Accuracy of Patient-Specific Drill Guide Template for Bilateral C1-C2 Laminar Screw Placement: A Cadaveric Study

We sought to evaluate the accuracy of using patient-specific drill guides to place bilateral laminar screws in C1 and C2.Nine cervical specimens (8 males; mean age: 66.6 [56-73]) with the occiput attached (C0-C3) were used in this study. Preoperative computed tomography (CT) scans were used to create digital anatomic models for templating and guide creation. A total of 36 screws were placed with the aid of 3-dimensional printed, patient-specific guides (2 screws at C1 and C2). Postoperative CT scans were performed following screw insertion. The planned and actual trajectories were compared using preoperative and postoperative imaging based on the angular and entry point deviation. After screw placement and postoperative imaging, each specimen was dissected and performed a visual inspection for breaches.No breaches or violations were observed on postprocedural CT and visual inspection. The average variation of the entry point in the X, Y, and Z axes was 0.3 ± 0.28, 0.41 ± 0.38, and 0.29 ± 0.24, respectively. No statistically significant difference (P0.05) was observed between the planned and obtained entry points. There was no significant difference (P0.05) in the deviation analysis between the planned and obtained angles in the axial and coronal planes.The study demonstrates that patient-specific drill guides allow for accurate C1 and C2 bilateral laminar screw placement, with a low risk of cortical breach.