Anatomic study of upper cervical reconstruction by posterior arch of atlas

Abstract

Objective To investigate the anatomy of upper cervical vertebrae's stable reconstruction by poster arch of atlas screw by anatomic study. Methods To collect the anatomical data of 39 dry atlas with the average inner diameter of vessel of atlas, the average high and wide of the screw point of poster arch of atlas, the average high and wide of poster arch of atlas beneath the groove for vertebral artery, the tract length of poster arch screw, the tract length of lateral mass screw, the direction and angle of poster arch screw, and the direction and angle of lateral mass. Statistical comparison were performed with Student test between the tract length of poster arch screw and the tract length of lateral mass screw. Results The average inner diameter of vessel of atlas was (26.8±2.58) mm(21.7-31.0 mm). The screw point high and wide of poster arch of atlas were (6.83±1.97) mm and (6.40±1.36) mm respectively. The average high and wide of poster arch of atlas beneath the groove for vertebral artery were (4.37±1.11) mm and (8.05±1.33) mm respectively. The tract length of poster arch screw were (30.54±1.705) mm. The direction and angle of poster arch screw was 15°-20° incline laterally and 0°-5°incline cephalo. 25.6%(10 cases) patients with the diameter less than 3.5mm beneath the groove for vertebral artery. The direction and angle of lateral mass screw was 32.05°±6.03° incline medially and 5° incline cephalo. There were significant differences between the tract length of poster arch screw and the tract length of lateral mass screw(t=59.528, P＜0.001 ). Conclusion About 74.4% patients can reconstruct the upper cervical stable by poster arch of atlas screw. The technique can gain instant upper cervical stable, and reduce the risk of injury of blood vessel by over explore the atlas arch compare with the technique of lateral mass screw fixation of atlas. The technique is worth to promoting with its character of safe, easy perform and rigid fixation. Key words: Atlas; Spinal fusion; Bone screws; Anatomy