Endoscopic Transnasal Approach to Atlantoaxial Decompression and C1-2 Fixation in Basilar Invagination of Adults: A Feasibility Study.

Objective: To explore a surgical technique for completing ventral bone decompression and C1-2 plate-screw fixation in the craniocervical junction (CVJ) through nasal approach by stage I at the imaging and physical anatomy levels, and to evaluate its feasibility.

Methods: Radiographic parameters of 80 patients with basilar invagination (BI) and 56 with normal CVJ anatomy were retrospectively analyzed. Three-dimensional (3D) reconstructions were performed in 31 patients with BI. Key anatomical landmarks, screw entry points, and fixation trajectories were evaluated. Customized plate-screw constructs were designed. Finally, surgical feasibility was tested on a 3D-printed anatomical model and a cadaveric.

Results: In 80 BI patients, the average distances between 4 screw insertion points were 16.04 mm, 21.10 mm, 6.83 mm, and 7.10 mm. C2 lateral mass oblique lengths were 16.81 mm (right) and 17.12 mm (left); C1 lengths were 18.71 mm (right) and 19.07 mm (left), with significant differences between C1 and C2 (p<0.001). A 28.5×14.1-mm titanium plate with 16 mm screws was successfully implanted via the nasal route in the polyether ether ketone 3D-printed BI model and the cadaveric. Radiology indicated that the screws were all in the lateral mass and the plates fit tightly.

Conclusion: In BI, transnasal odontoidectomy and plate-screw fixation of C1-2 are feasible theoretically. This may enable a new alternative approach for nasal minimally invasive decompression and immobilization, following the completion of biomechanics and clinical trials.