Publication:Pedicle screw navigation using surface digitization on the Microsoft HoloLens

Publication: Pedicle screw navigation using surface digitization on the Microsoft HoloLens

Authors: Liebmann, Florentin; Roner, Simon; von Atzigen, Marco; Scaramuzza, Davide; Sutter, Reto; Snedeker, Jess; Farshad, Mazda; Fürnstahl, Philipp

Purpose: In spinal fusion surgery, imprecise placement of pedicle screws can result in poor surgical outcome or may seriously harm a patient. Patient-specific instruments and optical system have been proposed for improving precision through surgical navigation compared to free-hand insertion. However, existing solutions are expensive and cannot provide in situ visualizations. Recent technological advancement enabled the production of more powerful and precise optical see-through head-mounted displays for the mass market. The purpose of this laboratory study was to evaluate whether such a device is sufficiently precise for the navigation of lumbar pedicle screw placement.

Methods: A novel navigation method, tailored to run on the Microsoft HoloLens, was developed. It comprises capturing of the intra operatively reachable surface of vertebrae to achieve registration and tool tracking with real-time visualizations without the need of intraoperative imaging. For both, surface sampling and navigation, 3D printable parts, equipped with fiducial markers, were employed. Accuracy was evaluated within a self-built setup based on two phantoms of the lumbar spine. Computed Tomography (CT) scans of the phantoms were acquired to carry out preoperative planning of screw trajectories in 3D. A surgeon placed the guiding wire for the pedicle screw bilaterally on ten vertebrae guided by the navigation method. Postoperative CT scans were acquired to compare trajectory orientation (3D angle)and screw insertion points (3D distance) with respect to the planning.

Results: The mean errors between planned and executed screw insertion were 3.38±1.73◦ for the screw trajectory orientation and 2.77±1.46 mm for the insertion points. The meantime required for surface digitization was 125±27s.