Feasibility and safety of anterior transarticular screw fixation from axis to occiput

Objective To investigate the feasibility and safety of anterior transarticular screw fixation from axis to occiput. Methods The data of head-neck CT angiography for 30 healthy adults were used in the present study.The angle,length and distance to the vertebral artery of the ideal screw trajectory were measured with the software Vitreal 4.0.According to the measurements,anterior transarticular screw fixation from axis to occiput was performed on 2 embalmed craniovertebral junction specimens.Three-dimensional CT reconstruction was performed postoperatively to study positions of the screws. Results The vertebral artery had 5 physiologic curves between the entrance point plane and the anchor point plane.The distance between bilateral vertebral arteries was 25.59 ± 1.04 mm on the entrance point plane.The angle of the screw ideally placed was 18.62±2.17 degrees laterally on the coronal plane and 24.35±3.02 degrees posteriorly on the sagittal plane.The mean length of the ideal screw trajectory was 35.95 ± 2.16 mm.The shortest distance between the vertebral artery and the screw trajectory was at the topmost point of the vertebral artery groove over the transverse foramen of atlas on CT images,with an interval of 3.66 ± 0.55 mm.Imageological examination of the simulated surgery demonstrated that the angle and length of the ideal screw trajectory were within the reference range,without piercing the bone or protruding into the hypoglossal canal. Conclusions The technique of anterior transarticular screw fixation from axis to occiput is feasible in normal Chinese,for there is a safe distance between the vertebral artery and the screw trajectory.However,the direction of screw emplacement should be rigorously controlled. Key words: Bone nails; Cervical vertebrae; Fracture fixation, internal; Imaging, three-dimensional