Figure 2.

Computed tomography reconstruction of Cervical oblique-sagittal image by multi-plane reconstruction. The dashed and dotted lines represent the corresponding vertebral horizontal level and the pathway of screw entry, respectively. a means the pedicle sagittal angle value of C3 obtained at the cranial side, so it's defined as positive value. -a means the pedicle sagittal angle value of C7 obtained at the caudal side, so it's defined as negative value