The objective of our study was to compare multidetector row CT and the plain radiographs for making the diagnosis and grading the sacroiliitis that accompanies ankylosing spondylitis. We wanted to determine the role of multidetector row CT for the evaluation of the sacroilitis in patients with ankylosing spondylitis.

One hundred ninety two patients with clinically suspected ankylosing spondylitis were evaluated by conventional radiography and multidetector row CT. Two musculoskeletal radiologists retrospectively analyzed the images, and they graded the sacroiliitis using the modified New York Criteria.

Multidetector row CT demonstrated a significantly higher sensitivity (74.5%, 83.3%) than did plain radiography (59.9%, 66.7%) for detecting early sacroiliitis (p <0.05). Multidetector row CT showed a higher grade of sacroiliitis in 114 and 127 of 384 sacroiliac joints.

Performing multidetector row CT rather than plain radiography for making the diagnoses of accompanying ankylosing spondylitis allows an early start of treatment with a subsequently improved prognosis.