score each sacroiliac joint individually from 0–4 (using the New York criteria) and sum the score

score range 0–8

score the lower border of T12 to the upper boarder of S1

use both antero-posterior and lateral views

use the mSASSS grading: 0–3 (0 normal; 1 erosion, sclerosis, squaring; 2 syndesmophyte non-bridging; 3 bridging syndesmophyte)

score range 0–36

score the lower border of C2 to the upper border of C6

use only lateral views

use the mSASSS grading: 0–3 (0 normal, 1 erosion, sclerosis, squaring; 2 syndesmophyte non-bridging; 3 bridging syndesmophyte)

add 1 point for every level fused posteriorly (C2/C3, C3/C4, C4/C5, C5/C6)

score range 0–28