Draw a transecting line to the center of the sacral end plate from the center of the left femoral head (cursor). By subtracting the angle shown in the figures from 90°, the orthogonal angle was obtained to display the pelvic incidence (PI). For example, this patient’s left-sided sided PI = 90° -28° = 62° for the left-sided PI. Add the right- and left-sided PIs and divide by 2 to obtain the average PI = 68°+ 62°=65°