Feasibility and safety of internal fixation with anterior atlantoaxial transarticular anatomic locking titanium plate and screws

Objective To investigate the feasibility and safety of internal fixation with anterior atlantoaxial transarticular anatomic locking titanium plate and screws.Methods Three-dimensional reconstruction was performed based on CT scans of 30 specimens of craniovertebral junction,soaked in formalin,from normal Chinese adult cadavers.Anatomic parameters were measured pertinent to internal fixation with anterior atlantoaxial transarticular anatomic locking titanium plate and screws.The surgical models of the fixation system were created on the specimens according to the parameters measured.Then the positions of internal fixation system and screw trajectory parameters were measured after postoperative three-dimensional CT reconstruction.Results The lateral angulation of the atlantoaxial transarticular screw trajectory to the coronal plane ranged from 14° to 32° while the ideal angle was 23.05° ± 1.90° and the actual angle 23.22° ± 1.71°; the posterior angulation to the sagittal plane ranged from 14° to 42° while the ideal angle was 27.89° ± 2.67° and the actual angle 27.96°± 3.05°; the length of screw trajectory ranged from 19 mm to 33 mm while the ideal length was 27.49 ± 1.23 mm and the actual length 27.50 ± 1.55 mm.There was no significant difference between the ideal and the actual screw trajectory parameters (P ＞ 0.05).The inner angulation of the atlantoaxial screw trajectory to the horizontal plane ranged from 0 to 15°,the upper angulation to the sagittal plane ranged from 0 to 50°,and the screw trajectory length ranged from 15 mm to 21 mm.The postoperative radiographs showed the titanium plate and the atlantoaxial surface matched well,and the angles and lengths of all the screw trajectories were within the preoperative reference range,with no screw protruding the bone.Conclusion The internal fixation system with anterior atlantoaxial transarticular anatomic locking titanium plate and screws is anatomically safe and feasible for Chinese patients. Key words: Atlas;  Axis;  Anatomy;  Instability;  Anterior