Fig. 2.

Postoperative computed tomography assessment of the pedicle screw position: grade 0, no perforation and the screw was completely contained in the pedicle (A); grade 1, perforations<2 mm (B); grade 2, perforations≥2 but <4 mm (C); and grade 3, perforations≥4 mm, with grades 2 and 3 representing perforation. In both groups C and D, no screw was categorized as grade 3 (A arrow, no perforation; B, C arrows, perforations).