不同内固定手术方式治疗寰枢椎复合骨折稳定性的有限元分析

The biomechanical study of different type of instruments for atlas and axis complex fracture: a finite element analysis

中文关键词:  寰椎  枢椎  骨折  内固定  生物力学  有限元

英文关键词:Atlas  Axis  Fracture  Internal fixation  Biomechanics  Finite element

中文摘要:

  【摘要】 目的：比较寰枢椎椎弓根螺钉固定及枕颈融合术两种内固定方式治疗寰枢椎复合骨折的生物力学稳定性，为临床治疗寰枢椎复合骨折提供理论依据。方法：选择1例27岁健康男性志愿者，采用64排螺旋CT机扫描枕颈部（C0~C3），利用Simpleware 3.0、Geomagic 8.0、Hypermesh 10.0等软件建立C0~C3节段三维有限元（FEM/intact）模型，并与Panjabi等的结果进行对比验证。在经验证的模型基础上断裂C1前弓和后弓及切断齿状突基底部，模拟Jefferson骨折＋Ⅱ型齿状突骨折的复合骨折有限元模型（FEM/fracture）。根据内固定系统的大小规格及临床手术方法在FEM/fracture上分别建立寰枢椎椎弓根螺钉固定术模型（FEM/PSF）及枕颈融合术模型（FEM/OCF）。对不同内固定模型加载前屈、后伸、侧屈、旋转工况，分析各模型在不同工况下Von Mises应力云图及各椎节活动度。结果：（1）建立的FEM/intact外观逼真，几何相似性好。各椎节的活动度与Panjabi发表的结果基本吻合。在相同条件下，FEM/fracture各个工况下的活动度均较FEM/intact明显增大，尤其是C1-C2旋转增加了43.7%，屈伸增加了72.1%。（2）两种加载内固定系统的上颈椎有限元模型与临床实际相符。FEM/PSF的C0-C1屈伸和旋转活动度较FEM/intact分别增加59.2%、68.3%；C1-C2屈伸、侧屈、旋转功能受限，分别降低92.2%、31.3%、99.6%；C2-C3屈伸、侧屈工况下活动度分别降低13.6%、0.6%，旋转工况下活动度增加0.7%。FEM/OCF中C0-C3各椎节活动度较FEM/intact均降低，其中C0-C1屈伸、侧屈、旋转工况下活动度分别降低93.8%、90.4%、90.2%；C1-C2分别降低89%、55.7%、97.4%；C2-C3分别降低92.8%、95.2%、90.5%。（3）FEM/PSF在左右旋转工况下应力值最大，为321.19MPa，主要集中在连接棒和螺钉根部。FEM/OCF在左右侧屈工况下应力值最大，为228.84MPa，主要集中在连接棒及螺钉根部。结论：寰枢椎椎弓根螺钉固定及枕颈融合两种手术方式治疗寰枢椎复合骨折均能起到早期稳定的目的，寰枢椎椎弓根螺钉固定后稳定C1-C2的同时能代偿性增加C0-C1的活动度。

英文摘要:

  【Abstract】 Objectives: To analyze the biomechanical stability of different instruments for atlas and axis complex fracture by finite element method, and to provide theoretical reference for the clinical application. Methods: The geometries from occiput(C0) to C3 were performed from CT images of a healthy volunteer. A three-dimensional finite element model of intact upper cervical spine(FEM/intact) was established by software of Simpleware 3.0, Hypermesh 10.0, Abaqus 6.9, and the model was validated through Panjabi′s data. Then, the bottom of the odontoid process and the junction between the anterior and posterior arch and lateral mass were removed to simulate FEM of Jefferson type Ⅱ odontoid fracture(FEM/fracture). A computer-aided software according to a fixed system specification was used to build the FEM of atlantoaxial pedicle screw fixation(FEM/PSF) and occipital-cervical fusion(FEM/OCF). Flexion, extension, lateral bending and rotation were imposed on the intact, fracture and two fixation models respectively. The Von Mises stress distribution and range of motion(ROM) of each segment in different models was compared. Results: (1)FEM/intact was established clearly with good geometric similarity, which was validated by Panjabi′s work. The ROM of FEM/fracture increased obviously than FEM/intact under same loading conditions, especially a increase of 72.1% in flexion and extension, and an increase of 43.7% in left and right rotation. (2)Each of the FEM of upper cervical spine loading in fixation system matched clinical practice. Compared with FEM/intact, the ROM of C0-C1 in flexion/extension and rotation in FEM/PSF increased by 59.2% and 68.3% respectively. The ROM of C1-C2 in flexion/extension, lateral bending and rotation decreased by 92.2%, 31.3% and 99.6% respectively. The ROM of C2-C3 in flexion/extension, lateral bending decreased by 13.6%, 0.6% and the ROM in rotation increased by 0.7%. Compared with FEM/intact, the ROM of C0-C1 in flexion/extension, lateral bending and rotation in FEM/OCF decreased by 93.8%, 90.4% and 90.2% respectively. The ROM of C1-C2 decreased by 89%, 55.7%, 97.4% and the ROM of C2-C3 decreased by 92.8%, 95.2% and 90.5% in flexion/extension, lateral bending and rotation respectively. (3)The maximal Von Mises stress in the internal fixations was 321.19MPa in atlantoaxial pedicle screws in left rotation, and 228.84MPa in occipital-cervical fusion system in left bending. Stress was mainly concentrated in the junction of rods and screws. Conclusions: Two surgical methods are effective for the atlas and axis complex fracture, both procedures can ensure good stability. C1-C2 pedicle screws can increase the ROM of C0-C1.