与对照组治疗后的颈椎活动度评分明显低于治疗前,浮针组与对照组相比也明显降低（P<0.05）。浮针组与对照组治疗后的疼痛视觉模拟评分法（VAS）评分明显低于治疗前,颈椎日本骨科协会评估治疗分数（JOA）评分明显高于治疗前,治疗后浮针组与对照组对比也有明显差异（P<0.05）。浮针组与对照组治疗后的颈椎生理曲度明显高于治疗前,浮针组也明显高于对照组（P<0.05）。结论：浮针埋线联合推拿疗法在神经根型颈椎病患者的应用能促进缓解疼痛,改善颈椎功能,能提高治疗疗效,改善患者的颈椎活动度,还可促进颈椎生理曲度恢复正常。     

C3、C4和C3-C4中间型植物的进化

介绍了有关C3、C4和C3-C4中间型植物进化的形态学、生理学、分子生物学、遗传学等方面的证据;推断地球上首先出现C3植物,然后是C3-C4中间类型植物,最后出现C4植物.     

威宁绵羊和贵州半细毛羊STAT5b基因部分外显子SNP研究

为给贵州本地绵羊选种选育提供更好的科学依据,本试验利用威宁绵羊和贵州半细毛羊构建DNA池,设计4对引物扩增其STAT5b基因部分外显子及内含子序列。PCR产物经纯化后进行双向测序。利用DNAStar和BLAST分析确定多态性位点。利用生物信息学软件分析SNPs位点对STAT5b基因RNA二级结构、STAT5b蛋白二级及三级结构的影响。结果表明,在扩增的STAT5b基因中筛选到6个SNPs:exon5-G12A、exon8-G56A、exon8-C104T、intron2-A3164C、intron4-C1026T和intron5-T3323C,其中exon8-G56A为错义突变,导致编码的谷氨酸(Glu)变为赖氨酸(Lys);exon5-G12A和exon8-C104T多态位点均未改变氨基酸的编码,为同义突变;intron2-A3164C、intron4-C1026T和intron5-T3323C均在内含子区,不参与氨基酸编码。     

构建基于患者个体化的Stanford B型主动脉夹层计算流体力学数值模拟分析模型

目的:探索简便、高效、精确的构建基于真实人体解剖形态结构的Stanford B型主动脉夹层计算流体力学数值模拟分析模型的方法.方法:利用Siemens Sensation Cardiac 64层螺旋CT薄层扫描技术,基于1mm层厚获取6例Stanford B型主动脉夹层连续断层DICOM格式图像,导入Materialise MIMICS v12.11软件,界定目标区域后生成三维动脉模型,经网格优化处理去除低质量及相交面网格,保存结果输出,导入TGrid 5.0软件,对主动脉面网格模型进行几何修复,使面网格扭曲率<0.75,采用自由分网方式生成Stanford B型主动脉夹层计算流体力学分析体网格模型,并对所构建模型进行血流属性、流场边界等界定,初步验证模型的有效性.结果:通过初步计算求解,确定所构建的6例Stanford B型主动脉夹层计算流体力学分析模型分别包含1857030,1820501,1844181,1849651,1858246及1814914个四面体单元.结论:利用64层螺旋CT薄层扫描技术获取DICOM格式连续断层CT图像可快速、准确地构建Stanford B型主动脉夹层计算流体力学数值模拟分析模型,为进一步的计算流体力学分析奠定了良好的基础.     

Finite element model of the human neck during omni-directional impacts. Part II: relation between cervical curvature and risk of injury

A detailed 3D FE model of the human neck was used to assess a possible relationship between risk of injury and cervical spine curvature for various impacts. A FE model was previously developed, representing the head and neck of a 50th percentile human with a normal lordotic curvature. The model behaviour was omni-directionally validated for various impacts using published results. For the present study, the model was deformed in order to obtain a straight and a kyphotic curvature, and for each geometry, rear-end, frontal, lateral and oblique impact were simulated. Although results showed similar kinematic patterns, significant differences were found in the distribution and peak values of ligament elongations, forces and moments along the cervical spine for the three configurations. It was concluded that the variability observed on the curvature of the human cervical spine may have a significant influence both on the behaviour and on the risk of injury of the neck during impact.     

Finite element model of the human neck during omni-directional impacts. Part II: relation between cervical curvature and risk of injury

A detailed 3D FE model of the human neck was used to assess a possible relationship between risk of injury and cervical spine curvature for various impacts. A FE model was previously developed, representing the head and neck of a 50th percentile human with a normal lordotic curvature. The model behaviour was omni-directionally validated for various impacts using published results. For the present study, the model was deformed in order to obtain a straight and a kyphotic curvature, and for each geometry, rear-end, frontal, lateral and oblique impact were simulated. Although results showed similar kinematic patterns, significant differences were found in the distribution and peak values of ligament elongations, forces and moments along the cervical spine for the three configurations. It was concluded that the variability observed on the curvature of the human cervical spine may have a significant influence both on the behaviour and on the risk of injury of the neck during impact.     

Biomechanical analysis of the anterior cervical fusion

This paper presents a biomechanical analysis of the cervical C5–C6 functional spine unit before and after the anterior cervical discectomy and fusion. The aim of this work is to study the influence of the medical procedure and its instrumentation on range of motion and stress distribution. First, a three-dimensional finite element model of the lower cervical spine is obtained from computed tomography images using a pipeline of image processing, geometric modelling and mesh generation software. Then, a finite element study of parameters' influence on motion and a stress analysis at physiological and different post-operative scenarios were made for the basic movements of the cervical spine. It was confirmed that the results were very sensitive to intervertebral disc properties. The insertion of an anterior cervical plate influenced the stress distribution at the vertebral level as well as in the bone graft. Additionally, stress values in the graft decreased when it is used together with a cage.     

Biomechanical analysis of the anterior cervical fusion

This paper presents a biomechanical analysis of the cervical C5-C6 functional spine unit before and after the anterior cervical discectomy and fusion. The aim of this work is to study the influence of the medical procedure and its instrumentation on range of motion and stress distribution. First, a three-dimensional finite element model of the lower cervical spine is obtained from computed tomography images using a pipeline of image processing, geometric modelling and mesh generation software. Then, a finite element study of parameters' influence on motion and a stress analysis at physiological and different post-operative scenarios were made for the basic movements of the cervical spine. It was confirmed that the results were very sensitive to intervertebral disc properties. The insertion of an anterior cervical plate influenced the stress distribution at the vertebral level as well as in the bone graft. Additionally, stress values in the graft decreased when it is used together with a cage.     

C4–C5 segment finite element model development,validation, and load-sharing investigation

Detailed cervical spine models are necessary to better understand cervical spine response to loading, improve our understanding of injury mechanisms, and specifically for predicting occupant response and injury in auto crash scenarios. The focus of this study was to develop a C4–C5 finite element model with accurate representations of each tissue within the segment. This model incorporates more than double the number of elements of existing models, required for accurate prediction of response. The most advanced material data available were then incorporated using appropriate nonlinear constitutive models to provide accurate predictions of response at physiological levels of loading. This tissue-scale segment model was validated against a wide variety of experimental data including different modes of loading (axial rotation, flexion, extension, lateral bending, and translation), and different load levels. In general, the predicted response of the model was within the single standard deviation response corridors for both low and high load levels. Importantly, this model demonstrates that appropriate refinement of the finite element mesh, representation at the tissue level, and sufficiently detailed material properties and constitutive models provide excellent response predictions without calibration of the model to experimental data. Load sharing between the disc, ligaments, and facet joints was investigated for various modes of loading, and the dominant load-bearing structure was found to correlate with typical anatomical injury sites for these modes of loading. The C4–C5 model forms the basis for the development of a full cervical spine model. Future studies will focus on tissue-level injury prediction and dynamic response.     

Cartilage thickness distribution affects computational model predictions of cervical spine facet contact parameters

With motion-sparing disk replacement implants gaining popularity as an alternative to anterior cervical discectomy and fusion (ACDF) for the treatment of certain spinal degenerative disorders, recent laboratory investigations have studied the effects of disk replacement and implant design on spinal kinematics and kinetics. Particularly relevant to cervical disk replacement implant design are any postoperative changes in solid stresses or contact conditions in the articular cartilage of the posterior facets, which are hypothesized to lead to adjacent-level degeneration. Such changes are commonly investigated using finite element methods, but significant simplification of the articular geometry is generally employed. The impact of such geometric representations has not been thoroughly investigated. In order to assess the effects of different models of cartilage geometry on load transfer and contact pressures in the lower cervical spine, a finite element model was generated using cadaver-based computed tomography imagery. Mesh resolution was varied in order to establish model convergence, and cadaveric testing was undertaken to validate model predictions. The validated model was altered to include four different geometric representations of the articular cartilage. Model predictions indicate that the two most common representations of articular cartilage geometry result in significant reductions in the predictive accuracy of the models. The two anatomically based geometric models exhibited less computational artifact, and relatively minor differences between them indicate that contact condition predictions of spatially varying thickness models are robust to anatomic variations in cartilage thickness and articular curvature. The results of this work indicate that finite element modeling efforts in the lower cervical spine should include anatomically based and spatially varying articular cartilage thickness models. Failure to do so may result in loss of fidelity of model predictions relevant to investigations of physiological import.     

A female head–neck model for rear impact simulations

Several mathematical cervical models of the 50th percentile male have been developed and used for impact biomechanics research. However, for the 50th percentile female no similar modelling efforts have been made, despite females being subject to a higher risk of soft tissue neck injuries. This is a limitation for the development of automotive protective systems addressing Whiplash Associated Disorders (WADs), most commonly caused in rear impacts, as the risk for females sustaining WAD symptoms is double that of males.In this study, a finite element head and neck model of a 50th percentile female was validated in rear impacts. A previously validated ligamentous cervical spine model was complemented with a rigid body head, soft tissues and muscles. In both physiological flexion-extension motions and simulated rear impacts, the kinematic response at segment level was comparable to that of human subjects. Evaluation of ligament stress levels in simulations with varied initial cervical curvature revealed that if an individual assumes a more lordotic posture than the neutral, a higher risk of WAD might occur in rear impact.The female head and neck model, together with a kinematical whole body model which is under development, addresses a need for tools for assessment of automotive protection systems for the group which is at the highest risk to sustain WAD.     

Influence of cervical disc degeneration after posterior surgical techniques in combined flexion-extension--a nonlinear analytical study

Laminectomy and facetectomy are surgical techniques used for decompression of the cervical spinal stenosis. Recent in vitro and finite element studies have shown significant cervical spinal instability after performing these surgical techniques. However, the influence of degenerated cervical disk on the biomechanical responses of the cervical spine after these surgical techniques remains unknown. Therefore, a three-dimensional nonlinear finite element model of the human cervical spine (C2-C7) was created. Two types of disk degeneration grades were simulated. For each grade of disk degeneration, the intact as well as the two surgically altered models simulating C5 laminectomy with or without C5-C6 total facetectomies were exercised under flexion and extension. Intersegmental rotational motions, internal disk annulus, cancellous and cortical bone stresses were obtained and compared to the normal intact model. Results showed that the cervical rotational motion decreases with progressive disk degeneration. Decreases in the rotational motion due to disk degeneration were accompanied by higher cancellous and cortical bone stress. The surgically altered model showed significant increases in the rotational motions after laminectomies and facetectomies when compared to the intact model. However, the percentage increases in the rotational motions after various surgical techniques were reduced with progressive disk degeneration.     

Effects of abnormal posture on capsular ligament elongations in a computational model subjected to whiplash loading

Although considerable biomechanical investigations have been conducted to understand the response of the cervical spine under whiplash (rear impact-induced postero-anterior loading to the thorax), studies delineating the effects of initial spinal curvature are limited. This study advanced the hypothesis that abnormal curvatures (straight or kyphotic) of the cervical column affect spinal kinematics during whiplash loading. Specifically, compared to the normal lordotic curvature, abnormal curvatures altered facet joint ligament elongations. The quantifications of these elongations were accomplished using a validated mathematical model of the human head-neck complex that simulated three curvatures. The model was validated using companion experiments conducted in our laboratory that provided facet joint kinematics as a function of cervical spinal level. Regional facet joint ligament elongations were investigated as a function of whiplash loading in the four local anatomic regions of each joint. Under the normal posture, greatest elongations occurred in the dorsal anatomic region at the C2-C3 level and in the lateral anatomic region from C3-C4 to C6-C7 levels. Abnormal postures increased elongation magnitudes in these regions by up to 70%. Excessive ligament elongations induce laxity to the facet joint, particularly at the local regions of the anatomy in the abnormal kyphotic posture. Increased laxity may predispose the cervical spine to accelerated degenerative changes over time and lead to instability. Results from the present study, while providing quantified level- and region-specific kinematic data, concur with clinical findings that abnormal spinal curvatures enhance the likelihood of whiplash injury and may have long-term clinical and biomechanical implications.