Radiographic studies are most helpful in establishing a diagnosis of ankylosing spondylitis. CT scanning and MRI may be useful in selected patients, but for reasons of expense are not typically part of routine evaluation.
The radiographic signs of ankylosing spondylitis are due to enthesitis, particularly of the annulus 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. 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).
The erythrocyte sedimentation rate or the C-reactive protein level is elevated in approximately 75% of patients and may correlate with disease activity in some (but not all) patients; these values may also be used as markers of response to treatment. Alkaline phosphatase is elevated in some patients with ankylosing spondylitis; this indicates active ossification but does not correlate with disease activity. Creatine kinase is occasionally elevated but is not associated with muscle weakness. The serum immunoglobulin A (IgA) level may be elevated, correlating with elevated acute-phase reactants.
Read more about the workup of ankylosing spondylitis.
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Cite this: Herbert S. Diamond. Fast Five Quiz: Spine Pain - Medscape - May 16, 2019.