Method used to measure disc height with plain radiography and computed tomography. (1) Consider the oblique projection or overlapping of bone images before measuring. (2) Determine the four corners of the two adjacent vertebral bodies (A, A', B, and B'). (3) Draw a straight bisecting line (C) passing through the centers of line A–B and A'–B'. (4) Calculate the sum of the shortest distances from the midpoint of the upper and lower endplates to the bisecting line (a + b).