Fig. 3.

The navigational template applied in the operation of a 42-year-old women with basilar invagination, occipitalization of the atlas and C2–3 vertebral fusion. a, b Preoperative CT and T1 sagittal MRI displaying ventral brainstem compression, c preoperative CT shows the pedicle of C2 is narrow and cannot accommodate the 3.5-mm pedicle screw, d navigational template fit the spinous process and lamina of C2 perfectly, e the high-speed drill is used along the navigational channel to drill the trajectory of laminar screw, f insert the cervical pedicle screw by navigational template, g, h, i postoperative CT showing accurate placement of C2 laminar screws