A three-dimensional finite element model of the cervical spine: an investigation of whiplash injury

Very few finite element models of the cervical spine have been developed to investigate internal stress on the soft tissues under whiplash loading situation. In the present work, an approach was used to generate a finite element model of the head (C0), the vertebrae (C1–T1) and their soft tissues. The global acceleration and displacement, the neck injury criterion (NIC), segmental angulations and stress of soft tissues from the model were investigated and compared with published data under whiplash loading. The calculated acceleration and displacement agreed well with the volunteer experimental data. The peak NIC was lower than the proposed threshold. The cervical S- and C-shaped curves were predicted based on the rotational angles. The highest segmental angle and maximum stress of discs mainly occurred at C7–T1. Greater stress was located in the anterior and posterior regions of the discs. For the ligaments, peak stress was at anterior longitudinal ligaments. Each level of soft tissues experienced the greatest stress at the time of cervical S- and C-shaped curves. The cervical spine was likely at risk of hyperextension injuries during whiplash loading. The model included more anatomical details compared to previous studies and provided an understanding of whiplash injuries.     

无骨折脱位颈髓挥鞭样损伤的临床特征

背景：无骨折脱位颈髓挥鞭样损伤是一种特殊颈椎、颈髓损伤,其损伤的原因、机制尚存争议,认识其发病机制可为临床诊断和治疗提供重要的理论基础。 目的：综述国内外无骨折脱位颈髓挥鞭样损伤的发病机制和诊断治疗方法。 方法：应用计算机检索中国生物医学文献数据库、中文科技期刊全文数据库(1975年1月至2011年5月)和PubMed数据库(1950年1月至2011年5月)中与无骨折脱位颈髓挥鞭样损伤有关的文章,检索词为“颈髓挥鞭样损伤、发病机制、影像学、治疗”和“cervical spinal cord whiplash injuries; pathogenesis; imaging; treatment”,并限定文章语种为中文和英文。纳入所述内容与颈椎无骨折脱位颈髓挥鞭样损伤定义、发病机制、影像学表现和治疗及预后相关的文章,排除重复性研究。 结果与结论：共检索到90篇相关文章,纳入符合要求的38篇文献进行综述。无骨折脱位颈髓挥鞭样损伤是一种特殊的颈椎、颈髓损伤,主要由过伸性和过屈性损伤引起。近年来对无骨折脱位颈髓挥鞭样损伤的进一步研究发现,其定义、发病机制、影像学表现和治疗标准存在不同的分歧。常规X射线和CT检查无阳性发现,MRI检查能降低无骨折脱位型颈髓挥鞭样损伤的误诊率,是一种最佳检查方法。根据损伤机制可选择前路手术、后路手术和前后路联合手术治疗。     

Detection of Altered Collagen Fiber Alignment in the Cervical Facet Capsule After Whiplash-Like Joint Retraction

The cervical facet joint has been identified as the source of pain in patients with whiplash-associated disorders, but most clinical studies report no radiographic evidence of tissue injury in these disorders. The goal of this study was to utilize quantitative polarized light imaging to assess the potential for altered collagen fiber alignment in human cadaveric cervical facet capsule specimens (n = 8) during and after a joint retraction simulating whiplash exposure. Although no evidence of ligament damage was detected during whiplash-like retraction, mechanical and microstructural changes were identified after loading. Retraction produced significant decreases in ligament stiffness (p = 0.0186) and increases in laxity (p = 0.0065). In addition, image analysis indicated that 21.1 ± 17.1% of the capsule sustained principal strains that were unrecovered immediately after retraction. Altered collagen fiber alignment was detected in 32.7 ± 22.9% of the capsule after retraction. The capsule regions with unrecovered strain and altered fiber alignment after retraction were significantly co-localized with each other (p < 0.0001), suggesting the altered mechanical function may relate to a change in the tissue’s fiber organization. The identification of altered fiber alignment in this ligament following retraction without any tears implicates the whiplash kinematic as a potential cause of microstructural damage that is not detectable using standard clinical imaging techniques.     

利用头颈有限元模型研究散打运动中颈椎韧带损伤的风险

目的研究颈椎有限元模型在预测散打中颈椎韧带损伤风险的作用,比较摆拳及直拳击打后颈椎韧带受力的差异。方法基于CT图像利用图像处理软件Mimics进行头颈骨骼部分的三维重建,并导入Hyper Mesh建立一个有效的头颈有限元模型,在对该模型的力矩-运动范围及击打后头部加速度进行验证后,比较不同击打力量(2.60、3.30、4.35 kN)下直拳及摆拳击打对颈椎韧带受力大小、分布的差异。结果所建颈部有限元模型具有良好的生物有效性,其预测的受击打后头部线性加速度及旋转加速度与参考文献相符。在摆拳模拟中,韧带最大受力部位位于环枕韧带,当击打力从2.60 kN增加至4.35 kN时,摆拳击打后韧带受力最大值分别为207、265、263 N;而在直拳击打后韧带受力最大部位位于环枢韧带,其受力最大值分别为96.8、91.4、101.4 N。在同样的击打力量下,摆拳所致的颈椎韧带受力较直拳更大。结论与直拳相比,散打摆拳更容易引起颈椎韧带损伤;头颈有限元模型可用于散打所致颈部损伤的生物力学机制研究,为散打的训练及损伤预防提供更精确的参考。     

脊柱颈段椎间盘平面椎管内前部结构的解剖学研究

目的　探讨经脊柱颈段椎间盘入路椎管内减压的相关解剖。 方法　取18具正常成人颈段脊柱防腐标本,通过不同断层,观察硬脊膜、后纵韧带与硬膜外前隙的毗邻关系和结构特点;测量椎间盘平面的硬脊膜厚度、后纵韧带宽度、椎体矢状径长度。 结果　颈段后纵韧带分为深、浅层,两层在中线两侧4～5 mm处分开,浅层与硬脊膜形成潜在的硬膜外前隙,该隙内有Hofmann's韧带连于硬脊膜与后纵韧带之间。深、浅层在硬脊膜前外侧形成一梭形腔隙－后纵韧带间隙; 椎体后面矢状正中线到两侧后纵韧带间隙外侧角的距离约为10 mm。 结论　根据后纵韧带的宽度和毗邻关系,颈椎前路手术经椎间盘达后纵韧带,逐渐由外进入后纵韧带间隙减压,可减少硬膜囊、脊髓或神经根的损伤。     

Viscoelastic properties of the cervical spinal ligaments under fast strain-rate deformations

The mechanical response of ligaments under fast strain-rate deformations is a necessary input into computational models that are used for injury assessment. However, this information frequently is not available for the ligaments that are routinely injured in fast-rate loading scenarios. In the current study, experiments were conducted at fast strain rates for the cervical spinal ligaments: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. Bone-ligament-bone complexes at three spine levels were harvested for mechanical testing. Displacement-controlled sub-failure uniaxial tensile tests were performed in both load-relaxation and sinusoidal conditions. A nonlinear (separable) viscoelastic model was used to examine the experimental data. An unexpected result of the modeling was that the instantaneous elastic functions could be approximated as linear for these strain rates. A five-parameter model was sufficient to characterize the ligament viscoelastic responses and had good predictive capacity under different applied loading conditions.     

PATHOLOGICAL STUDIES ON THE OSSIFICATION OF THE POSTERIOR LONGITUDINAL LIGAMENT (OPLL)

Ossification of the posterior longitudinal ligament (OPLL), which causes marked spinal cord compression, occurs more frequently in Japan than in other parts of the world. To investigate the mechanism of this ossification, we examined two cases of mixed type of OPLL inducing severe neurological signs due to spinal cord compression and three cases of segmental OPLL type without neurological signs. Ossification of the ligament begins at the upper end of posterior margin of the vertebral body and distends mainly downward along the posterior longitudinal ligament (PLL) and finally replaces the PLL completely. Ossification consists of compact bones with lamellar structures. In the upper end of the posterior margin of the vertebral body, where the PLL fuses with the cortical bone of vertebral body, ossification always has a direct contact with cortical bone and in this portion proliferation of cartilaginous tissue and calcification were observed. Proliferation of cartilaginous tissue plays a key role in the formation of OPLL and occurs mainly by an enchondral ossification. In three among twenty one cases of cervical vertebrae examined as the control, small foci of ossification were observed which might be related to the initial phase of OPLL. Spinal cords of case 1 and 2 showed marked indentation and flattening with the loss of nerve cells, severe fibrous gliosis of the gray matter and demyelination of the anterior column. Venous congestion due to compression and vulnerability of gray matter to anoxia is important for the histological changes of spinal cord.     

A Three-Dimensional Finite Element Model of the Cervical Spine with Spinal Cord: An Investigation of Three Injury Mechanisms

The spinal cord may be injured through various spinal column injury patterns (e.g., burst fracture, fracture dislocation); however, the relationship between column injury pattern and cord damage is not well understood. A three-dimensional finite element model of a human cervical spine and spinal cord segment was developed, verified using published experimental data, and used to investigate differences in cord strain distributions during various column injury patterns. For a transverse contusion injury, as would occur in a burst fracture, a 33% canal occlusion resulted in two peaks of strain between the indentor and opposing vertebral body and intermediate peak strain values. For a distraction injury, relevant to column distortion injuries, a 2.6 mm axial displacement to the cord resulted in more uniform strains throughout the cord and low peak strain values. For a dislocation injury, as would occur in a fracture dislocation, an anterior displacement of C5 corresponding to 30% of the sagittal dimension of the vertebral body resulted in high peak strain values adjacent to the shearing vertebrae and increased strains in the lateral columns compared to contusion. This model includes more anatomical details compared to previous studies and provides a baseline for mechanical comparisons in spinal cord injury.     

齿状韧带的形态观测及临床意义

目的　为临床SPR和SAR提供可靠的脊神经前、后根鉴别和定位的形态学依据。方法　对 30例 (6 0例 )成人尸体的齿状韧带进行了解剖学观测和测量。结果　齿状韧带位于椎管内脊神经前、后两神经根之间。颈部脊神经前、后根之间有恒定的齿状韧带。两侧形成平均 2 0个锯齿状齿尖 ,以齿尖在上、下脊神经根之间附着于硬脊膜。结论　在选择性脊神经根切断术中 ,齿状韧带可作为一标志 ,脊神经前、后根可通过齿状韧带加以鉴别和定位 ,特别在颈部。     

颈椎侧块钢板治疗颈椎后纵韧带骨化的探讨

目的探讨在颈椎后纵韧带骨化(OPLL)患者实施后路全椎板切除减压后,应用颈椎侧块钢板内固定的方式及疗效。方法1999年6月～2002年1月,12例OPLL患者采用后正中切口,显露至两侧关节突外缘,根据脊髓受压节段行全椎板切除后,采用Magerl方法行颈椎侧块钢板内固定加植骨术。结果随访8个月～2年4个月,平均18个月。根据JOA评分标准,平均改善率66%。未发生椎动脉或神经根损伤、脊髓损伤等严重并发症。结论OPLL患者行后路全椎板切除减压和颈椎侧块钢板内固定,既能有效改善颈椎管狭窄,又能避免全椎板切除对颈椎稳定性影响,疗效满意。     

影响下颈椎骨折脱位在麻醉下手法复位失败的多因素分析

目的探讨影响下颈椎骨折脱位在麻醉下闭合复位失败的相关影响因素。方法通过回顾我科于2006年1月~2011年1月治疗下颈椎骨折脱位病例85例。分别记录患者的年龄、性别、颅骨牵引重量、颅骨牵引时间、骨折脱位节段、交锁、并发多颈椎骨折、关节突关节骨折、前纵韧带及椎间盘损伤、后方韧带复合体损伤等相关因素,观察患者麻醉下复位的情况,分析引起复位失败原因。结果影响复位失败的相关因素和顺序为关节突关节交锁;前纵韧带及椎间盘损伤;多发颈椎骨折。结论下颈椎骨折脱位伴双侧交锁是麻醉下手法复位的适应症;单侧交锁或多发颈椎骨折受伤是相对禁忌症,选择适当的病例,可以减少医源性损伤,简化手术。     

颈椎前纵韧带的特点及其病理改变的研究进展

前纵韧带是脊柱中唯一限制椎体过伸的韧带组织结构,对于活动度更大的颈椎部分来说更是意义重大。为了对颈椎前纵韧带的相关知识有更好的理解及掌握,本文将从颈椎前纵韧带的解剖学、影像学、生物力学、病理学改变等几个方面进行相关文献的综述。通过对颈椎前纵韧带的解剖结构、力学特性能的回顾,探讨并总结其损伤时的影像学表现、病理变化及病因机制,以更好地理解其正常生理及病理过程。     

后路减压侧块螺钉置入内固定治疗颈椎多节段后纵韧带钙化：5年36例资料回顾

背景：后路减压侧块螺钉固定能够解除骨化灶对脊髓、神经根的压迫,扩大椎管矢状径,同时重建该区域的稳定。 目的：验证应用后路减压、侧块螺钉置入内固定治疗颈椎多节段后纵韧带骨化症5年36例资料的临床疗效。 方法：36例患者为3个节段9例,4个节段20例,5个节段7例。 结果与结论：随访6~26个月,JOA评分由内固定前平均5.2分提高到 10.2分。颈椎生理曲度由内固定前平均(3.6±0.5) mm提高到内固定后(9.1±0.7) mm,内固定物无松动。提示此方法治疗既能后方直接减压又能前方间接置入减压,既能恢复颈椎生理曲度,又能提供坚强的内固定效应。     

Chronic multiple knee ligament injuries: epidemiological analysis of more than one hundred cases

INTRODUCTION: Diagnosis and treatment of multiple ligament injuries of the knee remain a real challenge for most surgeons. OBJECTIVE: To find out the epidemiological profile of patients surgically treated at a Reference Service with more than one chronic ligament injury in the knee joint. MATERIALS AND METHODS: Of a total of 978 operated patients, 109 presented at least two associated ligament injuries in the same knee. Demographic and clinical variables were evaluated. RESULTS: The anterior cruciate ligament group presented a larger number of cases of ligament injuries related with sports practice and falls, while the posterior cruciate ligament and anterior cruciate ligament + posterior cruciate ligament groups presented more cases related to traffic accidents and trauma with object (weight on the knee) (p<0.001). The varus group presented significantly higher values of time since injury (p<0.01). In the group with new anterior cruciate ligament injury (neoligament) associated with other ligament injuries the disruption times were higher, showing statistical significance (p<0.001). CONCLUSIONS: Anterior cruciate ligament injury associated with other ligament injuries other than posterior cruciate ligament injury are related to sports practice and falls. Posterior cruciate ligament injury associated to other ligament injuries, including or not anterior cruciate ligament injury, are related to traffic accidents and direct trauma caused by an object on the knee. Significant delay between primary ligament injuries and their reconstructions generates varus deformity of the affected knee. In spite of the large delay in seeking medical treatment, few patients with neoligament anterior cruciate ligament injury and other combined disruptions will develop varus deformity.     

An ultrastructural study on the ligamentum flavum of the cervical spine in patients with ossification of the posterior longitudinal ligament

Some histological analyses of the ossification of the posterior longitudinal ligament (OPLL) have been reported, but no ultrastructural studies of the ligamentum flavum (LF) in patients with OPLL have been published to date. To understand the pathology of the ossification of the spinal ligament, we examined, by electron microscopy, ultrastructural changes in the LF in cases of OPLL and made a comparison with the LF in cervical spondylotic myelopathy (CSM). Subjects were three men and two women with cervical OPLL who underwent longitudinal spinous process-splitting laminoplasty. During surgery, a small piece of the LF was collected from C2–C3 to C7–T1 and was then analyzed by light and electron microscopy. We observed atrophic elastic bundles with a two-layer structure and disarrangement, a partially torn area, the disappearance of microfibrils, and an enlarged interstitium with an irregular alignment of collagen fibrils. We observed some properties of a cell preceding its death: the initial phase may be the disappearance of the plasma-membrane, followed by the scattering of many organellae around its degenerated nucleus. Finally, many extracellular plasma membrane-invested particles that resemble matrix vesicles remain there without phagocytosis. These results suggest that ultrastructural abnormalities exist in the spinal ligament in cases of ossification of the spinal ligament.     

3D打印模型在颈椎后纵韧带骨化手术减压方式选择中的应用

背景:目前3D打印技术已成功应用于辅助关节置换、骨折内固定及脊柱置钉等骨科手术,但关于3D打印技术在颈椎后纵韧带骨化症手术治疗领域的潜力尚有待探讨。目的:探讨3D打印模型在颈椎后纵韧带骨化症前后路手术减压方式选择中的应用价值。方法:回顾性分析2014年10月至2015年10月在徐州医科大学附属医院行术前CT数据搜集和3D模型打印的颈椎后纵韧带骨化症患者共15例,其中孤立型2例,节段型6例,连续型4例,混合型3例。通过对比分析术前、术后1个月及末次随访时的日本骨科协会评分、目测类比评分、患者症状及影像学资料,来评价3D打印模型在颈椎后纵韧带骨化症前后路手术减压方式选择中的应用价值。结果与结论:(1)15例患者均顺利接受颈椎减压治疗,均接受4-16个月随访。术后患者症状较术前明显缓解,颈椎后路手术中1例切口脂肪液化,经负压引流后治愈;(2)术前、术后1个月和末次随访时的日本骨科协会评分分别为(9.0±1.6)分、(11.7±1.8)分和(15.5±1.4)分,差异有显著性意义(P<0.05);颈肩部疼痛目测类比评分分别为(6.7±2.5)分,(2.13±1.4)分和(1.4±0.5)分,差异有显著性意义(P<0.05);(3)随访期间影像学结果显示,前路植骨均融合,后路手术门轴处愈合良好,无再关门现象;(4)结果提示,3D打印模型有助于对颈椎骨化后纵韧带的特点进行观察,并进行术前评估和模拟手术操作,对颈椎后纵韧带骨化症减压方式的选择有一定的参考价值。     

Clinical importance of ligamentous and osseous structures in the cervical uncovertebral foraminal region

The vertebral artery, cervical spinal nerves, spinal nerve roots, and the bony and ligamentous tissue related to the cervical vertebrae are structures whose anatomy determines the path of a surgical approach. Defining the anatomy and, in particular, determining the precise location of vulnerable structures at the intervertebral foramen and the uncovertebral foraminal region (UVFR), a region defined by the uncinate process anteriorly, the facet joint posteriorly and the foramen transversarium laterally, has critical significance when selecting the safest surgical approach. We studied the anatomy of the vertebral artery, cervical spinal nerves, and spinal nerve roots within the UVFR in six cadaver specimens. We also obtained measurements of bony structures in 35 dry cervical vertebral columns, from C3-C7. The uncinate process (UP) projects superiorly from the posterolateral aspect of each cervical vertebral body, except for the first and second vertebrae. Because the posterior part of the UP lies adjacent to the vertebral artery, spinal nerve, and spinal nerve roots, its resection creates sufficient space to decompress these structures directly. The posterolateral surface of the UP is covered by ligamentous tissue that originates from the posterior longitudinal ligament and protects the neural and vascular structures during their decompression in the UVFR.     

保留前纵韧带的椎体间植骨术的稳定性实验研究

目的：为评价保留前纵韧带的椎体间支撑植骨治疗脊柱爆裂骨折提供的生物力学稳定能力。方法：用传感器及电测技术，采用新鲜人体胸腰段脊柱标本。结果：除旋转外，轴压、前屈、后伸、侧弯四种运动方式皆能提供满意的稳定性。结论：实验提示，该方法能明显增加损伤脊柱的力学稳定性，有利于提高脊柱的融合率，是一种治疗脊柱骨折较为理想的植骨方法     

颈部脊柱部分结构的神经分布

对10具完整成人男尸颈部椎间盘、前纵韧带及椎前筋膜的神经支配进行了观察,颈部脊柱及其周围组织的神经支配丰富。由颈交感干和节直接发支到椎前筋膜,并由此分布至颈部软组织;至椎间盘的神经来自颈交感干及节、脊神经腹侧支和椎动脉神经丛;达前纵韧带的神经单独发自交感干和交通支。为了证实是神经组织,对3例2～5岁新鲜童尸作了组织学检查。     

“安全减压间隙”在前路椎体次全切除治疗颈椎后纵韧带骨化症中的应用

目的 探讨后纵韧带与硬脊膜间“安全减压间隙”在前路椎体次全切除术治疗颈椎后纵韧带骨化症(OPLL)中的应用价值。方法 回顾性分析2010年1月—2014年1月第二军医大学附属长征医院脊柱外科行颈椎前路椎体次全切除治疗的134例颈椎OPPL患者临床资料,其中男88例,女46例;年龄35～71岁,平均(50.5±16.7)岁。术前CT矢状面显示节段型105例,连续型12例,混合型17例,骨化均不超过3个椎体。术中以韧带未骨化处为突破口,使用后纵韧带钩钩起骨化物,形成后纵韧带与硬脊膜间“安全减压间隙”,锐利神经剥离子仔细分离,超薄型枪钳逐步咬除骨化的韧带。术中观察有无硬脊膜粘连及破损而导致脑脊液漏以及脊髓损伤,采用JOA评分评估患者术前、术后神经功能改善程度。结果 CT横断面上椎管狭窄率＜30%者58例,利用“安全减压间隙”行骨化物切除术,无硬膜破损;30%～60%之间者62例,1例硬脊膜破损导致脑脊液漏;＞60%者14例,4例脑脊液漏。术中发现硬脊膜粘连97例,在“安全减压间隙”下用锐利神经剥离子成功分离92例。患者均未出现脊髓损伤,术后JOA评分(14.9±2.7)分,较术前(9.3±1.9)分有显著改善,差异有统计学意义(t=2.210, P﹤0.05)。结论 利用后纵韧带钩钩起骨化后纵韧带创造 “安全减压间隙”,可有效地分离后纵韧带与硬脊膜的粘连,避免骚扰脊髓,减少硬脊膜破损及脊髓损伤。