Inertial Measurement Unit-Assisted Implantation of Pedicle Screws in Combination With an Intraoperative 3-Dimensional/2-Dimensional Visualization of the Spine

Abstract

Abstract BACKGROUND Inertial measurement units (IMUs) are microelectromechanical systems used to track orientation and motion. OBJECTIVE To use instruments mounted with IMUs in combination with a 3- and 2-dimensional (3D/2D) rendering of the computed-tomography scan (CT) to guide implantation of pedicle screws. METHODS Pedicle screws were implanted from T1 to S1 in 2 human cadavers. A software application enabled the surgeon to select the starting points and trajectories on a 3D/2D image of the spine, then locate these starting points on the exposed spine and apply the IMU-mounted instruments to reproduce the trajectories. The position of the screws was evaluated on the postoperative CT scan. RESULTS A total of 72 pedicle screws were implanted. Thirty-seven (77%) of the thoracic screws were within the pedicle (Heary I), 7 (15%) showed a lateral breach of the pedicle, and 4 (8%) violated the anterior or lateral vertebral body (Heary III). In the lumbar spine and S1, 21 screws (88%) were within the pedicle (Gertzbein 0), 2 (8%) screws had a pedicle wall breach < 2 mm (Gertzbein 1), and 1 > 2 to < 4 mm (Gertzbein 2). In the second cadaver, the position was compared to the intraoperatively shown virtual position. The median offset was 3°(mean 3° ± 2°, variance 5, range 0°–9°) in the sagittal plane and 3° (mean 4° ± 3°, variance 9, range 0°–12°) in the axial plane. CONCLUSION IMU-assisted implantation of pedicle screws combined with an intraoperative 3D/2D visualization of the spine enabled the surgeon to precisely implant pedicle screws on the exposed spine.