Preparation and Assessment of an Individualized Navigation Template for Lower Cervical Anterior Transpedicular Screw Insertion Using a Three-Dimensional Printing Technique

Study Design. Prospective trial. Objective. To establish an individualized navigation template for safe and accurate insertion of lower cervical anterior transpedicular screw (ATPS) based on a three-dimensional (3D) printing technique. Summary of Background Data. Conventional screw insertion manually under fluoroscopy easily leading to deviation of ATPS screw channel, cervical instrumentation procedures demand the need for a precise technique for screw placement. Methods. Twenty adult cervical spine specimens (10 men and 10 women, with a mean age of 50.29 ± 6.98) were selected for computed tomography pre- and postoperatively. A 3D lower cervical spine model was reconstructed using Mimics software to measure the screw-related parameters and generate a reverse template with optimal screw channel as well as a prototype using 3D printing. Assisted by the navigation template, bilateral ATPS were inserted into the cadavers. Results. The mean outer width and height of pedicle were 5.31 ± 1.23 and 6.78 ± 1.10 mm, respectively. The average length, sagittal, and axial angles of the optimal screw channel obtained through the optimal entry point were 36.34 ± 4.39 mm, 40.67° ± 5.10°, and 93.7° ± 7.96°, respectively. The adjustable safe ranges of sagittal and axial angles were 3.89° ± 1.13° and 5.64° ± 0.97°, respectively. The axial and sagittal accuracies of the 200 screws were 99.5% and 97%, respectively. The average deviations of the actual entry point and the preset opening in the X, Y, and Z axes were 0.39 ± 0.43, 0.21 ± 0.41, and 0.29 ± 0.14 mm, respectively (P > 0.05). Conclusion. An individualized ATPS navigation template was developed using Mimics software and 3D printing prototyping, based on computed tomography, for highly accurate screw insertion. Level of Evidence: 4