建立正常人C2~7的三维有限元模型

背景：随着计算机技术的发展,颈椎生物力学研究不再局限于动物或人体尸体实验,计算机模型可以进行更准确的生物力学研究。 目的：在已有研究的基础上,建立人体C2~7三维有限元模型,以期为颈椎前路分节段减压融合的生物力学研究提供参考数据。 方法：选择1名28岁健康男性志愿者为观察对象,无明显的颈椎病史,扫描前先拍摄颈椎正侧位、斜位、过伸过屈位X射线片以排除颈椎病变。首先根据志愿者CT扫描图片,采用计算机辅助设计数据处理技术,输入相关的材料特性,构建C2~7三维有限元模型。模型重建采用先进的Geomagics系统,可以准确模拟颈椎结构,有限元部分则采用广泛使用的ANSYS系统。其次在1.8 N•m作用力下,观察节段运动与力-位移反应,并与国外的实验结果对比,在前屈、后伸、侧弯和旋转等4种工况(载荷状态)下对模型进行验证。 结果与结论：整个模型包括C2~7六个椎体、C2/3~6/7五个椎间盘以及后部结构与主要韧带,共有23 348个节点和215 749个单元。在模拟外力的作用下,模型前屈、后伸、侧弯和旋转工况下的颈椎活动度与以往实验模型结果数据基本吻合。提示所建立的颈椎有限元模型可以模拟颈椎生物力学实验,进行生物力学分析。     

人工椎间盘置换对腰椎小关节应力影响的三维有限元分析

背景：近年来随着对脊柱生物力学研究的深入,人工椎间盘被认为是治疗腰椎退行性变较理想的方法,但目前对人工腰椎间盘的生物力学研究还非常有限。 目的：建立腰椎运动节段人工椎间盘置换的三维有限元模型并进行生物力学分析,观察人工椎间盘置换对腰椎小关节应力的影响。 方法：在已建立的正常腰椎运动节段三维有限元模型的基础上去除L4~5椎间盘、上下终板的有限元单元,加入SB-Chaite Ⅲ型人工椎间盘的有限元模型,保留L4~5椎间隙的纤维环及相关韧带,形成L4~5运动节段人工椎间盘置换的三维有限元模型。对三维有限元模型在垂直压缩、前屈、后伸、侧弯等不同载荷下进行生物力学分析,记录小关节的应力,并与正常运动节段三维有限元模型相应部位的应力进行对比。 结果与结论：生物力学分析结果显示,人工椎间盘置换后：①垂直压缩时上下椎体、双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01)。②前屈、后伸时上下椎体前、后方及双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01)。③侧弯时上下椎体左右两侧及双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01)。提示人工腰椎间盘置换后小关节应力可保持在正常运动节段的水平,人工腰椎间盘置换可以达到腰椎生物力学性能重建的目的。     

一个新枕寰枢有限元模型的建立与生物力学分析

目的 建立一个新型枕寰枢复合体有限元模型并对其进行生物力学分析.方法 采集CT断层资料,应用Mimics软件完成枕寰枢的三维重建并获取点云数据,辅助以逆向工程完成骨性结构的曲面重构;采用Ture Grid软件建立包括关节软骨在内的全六面体有限元网格模型,建立模拟韧带的弹簧单元;在0.3 Nm和1.5 Nm外载荷下进行了前屈、后伸、侧屈和轴向旋转四种生理运动的生物力学分析及有效性验证.结果 该枕寰枢模型能对正常情况下生物力学特性如运动学、韧带应变、关节应力等进行预测.结论 枕寰枢有限元模型对枕颈交界区生物力学的改变及其稳定性的影响可以进行有效的、可重复的仿真分析,具有较高的实用性和临床参考价值.     

人工颈椎间盘置换对下颈椎活动影响的三维有限元分析

建立人工椎间盘置入后下颈椎C3~7的三维模型,分析颈椎人工椎间盘置换后下颈椎运动情况。根据1例人工椎间盘置入患者术后6个月CT片,应用有限元方法建立其包含BryanTM人工颈椎间盘假体的下颈椎三维有限元模型,导入Ansys 9.0中,对椎体皮质骨、松质骨、椎间盘用三维十节点四面体结构实体单元进行网格划分后进行分析。对模型加载2 N•m的力矩,观察其在前屈/后伸、侧屈及旋转几种状态下的运动情况,了解其运动特性。通过与以往的研究结果比较,试验结果基本符合或趋势基本一致。结果提示,颈椎间盘置换后能基本保证下颈椎运动稳定性。     

带有枕骨全颈椎三维有限元模型的构建及生物力学分析

目的 构建含有枕骨的全颈椎三维有限元模型,并验证其有效性,为颈椎及颅颈交界区疾病的生物力学研究提供良好的力学模型。方法 基于健康男性志愿者的枕颈部薄层CT构建模型,将CT的原始数据导入Mimics软件中,构建三维点云模型,进而导入Geomagic Studio软件构建全颈椎曲面模型,并在Hypermesh软件中进行实体网格划分、材料赋值等步骤构建枕骨~T1的全颈椎实体模型,最后导入有限元软件Abaqus进行有效性验证。结果 构建的带有枕骨的全颈椎有限元模型同真实脊柱解剖学形态一致,材料属性正确,且各节段活动度在既往文献标准差范围以内,通过了模型的有效性验证。结论 本研究所建立的带有枕骨的全颈椎有限元模型符合脊柱生物力学研究所要求的解剖学一致和生物力学相似,可用于颅颈交界区及颈椎的生物力学研究。     

生物活性颈椎椎间融合器的三维运动稳定性实验

背景：前期实验已证实，以自行合成的羟基磷灰石/左旋聚乳酸复合材料研制的生物活性颈椎椎间融合器有良好的生物相容性。 目的：进一步比较该生物活性颈椎椎间融合器和髂骨块的三维运动稳定性，以评价生物活性颈椎椎间融合器置入椎间后重建颈椎稳定性的效果。 设计、时间及地点：体外生物力学实验，于2003-08/11在南方医科大学全军及广东省重点生物力学实验室完成。 材料：生物活性颈椎椎间融合器是利用羟基磷灰石/左旋聚乳酸复合而成由南方医科大学珠江医院提供（专利号为：03236843.7）。6具新鲜人尸体颈椎标本C1~T1节段，均分为3组：正常组、髂骨组及生物活性颈椎椎间融合器组。 方法：在6具新鲜人尸体颈椎标本的C5与C6椎间盘处，行颈前路环锯减压后，髂骨组及生物活性颈椎椎间融合器组分别置入自体髂骨和生物活性颈椎椎间融合器，正常组为完整结构标本，不予进行任何处理。 主要观察指标：利用测量系统测量3组颈椎节段间前屈、后伸、左/右侧弯和左/右轴向旋转等三维运动范围。 结果：在椎间盘切除椎间置入生物活性颈椎椎间融合器后，在前屈、左右侧弯和左右轴向旋转的运动范围均较椎间置入髂骨组减少，较髂骨组稳定，差异有统计学意义（P < 0.01）。在后伸状态下椎间置入生物活性颈椎椎间融合器和髂骨置入物与正常组比较运动范围增大，但差异无统计学意义。 结论：生物活性颈椎椎间融合器置入椎间后颈椎稳定性良好，置入椎间后较椎间置入髂骨稳定。     

下颈椎前路内固定联合后路经关节金属螺钉置入固定的生物力学稳定性

背景：对退变性颈椎管狭窄单纯采用前路椎体次全切除或椎间盘切除或单纯后路单开门椎管扩大成行均不能彻底完成脊髓减压和脊柱三柱稳定。 目的：探讨下颈椎前路固定联合后路经关节螺钉固定的生物力学稳定性。 方法：正常成人尸体颈椎标本,每具分别制作以下两种模型：①经后路C3~C7单开门和下颈椎前路C5椎体次全切除钛网支撑植骨、ORION内固定模型(对照组)。②经后路C3~C7单开门和经关节螺钉内固定及下颈椎前路C5椎体次全切除钛网内植骨、ORION内固定模型(实验组)。 结果与结论：实验组在前屈、后伸、左、右侧屈及左、右旋转移位角度均小于对照组(P < 0.001)。提示：①在生物力学实验中,下颈椎前路固定联合后路经关突节螺钉固定的生物力学性能优良,对抗前屈、后伸、左、右旋转的作用力更强,颈椎可获得更可靠的稳定性。②下颈椎前路固定联合后路经关节螺钉固定在对抗颈椎前屈运动时力学稳定性更为强大。     

腰椎间盘突出症有限元模型的建立与分析

目的建立人体腰椎运动节段(L3~5)有限元模型,于轴向正压力、前屈、侧弯、后伸及旋转等载荷下研究椎间盘的生物力学特征。方法根据健康成年人腰椎运动节段(L3~5)的CT影像学资料,采用Mimics10.0医学图像处理软件和Geomagic10.0逆向工程软件分别建立腰椎运动节段(L3~5)椎体和椎间盘的几何模型,Ansys软件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,构建正常模型和腰椎间盘突出(L34)模型,运用有限元方法模拟正常椎间盘和突出椎间盘于轴向正压力、前屈、侧弯、后伸和旋转等载荷下生物力学特征参数。结果腰椎运动节段(L3,4)发生椎间盘突出后即改变了椎间盘的应力分布及传递载荷能力,应力主要集中于纤维环之后外侧。结论腰椎运动节段(L34)椎间盘突出后椎间盘的承载功能明显下降。     

颈椎后凸畸形山羊动物模型：力学失衡及异常应力☆

背景：颈椎后凸畸形发生的同时其生物力学行为也发生变化，但关于颈椎后凸畸形动物模型的生物力学研究少见文献报道。 目的：分析颈椎后凸畸形山羊动物模型的生物力学变化。 方法：通过外加因素，模拟颈椎后凸畸形的形成病因，构建颈椎后凸畸形山羊的动物模型，并对颈椎后凸畸形山羊和正常山羊的新鲜颈椎标本作生物力学的对比研究，测量其三维运动范围和弯曲刚度。 结果与结论：与正常山羊颈椎标本比较，颈椎后凸畸形山羊后凸范围在C2~5, 颈椎后凸畸形山羊在C2/3~C4/5节段的三维运动范围明显减小，而在C5/6节段此差距明显缩小，在C6/7节段基本无差别，甚至会略大于正常山羊颈椎三维运动范围，在屈伸、左右侧屈、左右旋转运动中，旋转运动下降最多，旋转活动基本被限制；颈椎后凸畸形山羊在C2/3~C4/5节段的弯曲刚度明显增大，而在C5/6和C6/7节段两者较接近。反映了在施加实验因素后，羊的颈椎出现了生物力学的改变，羊颈椎在出现后凸畸形后变得僵硬了。结果提示后颈椎后凸畸形形成后，后凸节段颈椎的力学失衡和异常应力的存在造成颈椎关节的异常融合,导致了颈椎生物力学特征的改变。 关键词：颈椎；后凸畸形；生物力学；动物模型；应力     

E有限元方法在颈椎生物力学中的应用

目的:研究重建颈椎三维有限元模型。方法:通过CT扫描、Unigraphics V18.0 软件进行影像边界记录、定标等方法,按照点、线、面、体的顺序重建三维结构,采用CAD数据处理技术,输入相关的材料特性,验证重建模型的有效性。结果: 建立颈椎的三维有限元模型（C3/4）,分析结果证明其在仿真分析中是可行的。结论:建立的颈椎三维有限元模型可以模拟生物力学实验。     

Denervation study of synapses of organ of corti of old world monkeys

Fine structural characteristics of synapses in the spiral organ of Corti were examined, with reference to differences between inner and outer haircell systems, and to location of neurons of origin of efferent axons. Surgical interruption of crossed olivocochlear bundle, of vestibular nerve, of facial nerve, and excision of superior cervical ganglia were used to determine the pathways of efferent axons. Interruption of the vestibular nerve near the brainstem results in degeneration of all efferent terminals on outer hair cells. Mid-line lesions at, and caudal to, the facial colliculus result in degeneration of about half of these efferent terminals. Efferent synaptic bulbs to the inner hair-cell system are small, of the order of one micron, and form type 2 junctions with afferent dendrites. They tend to have more large dense-core vesicles (about 80 nm) than the large efferent terminals of the outer hair-cell system, and appear to be the terminals of axons in the habenula perforata, which exhibit varicosities laden with large dense core vesicles. The varicosities are unaffected by excision of the superior cervical ganglia. So far as our material can reveal, it appears that the varicosities in the habenula perforata do not survive vestibular root interruption, nor do the efferent processes in the internal spiral bundle or at the base of inner hair cells. Most interestingly, the afferent processes of the inner hair-cell system, as identified for example by their relation to pre-synaptic bodies in the inner hair cells, are subject to a trans-synaptic reaction after severance of the vestibular root. They undergo a dramatic cytological transformation, characterized by increase of volume, engorgement with microtubules, microfilaments, microvesicles of various sizes, and clusters of lysosomes. Thus, both the efferent and afferent terminals of the inner hair-cell system show marked cytological differences from the corresponding terminals of the outer hair cell system.     

Mechanism of action of tubocurarine on nicotinic cholinoreceptors of neurons of the sympathetic ganglia of rats

Tubocurarine (Tc) effect on membrane currents elicited by acetylcholine (ACh) was studied in isolated superior cervical ganglion neurons of rat using patch-clamp method in the whole-cell recording mode. The "use-dependent" block of ACh current by Tc was revealed in the experiments with ACh applications, indicating that Tc blocked the channels opened by ACh. Mean lifetime of Tc-open channel complex, tau, was found to be 9.8 +/- 0.5 s (n = 7) at -50 mV and 20-24 degrees C. tau exponentially increased with membrane hyperpolarization (e-fold change in tau corresponded to the membrane potential shift by 61 mV). Inhibition of the ACh-induced current by Tc (3-30 microM/1) was completely abolished by membrane depolarization to the level of 80-100 mV. Inhibition of ACh-induced current was augmented at increased ACh doses. It is concluded that the open channel block produced by Tc is likely to be the only mechanism for Tc action on nicotinic acetylcholine receptors in superior cervical ganglion neurons of rat.     

The effect of age of onset of PD on risk of dementia

Background Dementia occurs in the majority of patients with Parkinson’s disease (PD). Late onset of PD has been reported to be associated with a higher risk for dementia. However, age at onset (AAO) and age at baseline assessment are often correlated. The aim of this study was to explore whether AAO of PD symptoms is a risk factor for dementia independent of the general effect of age. Methods Two community-based studies of PD in New York (n = 281) and Rogaland county, Norway (n = 227) and two population-based groups of healthy elderly from New York (n = 180) and Odense, Denmark (n = 2414) were followed prospectively for 3–4 years and assessed for dementia according to DSM-IIIR. All PD and control cases underwent neurological examination and were followed with neurological and neuropsychological assessments. We used Cox proportional hazards regression based on three different time scales to explore the effect of AAO of PD on risk of dementia, adjusting for age at baseline and other demographic and clinical variables. Findings In both PD groups and in the pooled analyses, there was a significant effect of age at baseline assessment on the time to develop dementia, but there was no effect of AAO independent of age itself. Consistent with these results, there was no increased relative effect of age on the time to develop dementia in PD cases compared with controls. Interpretation This study shows that it is the general effect of age, rather than AAO that is associated with incident dementia in subjects with PD. Received in revised form: 22 December 2005     

Limits of deinstitutionalization--perspectives of relatives of psychiatric patients

After a hopeful beginning, the social process of the reintegration of those with severe mental illness has come to a standstill. I am led to wonder whether "the community" really wants to live together with people suffering from severe mental illness, and if so, how closely? As long as the medical treatment of mental illness provided by the general practitioners is fundamentally deficient, as they are not able to prescribe the necessary interventions--such as out-patient psychiatric nursing, and service providers in the out-patient sector are content with offering increasingly intensive forms of care for the less seriously ill at the cost of the Social Welfare System--the reintegration of those with serious mental illness remains an illusion--which is mainly to the benefit of providers of residential care in homes and hostels.     

Summary of legislation of 1935 of interest to the department of Mental Hygiene

Psychiatric Quarterly -