椎间盘退变模型技术进展

椎间盘退变是多种因素长期慢性刺激椎间盘,从而引起的椎间盘结构稳定性下降,逐步缓慢发生相关变化的反应过程。通过对动物退变椎间盘模型的研究,可以为人椎间盘退变疾病的研究提供重要手段。随着动物模型制作手段不断丰富及控制指标精确程度不断提高,动物所模拟人椎间盘退变模型相似度有了显著提高,因此动物造模在椎间盘退变性疾病的研究中将具有更为广阔的发展前景。本文就近年来各种常用椎间盘退变模型的研究进展作一综述。     

颈椎椎间盘切除融合术后邻近节段退变比较

目的 :分析颈椎椎间盘切除融合术后邻近节段退变情况。方法 :回顾性分析我院2013年1月至2017年2月收治的63例颈椎退行性病变患者临床资料,手术方式为颈椎椎间盘切除融合术,手术及随访资料均完整,比较手术前及末次随访时患者COC2角(C2下终板与McGregor线夹角)、C2C7角(C7与C2下终板垂线间夹角)、T1S(T1倾斜角)、NT(颈倾角)、TIA(胸廓入口角)、日本矫形外科协会评分(JOA)及邻近节段颈椎间盘退变情况。结果 :术后随访21～56个月,平均(30.04±6.73)个月。术前患者JOA评分为(9.32±1.06)分,末次随访时为(14.87±0.65)分,术前与末次随访比较差异有统计学意义(P<0.05)。末次随访时C2C7角、T1S及NT均较手术前改善,差异有统计学意义(P<0.05)。末次随访时12例(19.05%)患者邻近节段发生退变,其中1例2级和1例1级退变为4级,3例1级退变为3级,6例0级退变为2级,1例0级退变为1级,手术前及末次随访时邻近节段退变情况分布比较差异无统计学意义(P> 0.05)。3例(4.76%)患者因邻近节段退变神经症状加重,再次手术后神经症状得到改善。结论 :颈椎间盘切除融合术治疗颈椎退行性病变神经症状改善效果显著,但术后存在邻近节段椎间盘退变风险,应灵活处置尽量降低退变发生率。     

基于变权分层激活扩散模型的产品设计知识动态推送技术

为了实现精确、动态的产品设计知识推送,提出了基于变权分层激活扩散模型的设计知识动态推送技术。分析了产品设计知识推送系统架构,建立了面向产品设计知识推送的变权分层激活扩散模型。以集聚关联分析方法获得设计知识节点的关联关系,通过层次激活扩散过程获得设计知识推送结果。结合设计人员反馈行为的分析,提出了设计知识单源与多源动态推送方法。通过在数控机床设计资源共享平台上建立的原型系统对提出的方法进行了说明与验证。     

多支承变截面转子轴系模型求解及有限元验证技术

以200WM汽轮发电机组模拟轴系为例,运用模态综合法建立了动力学模型.采用二分法和LU分解法分别获得系统的固有频率和主模态,并采用Nastran软件进行有限元分析验证上述理论和方法的正确性.最后,根据工程实际中出现的激励方式,采用Newmark时间差分法和五点空间差分法联合求解强迫弯曲振动动力学响应,该工作不仅对于这类多支承变截面转子轴系的理论分析具有重要的研究意义,还对其结构优化设计具有十分重要的指导作用.     

220kV变电站主变保护配置及压板投退原则

介绍了首钢京唐公司能环部220kV变电站主变保护装置的配置,简要分析了一些比较特殊或在操作中容易出错的压板及其投、退时应注意的问题,以避免事故的发生.     

压力容器技术进展

国产最大的钛制板式换热器中国四联钛设备设计制造公司的成员单位——天津板式换热器厂已研制成功国产最大的钛制板式热交换器,液一液型BR 130,单片面积1.3米~2,汽一液型BL80,单片面积O.8米~2。在天津碱厂运转正常。1987年9月7日在化     

压力容器技术进展

表1超高压容器用钢30 CrNi5MoV 化学成份(肠) ┌───┬───┬───┬─────┐ │Mo │V │Si │M·… │ ┌──┼───┼───┼───┼─────┤ │5 .0│0 .50 │0 .050│嗬0 .4│0 .20 │┌───┬───┼──┼───┼───┤ ├─────┤│0 .34 │0 .80 │5 .5│0 .60 │0 .12 │ │l ││ │ │ │ │ │ │ 0 .50 │└───┴───┴──┴───┴───┴───┴─────┘PS《0 .0150 .015裹2机械性能一一0 505︸44一门.、口了﹂n︸八J lfl甘O﹃一81知一一一勺5 lal卜口55容器尺寸机械乙性能(…     

压力容器技术进展

宽板试验研究进展近年来,机械部通用机械研究所安装调试600吨结构试验机的工作已经完成,可对高1.7米、宽0.9米的结构件,长2米、宽0.5米的板和长1.7米的圆棒作拉伸、压缩和三点弯曲试     

压力容器技术进展

压力容器焊接专家系统专家系统约出现于七十年代,它是人工智能的一个分支。据美刊《焊接设计与制作》1987年No3期报导:专家系统在焊接车间中的应用已指日可待。所谓专家系统是由四个部分组成的电脑程序,即储存规则的知识库;应用规     

压力容器技术进展

压力容器缺陷评定规范第二阶段研究动态由国家科委及机械工业部、化学工业部下达的重点科研项目—“压力容器缺陷评定规范的研究及编制”,经过课题组21个成员单位近三年的联合功关,进行了上万次试验和近百台容器试验,撰写了300多篇论文及试验报告,     

Effect of intervertebral disc degeneration on biomechanical behaviors of a lumbar motion segment under physiological loading conditions

The consideration of biomechanical alterations due to intervertebral disc (IVD) degeneration is crucial for the accurate analysis of spine biomechanics. In this study, finite element (FE) models of the L4-L5 motion segment with full coverage of the degeneration grades from healthy IVD to severe degeneration were developed. The effects of IVD degeneration on spine biomechanics were analyzed under physiological loading conditions using compressive forces and bending moments. The FE models of all degeneration grades were consistent with published data in terms of the ranges of motion. Severe IVD degeneration showed lower inter-segmental rotations in flexion-extension and lateral bending, lower intradiscal pressure in all motions, higher facet joint forces in lateral bending and axial rotation, and higher von-Mises stress in annulus ground substance in all motions versus the healthy IVD. These findings could provide fundamental information for understanding the characteristics of the biomechanical behaviors of degenerated lumbar motion segments.     

Tribological examination of lumbar intervertebral disc implants

The article presents results of friction and wear tests of three-piece systems of the intervertebral disc implant. The number of work cycles proved to have an effect on the coefficient of friction for polyethylene-on-metal and metal-on-metal tribojoints. In addition, for polyethylene-on-metal tribojoints, the effect of compressive force on the coefficient of friction was specified. The influence of working cycles on roughness changes of implant’s working surfaces was analyzed. Based on the microscopic examination of the working surface of implants and morphology of the wear products, the wear mechanism was described. Studies were performed at the Laboratory of Surface Engineering and Tribology in the Metal Forming Institute in Poznan using a SBT-03 simulator.     

Biomechanical disc culture system: feasibility study using rat intervertebral discs

A small-scale biomechanical disc culture system was designed to stimulate intervertebral disc (IVD) 'motion segment' in culture environment with load-controlled compression and combined load (compression+shear). After 7 days of diurnal mechanical loading, cell viability of discs stimulated with static compression load (0.25 MPa) and static combined load (compression (0.25 MPa)+shear (1.5N)) were similar (>90 per cent) to unloaded controls. Mechanically stimulated discs showed decrease in static/dynamic moduli, early stress relaxation, and loss of disc height after 7 days of diurnal loading. Histological data of discs indicated load-induced transformations that were not apparent in controls. The feasibility of studying the mechanobiology of intact IVD as a motion segment was demonstrated. Media conditioning (improve tissue stability in long-term culture) and application of biochemical gene expression assays (differential tissue response to types of mechanical stimulation) are proposed as future improvements. The study suggests that the limitations in studying mechanobiology of IVD pathology in vitro can be overcome and it is possible to understand the physiologically relevant mechanism of IVD pathology.     

Non-linear finite element analysis of formation and treatment of intervertebral disc herniae.

A biomechanical model of the spine motion segment L2/L3 consisting of the truncated vertebrae, endplates, intervertebral disc and pieces of anterior and posterior longitudinal ligaments has been used for a computer simulation study. A non-linear finite element analysis has shown that small loads compressing the spine, not greater than those occurring in everyday life, cause loss of stability of an intervertebral disc, resulting in lateral dislocation of its nucleus pulposus. This could be a potential cause of discopathy. The model indicates that conservative therapy of herniated disc by the traction method may result in retraction of hernia by about 40 per cent.     

Simulation of the disc degeneration with a poroelastic finite element model

To predict the degeneration process in the intervertebral disc, a finite element model of the spinal motion segment model was developed. The relationship between the biomechanical characteristics of fluid and solid matrix of the disc and cancellous core of the vertebral body, modeled as 20 node poroelastic elements, during the degeneration process was investigated. Excess von Mises stress in the disc element was assumed to be a possible source of degeneration under compressive loading condition. Recursive calculation was continued until the desired convergence was attained by changing the permeability and void ratio of those elements. The degenerated disc model showed that relatively small compressive stresses were generated in the nucleus elements compared to normal disc. Its distribution along the sagittal plane was consistent with a previously reported experimental result. Contrasts to this result, pore pressures in the nucleus were higher than those in the normal disc. Total stress, sum of compressive stress and pore pressure, indicated similar values for two different models. This study presented a new approach to study the likely mechanism responsible for the initiation and progression of the degenerative process within the intervertebral disc.     

Effects of electroacupuncture on a degenerated intervertebral disc using an in-vivo rat-tail model

Electroacupuncture (EA) has long been used as conservative treatment for low back pain (LBP). Its effect on relief of back pain has been demonstrated in many clinical studies. However, whether it has any effect on the biological properties of an intervertebral disc, which is one of the major causes of LBP, is still unclear. The aim of this study was, therefore, to investigate the effects of EA with different simulation frequencies on an intervertebral disc with simulated degeneration using an in-vivo rat-tail model. In this study, 33 rats were used. Disc degeneration was simulated in the rat caudal 8-9 disc via continuous static compressive loading of 11 N for 2 weeks. EA with a frequency of 2 or 100 Hz was then applied to the degenerated disc for 3 weeks with 3 sessions/week and 20 min/session. The intervertebral disc height was measured before and after compression as well as after EA intervention for 3 weeks. The static compression was found to result in a reduction in the disc height of about 22 per cent. There was no evidence that this change could be reversed after resting or the EA intervention. However, EA at 100 Hz was found to induce a further decrease in disc height, which was not shown for the rats after resting or EA at 2 Hz. The results of this study showed that effects of EA on disc degeneration are frequency dependent and adverse effects could result if EA at a certain frequency was used.     

Influence of vibration frequency variation on poroelastic response of intervertebral disc of lumbar spine

Journal of Mechanical Science and Technology - Long-time working under whole body vibration might accelerate the degeneration of spine and lead to low back pain and other spinal diseases. A...     

Adrenal chromaffin cells as transplants in animal models of parkinson's disease

The field of neural transplantation has moved rapidly forward in the last decade. Initially, fetal cells were used as implants to investigate their potential to ameliorate deficits in animal models of Parkinson's disease. However, because of the moral and legal problems associated with the use of fetal tissues in humans, alternative sources of donor tissue were sought which possessed the structural and functional characteristics needed to improve motor function in Parkinsonian patients. To date, one of the most promising tissues being investigated is the adrenal medulla, whose chromaffin cells possess an inherent plasticity of form and function. Transplanted chromaffin cells currently are being studied by a variety of approaches, including electron microscopy, in mouse, rat, and primate models of Parkinson's disease. An overview of the role of the chromaffin cell in this exciting and clinically important arena is briefly reviewed, with an emphasis on the fine structure of implanted chromaffin cells.     

A one-dimensional theoretical prediction of the effect of reduced end-plate permeability on the mechanics of the intervertebral disc

The permeability of the cartilage end-plate (CEP) may play an important role in intervertebral disc (IVD) degeneration by controlling the convective and diffusive transport of metabolites into the nucleus pulposus. A one-dimensional poroelastic model was used to predict the effect of a CEP of lower permeability than the disc tissue on the convective transfer into and out of the IVD. With decreasing CEP permeability, associated with degeneration, the model predicted that the change in disc height with time became more linear; the disc could not rehydrate as quickly; and internal fluid movement was slowed. This study has shown that CEP permeability will only markedly have an effect on fluid movement, and hence convective nutrition, if the permeability of the CEP is reduced to less than that of the disc tissue.     

The effects of disc degeneration and muscle dysfunction on cervical spine stability from a biomechanical study

Disc degeneration and muscle dysfunction are common spinal degenerations in the elderly. This in vitro study was carried out to investigate the effects of these two degenerative changes on spinal stability. The stability of nine porcine cervical spines (C2-T1) with mechanically simulated cervical muscles (sternocleidomastoid (SCM), splenius capitis (SPL), semispinalis capitis (SSC)) was tested before and after experiment-induced disc degeneration. The patterns of muscle recruitments included: no muscle recruitment, normal recruitment of SCM/SPL/SSC, and SCM/SPL/SSC muscle dysfunctions. The neutral zone (NZ) and the range of motion (ROM) in the sagittal plane were measured to determine spinal stability. The results showed that the NZ and the ROM of a degenerative spine were larger than those of an intact spine under no muscle recruitment, but not under muscle recruitments. For both intact and degenerative spines, the NZ and the ROM were greatest under no muscle recruitment, followed by SSC dysfunction, SCM dysfunction, and SPL dysfunction, and smallest under normal muscle recruitment. In conclusion, muscle recruitments stabilize both intact and degenerative cervical spines, while dysfunctional muscles do not maintain stability efficiently as normal muscles do. Thus, spinal stability is more significantly affected by muscle dysfunction than by disc degeneration. Muscle training is suggested for the elderly with spinal degeneration to improve stability.