THU0270 The propensity to fat metaplasia of sacroiliac joint in spondyloarthropathy: results from the single regional centrecohort

Background The predictor of radiographic spinal progression is the presence of syndesmophytes at baseline in axial spondyloarthritis (axSpA) and fat metaplasia on spine maybe predict the formation of new syndemophytes. Some studies suggests that fat metaplasia maybe a potential starting point for new bone formation and have a general systemic effect on new bone formation in spine, rather than results from local inflammation. Recent studies suggest that fat metaplasia on sacroiliac joint (SIJ) MRI at baseline is associated with spinal radiographic progression in axSpA patients. Objectives So in this study, we investigated for propensity to fat metaplasia on SIJ in axSpA patients. Methods The 357 patients who fulfilled the ASAS axSpA criteria were enrolled. All underwent MRI on SIj with T2 MR image, T1 fat suppressed with enhanced and short τ inversion recovery (STIR) image at baseline and lumbar spine radiographs at baseline and after 2 years. Inflammatory and structural lesions on SIJ MRI was scored using the SPondylo Arthritis Research Consortium of Canada (SPARCC) method. spinal radiographs were scored using the Stoke AS Spinal Score (SASSS). Multivariate logistic regression analysis was performed to identify for propensity to fat metaplasia on SIJ in axSpA patients. Results Among the 357 patients on baseline SIJ MRI finding, 182 patients showed fat metaplasia on SIJ, 148 patients showed erosion and 27 patients showed ankylosis. Propensity to fat metaplasia in axSpA patients showed the male, HLA-B27 negative, smoking, back pain onset time within 6–12 months at time of diagnosis, uveitis, peripheral arthritis, compared to erosion and anylosis on SIJ in axSpA patients. The patient with fat metaplasia or ankylosis on SIJ at baseline showed increased SASSS but there was no significant change in SPARCC over 2 years. univariate logistic regression analysis showed back pain onset time within 6–12 months at time of diagnosis and uvitis as a significant predictors of fat metaplasia. multivariated logistic analysis showed back pain onset time within 6–12 months at time of diagnosis as an affecting factor for fat metaplasia on SIJ (OR,5.67; 95% CI 4.71–17.95). Conclusions The back pain onset time within 6–12 months at time of diagnosis was affecting factor for propensity to fat metaplasia on SIJ in axSpA patients statistically and fat metaplasia on SIJ was associated with radiographic spinal progression in axSpA patients. so the early detection of fat metaplasia on SIJ in axSpA patients was important to protection of radiographic spinal progression. References [1] Maksymowych, et al. MRI evidence of structural changes in thesacroiliac joints of patients with nonradiographicaxial spondyloarthritis even in the absence of MRI inflammation. Arthritis Research & Therapy2017;19:126. [2] Fat Metaplasia on Sacroiliac Joint Magnetic Resonance Imaging at Baseline Is Associated with Spinal Radiographic Progression in Patients with Axial Spondyloarthritis. Plos oneaugust 2015 13. Acknowledgements none Disclosure of Interest None declared