Figure 2.

(a–d) are the corner points of the adjacent vertebral body. (e) is the orthogonal projection point on the endplate (a and b) of (c), and (f) is the orthogonal projection point of (b). The disc height is defined as the distance between the corner point of the vertebral body and the point of its orthogonal projection on the endplate of the adjacent vertebral body. For example, the anterior disc height is the length from (e) to (c), and the posterior disc height is the length from (b) to (f).