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Table 2 Radiographic grading of sacroiliac joint changes [
48
]
Grade 0
Normal
Grade 1
Suspicious changes
Grade 2
Minimum abnormality (small localized areas with erosion or sclerosis,
without alteration in the joint width)
Grade 3
Unequivocal abnormality (moderate or advanced sacroiliitis with erosions,
evidence of sclerosis, widening, narrowing, or partial ankylosis)
Grade 4
Severe abnormality (total ankylosis)
in
ammatory lesions are best visualized in T2 weighted fat-saturated sequence or
short tau inversion recovery (STIR) sequence as hyperintense signals. When the
hyperintense signal appears in the sacrum or iliac bone, it represents bone marrow
edema or osteitis, which is thought to represent in
fl
ammation of the bone. It may
appear in other locations, such as tendon insertions or synovium,
fl
indicating
enthesitis or synovitis. Active sacroiliitis is de
ned by the presence of bone marrow
edema/osteitis, and is very suggestive of AS or a condition in the spondyloarthritis
family. Erosions, sclerosis, and fatty change can also be detected by MRI. They are
chronic sequelae of active in
fl
ammation, but their utility in diagnosing AS is not
clear at this time.
Spine radiographs are useful to exclude other conditions, and are also useful to
assess disease progression in patients with an established diagnosis of AS. Anter-
oposterior and lateral views of the cervical and lumbosacral spine are usually
obtained for evaluation. The vertebral bodies are best visualized on the lateral views.
Erosions, sclerosis, or squaring of the vertebral bodies are early
findings; with
disease progression, syndesmophytes may develop, bridging syndesmophytes form
between the neighboring vertebras, and may eventually lead to a completely fused
spine, or a
ed Stoke Ankylosing Spondylitis
Spinal Score (mSASSS) is a scoring system used to assess the extent of this process
by examining changes at the anterior corners of the cervical and lumbar vertebrae on
lateral radiographs. Structural changes of the facet joints can be visualized on AP
view, with sclerosis and loss of the joint space being the most common
'
bamboo spine
'
(Fig.
9
). The modi
findings.
ammation and to reduce new bone
formation. To assess treatment response objectively, imaging modalities to visu-
alize in
The treatment goal for AS is to reduce in
fl
ammation and that are sensitive to bone growth are ideal. Plain radiography
has several disadvantages for these purposes. First, as two-dimensional imaging
modality, it has poor visualization of syndesmophytes due to overlying shadows.
Second, scoring systems based on plain radiograph are semi-quantitative, and
therefore tend to be insensitive to change. Third, as mentioned earlier, it does not
detect in
fl
ammatory changes. Three-dimensional imaging modalities may poten-
tially address these issues.
MRI of the spine is considered the
fl
ammation.
Similar to the changes seen in the sacroiliac joints, hyperintense signal on T2 fat
saturated sequence or STIR sequence depicts in
“
gold standard
”
for visualizing in
fl
ammation in the spine (Fig.
10
b).
Structural changes, such as erosions, can be detected as well (Fig.
10
a). Studies
fl
