Pedicle screw navigation using surface digitization on the Microsoft HoloLens.

Florentin Liebmann,Simon Roner,Philipp Fürnstahl,Davide Scaramuzza,Mazda Farshad,Jess Snedeker,Reto Sutter,Marco Von Atzigen

doi:10.1007/s11548-019-01973-7

Abstract

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 systems have been proposed for improving precision through surgical navigation compared to freehand 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. A novel navigation method, tailored to run on the Microsoft HoloLens, was developed. It comprises capturing of the intraoperatively 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. The mean errors between planned and executed screw insertion were [Formula: see text] for the screw trajectory orientation and 2.77±1.46 mm for the insertion points. The mean time required for surface digitization was 125±27 s. First promising results under laboratory conditions indicate that precise lumbar pedicle screw insertion can be achieved by combining HoloLens with our proposed navigation method. As a next step, cadaver experiments need to be performed to confirm the precision on real patient anatomy.

Highlights

Spine disorders are among the most frequent musculoskeletal pathologies in developed countries [1]
Purpose: In spinal fusion surgery, imprecise placement of pedicle screws can result in poor surgical outcome or may seriously harm a patient
Computed Tomography (CT) scans of the phantoms were acquired to carry out preoperative planning of screw trajectories in 3D

Summary

Introduction

Spine disorders are among the most frequent musculoskeletal pathologies in developed countries [1]. They cause diminished quality-of-life to the patients and result in substantial socio-economical costs [2]. Surgery is indicated in patients with more severe conditions such as degenerative disc disease, fracture treatment, and scoliosis. In such pathologies, spinal fusion has been established as the benchmark surgical treatment [4,5,6]. Screw insertion relies on the preparation of guiding holes with a surgical awl or by drilling K-wires. Deviation from the optimal position can result in pedicle screw penetration which in turn can lead to serious injury of the spinal cord, nerve roots, and major vessels

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