【作者】 段景柱；

【导师】 王欢；

【作者基本信息】 中国医科大学 ， 外科学， 2004， 硕士

【摘要】 目的 比较通常的的L₅S₁椎弓根钉固定方法和经骶骨空心钉纵向固定腰骶部方法的生物力学强度。 背景资料 腰骶固定是脊柱外科的难题，目前尚无理想可靠的手术固定方法。结合骨盆骨折内固定经验及其解剖学研究的基础，我们设计和应用了后路经骶骨空心钉纵向固定腰骶部技术。这种新的内固定技术需要在生物力学方面进行充分相关的研究，以使其更安全广泛的应用于腰骶滑脱的内固定治疗。 材料和方法 1．尸体材料 6具由甲醛溶液固定的成年尸体脊柱标本（男4具，女2具，死亡年龄32-78岁，平均62.3岁），取L₃-S₄的活动节段，除外结构异常（如椎体部分缺陷，压缩性骨折）者。每具标本保留骨膜，椎间盘，关节囊及所有的韧带组织，剔除椎旁的肌肉。标本两端用骨水泥（PMMA）固定于自制钛合金夹具（沈阳铸造研究所制作）上。 2．生物力学试验 本实验采用的方法属于稳定性实验，生物力学加压最大载荷500N，最大扭矩7.5Nm，属于非破坏试验，每具标本可以重复利用。将脊柱标本固定于BIONIX 858生物力学实验机上（Material Test System，Eden，Prairie，MN，中科院沈阳金属研究所提供），每个标本均连续测试5种状态，首先测量完整标本的三维运动（包括轴向加压，屈曲，伸展，右侧弯，左侧弯试验），反复测量三次并记录最后一次的载荷-位移曲线。然后按同样的方法分别依次测量损伤后滑脱标本，空心钉固定标本，空心钉联合应用椎弓根钉（USS）固定标本和椎弓根钉（USS）固定标本的三维运动。为消除生物力学测试对脊柱的影响，每次测试完毕后都给予标本一个周期性的压载负荷（大小500土150N，频率IHz，次数1以X）次)，以去除弹性蠕变和测试的影响，使其恢复到测试前的状态。 滑脱标本的制作采用Panjabi法，切断玛、，玩，魏S:棘上韧带，棘间韧带及黄韧带，离断双侧甄椎体峡部，坑S，小关节囊，将玩椎体后弓完整游离取出，于几S，椎间隙切断后纵韧带并摘除后半髓核。 通过载荷一变形位移曲线上的斜率确定sooN载荷下各标本活动节段的刚度，用标本固定后的刚度比其完整时的刚度，得出相对比率进行比较。 应用配对t检验进行统计学分析，p<0.05认为有统计学意义。结果 在所有的模式测试中（加压、屈曲、伸展、右侧弯、左侧弯），经能骨空心钉纵向固定明显比通常的腰骸椎弓根钉固定牢固。伸展测试的差异是最显著的。经骸骨空心钉纵向固定比通常的腰能椎弓根钉固定牢固1.2一1.4倍。 经能骨空心钉纵向固定与经骸骨空心钉纵向固定联合应用椎弓根钉固定在刚度值上没有显著差异。这两组在固定强度上几乎相等。结论 在模拟LS一S，滑脱的尸体标本中，经能骨空心钉纵向固定刚度强于通常的的腰骸椎弓根钉固定刚度。经能骨空心钉纵向固定产生的刚度与经能骨空心钉纵向固定联合应用椎弓根钉固定产生的强度相等。更多还原

【Abstract】 The purpose of the current study was to compare the biomechanical stiffness of traditional pedicle screw fixation and transdiscal longitudinal lumbosacral cannulated screws fixation in a cadaveric model of simulated L5-S1 spondylolisthesis.Summary of background dataThe surgical management of L5-S1 spondylolisthesis is a challenge because of the difficulties in achieving a reliable arthrodesis in the face of high mechanical forces. A method of lumbosacral fixation that has been used successfully in severe spondylolisthesis at our institution involves the use of 2 cannulated screws which were longitudinal inserted through lateral mass of the sacrum, sacral body, L5S1 disc to L5 vertebral body combinding lumbosacral pedicle screws. The biomechanical study related to this procedure need to be performed in detail.MethodsCadaveric MaterialSix human formaldehyde preservative cadaveric L3-S4 motion segments (mean age 62.3 years; range 32-78 years 2 females, 4 males) were harvested. Each motion segment was radiographed to ensure that no major structural abnormalities were present ( e. g. , pars defects, compression fractures). Specimens were then carefully stricped of soft tissues with the intact of bone membrane, in-tervertebral disc, facet sac and all ligaments- The end of the each motion segment was fixed to the materials testing machine using the self-made clamp and bone cement (PMMA).Biomechanical Loading SequenceThe currentstudy was to compare the biomechanical stability in cadaveric models. The specimen was positioned and clamped in a materials testing machine (BIONIX 858, Material Test System, Eden, Prairie, MN, USA). The intact specimen was then biomechanically tested as follows: 1) axial compression (500 N) , 2) flexion (7.5 Nm) , 3) extension (7.5Nm) , 4) right lateral bending (7.5 Nm) , and 5) left lateral bending (7. 5Nm). Stiffness values were calculated from the load-deflection curves obtained.After the intact specimen had been tested according to the six-step loading sequence, an L5 laminectomy, a bilateral L5-S1 facetectomy, and a radical dis-cectomy ( with resection of both anterior and posterior longitudinal ligaments) were performed. All the simulated Spondylolisthesis specimens were biomechanically tested as above, Stiffness values were calculated from the load-deflection curves obtained. The specimens with 3 different flxational techniques, transdis-cal longitudinal lumbosacral cannulated screws fixation, traditional L5S1 pedicle screws ( USS) fixation, and combining of above two fixation, were tested respectively. Load-deflection curves were obtained each time, and stiffness values were calculated from the curve. A cyclic compression force was applied as conditioning (500 ?150 N at 1 Hz for 1000 cycles) to remove excess fluid from the disc and return the disc to its predeath height.Load-Displacement CurvesThe stiffness of the motion segment was determined each time from the slope of the load-displacement curve obtained. To adjust for variations in stiffness between motion segments, a normalized stiffness ratio was calculated by dividing the value of stiffness obtained for the experimental condition ( e. g. , after transdiscal longitudinal lumbosacral cannulated screws fixation or pedicle fixation or combined fixation) by the stiffness value obtained for the intact specimen.StatisticsStatistical analysis consisted of analysis of variance and paired t test. Statistical significance was defined at the p <0.05 level.ResultsThe experiments showed that transdiscal longitudinal lumbosacral cannulated screws fixation was significantly stiffer (p <0.01) than traditional L5S1 pedicle screws in all modes tested ( compression, flexion, extension, right lateral bending, and left lateral bending). The greatest difference was noted in extension. The normalized stiffness values for the transdiscal longitudinal lumbosacral cannulated screws were 1.2-1,4 times greater than the values for the traditional L5S1 pedicle screws. In contrast, no significant differences i更多还原