齿突下软骨基质融合部对枢椎骨折类型影响的有限元分析

目的 建立并验证精细枢椎三维有限元模型,应用该模型探讨在前、后不同载荷条件下枢椎齿突下软骨基质融合部骨质不同发育程度对枢椎骨折类型的影响.方法 基于正常成人颈椎CT图像建立枢椎精细三维有限元模型.模拟体外生物力学实验验证模型.模型经验证后对齿突施加不同角度载荷,通过降低枢椎软骨基质融合部位松质骨的弹性模量以模拟该部位松质骨发育不同程度,分析枢椎在2种不同约束条件下的应力、应变分布情况,并探讨可能发生的相应骨折类型.结果 模型验证结果与体外生物力学实验结果基本一致.边界约束模式1下齿突前部垂直和水平方向不同角度加载模型预测结果与屈曲位水平角度载荷下预测应力分布图显示,应力集中区域随加载角度变化而发生转变,骨折类型可由Ⅲ型转变为Ⅱ型齿突骨折.边界约束模式2下受不同水平载荷角度加载后,模型预测骨折类型可由对称性Hangman骨折向不对称性Hangman骨折的转变.垂直方向上不同角度载荷下,预测骨折类型可由对称性Hangman骨折向Ⅱ型齿突骨折转变.齿突下软骨基质融合部位松质骨的发育程度不改变枢椎在垂直、水平、屈曲位不同角度受力下的应力集中带分布情况,皮质骨承受主要应力.结论 枢椎骨折的发生类型除了与所遭受暴力的方向、大小有关外,同时还与受伤瞬间寰枢椎相对应的位置情况和枢椎齿突的解剖差异有关.体外对枢椎骨折的生物力学研究实验中,除了加载暴力的方向外,尸体标本的固定与加载方式直接影响枢椎骨折类型的复制.齿突下软骨基质融合部对枢椎骨折类型无明显影响.     

骨科——脊柱

经口咽前路寰枢椎复位钢板内固定的外科解剖学研究；用Gallie术式治疗寰枢关节不稳定的临床问题研究；枢椎椎体骨折;颈椎前路手术并发食道瘘的诊断与治疗；颈部旋转与侧屈活动对椎动脉血供的影响；颈脊柱姿势及预负荷史对压缩强度影响的生物力学研究；颈椎前路带锁钢板内固定治疗颈椎骨折并四肢瘫痪；前路螺钉固定治疗齿状突骨折脱位合并颈髓不全损伤27例；经寰椎后弓侧块螺钉固定治疗上颈椎损伤；短节段内固定、ACPC椎体成形治疗胸腰椎骨折的围手术期观察；颈椎疾病前后路手术的选择与并发症的防治(附512例报告)；     

寰枢关节旋转固定脱位后路手术一例

患者 男，39岁，3周前高处坠落，头部着地，伤后有昏迷，右侧颞顶部头皮裂伤，经当地医院治疗后颅脑神经症状逐渐消失。1周前出现颈部疼痛、头偏向左侧，下骸转向右侧，活动受限。颈椎CT检查示齿状突骨折伴寰枢关节脱位，颈托固定转至我院。入院查体：神志清，GCS评分15分，左颞顶部有外伤痕迹，颈椎左侧弯斜，颈项肌痉挛，C1,2棘突压痛。四肢肌力及感觉正常，腱反射正常，病理反射未引出。X线片及颈椎CT发现寰椎左侧块位于枢椎上关节突前下方，CT横断面上连续多个层面寰椎的一侧下关节面位于枢椎上关节面之前，提示存在齿状突骨折伴寰枢关节交锁。     

颈椎损伤的内固定Ⅰ：上颈椎内固定

上颈椎由环枢椎构成,解剖结构复杂,运动特殊,上借环椎侧块上关节面与枕骨髁关节面和颅骨相连,下借枢椎下关节突,椎间盘与第三颈椎相连。所以上颈椎的内固定就将枕．环、枢椎和第三颈椎联系在一起。环枕枢复合结构(0ccipitoatlantoaxial complex)包括枕环枢关节及其韧带组成的复合体,是人体内最复杂的关节组合。环枢椎间没有椎问盘,齿状突与环枢前结节和横韧带分别组成环齿前后关节。枕颈部的韧带主要有覆膜,横韧带,翼状。     

前路经寰枢关节螺钉内固定生物力学性能的有限元分析

目的:通过有限元分析的方法评估前路经寰枢关节螺钉内固定的生物力学性能。方法:选择一名21岁健康男性志愿者,采用螺旋CT对枕骨底到C3椎体进行层厚1mm的薄层扫描,利用MIMICS 13.0软件、Freeform Plus软件及ANSYS 9.0软件,建立正常上颈椎有限元模型。去除模型中横韧带的所有单元模拟寰枢关节不稳,以枢椎前弓下缘与枢椎椎体侧缘交界点上方4mm处为进钉点,经寰枢关节分别向两寰椎侧块外上角中部置钉,最终建立前路经寰枢关节螺钉内固定治疗寰枢关节不稳的有限元模型。给予模型分别施加前屈、后伸、侧屈、旋转四种生理载荷,观察不同载荷下螺钉的三维运动范围与应力变化,分析前路经寰枢关节螺钉内固定的生物力学性能。结果:前路经寰枢关节螺钉内固定在不同载荷下三维运动范围均较小,但前屈、后伸状态下三维运动范围(0.72°,1.08°)明显大于侧屈、旋转状态(0.39°,0.32°)。不同状态下应力集中区域均为螺钉经寰枢关节部位,最大应力值为10.58×107Pa,出现在后伸状态。结论:前路经寰枢关节螺钉内固定具有可靠的生物力学性能,在侧屈、旋转状态下的力学性能优于前屈后伸状态,螺钉经寰枢关节部位易产生应力集中,为可能的断钉部位,临床应用时应采取有效预防措施。     

数字骨科技术在寰枢椎手术中的应用 寰枢椎脱位系列讲座(七)

正1概述寰枢椎位于颅脊交界区,解剖结构上具有独特性。寰椎由前后弓、侧块、横突构成,侧块上接枕骨髁、下邻枢椎关节突上关节面,形成寰枢外侧关节,而枢椎齿突与寰椎前弓构成寰齿关节,寰枢、寰枕之间由横韧带、翼状韧带和齿突尖韧带等多个韧带连接,这样就形成了一个复杂的三维复合结构;寰枢椎还毗邻诸多重要的血管和神经,因此治疗难度较大,风险较高[1-2]。寰枢椎脱位是各种上颈椎与颅脊交界疾患的病理转归,临床上并不少见,除了部分儿童自发性     

枢椎有限元模型建立及齿突骨折的有限元分析

目的 建立并验证枢椎三维有限元模型,并应用该模型探讨齿突垂直和水平方向不同角度载荷下的损伤机制和骨折类型.方法 对健康成年男性颈部进行CT扫描,层厚0.6mm,无间隔.将DICOM图像数据导入Mimics软件中,生成网格化的枢椎表面三维图像,再经ANSYS ICEM CFD处理,生成包括皮质骨和松质骨的实体模型.模拟体外生物力学试验验证模型.模型验证后,通过对齿突前部垂直和水平方向上施加不同角度的载荷,分析各种条件下齿突的应力分布并探讨相应的骨折类型.结果 (1)模型验证结果与体外生物力学试验的数据基本一致,后伸载荷下产生Ⅲ型齿突骨折,最大应力为123 Mpa;倾斜45°载荷下产生Ⅱ型齿突骨折,最大应力为121 Mpa,与皮质骨的屈服应力(138 Mpa)分别相差11%和12%.(2)齿突前部垂直和水平方向不同角度外力加载的应力分布图显示,应力集中区域可发生转变,预示骨折类型可能由Ⅲ型转变为Ⅱ型,且最大应力值逐渐增大.皮质骨承受主要应力.结论 我们建立的枢椎有限元模型经过验证可以很好地模拟枢椎的生物力学特性,其中包括皮质骨和松质骨结构.两种力学加载模式的应力分布图显示随着作用力角度的变化,会出现齿突骨折类型的转变,预示外力作用的方向是决定齿突骨折类型的关键因素.     

寰枢椎骨性关节炎的研究进展

正寰枢关节骨性关节炎(atlantoaxial osteoarthritis,AAOA)是指寰枢关节发生的慢性、退变性、非炎症性骨关节病,主要表现为一侧枕颈部疼痛,部分患者可能出现脊髓病变~([1])。寰枢关节由寰齿关节和寰枢侧块关节两部分组成。寰齿关节属于车轴关节,枢椎齿状突的前后面分别同寰椎前弓的齿状突关节面和寰椎横韧带中心的纤维软骨面组成寰齿前关节和寰齿后关节,寰枢侧块关节左右各一,关节面方向近乎水平,关节囊松弛~([2])。寰枢侧块关节占颈椎旋转运动的40%～70%~([3])。由于该关节活动度较大,缺乏强大的肌肉保护,容易发生创伤及退行性改变~([4])。AAOA在临床中并不少见,却是一个容易被忽视的疾病,国内报道甚少。笔者结合文献研究,对AAOA的临床特点、影像学表现及治疗做一综述,以增加临床医生对该病的系统性认知,减少漏诊、误诊。     

老年寰椎骨折的诊断与治疗进展

正寰椎即第一颈椎(C_1),寰椎骨折被认为是摔倒或其他偶然因素导致寰椎过度伸展或纵向挤压暴力导致的结果~([1])。寰椎骨折约占成人颈椎骨折总数的11%~([2-3])。在解剖结构上,寰椎无棘突和椎体,呈环形,由2个侧块组成,并由前、后弓相连。枕骨、寰椎和枢椎通过韧带结构和滑膜直接连接,为上颈椎提供了重要的稳定性。寰枢横韧带是寰枢关节的主要稳定结构,其主要功能是防止齿状突向脊髓后移和寰枢椎脱位。     

上颈椎非融合固定技术的研究进展

上颈椎包括寰椎和枢椎,主要涉及寰枕关节和寰枢关节,上承头颅,下接下位颈椎,生物力学复杂。颈椎具有旋转、屈伸和侧屈的运动功能,旋转运动的一半主要来自上颈椎的寰枢关节,屈伸主要来自寰枕关节。上颈椎损伤多由身体或头部加速撞击到静止物体上所致,主要包括寰枕关节脱位、寰枢关节脱位、寰椎骨折、枢椎齿状突骨折、枢椎创伤性滑脱和以上病变的叠加损伤。传统治疗上颈椎损伤的术式主要是寰枢椎融合术和枕颈融合术,但植骨融合技术在稳定结构的同时,导致上颈椎大部分活动度的丧失,旋转、屈曲等功能明显受限。上颈椎活动度的丧失对颈椎的生理和生物力学产生长期的负面影响,并对患者的生活质量产生不利影响。近年来,随着非融合理念和技术的推广,人工寰齿关节、经椎弓根动态固定系统等上颈椎非融合固定方式开始出现,以达到不植骨融合就可以同时实现稳定上颈椎结构和保留一定活动度的治疗目的。为进一步了解上颈椎非融合固定技术的研究进展,笔者对其做一综述。     

Biomechanical behavior of the posterior elements of the lumbar spine under loading--a study of stress analysis by means of three dimensional photoelastic experiments

To investigate the biomechanical behavior of the lumbar posterior elements under loading, stress analysis was carried out. The three dimensional photoelastic method was used for stress analysis in this study. The forces applied to the superior and the inferior articular facets were concentrated on the pars interarticularis and transmitted to the pedicle. However, almost no stress was generated in the lamina. Highly stressed areas were found in the pars interarticularis and around the lateral recess. The highest compressive stress was present in the pars interarticularis. The deformation pattern of the lumbar spinal canal was recognized and it became flat as the lateral recess was narrowed and deepened. These results very interestingly correspond to the fact that spondylolysis and lumbar canal stenosis are found in the above-mentioned areas clinically.     

Combined injuries in the upper cervical spine: clinical and epidemiological data over a 14-year period

Concomitant traumatic injuries in the upper cervical spine are often encountered and rarely reported. We examined the data concerning 784 patients with cervical spine injuries following trauma, including 116 patients with upper cervical spine injuries. Twenty-six percent of patients with upper cervical spine injuries (31 cases) were found to have combined injuries involving either the upper or the upper and lower cervical spine. The frequent patterns were combined type I bipedicular fracture of the axis and dens fracture, and combined dens fracture and fracture of the posterior arch of C1. Other patterns posed specific problems, such as combined dens and Jefferson fracture and combined dens and C2 articular pillar fracture. Seventy percent of atlas fractures, 30% of C2 traumatic spondylolistheses and 30% of dens fractures were part of a combination. A total of 1.7% of patients with lower cervical spine injuries had a combined injury in the upper cervical spine. A comprehensive therapeutic schedule is outlined. Combined injuries in the upper cervical spine should be sought in any patient with a cervical spine injury. Received: 11 October 1999/Revised: 12 February 2000/Accepted: 1 March 2000     

Unilateral cervical facet fractures with subluxation: injury patterns and treatment

STUDY DESIGN: This is a retrospective study of patients with unilateral cervical facet fractures from a Level I academic trauma center. OBJECTIVE: We sought to examine fracture patterns involving only the facets, to examine the incidence of associated neurologic and vascular injuries, and to determine optimum management strategies for these injuries. SUMMARY OF BACKGROUND DATA: Most of the literature regarding unilateral cervical facet injuries has resulted from studies evaluating dislocated locked facets, "fracture-dislocations," or fractures of the lateral mass and pedicle. METHODS: We retrospectively reviewed our experience with unilateral fractures of the facets, identifying 25 cases over a 5-year period. Presenting history, neurologic examination, imaging findings, method of reduction, interval to surgery, type of surgery, and evaluation for vascular injuries were recorded. Fusion was assessed by plain radiographs and computed tomography scans at follow-up. RESULTS: All 25 patients were treated operatively. Ten of the fractures involved the superior articular process, 13 involved the inferior articular process, and 2 cases involved both. The most commonly affected level was at C6/7. Twenty-one of the 25 patients underwent anterior stabilization, 3 underwent posterior stabilization, and 1 underwent anterior-posterior stabilization. Eleven patients underwent diagnostic 4-vessel angiography, revealing 2 patients with vertebral artery injuries. Average follow-up was 11.5 months. There were no identifiable nonunions. CONCLUSIONS: We conclude the following: (a) anterior discectomy and fusion with a static (constrained) plating system is appropriate treatment for this type of injury, (b) in the absence of significant neurologic deficit with residual canal or foraminal stenosis, preoperative closed reduction is not necessary, (c) a small percentage of these patients will have vertebral artery injury, thus warranting screening with 16-slice computed tomographic angiography.     

A biomechanical comparison of posterolateral fusion and posterior fusion in the lumbar spine

Late postoperative complications occurred after posterior fusion and posterolateral fusion as a result of biomechanical alterations. The stress change between the two fusion procedures has not been well reported. To differentiate the biomechanical alteration that occurs with posterior fusion and posterolateral fusion of the lumbar spine, the load sharing of the vertebrae, disc, facet joint, bone graft, and the range of motion were computed in a finite element model. Five finite element models, including the intact lumber spine, posterior fusion, posterior fusion with implant, posterolateral fusion, and posterolateral fusion with implant, were created for stress analysis. The finite element model estimated that the differences between these two fusion procedures were within 7% in stress of the adjacent disc, 3% in force of the facet joint above the fusion mass, and 5% in the range of motion. However, the stress of the pedicle in posterolateral fusion without an implant was at most two times greater than that in the intact lumbar spine under lateral bending. The stress of pars interarticularis in posterior fusion without an implant was also at most two times greater than that in the intact lumbar spine under lateral bending. After the implant was added, the discrepancy between the two fusion procedures decreased but still remained a relatively large difference. Therefore, the largest changes of posterior fusion and posterolateral fusion were in the pars interarticularis and pedicle, respectively.     

Acute traumatic spondylolysis. Report of a case and review of the literature

Acute traumatic bilateral spondylolysis and spondylolisthesis was observed in a 34-year-old man. The literature on pathologic and biomechanical factors leading to acute fracture of the pars interarticularis emphasizes the importance of distinguishing spondylolysis resulting from acute trauma from the more common lytic-fatigue pars defect.     

Cervical spondylolysis: a case report

Cervical spondylolysis is defined as a corticated cleft between the superior and inferior articular facets of the articular pillar, the cervical equivalent of the pars interarticularis in the lumbar spine. Of primary importance is its recognition to avoid confusion with more clinically significant abnormalities such as fracture or dislocation. This case report describes bilateral spondylolysis and associated dysplasia of C5 in a 31-year-old female. We describe the radiographic presentation of this anomaly, stressing the importance of computed tomography for correct diagnosis. A review of the literature on this interesting abnormality and a complete differential diagnosis are presented.     

角度人工颈椎间盘置换对关节突应力的影响

目的探讨带角度人工颈椎间盘置换后关节突及相邻关节突应力变化。方法选择400名西北地区40岁以上人群颈椎侧位X线片,计算机辅助设计软件测量颈椎间盘角,设计10°人工颈椎间盘;对已建立的C4、C5两节段带椎间盘的正常颈椎有限元模型、C4、5置换0°椎间盘假体和置换10°椎间盘假体后的颈椎模型进行轴向加压、前屈/后伸、侧弯、扭转加载,对比观察C4、5关节突应力变化;对已建立的C4～C6三节段带椎间盘的正常颈椎有限元模型、C4、5置换0°椎间盘假体和置换10°椎间盘假体后的颈椎模型同样方式进行加载,对比置换节段及相邻节段的关节突应力变化。结果 C3～C7椎间盘角分别为:C3、4(9.97±3.64)°,C4、5(9.95±4.34)°,C5、6(8.59±3.75)°,C6、7(8.49±3.39)°,各椎间隙之间椎间盘角两两比较,C3、4与C4、5,C5、6与C6、7差异无统计学意义(P>0.05),其余各椎间隙之间差异均有统计学意义(P<0.05)。C4、C5两节段模型加载中,轴向加载下三者等效剪应力(Se)无明显差异;前屈/后伸时正常模型Se最大,10°假体置换组最小;侧弯时正常椎体Se最大,10°假体置换组最小;扭转时10°假体置换组更接近正常椎体生理状态力学特性。C4～C6三节段模型加载中,C4、5节段的关节突关节Se在轴向加载、前屈/后伸、侧弯时较正常椎体明显减小;扭转时减小不明显,接近正常状态。相邻下位节段C5、6关节突应力在轴向加载和侧弯时应力明显减小,扭转时应力减小较少,前屈/后伸时无明显改变,接近正常节段力学特性。结论 10°椎间盘假体植入椎间隙对颈椎相邻节段的关节突应力影响小,接近正常颈椎间盘力学性能。     

Percutaneous and limited open fixation of fractures of the distal radius

Percutaneous and limited open fixation of fractures of the distal radius is an important method of treatment for many unstable fractures such as unstable dorsal bending fractures, shearing fractures of the radial styloid and lunate facet, and simple articular fractures. The quality of the reduction is monitored with image intensification and the tactic of the reduction is based on manipulation of the fracture fragments by longitudinal traction, percutaneous manipulation, and in some instances by direct manipulation through small incisions. The role of arthroscopy remains uncertain and may represent an alternative to open exposure of the articular surface in some patients although bone grafting may be necessary in patients with fractures with significant metaphyseal defects.     

Injuries to the cervical spine causing vertebral artery trauma: case reports

In four patients with lesions of the vertebral artery resulting from cervical spine injury, two were due to unilateral facet dislocation and two to fractures of the dens. There was one arterial occlusion with minor vertebrobasilar symptoms, and an arterial lesion with thrombosis causing embolic occlusion of the basilar artery with lethal outcome. In one patient a fresh fracture of the dens caused dislocation of C1/2 with reversible occlusion of the left and stenosis of the right vertebral artery, resulting in unconsciousness. In a patient with pseudarthrosis of the dens an aneurysm of the vertebral artery could be detected. Cerebellar or cerebral symptoms associated with cervical spine injury should be investigated by vertebral angiography because vertebral arterial injury may be more common than suspected and may simulate traumatic brain damage.     

The location of the pedicle and pars interarticularis in the axis

STUDY DESIGN: This is an anatomic and radiologic study on the lateral mass of the C2 vertebra. OBJECTIVES: To define the location of the pedicle and pars interarticularis in the C2 vertebra. SUMMARY OF BACKGROUND DATA: Transpedicular screw fixation of the C2 has been addressed in the literature. However, the use of the anatomic terminology of the pedicle or pars interarticularis (isthmus) in C2 is confusing in most of orthopaedic and neurosurgical literature since C2 is considered a transitional vertebra. METHODS: Twenty dry C2 vertebrae were obtained for observation of the external anatomy of the C2 from superior, lateral, and inferior views. Six C2 vertebrae were harvested from cadavers and sectioned in the sagittal, horizontal, and coronal planes to observe the internal structures of the lateral mass using high resolution radiographs. RESULTS: Based on observation, the pedicle of the C2 vertebra is defined as the portion beneath the superior facet and anteromedial to the transverse foramen. The pars interarticularis or isthmus is defined as the narrower portion between the superior and inferior facets. No remarkable difference in bone density and trabecular bone orientation between the pedicle and pars interarticularis was noted. CONCLUSIONS: It is still more appropriate to call this procedure "transpedicular screw fixation" in the C2 to avoid confusion, although this technique requires placing a screw from the posterior aspect of the inferior articular process through the isthmus and pedicle into the vertebral body.