Fig. 4
The simulation of screw insertion in Mimics software: the upper and lower screw paths do not overlap (A), the screw entry point (P1) nearest to the midline of the intervertebral space (B), the angle α1 formed between the simulated screw axis and mid-sagittal plane (C), the angle β1 formed between the middle section of the cervical intervertebral space and the simulated screw axis (D); the screw entry point (P2) farthest from the midline of the intervertebral space (E), the angle α2 formed between the simulated screw axis and mid-sagittal plane (F), the angle β2 formed between the middle section of the cervical intervertebral space and the simulated screw axis (G)