Prognostic Significance of Magnetic Resonance Imaging Changes of the Sacroiliac Joints in Spondyloarthritis - A Followup Study

Objective. To evaluate the prognostic significance of sacroiliac joint (SIJ) changes by magnetic resonance imaging (MRI) based on 2-7 years of followup of patients with axial spondyloarthritis (SpA). Methods. Ninety-four patients (50 women, 44 men) with axial SpA obtained MRI of the SIJ from 1998-2004. They were examined at followup after 25-95 months (mean 51), including MRI and radiography of the SIJ and the spine. The Danish scoring method was used to quantify the activity and chronic SIJ changes by MRI. The activity score included subchondral edema and/or enhancement, while chronic changes encompassed erosions and subchondral fatty marrow deposition (FMD). Results. The MR score values for chronic SIJ changes increased significantly during followup, and were most pronounced in HLA-B27-positive patients and patients fulfilling the modified New York criteria for ankylosing spondylitis (AS) at followup. SIJ activity scores >= 2, total chronic scores >= 1, erosion scores >= 1, and FMD scores >= 4 at baseline were significantly related to progression of chronic SIJ changes. Activity score values >= 3 at baseline had a sensitivity of 0.83, specificity of 0.75, and accuracy of 0.80 in relation to the presence of AS at followup. The similar values for total chronic SIJ scores >= 4 at baseline were 0.86, 0.75, and 0.82, respectively, and for erosion scores >= 2 they were 0.88, 0.75, and 0.83. Conclusion. The occurrence of manifest SIJ activity by MRI or chronic changes at baseline was related to progression of chronic changes and the presence of AS at followup. (First Release June I 2010; J Rheumatol 2010;37:1718-27; doi:10.3899/jrheum.091155)