寰枕融合后C_1侧块螺钉置入的可行性及局限性研究

C_1 lateral mass screw insertion in patients of C_1 assimilation:the feasibility and limitations

目的研究寰枕融合后C1侧块螺钉置入的可行性及局限性。方法收集2008年4月～2009年3月寰枕融合的17例寰枢椎脱位和/或Chiari畸形患者,利用CT扫描及重建观察并测量C1侧块的形态学变化;收集同期20例正常者做对照研究。结果在矢状位上,多数C1侧块(31/34)在寰枕融合后变为前高后低的楔形;17例患者中31个C1侧块可以虚拟置入3.5 mm直径的螺钉,螺钉最大长度达18.1 mm,但进钉点需调至C1侧块下关节面的后部;理想的进钉角度为向上35.0°±16.5°,向内15.7°±4.5°。15例行CT血管造影的寰枕融合患者中,6例(6/30)椎动脉走行在寰枢侧方关节的后方。由于枕髁与C1侧块融合,螺钉置入过程中有舌下神经管损伤的可能。结论解剖学上,多数寰枕融合患者可以置入C1侧块螺钉,但许多因素可能限制其实际应用。

Objective To study the feasibility and limitations of C1 lateral mass screw insertion in patients of C1 assimilation（C1A）.Methods From April 2008 to March 2009,the morphological changes of C1 lateral mass were observed and measured using CT scan and reconstruction in 17 C1A patients with atlantoaxial dislocation（AAD） and/or Chiari＇s malformation.Twenty patients without C1 assimilation（Non-C1A） at the same period were used as controls.Results Most of C1 lateral masses（31/34） formed into a relative cuniform in the sagittal plane in C1A,with high anterior part and low posterior part.Screws with 3.5 mm diameter could be virtually inserted into the C1 lateral masses on 31 sides in 17 C1A patients,with the maximal length of the screw being 18.1 mm;but the screw should be inserted at the posterior part of inferior facet of C1,not the posterior aspect of C1 lateral mass.The ideal angulation of the screw trajectory was 35.0°±16.5° superiorly and 15.7°±4.5° interiorly.Six of the 15（20%） C1A patients undergoing CT angiography had an abnormal course of vertebral artery.During insertion of C1 lateral mass screw,the hypoglossal canal was at high risk of injury due to fusion of C1 lateral mass and condyle.Conclusion Anatomically most C1 lateral masses can be inserted with a screw for fixation in patients of C1A,but in practice many factors may limit its use.