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, topography (in thirds) and affected margin, considering that this issue is rarely addressed in the literature.

METHODS: Cross-sectional study evaluating MRI (1.5T) of SI joints in 16 patients with axial spondyloarthritis for the presence of acute changes (subchondral bone edema, enthesitis, synovitis and capsulitis) and chronic changes (erosions, subchondral bone sclerosis, bony bridges, and fatty infiltration), performed by two radiologists blind for clinical data. 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 and erosions were predominant in the upper third of SI joints (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 bony bridges with BASMI (p=0.028) and mSASSS (p=0.014). Patients with osteitis in the lower third showed higher values of ASDAS (ESR: p=0.011 and PCR: p=0.017).

CONCLUSION: Chronic inflammatory changes and bone edema predominated in the upper third of SI joints, 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 joints is insufficient to differentiate between degeneration and inflammation.