What are the early radiographic signs of ankylosing spondylitis (AS)?

Updated: Jul 17, 2018
  • Author: Lawrence H Brent, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

The radiographic signs of AS are due to enthesitis, particularly of the anulus fibrosus. Early radiographic signs include squaring of the vertebral bodies caused by erosions of the superior and inferior margins of these bodies, resulting in loss of the normal concave contour of the anterior surface of the vertebral bodies (see the images below). The inflammatory lesions at vertebral entheses may result in sclerosis of the superior and inferior margins of the vertebral bodies, called shiny corners (Romanus lesion).

Anteroposterior radiograph of spine of patient wit Anteroposterior radiograph of spine of patient with ankylosing spondylitis. Ossification of anulus fibrosus at multiple levels and squaring of vertebral bodies can be observed.
Anteroposterior radiograph of spine of patient wit Anteroposterior radiograph of spine of patient with ankylosing spondylitis.
Anteroposterior (left) and lateral (right) radiogr Anteroposterior (left) and lateral (right) radiographs of patient with ankylosing spondylitis.

Ossification of the anulus fibrosus leads to the radiographic appearance of syndesmophytes, which, in AS, are typically marginal. Over time, development of continuous (bridging) syndesmophytes may result in a bamboo spine, which is essentially fused (see the images below).

Anteroposterior radiograph of spine of patient wit Anteroposterior radiograph of spine of patient with ankylosing spondylitis. Ossification of anulus fibrosus can be observed at multiple levels, which has led to fusion of spine with abnormal curvature.
This radiograph of the lumbar spine of a patient w This radiograph of the lumbar spine of a patient with end-stage ankylosing spondylitis shows bridging syndesmophytes, resulting in bamboo spine.
This radiograph of the cervical spine of a patient This radiograph of the cervical spine of a patient with ankylosing spondylitis shows fusion of vertebral bodies due to bridging syndesmophytes.

Spinal disease associated with inflammatory bowel disease (IBD) is similar to AS with bilateral symmetric sacroiliitis and gradually ascending spondylitis and marginal syndesmophytes. On the other hand, reactive arthritis (ReA) and psoriatic arthritis (PsA) typically exhibit asymmetric sacroiliitis and discontinuous spondylitis with nonmarginal syndesmophytes.


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