枢椎4层皮质骨椎弓根螺钉的影像学测量及置钉策略

目的　探讨枢椎经椎管4层皮质骨椎弓根螺钉置钉策略的可行性及技术方法。 方法　利用PACS系统调阅92例正常成人枢椎椎弓根水平横断面MRI图像，测量椎弓根内侧壁切线（tangent of pedicle medial wall，TPMW）与脊髓切线（tangent of spinal cord，TSC）、硬膜切线(tangent of dura mater，TDM)间距离及椎管内侧壁切线 (tangent of spinal canal medial wall，TSCMW)与TSC、TDM间距离，以及脊髓和椎管横径、矢状径等参数。 结果　同性别双侧参数差异无统计学意义。男性枢椎TPMW与TSC的距离为9.05 mm，女性为8.57 mm；男性TPMW与TDM的距离为5.04 mm，女性为4.76 mm。男性TSCMW与TSC的距离为7.14 mm，女性为6.70 mm；男性及女性TSCMW与TDM的距离均为3.28 mm。 结论　在枢椎椎弓根水平，经椎管行枢椎4层皮质骨椎弓根螺钉理论上可行，但需根据具体情况采用个性化的策略。

Radiographic measurement and the screw placement strategies of axis quadricortical pedicle screw

Objective　To study the feasibility of screw placement strategies and the technique of axis quadricortical pedicle screw. 　Methods　49 males and 43 females with normal cervical spine were included. At the C2 pedicle level of MRI images, we marked the tangent of pedicle medial wall which was parallel with central axis of C2 pedicle, and measured the distance between the tangent and spinal cord and the distance between the tangent and dura mater. At the same time, the tangent of C2 spinal canal medial wall which was parallel with sagittal axis of C2 was marked too, also we checked the distance between the tangent and spinal cord and the distance between the tangent and dura mater. Spinal cord diameter, spinal canal diameter and other associated parameters were recorded too.　Result　No statistical difference occurred between same sex.The mean distance between C2 pedicle medial wall and spinal cord was (male 9.05 mm, female 8.57 mm); The mean distance between C2 pedicle medial wall and dura mater was (male 5.04 mm, female 4.76 mm); The mean distance between the C2 spinal canal medial wall and spinal cord was (male 7.14 mm, female 6.70 mm); The mean distance between the C2 spinal canal medial wall and dura mater was (male 3.28 mm, female 3.28 mm). Conclusion At the C2 level, the space between the C2 spinal canal medial wall and dura mater was safe for C2 quadricortical pedicle screw；However, there were individual differences among patients.Therefore, different screw placement strategies should be applied based on different situations.