Freehand Regional Techniques for Subaxial Cervical Pedicle Screw Placement

Abstract

Background: Although various subaxial cervical pedicle screw implantation techniques have been proposed, clinical operators have been unable to exactly determine the entry points and trajectory . The objective of this article is to propose freehand regional techniques (FRT) for subaxial cervical pedicle screw placements and to investigate the clinical effectiveness of FRT.

Methods: A total of 80 consecutive patients who underwent open subaxial cervical pedicle screw fixation using FRT from January 2015 to December 2020 were retrospectively reviewed, and preoperative cervical computed tomography (CT) images were used to observe the entry point and screw trajectory. The horizontal and vertical lines at the center of the cervical lateral mass was marked, and the entry point was chosen at the outer upper quadrant of the lateral mass. Both sagittal and axial trajectories were determined by CT images, generally perpendicular to the cervical laminae. Screw implantation accuracy was assessed using postoperative CT.

Results: After virtually inserting pedicle screws by FRT on preoperative cervical CT images, all of the entry points were located in the outer upper quadrant of the lateral mass and the trajectory perpendicular to the cervical laminae was just parallel to the pedicle's axis. A total of 694 pedicle screws were placed by FRT clinically, with a 96% accuracy rate.

Conclusions: Pedicle screw implantation by FRT for subaxial cervical spine can be performed with acceptable safety and accuracy.

Keywords: freehand regional techniques; pedicle screws; subaxial cervical.

Figure 1

Diagram of freehand regional techniques (FRT). The entry point of FRT was located in outer upper quadrant of lateral mass.

Figure 2

Typical cases. (A-C) Preoperative imaging shows cervical spondylotic myelopathy. (D-F) postoperative imaging shows good pedicle screw position.