目的 　评价新型寰枢椎后路动态固定系统的稳定性。  方法　8具较新鲜的成人枕颈标本（C0~4），随机分成4组：①完整状态组（A组）、②寰枢椎不稳状态组（B组）、③寰枢椎后路动态固定状态组（C组）和④寰枢椎后路椎弓根螺钉固定状态组（D组）。测量在1.50 Nm的力矩下，寰枢关节前屈/后伸，左/右侧弯和左/右旋转等6种运动方式下的运动范围（ROM）及稳定性指数（Sf值），进行统计学分析。  结果　C组与A组的各方向ROM比较，差异无统计学意义（P>0.05）；而C组与D组的各方向ROM比较，差异有统计学意义（P<0.001）。C组与B组和D组的屈伸、侧屈和旋转的稳定性指数（Sf值）比较，差异有统计学意义（P<0.05）；C组的屈伸、侧屈和旋转的Sf值最接近完整状态组（A组），差异无统计学意义（P>0.05）。  结论　寰枢椎后路动态固定在重建寰枢关节稳定性上有独特优势，既可维持寰枢椎的活动性，又可达到坚强固定的稳定性，为寰枢椎后路固定提供一种新的选择。

Objective　To evaluate the stability of a new posterior dynamic fixation system in atlanto-axial spine.    Methods　Eight fresh human cadaveric specimens (C0~4) were divided randomly into 4 groups: The intact state group (group A), instable state group (group B), posterior atlanto-axial dynamic fixation group (group C) and posterior atlanto-axial pedicle screw fixation group (group D). The rage of motions C1 relative to C2 by loading 1.50 Nm were measured under the six conditions of flexion/extension, left/right lateral bending and left/right rotation．The obtained data was statistically analyzed.     Results    Under the six conditions, there were no significant differences between group C and group A in ROM (P>0.05), but there were significant differences between group C and group D in ROM (P<0.001). There were significant differences between group C and group B, D in stability index under the conditions of flexion/extension, left/right lateral bending and left/right rotation (P<0.05). However, the stability index of group C was mostly similar to the intact state group．Conclusion    In vivo biomechanical studies show that the new posterior atlanto-axial dynamic fixation has unique superiority in the reconstruction of atlanto-axial stability. It may ideally restore the stability of atlanto-axial joint, as well maintain the atlanto-axial range of motion．It is a new surgical choice for treatment of atlanto-axial instability.