Researchers K. Puhakka and colleagues from Denmark sought to analyze the type and frequency of abnormalities of the sacroiliac joint in early seronegative spondyloarthropathy (SpA) by MRI in comparison with CT and radiography (x-rays).

There are five diseases that make up the SpA's, which include ankylosing spondylitis, psoriatic spondylitis, reactive arthritis/ reiter's syndrome, spondylitis associated with inflammatory bowel disease/ Crohn's disease, and undifferentiated spondyloarthropathy. All of these diseases are "seronegative"- "sero" means blood and "negative" indicates that people with SpA usually do not have the antibody known as rheumatoid factor present in their blood. This is a feature that distinguishes SpA from rheumatoid arthritis, in which high levels of rheumatoid factor are usually found.

One of the primary ways that a doctor makes the diagnosis of SpA is through radiological changes of the sacroiliac joint, although early disease does not always produce visible radiological changes. Therefore, researchers have been studying whether MRI and CT techniques provide more visual information that could help doctors diagnose the disease at a much earlier age than is currently the norm. Previous research suggests that MRI and CT are superior at detecting sacroiliitis in early SpA.

Puhakka and colleagues evaluated the sacroiliac joints of 41 patients with early SpA (median duration of inflammatory low back pain of 19 months) by MRI. They compared these results with those obtained by CT and radiography.

MRI and CT were both found to be equally superior to radiography in viewing erosions and hardening of the tissue. Only MRI allowed visualization and grading of active inflammatory changes in the subchondral bone and surrounding ligaments, in addition to bone marrow fatty accumulations.

The researchers felt that MRI of the sacroiliac joints is reliable of joint erosions in early SpA and allows differentiation between active and chronic sacroiliitis.