枢椎椎弓峡部引导下寰椎椎弓根置钉的CT测量及其应用

The CT scanning and clinical application of atlas pedicle screw placement guided by the morphology of interarticularis

中文关键词:  寰椎  枢椎  椎弓峡部  椎弓根螺钉

英文关键词:Atlas  Axis  Interarticularis  Pedicle screw

中文摘要:

  【摘要】 目的：探讨在枢椎椎弓峡部引导下实施寰椎椎弓根螺钉置钉的可行性及安全性。方法：对48例成人寰枢椎行三维CT重建，取枢椎椎弓峡部内上缘与寰椎的横断面图像。测量椎管正中线至寰椎椎弓根内壁、外壁及枢椎椎弓峡部内壁、外壁的距离，分别为L1、D1、L2、D2；0°内倾角置钉时，以枢椎椎弓峡部内上壁为解剖标志，确立最内侧进钉点A和最外侧进钉点B，减去螺钉半径1.75mm，A、B点至枢椎椎弓峡部内上壁的距离分别为（L1-L2+1.75mm）、（D1-L2-1.75mm），寰椎后弓上置钉时螺钉允许的最大内倾角与最大外倾角大致相等时的点为最佳进钉点（M点），记录M点至枢椎椎弓峡部内上壁水平间距。自2004年3月～2009年3月对29例患者采用以枢椎椎弓峡部为标志实施后路寰枢椎椎弓根螺钉内固定手术，其中陈旧性齿状突骨折24例，横韧带损伤并寰椎前脱位5例。观察手术过程中与寰椎椎弓根螺钉置钉相关的并发症，术后三维CT重建观察螺钉的位置。结果：0°内倾角置钉时，CT测量最内侧进钉点A、最外侧进钉点B、最佳进钉点M至枢椎椎弓根峡部内上壁的水平间距分别为4.22±0.54mm、8.66±0.73mm、5.79±0.63mm。临床共置入寰椎椎弓根螺钉58枚，术中枢椎椎弓峡部内上壁均得到良好显露，未出现椎动脉、静脉丛损伤出血及脊髓、C2神经根损伤等并发症。术后三维CT复查显示所有寰椎椎弓根螺钉均未误入椎管或椎动脉孔，测量寰椎椎弓根螺钉进钉点与枢椎椎弓峡部内上壁水平间距为5.45±0.82mm，与术前M点测量值相比较无显著性差异。结论：在纠正寰椎旋转移位后，以枢椎椎弓峡部内上壁作为解剖参照，寰椎椎弓根存在一定的置钉安全区间，利用该解剖标志行寰椎椎弓根置钉是安全可行的。

英文摘要:

  【Abstract】 Objective：To evaluate the feasibility and reliability of atlas pedicle screw placement guided by the morphology of interarticularis.Method：Three-dimensional CT reconstruction weas performed on C1-2 of 48 normal adults.The cross sectional images between atlas and medialsuperior edge of axis were used for study.The distance from the middle line to the medial border of atlas pedicle（L1），to the lateral border of C1 pedicle（D1），to the medial border of C2 interarticularis（L2） and to the lateral border of C2 interarticularis（D2） were measured respectively.When the screw was placed with zero introversion，the extreme medial and lateral entry point（termed as A and B） were marked on the posterior arch of atlas，when ignoring the screw diameter of 1.75mm，the horizontal distance between the medial border of C2 interarticularis to point A and B were （L1－L2＋1.75mm） and （D1－L2－1.75mm） respectively.The best entry point M was defined as the maximum introversion angle equal to the maximum extroversion angle.The horizontal distance from the medial border of C2 interarticularis to entry point M was be recorded.From March 2004 to March 2009，29 cases underwent posterior atlantoaxial pedicle screw fixation by this method.Of these，24 cases suffered from old odontoid fracture，and 5 cases had transverse ligment injury.Intraoperative and postoperative complications associated with instrumentation were evaluated.Screw position was also measured under three-dimensional CT scan after operation.Result：When screws were inserted as 0° introversion，the horizontal distance between the medial border of C2 interarticularis to point A and B was 4.22±0.54mm and 8.66±0.73mm respectively.While the distance between the ideal point M and medial border of C2 interarticularis was 5.79±0.63mm.A total of 58 atlas pedicle screws placement were based on the landmark of medial border of C2 interarticularis.There were no neurovascular complications noted.Postoperative three-dimensional CT scan after operation showed no infiltration of screw into spine canal and transverse foramen.The distance between the entry point to the medial border of C2 interarticularis was 5.45±0.82mm，which showed no significant difference with point M.Conclusion：There is a safe zone in C1 posterior arch，and the medialsuperior border of C2 interarticularis can be used as anatomic landmark for screw anchoring.