Determination of optimal design of navigation templates for transpedicular implantation in the cervical and thoracic spine: results of cadaveric studies

Abstract

Objective. To perform comparative analysis of safety and accuracy of pedicle screw placement in the cervical and thoracic vertebrae using custom-made 3D-printed navigation templates of various designs. Material and Methods. The study was performed on three cadaver preparations. A total of 60 pedicle screws were placed in C2–T4 using navigation templates of different designs. Three types of templates were used to install 20 screws in each group: monolateral templates in group A, bilateral templates in group B, and bilateral three-point templates supported by the spinous process in group C. The safety and accuracy of screw placement were evaluated by CT with following comparative evaluation. Results. Three-point templates (group C) demonstrated the highest implantation safety, only one screw (5 %) perforated pedicle’s wall with grade 1, 19 screws (95 %) were completely surrounded by bone tissue. In group A, three screws (15%) were placed with grade 1, two screws (10 %) with grade 2, and one screw (5 %) with grade 3. In group B, two screws (10 %) were placed with grade 1, and one screw (5 %) – with grade 2.The average deviation at the screw entry point was 5.0 ± 0.5 mm in group A, 1.7 ± 0.3 mm in group B, and 0.35 ± 0.05 mm in group C. The average deviation at the end point was 5.1 ± 0.7 mm in group A, 3.5 ± 0.6 mm in group B, and 0.53 ± 0.05 mm in group C. Differences between groups in terms of implantation safety and accuracy are statistically significant (p < 0.05). Conclusion. Bilateral three-point navigation templates supported by spinous process are recommended for pedicle screw placement in the cervical and thoracic spine.

Keywords

• navigation templates
• spinal navigation
• 3d printing
• pedicle screwplacement