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.