In-Human Report of S2 Alar-Iliac Screw Placement Using Augmented Reality Assistance

BACKGROUND: S2 alar-iliac (S2AI) screws provide spinopelvic fixation with the advantages of minimized dissection, easier rod contouring, and decreased symptomatic screw-head prominence. However, placement of S2AI screws may be challenging because of the anatomy of the lumbosacral junction. Augmented reality is a nascent technology that may enhance placement of S2AI screws. OBJECTIVE: To report the first in-human placement of augmented reality (AR)-assisted S2 alar-iliac screws and evaluate the accuracy of screw placement. METHODS: A retrospective review was performed of patients who underwent AR-assisted S2AI screw placement. All surgeries were performed by 2 neurosurgeons using an AR head-mounted display (Xvision, Augmedics). Screw accuracy was analyzed in a blinded fashion by an independent neuroradiologist using the cortical breach grading scale. RESULTS: Twelve patients underwent AR-assisted S2AI screw placement for a total of 23 screws. Indications for surgery included deformity, degenerative disease, and tumor. Twenty-two screws (95.6%) were accurate-defined as grade 0 or grade 1. Twenty-one screws (91.3%) were classified as grade 0, 1 screw (4.3%) was grade 1, and 1 screw (4.3%) was grade 3. All breaches were asymptomatic. CONCLUSION: AR-assisted S2AI screw placement had an overall accuracy rate of 95.6% (grade 0 and grade 1 screws) in a cohort of 12 patients and 23 screws. This compares favorably with freehand and robotic placement.(1,2) AR enables spine surgeons to both better visualize anatomy and accurately place spinal instrumentation. Future studies are warranted to research the learning curve and cost analysis of AR-assisted spine surgery.