Detailed analysis of the anatomical location and number of MRI lesions in the sacroiliac joints can help differentiate patients with axial spondyloarthritis (axSpA) from others such as athletes who may have bone marrow oedema, according to research findings presented at the 2018 ACR/ARHP Annual Meeting in Chicago.

While MRI-detected bone marrow oedema plays a central role in the ASAS (Assessment of Spondyloarthritis International Society) classification criteria for axial spondyloarthritis (axSpA), lesions in the sacroiliac joints are also present in other conditions, Danish researchers told the meeting.

In a study of more than 200 patients with back pain including some with axSpA or other conditions, as well as healthy  athletes, they showed that bone marrow oedema adjacent to the joint space, erosions and adipose tissue were more frequently seen in patients with axSpA, but these lesions were also seen in patients in the other groups, mainly women with postpartum pain.

But using higher cut-offs for numbers of lesions can help confine positive findings to mostly axSpA patients, according to co-investigator Dr Sengül Heidi Seven, MD, of the Copenhagen Centre for Arthritis Research.

The prospective study involved 41 patients with axSpA; 46 women with prenatal or postpartum pain within 12 months of delivery and 14 without; 25 patients with lumbar disc herniation, 26 people who worked in jobs involving hard physical labour; 23 long-distance runner; and 29 healthy men.  Participants with pain all had a score of two or higher on the Visual Analogue Scale for two months or longer.

All participants underwent clinical, laboratory and MRI examination including semi-coronal STIR and T1-weighted sequences of the SIJs. MRIs were evaluated for BME, erosion, fat, ankylosis, and sclerosis by two independent readers.

The results showed that bone marrow oedema located adjacent to joint space, adjacent to erosion and adjacent to fat was most frequent, but did not exclusively occur in patients with axSpA, whilst bone marrow oedema adjacent to sclerosis was most frequent in women with postpartum pain. BME adjacent to ankylosis was only seen in patients with axSpA.

“We have very effective medical treatments for axSpA that reduce disease activity, and improve the signs and symptoms of the disease. However, it’s clinically difficult to differentiate patients with axSpA from patients with buttock pain for other reasons,” commented Dr Seven.

“Data from this study will potentially help rheumatologists diagnose axSpA patients more accurately in clinical practice, and this may also potentially improve selection of patients for clinical trials,” she concluded.