Microscope-Integrated Augmented Reality-Assisted Navigation for C1-C2 Instrumentation: A Retrospective Single-Center...

Objective: Posterior C1-C2 instrumentation is technically demanding because of the complex osseous and vascular anatomy of the atlantoaxial region. This retrospective single-center case series aimed to describe the technical feasibility and observed screw-placement outcomes of a combined microscope-integrated augmented reality (AR)-assisted navigation workflow in patients with atlantoaxial instability. Methods: Two neurosurgeons and one radiologist assessed screw placement accuracy on computed tomography (CT) images using the Gertzbein-Robbins classification, applying the Bredow modification for the cervical spine. Cortical breaches were classified as Grade 1, <1 mm; Grade 2, 1 to <2 mm; Grade 3, 2 to <3 mm; Grade 4, 3 to <4 mm; and Grade 5, ≥4 mm, or as transverse foramen obstruction exceeding half the screw diameter. Grades 1 and 2 were considered acceptable for screw insertion. Results: A total of 40 screws were successfully placed in 10 patients, comprising 20 C1 lateral mass screws and 20 C2 pedicle screws, achieving an overall acceptable placement rate of 97.5% (39/40; 95% CI, 86.8-99.9%). All 20 C1 lateral mass screws were accurately positioned, while the acceptable placement rate for C2 pedicle screws was 95.0%. One C2 pedicle screw in a 1.7 mm pedicle was graded as Grade 3. No clinically apparent vascular or neurological injuries were observed. Conclusions: The combined microscope-integrated AR-assisted navigation workflow was feasible in this small case series, with a high observed acceptable screw-placement rate and no observed neurovascular complications. The independent contribution of AR and its effects on outcomes relative to other guidance techniques require evaluation in larger comparative studies.