Visible light navigation for C1/C2 fixation and a rare complication related to C2 lamina fracture: case report

Os odontoideum is a rare craniocervical osseous anomaly leading to instability and cord compression that may require surgical stabilization. The increased precision and expedited workflow from visible light navigation allows for C1 lateral mass screw placement through the posterior arch while reducing dissection and venous bleeding compared to traditional entry at the arch-lateral mass junction.

A 57-year-old male presented with progressive myelopathy due to os odontoideum and C1/2 instability. Posterior C1-C2 fusion was performed via C1 through-the-arch screws and bilateral C2 laminar screws, with the assistance of visible light navigation (7D FLASH Navigation). Five weeks postoperatively, he developed progressive right arm pain and weakness. Computed tomography/magnetic resonance imaging (CT/MRI) demonstrated the lateral mass screws to be in situ, but there were bilateral C2 laminar fractures with screw loosening and cord impingement, requiring urgent screw removal with extension of fusion down to C4. Evaluation of the preoperative CT revealed unusually narrow C2 laminar width (3.2-3.4 mm). We posit that cyclic stress may have led to fatigue failure, although the initial C2 navigated screw placement was accurate.

This is the first report of visible light navigation being used for posterior C1/C2 fixation. Navigation, however, cannot compensate for inadequate bony dimensions for screw placement with risk of subsequent mechanical failure. C2 lamina width should be evaluated prior to consideration of laminar screw insertion.