腰部推拿手法生物力学和有限元比较研究

目的：应用生物力学方法和三维有限元模型，模拟不同腰部推拿手法，比较其腰椎内部结构的变化。方法：标本固定于生物力学材料实验机（MTS）应用计算机定量控制，同时使用ABAQUS6.1有限元软件建立腰椎L4-5有限元模型，分别模拟斜板手法、坐位旋转和牵扳手法。结果：生物力学模型显示斜扳手法和坐位旋转手法髓核内压力明显升高，牵扳手法髓核内压力降低或轻度升高；神经根与椎间盘之间有一位移；腰椎小关切内应力低于关节内骨折的限度。有限元模型模拟手法作用时，椎间盘的髓压力在坐位旋转最大；牵扳手法最小且为负值。3种手法作用时，小关节合力均无明显差别。斜扳手法和坐位旋转手法外层纤维环应力最大，牵扳手法内层纤维环应力最大，3种手法均可造成椎间盘的后外侧与神经根之间有一位移。结论：模拟手法作用时椎间盘与相邻神经根之间有一相对位移，这可能是其治疗机制，有的手法作用时髓核内压升高，应注意其安全性。同时应用三维有限元模型可以很好的模拟各种腰部推拿手法，并得到与生物力学实验基本一致的结果。     

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.     

针刺损伤免椎间盘退变模型组织病理变化及软骨样细胞的迁移规律

背景：兔椎间盘退变模型间盘退变表现为随时间进展脊索细胞将被软骨样细胞逐渐替代,但兔针刺纤维环间盘退变模型中软骨样细胞的来源和移行规律尚不明确。目的：观察针刺兔纤维环间盘退变模型椎间盘病理变化过程,并初步探讨软骨样细胞来源及移行规律。方法：将24只新西兰大白兔随机分为手术组与假手术组。手术组使用16G穿刺针针刺L2/L3、L3/L4、L4/L5及L5/L6椎间盘纤维环,假手术组暴露至相同椎间盘前方后冲洗闭合伤口。结果与结论：针刺损伤椎间盘退变过程中的软骨样细胞来源于终板。在髓核与上下终板交界处,软骨细胞脱离终板成串向髓核中心迁移;在髓核与内层纤维环交界处,软骨细胞沿纤维走行迁移并随之向皱缩的髓核边缘迁移。椎间盘退变过程中非钙化层逐渐变薄,非钙化层/钙化层比值逐渐降低。     

腰椎间盘摘除三维有限元模型的生物力学分析

目的：建立腰椎运动节段椎间盘摘除的三维有限元模型，分析椎间盘摘除后腰椎生物力学的改变。 方法：实验于2003-12／2004-08在中南大学湘雅医院骨科研究室完成。以1名健康男性志愿者作为模拟对象，对其脊柱T12～S1节段进行层厚2mm的连续扫描，共获得CT断层图像264幅，并对CT图像每隔15&;#176;进行三维重建。将CT扫描的腰椎图像结合人体解剖学数据通过3DSMAX软件建模形成正常中国男性k运动节段的三维模型，用有限元分析软件转换成有限元模型。在此模型上去除L4-5椎间盘右后侧1／4的纤维环中部全层及约1／4的髓核，以模拟腰椎间盘摘除手术。分别在椎体、椎间盘及小关节选取节点进行计算。 结果：①2000N垂直压缩载荷下椎间盘摘除后运动节段应力与正常运动节段的比较：与正常运动节段比较，垂直压缩时上下椎体、纤维环及髓核右后方压力均升高；其余部分压力降低；双侧小关节内压力升高（P均〈0．01）。②10N&;#183;m前屈载荷下椎间盘摘除后运动节段应力与正常运动节段的比较：与正常运动节段比较，前屈时上下椎体、髓核左前方压力均升高；纤维环前方压力、后方张力均升高；双侧小关节内压力降低（P均〈0．01）。③10N&;#183;m后伸载荷下椎间盘摘除后运动节段应力与正常运动节段的比较：与正常运动节段比较，后伸时上下椎体、纤维环前方张力、后方压力均升高；髓核前方压力降低，后方压力升高；双侧小关节内压力升高（P均〈O．01）。④10N&;#183;m侧弯载荷下椎间盘摘除后运动节段应力与正常运动节段的比较：与正常运动节段比较，侧弯时上下椎体、纤维环、髓核右侧压力均升高，左侧压力降低；右侧小关节内压力升高，左侧小关节承受的张力改变为压力（P均〈0．01）。 结论：成功建立了L4-5腰椎运动节段椎间盘摘除的新型三维有限元模型，应力分析证实腰椎间盘摘除改变了腰椎运动节段正常的承载方式，小关节等部位存在较高的应力，提示这可能是术后邻近部位发生继发性退行性变的原因。     

针刺损伤兔椎间盘退变模型组织病理变化及软骨样细胞的迁移规律

背景:兔椎间盘退变模型间盘退变表现为随时间进展脊索细胞将被软骨样细胞逐渐替代,但兔针刺纤维环间盘退变模型中软骨样细胞的来源和移行规律尚不明确.目的:观察针刺兔纤维环间盘退变模型椎间盘病理变化过程,并初步探讨软骨样细胞来源及移行规律.方法:将24只新西兰大白兔随机分为手术组与假手术组.手术组使用16 G穿刺针针刺L2/L3、L3/L4、L4/L5及L5/L6椎间盘纤维环,假手术组暴露至相同椎间盘前方后冲洗闭合伤口.结果与结论:针刺损伤椎间盘退变过程中的软骨样细胞来源于终板.在髓核与上下终板交界处,软骨细胞脱离终板成串向髓核中心迁移;在髓核与内层纤维环交界处,软骨细胞沿纤维走行迁移并随之向皱缩的髓核边缘迁移.椎间盘退变过程中非钙化层逐渐变薄,非钙化层/钙化层比值逐渐降低.     

平面力推拿揉法与腰椎间盘生物力学关系的有限元分析

目的通过腰椎三维有限元建模方法，研究平面力推拿揉法对腰椎间盘生物力学的影响。 方法选取1例女性健康受试者，采用Somatom Sensation16型螺旋CT扫描机采集数据，进行精确三维分割与模型重建，生成正常人体L3～S1节段独立的三维实体模型，结合解剖知识构建肌肉实体模型后，采用专用生物力学软件建立L3～S1节段腰椎三维有限元，根据推拿揉法的作用规律，按循环旋转方向在L4和L5棘突的外部肌肉处施加平面作用力50N，观察腰椎间盘纤维环和髓核的变化。 结果在推拿揉法的左右摆动作用下，纤维环和髓核在水平方向上产生一定的循环旋转运动，运动的主要趋势是向椎间盘的中部及周边集中，髓核水分也向中部及周边聚集，椎间盘内密度发生变化，中部及周边密度增高。整个模型中骨皮质的应力分布较为均匀，说明推拿揉法的力传递过程在很大程度上依靠腰椎实体肌肉的协同和拮抗作用，L4-5椎间盘的纤维环和髓核应力分布显示椎间盘中部及周边的两侧应力较大。 结论在平面力推拿揉法作用下，腰椎纤维环和髓核向椎间盘中部及周边集中，椎间盘中部及两侧的应力较大。     

坐位旋转手法对正常腰椎间盘内在应力和位移的实时监测的实验研究

目的:了解坐位旋转手法对正常腰椎间盘的内在应力及位移分布的特点.方法:使用正常L4-5腰椎CT片,以Mimics软件系统逐层重建,建立L4-5三维有限元模型.根据手法原理,将坐位腰椎旋转手法进行分解,把各项力学参数代入三维有限元模型进行计算分析.即时显示手法作用时腰椎间盘的位移和内在应力的变化.结果:纤维环旋转侧的前部所受压力和旋转对侧的后部受到张力都逐渐增加;旋转侧的前部出现明显垂直压缩,并向前、向外侧膨出移位;纤维环旋转对侧的后部出现拉伸变形,并向前、向内侧回缩移位.结论:模拟坐位腰椎旋转手法时,椎间盘在旋转侧的前部为压力主要集中区,同时在旋转对侧的后部为张力集中区.椎间盘的最大位移在旋转侧的前部上缘;旋转对侧的后部受到张力也相应出现拉伸.髓核内的应力和位移变化相对较小.     

退变性脊柱侧弯的生物力学有限元分析☆

背景：脊柱在结构、形状、材料特性以及承受载荷方面都比较复杂,传统的生物力学方法不能完全解决这些特性问题。目的：探讨退变性脊柱侧弯椎间盘、关节突关节、椎体等的应力分布,为其发生、发展的生物力学机制提供依据。方法：基于退变性脊柱侧弯患者T12-S1上段连续的CT扫描图像,赋予模型特定的材料属性,建立完整、有效的退变性脊柱侧弯三维有限元模型。在前屈、后伸、左侧弯、右侧弯、左旋转、右旋转6种工况下对模型进行加载,计算和分析脊柱的活动度、椎间盘、椎体及关节突关节软骨的应力分布。结果与结论：退变性脊柱侧弯有限元模型比正常腰椎的活动度要小,椎间盘应力分布趋向于椎间盘的四周,后伸运动时各椎间盘应力最大,侧弯顶点椎体容易出现应力集中的情况,在旋转工况下关节突软骨的应力集中最明显,后伸工况下次之,尤其以侧弯顶点节段的关节突软骨影响最大。退变性脊柱侧弯侧弯顶点容易出现应力集中,后伸、旋转运动可加重退变性脊柱侧弯发展。     

腰椎牵引三维有限元模型分析

目的 :研究腰椎牵引条件下三维有限元分析。方法 :使用Abaqus 6 .1有限元软件建立有限元模型。平卧位腰椎的轴向荷载为 1 50N ,垂直位轴向荷载为 40 0N。牵引力作用于腰椎设定为 40 0N。结果 :牵引下髓核内压力下降 ;牵引下可将垂直位小关节应力解除 ;牵引下纤维环应力增加 ;椎间盘后外侧边缘和中点均有位移。结论 :三维有限元分析可以用于研究腰椎牵引的研究 ,以验证生物力学的研究结果并弥补其不足     

腰椎人工髓核植入对上位邻近节段椎体椎间盘影响的生物力学研究

目的探讨腰椎人工髓核植入对邻近节段腰椎稳定性的生物力学影响。方法新鲜小牛腰椎脊柱标本8具，分别制备成正常组、腰椎髓核摘除组、人工髓核植入组模型，自体对照，分别记录髓核摘除后、人工髓核植入与正常组对腰椎邻近节段的应变及应力改变，以此评估其对腰椎生物力学稳定性的影响。结果单纯髓核摘除术后病变节段上方相邻节段椎体的应变明显下降（P〈0．05）；人工髓核植入后其相应部位的应变与正常相比仅有数值上的增加，无统计学意义（P〉0．05）；髓核摘除后上位节段邻椎的椎体、椎间盘的应力均有增加，髓核植入后其应力基本恢复正常。结论人工髓核植入能有效维持上位相邻腰椎椎间盘、椎体的正常应力以及应变水平，维持脊柱正常的生物力学，延缓上位邻近椎体、椎间盘的退变。     

Outer annulus tears have less effect than endplate fracture on stress distributions inside intervertebral discs: relevance to disc degeneration

BACKGROUND: Annulus tears and endplate fracture are common lesions in human intervertebral discs. Both cause degenerative changes in animal models, but the time course appears to be different. The purpose of the present experiment is to compare the effects of outer annulus tears and endplate fracture on intradiscal stresses. We hypothesise that endplate fracture provides a greater stimulus for disc degeneration. METHODS: Seven cadaveric lumbar "motion segments" aged 49-70 years were compressed at 2 kN while the distribution of compressive stress was measured in each disc by pulling a 1.3 mm-diameter pressure transducer along its mid-sagittal diameter. Measurements were repeated after rim tears were simulated by 10 mm-deep scalpel cuts into the outer anterior annulus. The first cut was horizontal, 15 mm to the right of the disc midline, near the junction with the upper endplate. The second cut was vertical, 15 mm to the left of the disc midline, at mid-disc height. The third cut was horizontal, in the disc midline and at mid-disc height, so that the cut passed through the needle hole of the pressure transducer. Stress profiles were recorded in three postures and at two load levels, after each cut. Stress measurements were repeated a final time following compressive overload sufficient to fracture the endplate. FINDINGS: Outer annulus tears had negligible effect on compressive stress distributions in the annulus fibrosus more than 15 mm from the scalpel cut, and they caused nucleus pressure to fall by only 1% (SD 1.3%, NS). In contrast, endplate fracture reduced nucleus pressure by 37% (P=0.004) and increased maximum stress within the posterior annulus by 93% (P=0.033). INTERPRETATION: Outer annulus tears have less (immediate) effects on intradiscal compressive stresses than endplate fracture, supporting our hypothesis.     

腰椎间盘突出症磁共振成像下终板形态及其与椎间盘退变的关系

目的研究腰椎间盘突出患者下腰椎MRI 终板形态的分布规律,分析终板形态和椎间盘突出、Modic 改变的关系。方法回顾分析110 例腰椎间盘突出患者术前腰椎MRI。根据正中矢状面T1像将终板形态分型。根据Pfirrmann 法评定椎间盘退变等级。结果下腰椎终板最常见形态为凹面型。随着节段的下降,平坦型终板逐渐多见,L5~S1节段主要为平坦型。不规则型终板最少,且主要集中在L5~S1节段。终板形态由凹面型到平坦型再到不规则型,对应的间盘退变程度逐渐加重(P<0.05)。椎间盘突出节段以平坦型和不规则型终板多于凹面型多见,无突出节段则以凹面型多见(P<0.01),而平坦型和不规则型间无显著性差异(P>0.01)。不规则型终板比凹面型和平坦型更容易伴发Modic 改变(P<0.01),凹面型和平坦型间无显著性差异(P>0.01)。结论终板形态变化能在一定程度上反映椎间盘突出时间盘的退变情况。不规则型终板更容易伴发Modic 改变。     

软骨终板形态与椎间盘退变的相关性

背景:以往研究证明多种内环境因素共同作用引发椎间盘退变,最重要的机制为椎间盘软骨终板的退变。目的:分析椎间盘退变与终板形态的关系。方法:回顾性分析62例因椎间盘源性慢性下腰痛和79例因髓核脱出致神经根性症状患者的腰椎MRI正中矢状位图像资料。根据腰椎MRI正中矢状位T1W1图像确定终板形态,T2W1图像确定椎间盘退变程度分级。结果与结论:平坦型和不规则型终板最常见于椎间盘退变人群下腰椎,L5/S1平坦型最多见。髓核脱出组与椎间盘源性慢性下腰痛组中凹陷型终板椎间盘退变程度均较平坦型、不规则型低,平坦型终板椎间盘退变程度较不规则型低(P<0.01)。两组间凹陷型与不规则型终板椎间盘退变程度差异无显著性意义,髓核脱出组平坦型椎间盘退变程度较椎间盘源性慢性下腰痛组高(P<0.05)。提示随着椎间盘退变程度的加重,软骨终板形态有由凹陷型向平坦型、不规则型依次转变的趋势。     

Buck's direct repair of lumbar spondylolysis restores disc stresses at the involved and adjacent levels

BACKGROUND: Lumbar spondylolysis was reported to cause disc degeneration at both caudal and cranial adjacent level. However, basic disc biomechanics in the spondylolytic spine is not fully understood. Purpose of this study was to analyze the disc stresses at cranial and caudal adjacent level of lumbar spondylolysis. Also, the biomechanical effects of Buck's technique on disc stresses at these two segments were evaluated. METHODS: An experimentally validated three-dimensional non-linear finite element model of the intact ligamentous L3-S1 segment was used. Bilateral lumbar spondylolysis was simulated by creating bilateral pars defects with 1.0 mm gap at L5. Buck's direct repair model was simulated with 4.0 mm cannulated Titanium screws, placed bilaterally across the defect. Von Mises stresses in the annulus fibrosus and nucleus pulposus at L4/5 (cranial adjacent) and L5/S (caudal adjacent) disc levels were analyzed in flexion, extension, lateral bending and axial rotation in response to 400 N of axial compression and 10.6 Nm moment. The highest values were compared among the three models, intact, spondylolysis and Buck's technique. FINDINGS: After spondylolysis occurred at L5, annulus fibrosus and nucleus pulposus stresses at L4/5 increased to 111% and 120%, respectively. After the Buck's technique it recovered to 102% and 105%, correspondingly. On the other hand, at L5/S, annulus fibrosus stress increased to 168%, and nucleus pulposus, 155%, which was much higher when compared to the stresses at L4/5. After the Buck's technique the stresses were decreased to 125% and 120%, correspondingly. During rotation motion, especially, the operation normalized the disc stress completely. INTERPRETATION: Spondylolysis increases disc stresses at the affected as well as cranial adjacent level, and it may lead to disc degeneration at both levels. However, the increase in stresses is higher at the affected caudal level, when compared to the cranial level. Buck's technique may restore the disc stresses back to normal at both disc levels. Thus, this technique may be beneficial from a biomechanical perspective as well.     

Stress distribution in the intervertebral disc correlates with strength distribution in subdiscal trabecular bone in the porcine lumbar spine

BACKGROUND: It is understood that an interdependence of properties exists between the intervertebral disc and the subdiscal trabecular bone. Determining the biomechanics of this relationship is important in the development of novel spinal implants and instruments. The aim of this study was to analyze this relationship for the porcine lumbar spine and to compare it with that of the human spine. METHODS: The stress distribution within the intervertebral disc of 10 porcine lumbar (L4/L5) motion segments was recorded using a 1.5mm needle pressure transducer. For dynamic loading a specialized testing rig was developed to apply flexion/extension and medial/lateral bending while intervertebral disc stress was simultaneously recorded. The regional variation in mechanical properties of trabecular bone was also examined for an additional 10 porcine (L5) vertebral bodies. For compressive testing of the subdiscal bone, columns were prepared using a low speed cutting saw and subjected to axial compression. FINDINGS: Under pure compressive loading, stress levels within the intervertebral disc were relatively uniform. However, during asymmetric loading large peak stresses were evident in the periphery of the intervertebral disc in areas underlying the annulus fibrosus. The mechanical properties of trabecular bone demonstrated regional variations within the vertebral body. The ratio of compressive yield strength of bone underlying the outer annulus fibrosus to that of bone underlying the nucleus pulposus averaged 1.36. INTERPRETATION: Although the effects of stress distribution and bone mass adaptation cannot be directly related, it is probable that peak stresses arising in the annulus fibrosus during asymmetric loading provide greater stimuli for the underlying bone to undergo adaptive remodeling to withstand the greater forces experienced. Findings of intervertebral stress distribution and strength distribution of subdiscal trabecular bone for the porcine spine may aid in the development of strategies for preclinical animal testing of spinal implants.     

非融合棘突间固定器不同棘突间撑开高度对植入节段椎间盘压力分布的影响

背景：腰椎退变性疾病目前的非融合内固定特别是棘突间固定理论上可以保留有益活动,在缓解疼痛的同时预防邻近节段退变。目的：测量棘突间不同的撑开程度情况下节段椎间盘负荷分担及应力分布情况。方法：新鲜成人腰椎标本L2～5,采用电子万能实验机模拟腰椎前屈、中立、后伸运动负荷。实验分为7组：正常脊柱组,形状记忆合金棘突间固定器支撑高度10,12,14,16,18,20mm组。结果与结论：支撑高度为10mm的形状记忆合金棘突间固定器对植入节段椎间盘的压力分布无显著性影响;支撑高度为12mm的形状记忆合金棘突间固定器在过伸时可分担46%的椎间盘后纤维环负荷（P〈0.05）;支撑高度为14mm的形状记忆合金棘突间固定器可维持植入节段的轻度前屈,在过伸时可分担约47%的后环负荷（P〈0.05）,但后伸时会增大前环的负荷,当支撑高度远大于植入节段中立位时的棘突间高度时,屈伸活动时,后环的负荷显著降低的同时,前环负荷可增大达400%。提示支撑高度等于或略大于中立位棘突间高度的非融合棘突间固定器可分担椎间盘负荷并使椎间盘应力更均匀分布;但支撑高度过大会明显增大前环的负荷,如果用于神经源性间歇性跛行患者的椎间孔撑开,可能会加快椎间盘的退变。