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Generel imaging aspects
Sacroiliitis - radiography
Sacroiliitis - MRI
Spine - radiography
Spine - MRI
Spinal fractures
Other joints
Diagnosis of spinal changes by radiography

Conventional radiography is a well established method for detecting structural changes in the spine such as new bone formation between the vertebral bodies and fusions. In manifest disease radiography often gives a good overview of chronic changes, but supplementary MRI may be needed in early stages and for monitoring the disease during therapy. MRI can display signs of activity which cannot be obtained by other means.

Supplementary CT may be necessary when fracture is suspected and also MRI in the case of spinal cord or nerve lesion.

Grading methods

There are several methods for assessing the severity of abnormalities in ankylosing spondylitis and the method often used depends on local tradition. The method internationally recommended by rheumatologists is the modified SASS method. It is simple to use, but from a radiologist’s point of view all relevant image information is not taken into account. This is more the case when using the BASRI method.


BASRI = Bath Ankylosing Spondylitis Index



Is based on lateral view of the cervical spine (C1-C7), and frontal + lateral view of the lumbar spine (Th12-S1); grade 0-4:

  • Grade 0: Normal findings.
  • Grade 1: Dubious changes.
  • Grade 2: Slight changes, including erosion, vertebral squaring or sclerosis, with or without syndesmophytes, on < 2 vertebrae.
  • Grade 3: Syndesmophytes on > 3 vertebrae, with or without fusion involving 2 vertebrae.
  • Grade 4: Fusion involving > 3 vertebrae.

added the sacroiliac joint grade according to the New York criteria, grade 0-4.



Added hip involvement, grade 0-4.





SASSS = Stoke Ankylosing Spondylitis Spine Score:

Anterior and posterior changes in the lumbar spine (Th. 12 - S1) at lateral view.

  • Grade 0: Normal findings.
  • Grade 1: Erosion, sclerosis and/or squaring.
  • Grade 2: Syndesmophytes.
  • Grade 3: Total ankylosis.

Modified SASSS

Only anterior changes in both the cervical and lumbar spine at lateral view. Is recommended by OMERACT.



Slight/Dubious changes

Lateral view of the thoraco-lumbar region showing slight abnormalities in the form of slight vertebral squaring (arrows) compatible with grade 1 BASRI Spine.


Early changes

Frontal and lateral view of the lumbar spine showing a bridging syndesmophyte (black arrow) and a slight osseous deposition at the anterior surface of the first lumbar vertebral body (L1)(arrowhead); in addition sclerosis at the upper corner of L1 (white arrow) and L2, changes compatible with grade 2 BASRI Spine.

Manifest changes

Frontal and lateral views of the lumbar spine showing bridging syndesmophytes (arrows) between several vertebral bodies, changes compatible with grade 3 BASRI Spine.

Advanced changes

Frontal and lateral views of the lumbar spine showing fusion of several vertebral bodies (arrow), changes compatible with grade 4 BASRI Spine.

Fusion of the apophyseal joints and ossification of the posterior ligaments are also seen.

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