Table 1.

Scoring system of pedicle screws by Zdichavsky et al. [31]

Grade	Criteria of the pedicle screw scoring system
Ia	≥Half of PSD within the pedicle and ≥half of PSD within the vertebral body
Ib	≥Half of PSD lateral outside the pedicle and >half of PSD within the vertebral body
IIa	≥Half of PSD within the pedicle and >half of PSD lateral outside the vertebral body
IIb	≥Half of PSD within the pedicle and tip of PS crossing the middle line of the vertebral body
IIIa	>Half of PSD lateral outside the pedicle and >half of PSD lateral outside the vertebral body
IIIb	>Half of PSD medial outside the pedicle and tip of PS crossing the middle line of the vertebral body

PS pedicle screw, PSD pedicle screw diameter