ObjectivesBone marrow oedema (BMO) on MRI of sacroiliac joints (SIJs) represents a hallmark of axial spondyloarthritis (SpA), yet such lesions may also occur under augmented mechanical stress in healthy subjects. We therefore sought to delineate the relationship between pregnancy/delivery and pelvic stress through a prospective study with repeated MRI. Results were matched with maternal, child and birth characteristics.MethodsThirty-five women underwent a baseline MRI-SIJ within the first 10 days after giving birth. MRI was repeated after 6 months and, if positive for sacroiliitis according to the Assessment of SpondyloArthritis International Society (ASAS) definition, after 12 months. BMO and structural lesions were scored by three trained readers using the Spondyloarthritis Research Consortium of Canada (SPARCC) method.ResultsSeventy-seven per cent of the subjects (27/35) displayed sacroiliac BMO immediately postpartum, 60% fulfilled the ASAS definition of a positive MRI. After 6 months, 46% of the subjects (15/33) still showed BMO, representing 15% (5/33) with a positive MRI. After 12 months, MRI was still positive in 12% of the subjects (4/33). Few structural lesions were detected. Intriguingly, in this study, the presence of BMO was related to a shorter duration of labour and lack of epidural anaesthesia.ConclusionA surprisingly high prevalence of sacroiliac BMO occurs in women immediately postpartum. Our data reveal a need for a waiting period of at least 6 months to perform an MRI-SIJ in postpartum women with back pain. This study also underscores the importance of interpreting MRI-SIJ findings in the appropriate clinical context.
BackgroundMagnetic 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.ObjectivesTo 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.MethodsTwenty-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.ResultsTwenty 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).Table: Number of MRI-SIJ lesions in 25 postpartum women.Baseline6 monthsInflammatory lesionsMedianIQR95% CIMedianIQR95% CISPARCC (/72)51 – 111 – 800 – 10 – 1Capsulitis (/12)00 – 00 – 000 – 00 – 0Enthesitis (/12)00 – 00 – 000 – 00 – 0High signal intensity (/12)00 – 40 – 300 – 00 – 0Structural lesionsMedianIQR95% CIMedianIQR95% CIErosions (/48)00 – 00 – 000 – 00 – 0Fatty lesions (/48)00 – 10 – 000 – 00 – 0Sclerosis (/48)00 – 00 – 000 – 00 – 0Partial ankylosis (/48)00 – 00 – 000 – 00 – 0Ankylosis (/48)00 – 00 – 000 – 00 – 0Figure: Baseline MRI T2 short tau inversion recovery (STIR) images of sacroiliac bone marrow edema in a 33-year old postpartum woman.ConclusionA 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 de...
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