Fig. 2.

Anatomical orthogonal coordinate system. The origin was located at the most inferior point on the posterior wall of the vertebral body in the mid-sagittal plane. The Z-axis was defined as the line connecting the anterior and posterior points in the inferior plane of the vertebral body (anterior considered to be positive). The Y-axis was defined as perpendicular to the Z-axis, with superior being positive. The positive X-axis was directed to the left. Translation was calculated based on the origin of the coordinate system