Fig. 2

a to g. Illustration of various radiologic parameters for measurement. a. Antero-posterior (AP) midline axis. b. Distance to anterior cortex along pedicle axis (pedicle axis distance) (PAD). c. Distance to anterior cortex along AP midline axis (midline axis distance) (MAD).d. Distance from interface between transverse process and pedicle to anterior cortex of vertebra along pedicle axis (transverse pedicle axis distance) (TPAD). e. Lateral tangential lines (dotted lines E) along lateral borders of each vertebra. Transverse intertangential angle (TITA) was defined as the angle between two dotted lines E at each side of the vertebra. f. Point F was defined as the anterior border of the vertebra through midline axis and also taken as end point for pedicle screw insertion using the Weinstein method. PA (pedicle angle) was the angle between lines A and B. g. Pedicle diameter (PD) was taken as the line perpendicular to line B, which was also taken as pedicle axis distance (PAD)