新型寰枢椎后路动态固定系统的生物力学评价

目的测试并评价新型寰枢椎后路动态固定系统的生物力学性能。方法新鲜成人枕颈标本（C0-4）8例,分成4组：完整状态组、寰枢椎不稳状态组、寰枢椎后路动态固定状态组和寰枢椎后路椎弓根螺钉固定状态组。通过加载1.50 N·m的力矩,对4组标本C1/C2、C2/C3节段的前屈/后伸,左/右侧弯和左/右旋转等6种运动方式下的运动范围（range of movement,ROM）及稳定性指数（stability index,SI）进行测试。结果采用新型寰枢椎后路动态固定系统后,C1/C2、C2/C3节段的ROM与正常完整标本相比较,差异无统计学意义（P〉0.05）;而采用常规椎弓根螺钉固定与动态固定法相比,C1/C2、C2/C3节段的ROM差异有统计学意义（P〈0.001）。采用寰枢椎后路动态固定系统固定与采用后路椎弓根螺钉固定,C1/C2SI均上升,与完整状态组相比差异均有统计学意义,分别为（P〈0.05）和（P〈0.001）。C2/C3测试结果显示,采用动态固定时SI分别上升为109%、107%和112%;而采用椎弓根螺钉固定,三维运动范围SI反而分别下降为77%、71%和87%,比动态固定SI分别低29%、34%和22%,差异具有统计学意义（P〈0.001）。结论新型寰枢椎后路动态固定系统既可维持寰枢椎的部分旋转功能,又可达到坚固固定的稳定性,同时能够有效地减少对邻近节段的影响,具有良好的研究前景。

Biomechanical evaluation of new posterior atlanto-axial dynamic fixation system

Objective To evaluate biomechanics of a new posterior dynamic fixation system in atlanto-axial spine.Methods Eight fresh human cadaveric specimens (C_0-4) were divided randomly into 4 groups: The intact state group, instable state group, posterior atlanto-axial dynamic fixation group and posterior atlanto-axial pedicle screw fixation group. Th range of movement (ROM) C₁/C₂ and C₂/C₃ by loading 1.50 N·m were measured under the 6 conditions of flexion/extension, left/right lateral bending and left/right rotation.Results Under the 6 conditions, there were no significant differences in ROM of C₁/C₂ and C₂/C₃ between dynamic fixation group and intact group (P>0.05), but there were significant differences in ROM of C₁/C₂ and C₂/C₃ between dynamic fixation group and pedicle fixation group (P<0.001). There were significant differences between intact group and dynamic fixation group, pedicle fixation group in stability index(SI) of C₁/C₂ under the conditions of flexion/extension, left/right lateral bending and left/right rotation, respectively (P<0.05) and (P<0.001). However, the SI of dynamic fixation group was superior to pedicle fixation group in C₂/C₃.Conclusion In vivo biomechanical studies show that the new posterior atlanto-axial dynamic fixation may ideally restored the stability of atlanto-axial, meanwhile, maintain the atlanto-axial ROM.