Navigation template for vertebral pedicle passage in transpedicular screw fixation

Abstract

Transpedicular screw fixation is the most established means to stabilize the spine. Present study evaluates personalized navigation templates application for vertebral pedicle passage. Navigation templates were used for inserting 35 transpedicular screws in 5 patients with spinal deformity (age 2–16). Each patient underwent computed tomography preoperatively. Acquired data was processed into a virtual 3d-model of target zone. Life size virtual pedicular probes were placed onto transpedicular trajectories determined on multiplanar cross-sections of the model. Navigation template was created by modification and union of geometric primitives. Target zone model and navigation template were made with PLA by 3D-printer. In surgery the template was placed on skeletonized posterior surface of appropriate vertebrae. After confirmation of template stability trajectories were passed to a depth of 20 mm through guiding tubes by pedicular probe. Resulting channels were controlled with ball tip feeler, and the full depth trajectories were made by free hand technique. Postoperatively screws placement accuracy was assessed by plain X-rays in each patient. Two patients (16 screws) also underwent computed tomography. In these patients screw placement accuracy was assessed by system based on 2 mm breach increments. 15 screws (93. 7%) were fully contained within the pedicle (grade 0), 1 screw breached external cortex of the pedicle by 0. 8 mm (grade 1). Efficacy and safety of navigation template for transpedicular screws insertion was demonstrated.