The research on safe range of the anterior transpedicular screw in lower cervical vertebrae

Abstract

Objective: Exploring the safe range of anterior transpedicular screw (ATPS) in the lower cervical spine. Methods: Fifty healthy adult cervical spine CT imaging data were selected from our institution for this study. The image data was imported into Mimics 21.0 software in DICOM format for 3D model reconstruction. Then, using the intersection of the pedicle axis and the anterior wall of the vertebral body as the screw entry point, a 3.5 mm simulated screw was inserted. The simulated screw was rotated and moved with the intersection acting as its center. On the horizontal view, the included angle (α) between the simulated screw axis and the mid-sagittal plane, the width of the pedicle, and the distance between the transverse point and the mid-sagittal plane at the anterior vertebral body wall were measured from C3 to C7; On the sagittal view, the included angle (β) between the simulated screw axis and the plane of the anterior vertebral body wall, the height of pedicle, and the distance between the sagittal intersection point and the upper endplate were measured C3 to C7. Results: No matter in the transverse or sagittal planes, C7 had the largest average safety range, while C3 was the smallest. The average safety range of screw placement on the transverse plane increased from C3 to C7, ranging from 5.25°to 9.43°, of which C7 was the largest (9.43°) and C3 was the smallest (5.25°). The average safety range of screw placement on the sagittal plane showed a trend of first increasing, then decreasing, and then increasing, ranging from 12.57° to 14.70°, of which C7 was the largest (14.70°), and C3 was the smallest (12.57°). There was no statistical difference between the left and right pedicles of the same cervical level (P>0.05). Conclusions: When the entry point was determined, there was a certain safety range for ATPS in the lower cervical spine. Those are helpful for the clinical application of ATPS technology. However, the individual anatomy of the cervical spine is relatively different, and sufficient preoperative preparations should still be made to ensure the safety and accuracy of screw placement.