有限元模型分析髓核摘除术后腰椎生物力学特性变化

目的采用三维有限元模型分析方法,探讨腰椎间盘突出症髓核摘除术对腰椎生物力学特性的影响。方法采用新型CAD方法精确建立腰椎L4～L5活动节段有限元模型,构建正常模型、退变模型、髓核摘除即刻模型和瘢痕长入模型,分别模拟正常椎间盘、退变椎间盘、髓核摘除术后即刻和术后中长期随访时的椎间盘,并在压缩、屈曲、伸展、前剪及后剪5种载荷条件下对4组模型进行生物力学测试。结果 (1)各种载荷下退变模型的腰椎节段刚度较正常模型提高;(2)髓核摘除即刻模型的刚度较退变模型减小,但较正常模型提高;(3)瘢痕长入模型腰椎节段刚度大幅回升并超过退变模型;(4)髓核摘除即刻模型在屈曲、后伸和后剪载荷下关节突接触力减小,瘢痕长入模型则表现为在后伸、前剪和后剪载荷下关节突接触力增加;(5)各种载荷下退变模型后向膨出度较正常模型明显减小,髓核摘除即刻模型后向膨出度一定程度回升,但其纤维环内环会发生"内向膨出"。结论腰椎间盘髓核摘除术可在术后不同时段对腰椎运动节段生物力学特性产生不同影响,髓核摘除术后即刻对腰椎稳定性和后部结构应力影响较小,而髓核摘除中长期后则可有腰椎运动节段变硬和关节突的应力增加。     

腰椎间盘退变后应力变化的有限元分析

目的 利用有限元分析方法,评估腰椎间盘退变后的生物力学变化.方法 利用MIMICS软件对正常腰椎的CT图像进行预处理后,导入ABAQUS软件建立正常椎间盘L3～L4节段的三维有限元模型.通过改变椎间盘退变后对应的材料属性,建立退变椎间盘L3～L4节段的有限元模型.对模型施加0.3 MPa均布轴向压缩载荷,比较正常和退变椎间盘的纤维环、髓核、软骨终板、关节突关节的应力.结果 与正常椎间盘比较,退变椎间盘的应力分布发生改变,纤维环周边承受较大应力,髓核的压应力明显降低,软骨终板的应力集中在外周偏后;关节突关节面的应力明显增大.结论 有限元方法可以直观地观察椎间盘退变对腰椎的影响,是对临床研究的必要补充.     

腰椎退变影响拔伸按压手法生物力学作用的有限元研究

目的:研究腰椎退变对拔伸按压手法治疗腰椎间盘突出症的生物力学影响。方法:应用L_(3～5)运动节段轻度退变与中度退变模型进行研究。假定腰椎间盘突出发生于L_4椎间盘左侧,为模拟拔伸按压手法,L_3椎体上终板固定,L_5椎体下终板施以500 N拉力;在L_(4～5)运动节段左侧椎板分别施以50 N与80 N按压力,比较两模型在不同按压力作用下L_4椎间盘左后方位移与L_(4～5)运动节段左侧小关节接触力。结果:手法按压力分别为50 N与80 N时,与轻度退变模型相比,中度退变模型L_4椎间盘左后方位移分别下降18.1%与34.5%,小关节接触力分别下降17.6%与43.4%;当按压力由50 N增至80 N,轻度退变与中度退变模型L_4椎间盘左后方位移分别增加146.3%与96.8%,小关节接触力分别增加195.9%与103.3%。结论:腰椎退变影响拔伸按压手法生物力学效应,但并不增加腰椎小关节接触力。     

可膨胀椎间融合器治疗腰椎间盘轻度退变的有限元分析

目的: 建立可膨胀椎间融合器(EVIFC)和第4、5腰椎的有限元模型,分析EVIFC植入对腰椎生物力学的影响,为EVIFC的临床应用提供依据。方法: 根据健康成年男性腰椎CT扫描数据建立正常第4、5腰椎有限元模型,在此模型上模拟腰4-5椎间盘轻度退变,在三维模型上植入EVIFC。在屈伸、侧弯和旋转的载荷下,分析腰椎模型置入EVIFC前后的稳定性、椎间盘压力、终板压力及小关节载荷变化。结果: EVIFC的置入减少了退变节段终板、髓核和小关节的应力。屈伸时,腰4-5椎体退变模型的终板及髓核平均压力分别是6.1620和0.2016MPa,小关节载荷是32.8N;植入EVIFC后其数值分别是3.526、0.107MPa和8.5N。侧弯及旋转载荷结果一致。对于邻近的腰椎节段,与退变模型比较,植入EVIFC后,腰4-5终板和髓核应力值均有所减小,但其相邻节段纤维环的应力值均有所增加。结论: EVIFC对退变腰椎能起到良好的稳定效果,可满足人体生物力学需求,是一种适宜的新型腰椎融合器。     

复杂性腰椎管狭窄症的有限元建模与分析

目的精确建立复杂性腰椎管狭窄症(lumbar spinal stenosis,LSS)的退变腰椎全节段有限元模型,与正常模型进行对比。方法选取复杂性LSS患者采集CT数据,采用专用生物力学软件建立退变腰椎全节段模型,同时构建正常材质和几何形态的腰椎模型,用相同边界条件进行对比分析。结果复杂性LSS腰椎的刚度增加、活动度范围比正常模型要小,特别是后伸工况减少了25.4%。总体上,退变腰椎的应力有增大趋势,退变节段椎间盘L4～L5和邻近上位椎间盘L3～L4的终板、髓核和和维环基质应力分布趋向四周边缘集中,特别是基质应力最大增加129%。结论复杂性腰椎管狭窄症的腰椎有限元模型的活动度减少、刚度增加,退变椎间盘四周出现应力集中,促进邻近椎间盘退变。     

腰椎活动节段力学模型的研究

力学模型是研究脊柱生物力学的重要手段。我们运用有限元方法(Finite element meted)建立了腰椎活动节段(Motion segment)的三维线性力学模型,并根据这一模型分析了正常人站立时腰椎应力分布情况。该模型有388个节点,共组成293个单元,包括椎体、椎间盘、后部结构以及韧带等部分。研究结果表明,当腰椎活动节段承受120O N的轴向压缩载荷时,椎体皮质骨的应力明显高出松质骨,椎间盘纤维环的应力则以后方较高。此外,在后部结构中,椎弓根、椎弓峡部、小关节等处也产生明显的应力集中。上述     

腰椎三维有限元模型建立和应力分析

目的 建立完整的腰椎三维有限元模型,并对腰3-4运动节段的进行了有效性验证和生物力学分析.方法 利用交互式医学图像控制系统MIMICS软件对CT图片进行预处理,后导人大型通用有限元软件ABAQUS中建立三维有限元模型.分别建立了腰1-腰5各椎体及其椎间盘有限元实体,后组合成整体的腰椎和腰3-4有限元模型,并且还准确的模拟了腰椎的椎间盘、软骨终板、关节突关节以及连接韧带.验证了模型的收敛性,并针对腰34运动单元设置了0.3、0.5、1.0、2.0、4.0 mPa 5种载荷进行生物力学分析.结果 在轴向压力作用下,椎间盘纤维环后部存在着明显的应力集中,并向后外侧传导.最大压应力的部位在髓核和软骨终板的中央,椎弓根是椎体多种应力集中的部位.轴向压力增加,应力成比例增大.结论 本研究的有限元模型精确度高,结论符合腰椎的临床特点,较好的模拟了腰椎的生物力学特性.     

椎间盘与软骨终板退变机理及生物学治疗的研究进展

<正>椎间盘是由软骨终板、纤维环及髓核三部分组成的,软骨终板是位于椎体骨质与椎间盘髓核之间的纤维软骨,与椎间盘相贴并终生存在。软骨终板作为椎间盘的主要营养途径,对椎间盘的营养提供以及力学性能的维持都具有十分重要的作用,越来越多的证据表明软骨终板退变与椎间盘退变密切相关,因此探讨椎间盘与软骨终板退变机理的相关性及其转归对于研究其相关疾病的病理及治疗是至关重要的。     

融合与Topping-off术对腰椎影响的有限元分析

目的:应用有限元方法分析Topping-off术对融合节段的相邻节段的影响。方法:建立L1~L5正常腰椎有限元模型,经与文献结果对比验证有效性后分别建立2种手术模型:(1)L4/L5节段融合的后路腰椎椎间融合术(posterior lumbar intervertebral fusion,PLIF)模型,(2)L4/L5节段融合及L3/L4节段植入棘突间固定装置(interspinous spacer,ISP)的Topping-off模型。分别对两者L1椎体上终板施加500 N垂直压缩载荷以及10 Nm前屈、后伸、(左)侧屈和(右)旋转力矩载荷,观察L3/L4节段活动度、椎间盘压力、小关节应力及L3、L4棘突应力情况,使用SPSS 21.0统计软件对结果进行分析。结果:在前屈、后伸载荷下,Topping-off模型L3椎体相对位移、椎间盘纤维环及髓核压力、双侧小关节应力小于PLIF模型(P<0.05),L3、L4椎体棘突应力大于PLIF模型(P<0.05)。在左侧屈载荷下,Topping-off模型L3/L4节段左侧小关节应力小于PLIF模型(P<0.05)。结论:Topping-off术能够降低融合相邻节段的椎间盘和小关节负荷,具有潜在的预防融合相邻节段退变的作用。     

单侧椎板开窗髓核摘除术对相邻节段椎间盘的生物力学影响

目的 应用非线性有限元分析研究单侧椎板开窗髓核摘除术对相邻节段不同程度退变椎间盘应力分布的影响.方法 墓于断层CT图像建立L3～L5节段三维非线性有限元模型,并依据L3～L4椎间盘不同退变程度建立轻、中和重度退变有限元模型,以及单侧椎板开窗髓核摘除术后模型.在模拟前屈、后伸、左右侧弯和左右旋转六个主要生理活动条件下,分析相邻节段椎间盘L3～L4髓核和纤维环von Mises应力极值变化.结果 行L4～L5左侧椎板开窗髓核摘除后,相邻L3～L4椎间盘为健康椎间盘时,髓核和纤维环基质内von Mises应力极值后伸最大,左侧弯时最小;轻度退变时,应力极值在左侧弯时增加最明显;中度退变时,髓核和纤维环基质von Mises应力极值减小,但仍高于健康椎间盘应力;重度退变时,髓核内von Mises应力极值均较轻中度椎间盘退变时下降,除轴向旋转运动外,甚至低于健康椎间盘时的应力值;纤维环基质内von Mises应力值较轻中度退变时下降,但仍高于健康椎间盘内纤维环应力,尤以左侧弯时明显.结论 当相邻节段椎间盘退变时,行单侧椎板开窗髓核摘除后避免同侧侧弯可以减少异常应力的产生,降低椎间盘退变加速的风险.

Abstract：

Objectives To study the stress distribution of the adjacent different grades of disc degeneration underwenting unilateral laminectomy and discectomy surgery using non-linear finite element analysis. Methods Based on the lumbar CT scans, the finite element model (FEM) of lumbar spinal segment(L3-L3) was established. According to L3-L4 intervertebral disc degeneration, different grades of disc degeneration( healthy,mild, moderate and severe) models were established and unilateral laminectomy and discectomy surgery were also established. Physiological action such as flextion , extension , lateral bending and lateral rotation was simulated and the yon Mises stress in the nucleus pulposus and annulus fibrosus matrix of L3-L4 disc was investagated. Results After unilateral laminectomy and discectomy surgery, the extremum value of yon Mises stress of nucleus pulposus and annulus fibrosus matrix was maximum during extension and minimus left bending in the healthy intervertebral disc. Compared with healthy disc, the increment of extremum value was found during left bending in the mildly degenerated disc. When the value decreased in the moderately degenerated disc, but still higher than that in the healthy disc. When the adjacent disc is severly degenerated, the extremum value of nucleus pulposus decreased, in addition to axial rotation, and even lower than that of healthy disc. The value of annulus matrix decreased and still higher than that of healthy disc , especially during left bending. Conclusions After unilateral laminectomy and discectomy surgery, avoiding lateral bending will reduce the abnormal stress in the degenerated disc and decreased the risk of accelerating disc degeneration.     

腰椎椎管狭窄症的生物力学研究

目的；从生物力学角度对腰椎椎管狭窄症的病因、病理、临床表现、诊断和手术治疗进行研究。方法；采用三维有限元模型，三维运动学测量、腰椎测量、影像学测量等方法，探讨 椎椎管狭窄症的生物学改变，并对该手术治疗作改进。结果；椎间盘纤维环后外侧、椎体后表面、椎弓根部、椎弓峡部和关节突关节等部位均产生明显的应力集中，而椎间盘退变及腰椎后仲均这一趋势加剧。后部结构切除手术除对于腰椎的生物力学行为有明确的影响，改进     

LUMBAR SPINAL STENOSIS. A REVIEW OF BIOMECHANICAL STUDIES

ObjectS. To investigate the biomechanical aspects of etiology, pathology, clinical manifestation, diagnosis and surgical treatment of the lumbar spinal stenosis. Methods. A series of biomechanical methods, such as three-dimensional finite element models, threedimensional kinematic measurement, cadeveric evaluation, and imaging assessment was applied to correlate lumbar biomechanics and lumber spinal stenosls. Surgery of lumber spinal stenosis has been improved. Results.The stresses significantly concentrate on the posterolateral part of the annulus fibrcsms of disc, the posterior surface of vertebral body, the pedlcle, the interarticularis and the beet joints. This trend is intensified by disc degeneration and lumber backward extension. Posterior elcxnent resection has a definite effect upon the biomechanical behavior of lumbar vertebrae. The improved operations proved satisfactory. Conclusion. Stress concentration in the lumber vertebrae is of importance to the etiology of degenerative lumbar spinal stenosls, and disc degeneratkm is the initial key of this process. Than these will be aggravatnd by backward extension. Functloval radiography and myelography are of assistance to the diagnosis of the lumhar spinal stenosls. For the surgcal treatment of the lumber spinal stenosis, destruction of the posterior element should be avoid as far as possible based upon the thorough decmnpression. Maintaining the lumbar spine in flexion by fusion after decorapression has been proved a useftd method. When developmental spinal stenoals is combined with disc herniation, discectoray through laminotomy is recommend for decompression.     

Intervertebral disc degeneration and bone density in degenerative lumbar scoliosis: a comparative study between patients with degenerative lumbar scoliosis and patients with lumbar stenosis

Background  Degenerative lumbar scoliosis is common in older patients. Decreased bone density and the degeneration of intervertebral discs are considered to be correlated with degenerative lumbar scoliosis. A means of quantifying the relative signal intensity for degenerative disc disease has not been previously discussed. The purpose of this study was to compare bone mineral density and intervertebral disc degeneration between degenerative lumbar scoliosis and lumbar spinal stenosis patients in a nine-year retrospective study.

Methods  From January 2001 to August 2010, 96 patients with degenerative lumbar scoliosis were retrospectively enrolled and 96 patients with lumbar spinal stenosis were selected as controls. Cobb angle, height of the apical disc and the contiguous disc superiorly and inferiorly on convex and concave sides, the height of the convex and concave side of the apical and the contiguous vertebral body superiorly and inferiorly were measured in the scoliosis group. The height of L2/L3, L3/L4, L4/L5 discs and the height of L2/L4 vertebral body was measured in the control group. The grade of intervertebral disc degeneration was evaluated using T2WI sagittal images in both groups. The bone density of lumbar vertebrae was measured with dual-energy X-ray.

Results  In scoliosis group, the intervertebral disc height on the convex side was greater than the height on the concave side (P <0.001). The vertebral body height on the convex side was greater than the height on the concave side (P=0.016). There was a significant difference between the scoliosis group and the control group (P=0.003), and between T-value and the rate of osteoporosis between the two groups (both P <0.001). Results were verified using multiple linear regression analysis.

Conclusions  Degenerative lumbar scoliosis is accompanied by height asymmetry between the intervertebral disc and vertebral body regarding the convex and concave surfaces. There is a positive correlation between the angle of scoliosis and the disc index, the degree of degeneration of the intervertebral disc, and a negative correlation between the angle of scoliosis and bone density.

     

Transplantation of gene-modified nucleus pulposus cells reverses rabbit intervertebral disc degeneration

Background  Intervertebral disc degeneration is the main cause of low back pain. The purpose of this study was to explore potential methods for reversing the degeneration of lumbar intervertebral discs by transplantation of gene-modified nucleus pulposus cells into rabbit degenerative lumbar intervertebral discs after transfecting rabbit nucleus pulposus cells with adeno-associated virus 2 (AAV2)-mediated connective tissue growth factor (CTGF) and tissue inhibitor of metalloproteinases 1 (TIMP1) genes in vitro.

Methods  Computer tomography (CT)-guided percutaneous annulus fibrosus injury was performed to build degenerative lumbar intervertebral disc models in 60 New Zealand white rabbits. rAAV2-CTGF-IRES-TIMP1-transfected rabbit nucleus pulposus cells were transplanted into degenerative lumbar intervertebral discs (transplantation group), phosphate-buffered saline (PBS) was injected into degenerative lumbar intervertebral discs (degeneration control group) and normal lumbar intervertebral discs served as a blank control group. After 6, 10 and 14 weeks, the disc height index (DHI) and signal intensity in intervertebral discs were observed by X-ray and magnetic resonance imaging (MRI) analysis. The expression of CTGF and TIMP1 in nucleus pulposus tissue was determined by Western blotting analysis, the synthesis efficiency of proteoglycan was determined by a ³⁵S-sulfate incorporation assay, and the mRNA expression of type II collagen and proteoglycan was detected by RT-PCR.

Results  MRI confirmed that degenerative intervertebral discs appeared two weeks after percutaneous puncture. Transgenic nucleus pulposus cell transplantation could retard the rapid deterioration of the DHI. MRI indicated that degenerative intervertebral discs were relieved in the transplantation group compared with the degeneration control group. The expression of collagen II mRNA and proteoglycan mRNA was significantly higher in the transplantation group and the blank control group compared with the degeneration control group (P <0.05).

Conclusions  CT-guided percutaneous puncture can successfully build rabbit degenerative intervertebral disc models. Both CTGF and TIMP1-transfected cell transplantation helps to maintain disc height, and promotes the biosynthesis of type II collagen and proteoglycan in intervertebral discs, reversing the degeneration of intervertebral discs.

     

腰椎间孔成形幅度对腰椎生物力学影响的三维有限元分析

目的应用腰椎L3~5节段三维有限元模型,分析椎间盘摘除+不同幅度椎间孔成形前后对腰椎生物力学的影响。方法选取1位20岁既往无腰椎疾病史中国男性志愿者的CT数据,在Mimics15.0软件中建立L3~5节段三维有限元模型,在Geomagic12.0中修补、降噪及曲面化,在Pro/E5.0中行椎间盘的曲面建模,修改髓核和纤维环的材料参数模拟L4~5椎间盘中度退变（模型M1）,在Hypermesh12.0中进行有限元网格处理,并导入ABAQUS软件进行分析。模拟经皮椎间孔脊柱内镜技术侧后入路,以上关节突尖部到下位椎体后上缘中点为穿刺基线建立通道,去除椎间盘左后侧约1/4的纤维环中部及1/4的髓核,以模拟腰椎间盘摘除手术,构建模型M2,以圆柱体代替环锯模拟切除上关节突部分骨质行椎间孔扩大成形术,构建一级椎间孔成形模型M3（环锯直径5mm）、二级椎间孔成形模型M4（环锯直径6.5mm）和三级椎间孔成形模型M5（环锯直径7.5mm）,给予特定加载条件,比较其在前屈、后伸、左右侧弯、左右旋转6种工况下的生物力学特征。结果建立了有效的L3~5三维有限元模型,除了在后伸工况下L4椎体的位移无明显变化外,其他5种工况下椎间孔成形后L4椎体的位移均有所增加,但成形的幅度对L4椎体的位移无明显影响。M1模型在各种工况下L4~5关节突关节的应力左侧较右侧大。M2模型在腰椎前屈及右旋工况下L4~5左侧关节突关节的应力下降,右侧的应力上升;腰椎后伸下L4~5左侧关节突关节的应力上升,右侧的应力下降;腰椎左侧屈工况下L4~5关节突关节的左右两侧应力均上升;腰椎右侧屈工况下L4~5关节突关节的左右两侧应力均下降。除腰椎左旋工况下M5模型的L4~5右侧关节突关节应力增加明显外,其他各种工况下M3、M4、M5模型L4~5关节突关节应力变化不明显。结论在精确穿刺的指引下,1~3级椎间孔成形对术后即刻的腰椎稳定及关节突关节的应力分布无明显影响。     

纤维环穿刺法与腰椎失稳法建立椎间盘退变模型

目的应用纤维环穿刺法与腰椎失稳法建立大鼠腰椎间盘退变模型,比较两种方法的异同。方法针刺组选用21G穿刺针对大鼠L3,4、L4,5、L5,6椎间盘行全层针刺;失稳组切除大鼠L3～L6棘突、棘上、棘间韧带和两侧关节突。于术后2周、4周和8周每组各取6只大鼠行腰椎影像学和组织学检查。结果针刺组大鼠2周时出现椎间隙狭窄,纤维环断裂,T2信号强度减低;4周时退变进展;8周时出现髓核皱缩、纤维化,T2呈完全低信号。失稳组4周时出现退变征象,8周时退变加重。结论两种方法均能建立大鼠腰椎间盘退变模型,针刺法较失稳法退变出现早、进展快且程度严重。