应用两种不同材质融合器行腰椎椎间融合的三维有限元分析

发布时间：2018-09-13 14:31

【摘要】：背景:脊柱生物力学的发展日新月异,尤其近年来,各种新技术、新方法层出,椎弓根螺钉固定联合椎间融合器(cage)在临床上逐渐普及,使得脊柱手术节段广泛骨性减压后能得到即刻稳定,并通过植骨达到远期融合从而维持其正常功能。cage有着自身特有的一些优势,不但增加了椎体融合率,减少了植骨量的使用,又可以恢复椎间隙的既有高度,加快融合速率,减少手术时间,现在已发展为脊柱外科基本的技术之一。但随着融合器使用量的增加,也出现了一些融合失败的例子,如cage的移位、沉陷等。针对以上失败的例子,我们对椎弓根螺钉联合cage的生物力学特性做了大量实验探索及测试[1],对于椎弓根螺钉实验主要集中在器械抗疲劳,螺钉拔出力及螺钉的受力分析。而对于椎间融合器,则对其拉力抵抗力,剪力承受程度和稳定性进行了实验和测试分析。有限元法能够较好的预测螺钉固定和cage的生物力学特征,其在椎弓根螺钉和融合器的设计与分析上得到了广泛的应用。目的:借助有限元分析的方式来研究椎弓根螺钉固定联合两种不同材料cage在L4、5椎间融合中的生物力学特性。方法:选取自愿参与实验的健康女性1人,选用螺旋CT扫描方式获取正常脊柱L4~L5节段信息,应用Mimics和Geomagic软件对所采集的扫描图片信息进行立体模型重建,并将此立体模型导入有限元软件ANSYS15.0进而形成L4、5节段三维有限元模型(INT)。在建立的INT上,再分别建立双侧椎弓根螺钉联合两种不同材料cage的模型,Mod1为双侧椎弓根螺钉+Ti(钛)cage,Mod2为双侧椎弓根螺钉+PEEK(聚醚醚酮)cage。分别对两种立体模型加入500N预载荷以及8N·m的运动附加力,对于立体模型的预载荷和运动附加力等约束设定完成后,在腰椎前屈,后伸,左侧弯、右侧弯及左旋、右旋六种运动情况下算出L4、5节段角位移及双侧椎弓根螺钉和两种不同融合器所受力。结果:Mod1,Mod2在6种运动情况下的角位移均小于正常。受力测试中,Mod1应力最大值在6种运动情况下均高于Mod2。后伸位时,M1与M2的双侧椎弓根螺钉及cage的应力最大值较其他运动情况小。结论:对于需要融合的节段,椎弓根螺钉系统可以保证足够的强度。对于所需融合节段在同等稳定不变的前提下,PEEK材料的cage应力最大值均小于Ti材料的cage,因此,PEEK材料的cage发现移位及沉降的概率也低于Ti材料的cage,其椎间融合率也相应较高。实验中我们可以发现,在后伸运动情况下,融合器所受应力较小,由此推测运动情况下较为稳定的为后伸位。
[Abstract]:Background: the development of spinal biomechanics is changing with each passing day, especially in recent years, various new techniques and methods have been developed, pedicle screw fixation and interbody fusion cage (cage) are becoming more and more popular in clinical practice. So that the spinal segment can be stabilized immediately after extensive bone decompression, and through bone grafting to achieve long-term fusion to maintain its normal function. Cage has its own unique advantages, not only increased the fusion rate of vertebral body, reduced the use of bone graft. It can also restore the existing height of intervertebral space, accelerate the fusion rate, and reduce the operation time. Now it has developed into one of the basic techniques of spinal surgery. However, with the increase of the amount of fusion device, there are some examples of fusion failure, such as cage displacement, subsidence and so on. In view of the above failure examples, we have done a lot of experiments and tests on the biomechanical properties of pedicle screw combined with cage [1]. For the pedicle screw experiment, we mainly focus on the analysis of the device anti-fatigue, screw pull-out force and screw force. For interbody fusion cage, the tensile resistance, shear resistance and stability were tested and analyzed. Finite element method can well predict the biomechanical characteristics of screw fixation and cage. It has been widely used in the design and analysis of pedicle screw and fusion cage. Objective: to study the biomechanical characteristics of pedicle screw fixation combined with two different materials cage in L4 / 5 intervertebral fusion by means of finite element analysis (FEM). Methods: a healthy woman who volunteered to participate in the experiment was selected, and the normal spinal L4~L5 segment information was obtained by spiral CT scanning. The scanning images were reconstructed by Mimics and Geomagic software. The three-dimensional model is introduced into the finite element software ANSYS15.0, and then the (INT). Of the L4 / 5 segment 3D finite element model is formed. On the established INT, the model of bilateral pedicle screw combined with two different materials cage was established respectively. The model was Ti (Ti) cage,Mod2 and PEEK (polyether ether ketone) cage.. 500 N preload and 8 N m additional force were added to the two stereoscopic models respectively. After the pre-load and motion additional force of the three-dimensional model were set up, the lumbar vertebrae flexion, extension, left bending, right side bending and left rotation were set. The angular displacement of L4 and 5 segments and the force of bilateral pedicle screws and two different fusion cages were calculated under six right lateral motion conditions. Results the angular displacement of 1: 1 Mod2 was smaller than that of normal under 6 kinds of motion conditions. The maximum stress of Mod1 in stress test is higher than that of Mod2. in 6 kinds of motion conditions. The maximum stress of M 1 and M 2 pedicle screws and cage was smaller than that of other movements. Conclusion: for segments requiring fusion, the pedicle screw system can ensure sufficient strength. The maximum cage stress of peek material is smaller than that of Ti material under the same stable condition. Therefore, the probability of cage finding displacement and settlement of peek material is lower than that of Ti material cage, and the intervertebral fusion rate is also higher. In the experiment, we can find that the stress of the fusion device is small under the condition of the extension motion, so it can be deduced that the stable position of the fusion device is the extension position under the condition of motion.
【学位授予单位】：青海大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R687.3

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