以枢椎椎弓峡部内上壁为解剖标志行枢椎椎弓根置钉的CT测量及临床应用

The CT scanning and clinical application of axis pedicle screw placement guided by the morphology of C2 interarticularis

中文关键词:  枢椎  椎弓峡部  椎弓根螺钉  三维CT

英文关键词:Axis  Interarticularis  Pedicle screw  Three-dimensional CT

中文摘要:

  【摘要】 目的：探讨以枢椎椎弓根峡部内上壁为解剖标志的枢椎椎弓根螺钉置钉的可行性及安全性。方法：57例成人枢椎行三维CT重建，在三维重建图像上测量枢椎左右侧椎弓根的中部宽度L1和高度L2；以枢椎椎弓峡部内上壁为标志横断面确立左右侧的最外侧模拟进钉点B和最内侧模拟进钉点A到峡部距离；测量最佳进钉点S（经过枢椎椎弓根中部宽度连线的中垂线与峡部后侧皮质交点）到峡部内壁距离，分别测量A、B、S点横断面进钉角度最大置钉角度区间；冠状面上测量S点距离峡部内上壁距离；测量S点进钉最佳内倾角及上倾角。选择2007年10月～2011年7月收治的33例患者采用枢椎椎弓根峡部内上壁为标志实施枢椎椎弓根螺钉内固定术，其中新鲜齿状突骨折13例，陈旧性齿状突骨折10例，横韧带损伤伴寰枢椎脱位7例，寰椎骨折3例。观察手术中与枢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：CT横断面测量进钉点A、B、S到峡部的距离为1.75mm、9.01±0.62mm、5.77±0.53mm，S点置钉角度区间与A、B点置钉角度区间比较有显著性差异（P＜0.05）。冠状面上S点距离峡部内上壁距离为4.30±0.49mm；S点进钉内倾角为30°、上倾角为26°时为最佳进钉角度。临床共置入枢椎椎弓根螺钉66枚，术中显露良好，未出现椎动脉、静脉丛损伤出血及脊髓、神经根损伤等并发症。术后三维CT复查显示所有枢椎椎弓根螺钉均未误入椎管或椎动脉孔，术中测量枢椎椎弓根螺钉进钉点横断面上与枢椎椎弓峡部内壁水平间距为5.44±0.72mm，冠状面上距离峡部内上壁为4.50±0.52mm，与术前S点测量值相比较均无显著性差异。结论：枢椎椎弓根与峡部存在恒定位置关系，以枢椎椎弓峡部内上壁为解剖参照行枢椎椎弓根置钉是安全可行的。

英文摘要:

  【Abstract】　Objectives:　To evaluate the feasibility and reliability of axis pedicle screw placement guided by the morphology of interarticularis. Methods:　C2 three-dimensional CT reconstruction was performed in 57 normal adults.　The cross-sectional images were used for study. The width of the central(L1) and the height(L2) at left and right side were measured. The distances from the interarticularis to the outer anchoring point B and the most medial point A were used as anatomical sign in C2 interarticularis.The distances from the interarticularis to the best anchoring point S(the intersection between vertebral pedicle central line and interarticularis rear cortex), and the maximum safety for screw placement at cross-sectional plane through A, B and S point respectively were measured. The distance from the interarticularis to the best point S at coronal plane was measured, and the best introversion and uptroversion angle at point S was measured. From October 2007 to July 2011, 33 cases underwent posterior atlantoaxial pedicle screw fixation guided by this method. Of these, there were 13 with new odontoid fracture,　10 with old odontoid process fracture,　7 with transverse ligment rupture and 3 with Jefferson fractrue.　Intraoperative and postoperative complications associated with instrumentation were evaluated. Screw position was also determined under three-dimensional CT scan after operation. Results:　The distance between point A, B, S to interarticularis on CT coronal plane was 1.75mm,　9.01±0.62mm,　5.77±0.53mm respectively. There were statistical differences between piont S and A, B with respect to safety instrumentation(P＜0.05).　 The distance from point S to the superomedial part of C2 interarticularis at coronal plane was 4.30±0.49mm, with an introversion of 30° and uptroversion of 26°. A total of 66 C2 pedicle screws was placed. There was no neurovascular complication noted.　Postoperative three-dimensional CT scan showed no screw into spine canal and transverse foramen. The distance between the entry point to the medial border of C2 interarticularis was 5.44±0.72mm,　the distance from point S to the superomedial part of C2 interarticularis on coronal plane was 4.50±0.52mm, which showed no significant difference with point S of preoperation. Conclusions:　There is constant relationship between C2 pedicle and its isthmus.　Screw placement at superomedial part of C2 isthmus is safe and reliable.