SAT0526 THE COURSE OF ABERRANT FINDINGS ON MRI OF THE SACROILIAC JOINTS OVER 6 MONTHS IN POSTPARTUM WOMEN

Background: Sacroiliac bone marrow oedema (BME) on magnetic resonance imaging (MRI) can have different causes. Besides spondyloarthritis (SpA), other more rare causes as stress fractures, mechanical stress, infections or malignancies can be identified. There are limited data regarding the specificity of MRI lesions in a non-SpA population. Pregnancy and vaginal delivery might induce the presence of inflammatory and/or structural MRI lesions by mechanical stress. Objectives: To assess aberrant findings on MRI features of the sacroiliac joints (SIJ) in postpartum women and describe the course after a 6 month time period. Methods: Twenty-five women underwent an MRI of the SIJ within 10 days after childbirth; delivery by caesarean section was excluded. The scan was repeated after 6 months. One subject was lost to follow-up. Three trained readers systematically scored inflammatory and structural SpA-like lesions (not reported here) and qualitatively described other aberrant findings. Both time points were scored on T1-weighted and short tau inversion recovery (STIR) MRI images. Readers were blinded for time sequence and clinical and demographic information on the subjects. Results: In 16 out of 25 (64%) subjects there were aberrant MRI findings at baseline. Thirteen out of 25 (52%) showed BME at the symphysis pubis on the baseline MRI (fig. 1). After 6 months, 6 out of 24 (25%) subjects still showed BME; in 1 subject BME of the symphysis pubis was increased at 6 months. Two out of 25 (8%) displayed a sacral fracture on the baseline MRI. Both these fractures were asymptomatic and resolved completely after 6 months (fig. 2). One out of 25 subjects (4%) showed degenerative disc disease at level L5-S1 in the form of Modic type 2; vertebral and endplate related replacement of bone marrow with fat deposition. As expected, the presence of Modic type 2 did not decrease at follow-up. No other aberrant findings were seen. Conclusion: Aberrant findings, like sacral fractures and degenerative disc disease, are observed when assessing MRI-SIJ of postpartum women for SpA-like lesions. BME at the symphysis pubis was often seen shortly after birth and half of those lesions persisted at follow-up after 6 months. Disclosure of Interests: Anais Depicker: None declared, Thomas Renson: None declared, Ann-Sophie De Craemer: None declared, Manouk de Hooge: None declared, Liselotte Deroo: None declared, Gaelle Varkas: None declared, Nele Herregods: None declared, Lennart Jans: None declared, Kristien Roelens: None declared, Isabelle Dehaene: None declared, Philippe Carron: None declared, Dirk Elewaut: None declared, Filip van den Bosch Consultant for: AbbVie, BMS, Galapagos, Janssen, Lilly, Merck, Novartis, Pfizer and UCB, Speakers bureau: AbbVie, BMS, Janssen, Lilly, Merck, Novartis, Pfizer and UCB.