Topographic MRI evaluation of the sacroiliac joints in patients with axial spondyloarthritis.

OBJECTIVE: To evaluate the imaging features of spondyloarthritis in magnetic resonance imaging (MRI) of the sacroiliac (SI) joint and topography (in thirds) and affected margin, considering that this issue is rarely addressed in the literature.

METHODS: A cross-sectional study evaluating MRI (1.5T) of SI in 16 patients with axial spondyloarthritis, for the presence of acute (subchondral bone edema, enthesitis, synovitis and capsulitis) and chronic (erosions, subchondral bone sclerosis, bony bridges, and fatty infiltration) changes, performed by two blinded radiologists. MRI findings were correlated with clinical data, including age, duration of disease, medications, HLA-B27, BASDAI, ASDAS-ESR and ASDAS-CRP, BASMI, BASFI, and mSASSS.

RESULTS: Bone edema pattern and erosions were predominant in the upper third of SI (p=0.050 and p=0.0014, respectively). There was a correlation between disease duration and structural changes by affected third (p=0.028-0.037), as well as between the presence of bone bridges with BASMI (p=0.028) and mSASSS (p=0.014). Patients with osteitis in the lower third showed higher values for ASDAS (ESR: p=0.011 and PCR: p=0.017).

CONCLUSION: Chronic inflammatory changes and the pattern of bone edema predominated in the upper third of SI, but a simultaneous involvement of middle or lower thirds of the joint was also noted. The location of involvement in the upper third of SI is insufficient to differentiate between degeneration and inflammation.