Safe and Accurate Midcervical Pedicle Screw Insertion Procedure With the Patient-Specific Screw Guide Template System

Study Design. Clinical trial for midcervical pedicle screw insertion using a novel patient-specific intraoperative screw guiding device. Objective. To evaluate the availability of the "Screw Guide Template" (SGT) system for insertion of midcervical pedicle screws. Summary of Background Data. Despite many efforts for accurate midcervical pedicle screw insertion, there still remain unacceptable rate of screw malpositioning that might cause neurovascular injuries. We developed patient-specific SGT system for safe and accurate intraoperative screw navigation tool and have reported its availability for the screw insertion to C2 vertebra and thoracic spine. Methods. Preoperatively, the bone image on computed tomography was analyzed and the trajectories of the screws were designed in 3-dimensional format. Three types of templates were created for each lamina: location template, drill guide template, and screw guide template. During the operations, after engaging the templates directly with the laminae, drilling, tapping, and screwing were performed with each template. We placed 80 midcervical pedicle screws for 20 patients. The accuracy and safety of the screw insertion by SGT system were evaluated using postoperative computed tomographic scan by calculation of screw deviation from the preplanned trajectory and evaluation of screw breach of pedicle wall. Results. All templates fitted the laminae and screw navigation procedures proceeded uneventfully. All screws were inserted accurately with the mean screw deviation from planned trajectory of 0.29 +/- 0.31 mm and no neurovascular complication was experienced. Conclusion. We demonstrated that our SGT system could support the precise screw insertion in midcervical pedicle. SGT prescribes the safe screw trajectory in a 3-dimensional manner and the templates fit and lock directly to the target laminae, which prevents screwing error along with the change of spinal alignment during the surgery. These advantages of the SGT system guarantee the high accuracy in screw insertion, which allowed surgeons to insert cervical pedicle screws safely.