All that glitters is not gold: sacroiliitis.

Objectives: The aim of this study was to determine the prevalence of "rheumatic" and "non-rheumatic" changes of the sacro-iliac joints (SIJ).

Material and methods: We performed MRI in 210 patients with suspected inflammatory low back pain. We sorted and analysed the characteristics of sacroiliac bone lesions in "rheumatic" and "non-rheumatic" patients and assessed the diagnostic values of their extent and location. SIJ lesions were classified on the basis of their location into two categories: unilateral and bilateral. Their extent was then measured and assigned to one of two groups: <1 cm or ≥ 1 cm.

Results: In 45 cases (21%), the MRI findings matched the clinical diagnosis of "rheumatic" sacroiliitis. Interestingly, in 99 cases (47%) the SIJ changes were classified as "non-rheumatic". L5-S1 degenerative changes, scoliosis and pelvic asymmetry were most frequently encountered as concomitant phenomena in our study.

Conclusions: MRI of the sacroiliac joints in patients suspected of inflammatory low back pain demonstrated more often "non-rheumatic" changes.