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Technique at radiography
Radiography - sacroiliitis
Radiography - spinal changes
Spinal changes by radiography

Conventional radiography is a well established method for detecting structural spinal changes such as new bone formation between the vertebral bodies and fusions.

There are several methods for assessing the severity of abnormalities in ankylosing spondylitis and the method used often depends on local tradition. The internationally recommended method 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.


Knowledge about the normal composition of the spine is necessary for understanding the description of the different grading methods.


The spine is composed of 7 neck vertebrae (Cerv.), 12 thoracic vertebrae (Thor.) and 5 lumbar vertebrae (Lumb.) connected by intervertebral discs and small true synovial joints posterior (apophyseal joints). Distally, the spine continues in the sacrum and the tail bone (Coccygis).

Grading methods

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


Frontal and lateral view 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 ligaments posterior are also seen.

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