The use of augmented reality (AR) is widely accepted as a feasible training, planning, and prototyping tool. Unlike virtual reality (VR), which implies a complete immersion in a virtual world, AR adds digital elements to a live view by using a headset or camera on a smartphone. The ability to project digital elements into the physical world, combined with the Federal Food and Drug Administration (FDA) approval to use the Microsoft HoloLens in surgical procedures, presents a unique opportunity to explore and develop novel neurosurgical and orthopedic surgery training applications of AR, specifically in spine surgery. The potential of AR in spine surgery training lies in its ability to project CT-generated 3D models of the simulated patient's bony anatomy with overlaid pre-planned screw trajectories, thus allowing learners to practice with real-time guidance. As AR technologies become more mature, numerous research studies have identified AR's potential detriments to learning, including distraction and increased extraneous cognitive load. In this paper, we present our work on evaluating the effect of the presence of a Microsoft HoloLens 1 AR headset on extraneous cognitive load and on task performance during a simulated surgical procedure. A matched crossover trial design was used in which a combined group of 22 neurosurgery and orthopedic surgery residents, ranging in their training from the second postgraduate year (PGY-2) to chief resident (PGY-7 for neurosurgery and PGY-5 for orthopedic surgery, respectively. Participants were asked to place cervical lateral mass screws in a standardized, 3D-printed cervical spine with and without the Microsoft HoloLens 1 headset worn. Lateral mass screws were placed bilaterally at C4 to C6, with six cervical lateral mass screws placed by each participant in each trial, totaling 12 total screws placed. Overall time to drill six pilot holes, time for placement of each individual screw, pilot hole proximity to a predetermined entry point as defined by the Magerl method, and the presence of medial/lateral breaches were assessed and used as surrogate measures of mental taxation. The SURG-TLX questionnaire, a validated measure of extraneous cognitive load, was also used to compare cognitive strain of the task with and without the HoloLens 1.
