寰椎椎弓根螺钉联合经寰枢关节螺钉内固定稳定性的生物力学研究

Biomechanical study on the stability of atlantoaxial transarticular screw combined with atlas pedicle screw fixation technique

目的:评估寰椎椎弓根螺钉联合经寰枢关节螺钉固定技术的力学稳定性。方法:选取成人颈椎新鲜标本6具,解剖剔除肌肉制备上颈椎完整模型(完整组),用生物力学测试及计算机视觉分析软件测量在1.5Nm力矩下前屈后伸、左右侧弯和左右旋转时C1-C2的活动度(ROM);破坏寰椎前弓和侧块制备不稳模型(失稳组),再次测量相同力矩下各运动方向C1-C2的ROM活动度。随后暴露寰枢椎置钉点,根据先后顺序置入寰椎椎弓根螺钉+枢椎椎弓根螺钉固定(C1P+C2P组)、单纯经寰枢关节螺钉固定(TA组)、寰椎椎弓根螺钉+经寰枢关节螺钉固定(C1P+TA组),依次分别测量相同力矩下各运动方向C1-C2的ROM,比较各组C1-C2 ROM的差异。结果:失稳组相较于完整组在六个方向上有更大的ROM,两组所有方向上的ROM均有显著性差异(P<0.05);C1P+C2P组、C1P+TA组、TA组与失稳组比较,所有方向上的ROM均有显著性减少(P<0.05),三组间比较,前屈、后伸、左旋转和右旋转方向上的ROM存在统计学差异(P<0.05),C1P+TA组<C1P+C2P组<TA组;左侧弯和右侧弯方向上的ROM无统计学差异。结论:三种固定技术均可达到良好的固定效果,在侧弯时的稳定性相似,C1P+TA固定在屈伸和旋转稳定性方面更好,在严重寰椎爆裂骨折时可以考虑采用该固定方式。

Objectives: To investigate the advantages and disadvantages of atlas pedicle screw combined with atlantoaxial transarticular screw fixation technique over other commonly used atlantoaxial fixation techniques in terms of mechanical stability. Methods: Six fresh specimens of adult cervical spine were used to prepare an intact model of the upper cervical spine(intact group), and the range of motion(ROM) values of C1-C2 in flexion-extension, lateral bending and rotation at a torque of 1.5 Nm were measured using biomechanical testing instruments and computer visual analysis software. The anterior arch and lateral mass of atlas were destroyed to prepare the unstable model(unstable group), and measure the ROM values of C1-C2 in each direction under the same torque again. The atlas pedicle screw + axial pedicle screw fixation(C1 P+C2 P group), atlas pedicle screw + atlantoaxial transarticular screw fixation(C1 P +TA group), and atlantoaxial transarticular screw fixation alone(TA group) were prepared in sequential order, and the ROMs in each direction were measured under the same torque, and the differences in C1-C2 ROMs between the groups were compared. Results: The unstable group had greater ROM in six directions than the intact group, and there was a significant difference in ROM in all directions between the two groups(P<0.05);the C1 P+C2 P group, C1 P+TA group,and TA group had significant decreases in ROM compared with the unstable group(P<0.05);the ROM values in the flexion, extension, left and right rotation directions were statistically different between the three fixation groups(P<0.05), with the C1 P+TA group <C1 P+C2 P group <TA group in ROM. There was no statistically significant difference in ROM in the left and right bending directions between the three fixation groups. Conclusions: All three fixation techniques achieved good fixations and similar stability in lateral bending, C1 P+TA group was better than other two fixation groups in flexion-extension and rotation stability, and it can be considered in severe atlas burst fractures.