Anatomic relationship of vertebral artery and screw trajectory of posterior atalanto-axial transarticular screw fixation / 中国矫形外科杂志

ABSTRACT

[Objective]To study the screw trajectory in the posterior atalanto-axial transarticular screw fixation.[Methods](1)The anatomical parameters related to the screw fixation were measured on 30 paired dry atlantoaxial specimens;(2)The X ray and CT scan were taken after C1、2 was fixed by posterior transarticular screws on 6 cadavers.These iterms were used to explore the anatomical relation of the vertebral artery and the screw trajectory in the posterior C1、2 fixation.[Results]The depth of the vertebral artery groove on the inferior surface of the superior facet of the axial was(5.86 1.45)mm;the vertebral artery groove extented the superior facet up to its medial third in 15 sides,up to the middle third and its lateral third respective in 35 and 9 sides,and the ideal screw trajectory medial angle of these specimens were(26.4?3.44)?,(16.1?2.44)?,(15.1?2.24)? respectively。The shortest distance between the vertebral artery and the screw trajectory lied in the topmost point of the vertebral artery groove of the axial on CT images,and the interval was(2.75～5.78)mm.[Conclusion]The position of vertebral artery groove of the axial is the key to decide the angle of the screw trajectory.The shortest interval between screw trajectory and vertebral artery,safe for posterior atalanto-axial transarticular screw fixation,locates on the inferior surface of the superior facet of the axial.