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 males and 10 females, with a mean age of 50.29 ± 6.98) were selected for computed tomography (CT) pre- and post-operatively. 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 mm 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 mm, 0.21 ± 0.41 mm 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 CT, for highly accurate screw insertion.Level of Evidence3