OP0038 HIGH PREVALENCE OF SACROILIAC BONE MARROW EDEMA ON MRI IN POSTPARTUM WOMEN: A TEMPORARY PHENOMENON
Authors: Thomas Renson, Ann-Sophie De Craemer, Anaïs Depicker, Liselotte Deroo, Manouk de Hooge, Nele Herregods, Lennart Jans, Gaëlle Varkas, Kristien Roelens, Isabelle Dehaene, Philippe Carron, Filip van den Bosch, Dirk Elewaut
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Magnetic Resonance Imaging (MRI) is a sensitive method for detection of sacroiliitis. However, recently, concerns have been raised about its specificity. In contrast to radiographic spondyloarthritis (SpA), non-radiographic SpA has a more equal sex distribution. Hence, in young women with back pain a broad differential diagnosis has to be considered. In clinical practice, women occasionally present with inflammatory(-like) low back pain, following pregnancy and childbirth. Up until now, little is known regarding the presence of SpA-like MRI lesions in postpartum women. We hypothesized that physical stress on the pelvis during pregnancy may lead to signs of bone marrow edema on MRI. <h3>Objectives</h3> To explore (A) the association between pregnancy and giving birth on the one hand, and the occurrence of MRI lesions compatible with SpA on the other hand; and (B) if these lesions are transient. <h3>Methods</h3> Twenty-five women underwent an MRI of the sacroiliac joints (SIJ) in the first 10 days after vaginal delivery. The scan was repeated after 6 months. Both time points were scored in pairs by 3 trained readers, blinded for time sequence and subject characteristics. MRI assessment was done on 6 consecutive slices for inflammatory and structural SpA-like lesions; bone marrow edema (BME), capsulitis, enthesitis, high signal intensity in joint space, erosions, fatty lesions, sclerosis and (partial) ankylosis. In addition, the Assessment of SpondyloArthritis international Society (ASAS) definition of a positive MRI-SIJ was applied. MRI reader scores were reported as 2 out of 3 (median) scores. <h3>Results</h3> Twenty out of 25 (80.0%) subjects displayed BME; the median SPARCC score was 5 (IQR 1-11) (see table). One subject was lost to follow-up. After 6 months, 11 out of 24 (45.8%) subjects still showed BME; however, median SPARCC score dropped to 0 (IQR 0-1) (p = 0.002). At baseline, 16 out of 25 (64.0%) participants had a positive MRI-SIJ according to the ASAS definition, reducing to 4 out of 24 (16.7%) after 6 months (p = 0.002). 75.5% of the baseline lesions were located in the anterior part of the SIJ; 57.3% situated on the iliac side. Structural lesions were rarely detected in this study population (see table). <h3>Conclusion</h3> A very high prevalence of sacroiliac BME on MRI was seen in women immediately postpartum with 64.0% even having a positive MRI for sacroiliitis according to the ASAS definition. A significant decrease in BME was seen over 6 months time, yet a substantial fraction continued to display BME after follow up. History of a recent pregnancy is crucial to take into account when interpreting an MRI-SIJ. In case of a recent pregnancy and clinical suspicion of SpA, it may be wise to postpone MRI-SIJ imaging until at least 6 months after the delivery. <h3>Disclosure of Interests</h3> Thomas Renson: None declared, Ann-Sophie De Craemer: None declared, Anaïs Depicker: None declared, Liselotte Deroo: None declared, Manouk de Hooge: None declared, Nele Herregods: None declared, Lennart Jans: None declared, Gaëlle Varkas: None declared, Kristien Roelens: None declared, Isabelle Dehaene: None declared, Philippe Carron: 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., Dirk Elewaut: None declared