Fig. 2

2a.marked the center position of the fusion cage, that was, the center of gravity of the triangle formed by the three marker points of the cage; 2b.The distance between the center of the cage and the front edge of the vertebral body was A, and the sagittal diameter of the intervertebral disc was B. A/B represented the cage’s sagittal position; 2c.The distance from the center of the cage to the bisector of the coronal plane of the intervertebral disc was C, and C had positive and negative points. When the center of the cage was biased toward the side of the cage, it was negative. When the center of the cage was biased toward the other side, it was positive. D was the length of the intervertebral disc’s left and right diameters, and C/D represented the cage’s coronal position