Evaluation of the performances of 'typical' imaging abnormalities of axial spondyloarthritis: results of the cross-sectional ILOS-DESIR study

Spine abnormalities associated with bone edema on sacroiliac joints MRI in patients with non-inflammatory chronic back pain

OBJECTIVE

To investigate whether bone marrow edema (BME) fulfilling the ASAS definition of magnetic resonance imaging (MRI) sacroiliitis is associated with non-inflammatory spine abnormalities in patients with definite mechanical chronic back pain (CBP).

METHODS

Patients with definite mechanical CBP, according to the physician, started before the age of 45 and be lasting for more than 3months but less than 3years underwent a protocolized MRI and radiographs of sacroiliac joint (SIJ) and spine. BME and structural changes were scored, by three readers, for SIJ as well as non-inflammatory abnormalities for spine, including degenerative lesions and static disorders. Univariate analysis by Chi² test was performed to search a statistical association between BME fulfilling the ASAS definition of MRI sacroiliitis and the presence of at least one non-inflammatory spine abnormality.

RESULTS

A total of 94 patients were analyzed, 27 (29%) patients had BME and 16 (17%) patients had BME fulfilling the ASAS definition of MRI sacroiliitis; 86 (91.5%) patients had at least one non-inflammatory spine abnormality which are associated into 3 distinct clusters. BME was slightly more frequent at the lower and posterior part of the SIJ. MRI sacroiliitis was associated with interspinous bursitis, facet joint effusion and lateral spinal deviation and was more likely in patients with at least one non-inflammatory spine abnormality (OR: 4.96, 95% CI [1.47; 16.72]).

CONCLUSIONS

BME fulfilling the ASAS definition of MRI sacroiliitis is significantly associated with non-inflammatory spine abnormalities in patients with mechanical CBP.

Impact of filgotinib on sacroiliac joint magnetic resonance imaging structural lesions at 12 weeks in patients with active ankylosing spondylitis (TORTUGA trial)

OBJECTIVE

To assess the effect of filgotinib, which preferentially inhibits Janus kinase 1 (JAK1), on MRI measures of structural change in the SI joint in patients with active AS in the TORTUGA trial.

METHODS

Adults with active AS and inadequate response/intolerance to two or more NSAIDs were randomized 1:1 to filgotinib 200 mg (n = 58) or placebo (n = 58) once daily for 12 weeks. In this post hoc analysis, T1-weighted MRI scans of the SI joint were evaluated by two independent readers using Spondyloarthritis Research Consortium of Canada (SPARCC) Sacroiliac Joint Structural Score (SSS) definitions for erosion, backfill, fat metaplasia and ankylosis. Correlations between SPARCC SSS and improvement in clinical outcomes were also assessed.

RESULTS

MRI scans from 87 patients (48 filgotinib, 39 placebo) were evaluated. At baseline there were no notable differences between filgotinib and placebo for any MRI structural lesion types. From baseline to week 12, filgotinib was associated with a significant reduction in SI joint erosion score (P = 0.02) and an increase in backfill score (P = 0.005) vs placebo, with no significant between-group differences for ankylosis (P = 0.46) or fat metaplasia (P = 0.17). At week 12, the change in SPARCC MRI SI joint inflammation scores correlated positively with erosion scores but negatively with backfill scores.

CONCLUSION

The significant changes in MRI structural lesions induced by filgotinib in the SI joint by week 12 demonstrate that tissue repair can be observed very soon after starting treatment with a JAK1 preferential inhibitor. This could have prognostic implications for development of ankylosis.

TRIAL REGISTRATION

ClinicalTrials.gov, http://clinicaltrials.gov, NCT03117270.

Differences in topographical location of sacroiliac joint MRI lesions in patients with early axial spondyloarthritis and mechanical back pain

Background

Early diagnostics of axial spondyloarthritis (axSpA) remains a challenge. Traditional imaging one-plane sacroiliac joint (SIJ) MRI assessment is used. By introducing a two-plane assessment system, the objective was to analyse the differences in SIJ MRI changes in early axSpA compared with changes in patients with mechanical back pain (MBP) by exploring the differences in volume and location.

Methods

MRIs in the early diagnostic state of 25 axSpA patients (mean age 31.3 years) and 59 MBP patients (mean age 32.3 years) were included. The MRIs were assessed by two readers regarding the distribution of bone marrow edema (BME) in 14 joint portions and structural changes in six joint portions in addition to SIJ anatomical variations and lumbar spine disc degeneration.

Results

AxSpA patients had a significantly higher overall BME sumscore (volume) of 25.1 compared to MBP patients 6.8, p < 0.005. The MBP group had the highest prevalence (66%) and sumscore (5.7) in the middle anterior sacrum. The axSpA group had significantly higher prevalence and sumscores in all joint portions except the three cartilaginous anterior sacral joint portions, including the ligamentous compartments (prevalence 40–60% compared to 8–15%, p both < 0.005). The axSpA group had also a significantly higher prevalence of erosions and fatty marrow disposition, but there were no differences in the prevalence of anatomical variations except the bipartite iliac bony plate.

Conclusions

AxSpA patients demonstrated a widespread distribution of both inflammatory and structural changes, including high BME occurrence in the ligamentous joint portions whereas patients with MBP had the highest occurrence of BME in the middle anterior sacrum. These findings may help differentiate axSpA patients from other back pain conditions in the early diagnostic phase.

Australian Consensus Statements for the Assessment and Management of Non-radiographic Axial Spondyloarthritis

Background

The understanding of non-radiographic axial spondyloarthritis (nr-axSpA) has accelerated over the last decade, producing a number of practice-changing developments. Diagnosis is challenging. No diagnostic criteria exist, no single finding is diagnostic, and other causes of back pain may act as confounders.

Aim

To update and expand the 2014 consensus statement on the investigation and management of non‐radiographic axial spondyloarthritis (nr-axSpA).

Methods

We created search questions based on our previous statements and four new topics then searched the MEDLINE and Cochrane databases. We assessed relevant publications by full-text review and rated their level of evidence using the GRADE system. We compiled a GRADE evidence summary then produced and voted on consensus statements.

Results

We identified 5145 relevant publications, full-text reviewed 504, and included 176 in the evidence summary. We developed and voted on 22 consensus statements. All had high agreement. Diagnosis of nr-axSpA should be made by experienced clinicians, considering clinical features of spondyloarthritis, blood tests, and imaging. History and examination should also assess alternative causes of back pain and related conditions including non-specific back pain and fibromyalgia. Initial investigations should include CRP, HLA-B27, and AP pelvic radiography. Further imaging by T1 and STIR MRI of the sacroiliac joints is useful if radiography does not show definite changes. MRI provides moderate-to-high sensitivity and high specificity for nr-axSpA. Acute signs of sacroiliitis on MRI are not specific and have been observed in the absence of spondyloarthritis. Initial management should involve NSAIDs and a regular exercise program, while TNF and IL-17 inhibitors can be used for high disease activity unresponsive to these interventions. Goals of treatment include improving the frequent impairment of social and occupational function that occurs in nr-axSpA.

Conclusions

We provide 22 evidence-based consensus statements to provide practical guidance in the assessment and management of nr-axSpA.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40744-021-00416-7.

Classification Criteria in Axial Spondyloarthritis: What Have We Learned; Where Are We Going?

Spondyloarthritis (SpA) is a chronic inflammatory condition that can have a predominately peripheral or axial presentation. Axial SpA (axSpA) affects the axial skeleton with either radiographic (r-axSpA) or nonradiographic (nr-axSpA) changes. Radiographic changes are a late disease feature and earlier disease stages can be identified by incorporating other imaging methods. The diagnosis of axSpA is a clinical diagnosis and classification criteria are not aimed to be diagnostic tools. The split between r-axSpA and nr-axSpA is artificial and we should move toward the unifying concept of axSpA. Our understanding of genetics, biomarkers, and immunopathophenotypes will drive further refinement of classification criteria.

A predictive clinical-radiomics nomogram for diagnosing of axial spondyloarthritis using MRI and clinical risk factors

OBJECTIVES

Construct and validate a nomogram model integrating the radiomics features and the clinical risk factors to differentiating axial spondyloarthritis (axSpA) in low back pain patients undergone sacroiliac joint (SIJ)- magnetic resonance imaging (MRI).

METHODS

638 patients confirmed as axSpA (n= 424) or non-axSpA (n = 214) who were randomly divided into training (n = 447) and validation cohorts (n = 191). Optimal radiomics signatures were constructed from the 3.0T SIJ-MRI using maximum relevance-minimum redundancy (mRMR) and the least absolute shrinkage and selection operator (LASSO) algorithm in the training cohort. We also included six clinical risk predictors to build clinical model. Incorporating the independent clinical factors and Rad-score, a nomogram model was constructed by multivariable logistic regression analysis. The performance of the clinical, Rad-score, and nomogram model were evaluated by ROC analysis, calibration curve and decision curve analysis (DCA).

RESULTS

1316 features were extracted and reduced to 15 features to build the Rad-score. The Rad-score allowed a good discrimination in the training (AUC, 0.82; 95% CI, 0.77-0.86) and the validation cohort (AUC, 0.82; 95% CI, 0.76-0.88). The clinical-radiomics nomogram model also showed favorable discrimination in the training (AUC, 0.90; 95% CI, 0.86-0.93) and the validation cohort (AUC, 0.90; 95% CI, 0.85-0.94). Calibration curves (p > 0.05) and DCA demonstrated the nomogram was useful for axSpA diagnosis in the clinical environment.

CONCLUSION

The study proposed a radiomics model was able to separate axSpA and non-axSpA. The clinical-radiomics nomogram can increase the efficacy for differentiating axSpA, which might facilitate clinical decision-making process.

Imaging in Axial Spondyloarthritis: What is Relevant for Diagnosis in Daily Practice?

PURPOSE OF REVIEW

To explore how imaging may assist diagnosing axial spondyloarthritis in rheumatology practice.

RECENT FINDINGS

A diagnosis of axial spondyloarthritis is based on pattern recognition by synthesizing clinical, laboratory, and imaging findings. In health care settings providing low threshold access to advanced imaging, sacroiliac joint MRI is the preferred imaging modality in clinically suspected axial spondyloarthritis. In daily routine, the optimum protocol to assess suspected inflammatory back pain combines sacroiliac joint and spine MRI fitting a 30-min slot. Contextual assessment of concomitant structural and active MRI lesions is key to enhance diagnostic utility. In women with postpartum back pain suggestive of axial spondyloarthritis, recent reports advocate waiting 6-12 months after delivery before acquiring sacroiliac joint MRI. Major unmet needs are consistent MRI protocols, standardized training modules on how to evaluate axial MRI, and timely dissemination of imaging advances into mainstream practice both in rheumatology and in radiology. In rheumatology practice, MRI has become indispensable to help diagnose early axial spondyloarthritis. However, major gaps in training and knowledge transfer to daily care need to be closed.

MRI of the sacroiliac joints: what is and what is not sacroiliitis?

PURPOSE OF REVIEW

MRI has, as the only imaging modality, the ability to visualize both the inflammatory and destructive aspects of sacroiliitis and is a crucial element in the diagnosis and classification of axial spondyloarthritis (axSpA). However, the MRI appearance of several potential differential diagnoses may resemble axSpA sacroiliitis.

RECENT FINDINGS

The appearances of sacroiliac joint (SIJ) MRIs of various diseased and healthy populations have recently been intensively studied. BME, the key requirement in the Assessment of Spondyloarthritis international Society (ASAS) definition of a 'MRI positive of sacroiliitis' may also be found in degenerative disease, athletes and healthy persons, and, particularly, postpartum women. Certain pattern of BME (high extent, large depth from articular surface, close relation to other lesion types) as well as the presence of structural lesions, particularly bone erosion, backfill or ankylosis increase the likelihood/specificity of being axSpA. Furthermore, old and novel MRI approaches to best distinguish the sacroiliitis of early axSpA from differential diagnoses have recently been tested and compared.

SUMMARY

Significant new and clinically relevant knowledge has been gained, but further research is still needed to optimally distinguish what is and what isn't sacroiliitis.

Predictive values of inflammatory back pain, positive HLA B27 antigen and acute and chronic magnetic resonance changes in early diagnosis of Spondyloarthritis. A study of 133 patients

OBJECTIVES

To analyse the predictive values of inflammatory back pain (IBP), positive HLA B27 antigen, increased C-reactive protein (CRP), Spondyloarthritis (SpA) features, familial history (FH), magnetic resonance sacroiliac joints (MRI-SIJ) imaging and its weight in early SpA diagnosis.

METHODS

133 patients with back pain, aged <50, duration of the pain <2 years were included. Data such as IBP, HLA B27, increased CRP, SpA features, FH, SIJ´s radiography and MRI were collected for each patient. STIR sequences were classified as strongly positive bone morrow oedema (SPBME ≥2), clearly present and easily recognisable as positive according to the ASAS criterion, weakly positive (WPBME ≥2), suggestive, but not easily recognisable and, clearly negative none of those features. T1-weighted sequences were assessed as positive/negative for erosion, fat metaplasia, backfill and sclerosis, if ≥1, for each lesion was present. MRI images were read by three blinded readers.

RESULTS

The average age was 38.9 years. 47 (35.3%) patients received SpA diagnosis according to the clinical opinion. IBP was highly specific, 0.81 and sensitive, 0.83. HLA B27 was positive in a half of the SpA patients. SPBME ≥2 provided a great specificity, 0.94 and an acceptable sensitivity, 0.79. Erosion was significantly more frequent in SpA patients (72% vs 7%), specificity 0.93. The addition of erosion ≥1 to the WPBME ≥2 noticeably improved specificity, 0.98, although slightly decreased sensitivity, 0.64. Fat metaplasia and backfill were highly specific, but poorly sensitive. Factors forecasting positive diagnosis were IBP, followed by SpA features and increased CRP.

CONCLUSIONS

At the onset, IBP might be a good marker for selecting patients with suspicion of SpA. The addition of erosion to the ASAS criterion might be helpful for early diagnosis, especially in patients with doubtful STIR imaging where BME is present but it is hard to determinate whether the ASAS "highly suggestive" criterion is met.

Diagnostic utility of whole spine and thoracic spine MRI corner inflammatory lesions in axial spondyloarthritis

Background:

The presence of ⩾3 corner inflammatory lesions has been proposed as the definition of a positive spinal magnetic resonance imaging (MRI) for axial spondyloarthritis (axSpA), but subsequent studies showed inconclusive findings. Our objective was to evaluate whether locations of corner inflammatory lesions (CILs) would affect the diagnostic utility of MRI in axSpA.

Method:

Two groups were consecutively recruited from eight rheumatology centers in Hong Kong. The ‘axSpA’ group included 369 participants with a known diagnosis of axSpA. The ‘non-specific back pain’ (NSBP) control group consisted of 117 participants. Clinical, biochemical, and radiological parameters were collected and all patients underwent MRI of the spine and sacroiliac joints. CILs were assessed based on their locations (cervical, thoracic or lumbar) to determine the optimal cutoff for diagnosis.

Results:

The cutoff of ⩾5 whole spine CILs (W-CILs) and ⩾3 thoracic spine CILs (T-CILs) had comparable specificity to MRI sacroiliitis. Of 85/369 axSpA patients without sacroiliitis on conventional radiograph or MRI, 7 had ⩾5 W-CILs and 11 had ⩾3 T-CILs. Incorporating the proposed cutoffs into Assessment of SpondyloArthritis international Society axSpA criteria, ⩾5 W-CILs and ⩾3 T-CILs had similar performance when added to the imaging criteria for sacroiliitis (sensitivity 0.79 versus 0.80, specificity 0.92 versus 0.91).

Conclusion:

Spinal MRI provided little incremental diagnostic value in unselected axSpA patients. However, in patients without sacroiliitis on MRI or radiographs, 8–13% might be diagnosed by spinal MRI. Thoracic and whole spine MRI had similar diagnostic performance using the proposed cutoff of ⩾5 W-CILs and ⩾3 T-CILs.

Diagnostic performance of sacroiliac and spinal MRI for the diagnosis of non-radiographic axial spondyloarthritis in patients with inflammatory back pain

OBJECTIVE

The lack of specificity of the ASAS MRI criteria for non-radiographic axial spondylarthritis (NR-axSpA) justifies the evaluation of the discriminatory capacity of other MRI abnormalities in the sacroiliac joints and dorsolumbar spine.

METHODS

In patients hospitalized for inflammatory lumbar back pain, the diagnostic performance (sensitivity, specificity, positive likelihood ratio (PLR)) of MRI abnormalities was calculated using the rheumatologist expert opinion as a reference: (i) sacroiliac joints: Bone marrow edema (BME) (number and location), extended edema>1cm (deep lesion), fatty metaplasia (number), erosion (number and location), backfill. (ii) Dorsolumbar spine: BME (number and location), fatty metaplasia (number), posterior segment involvement.

RESULTS

In this prospective cohort, 40 NR-axSpA cases and 79 other diagnoses were included. The presence of at least 3 inflammatory signals in the sacroiliac joints (PLR: 25.67 [95% CI: 3.48-48.9]), the presence of at least one sacroiliac erosion (PLR: 12.80 [3.04-54]), the combination of an inflammatory signal and sacroiliac erosion (PLR: 11.85 [2.79-50]), the combination of deep lesion and fatty metaplasia (PLR: 15.80 [2.05-121.9]) or erosion (PLR: 11.86 [1.47-95.01]) had the best diagnostic performance. The combination of spinal and sacroiliac MRI criteria significantly increased diagnostic performance for the diagnosis of NR-axSpA.

CONCLUSION

When NR-axSpA is suspected, in addition to the presence and number of inflammatory lesions, MRI interpretation should include the location and the extent of the sacroiliac lesions, the presence of erosion or fatty metaplasia, and anterior involvement of the lumbar spine.

Axial involvement in patients with early peripheral spondyloarthritis: a prospective MRI study of sacroiliac joints and spine

OBJECTIVES

To assess axial involvement on MRI in early peripheral spondyloarthritis (pSpA) and to evaluate whether axial inflammation predicts relapse on treatment withdrawal.

METHODS

Fifty-six patients with early, active, newly diagnosed pSpA underwent MRI of the sacroiliac joints (SIJs) and spine prior to golimumab initiation. At sustained clinical remission of pSpA, treatment was withdrawn and a second MRI was performed. Bone marrow oedema (BME) was scored by three readers according to the Spondyloarthritis Research Consortium of Canada (SPARCC) method. Scores were compared with an axial spondyloarthritis cohort (Belgian Arthritis and Spondylitis cohort). Structural lesions were assessed using a similar method. Furthermore, fulfilment of the Assessment of Spondyloarthritis International Society (ASAS) definition of a positive MRI for sacroiliitis was assessed. Spinal images were evaluated for BME and structural lesions using the Canada-Denmark MRI spine scoring system by two readers.

RESULTS

Thirty-six per cent showed SIJ BME at baseline, all fulfilling the ASAS definition of sacroiliitis. No association with back pain was found. Twenty-one per cent displayed SIJ structural lesions. Spinal BME was limited: the median inflammation scores were low and no patients had ≥5 inflammatory corner lesions. On clinical remission, a significant decrease in SIJ SPARCC scores was detected. On clinical remission, no significant differences in SIJ SPARCC scores were noted between patients relapsing and those maintaining remission after treatment discontinuation.

CONCLUSION

In patients with early pSpA, a surprisingly high prevalence of sacroiliitis on MRI was observed; SPARCC scores decreased significantly on tumour necrosis factor inhibition. Residual inflammation on MRI was not predictive of relapse of peripheral manifestations. No relevant inflammatory spinal involvement was detected. Collectively, our findings suggest a higher inflammatory burden in patients with early pSpA than anticipated.

Bone turnover biomarkers, disease activity, and MRI changes of sacroiliac joints in patients with spondyloarthritis

The lack of valid biomarkers in patients with spondyloarthritis (SpA) requires searching for additional options to increase sacroiliac joint (SIJ) evaluation effectiveness. We assessed the serum levels of bone turnover markers and their relationships with active and chronic changes in SIJs using magnetic resonance imaging (MRI), indices, and laboratory parameters of disease activity in SpA patients. 102 patients with SpA and 15 healthy subjects were included. Testing of serum levels of transforming growth factor-beta (TGF-β1), Wnt3, sclerostin, and Dickkopf-1 (Dkk-1) was conducted. Active inflammatory lesions in SIJs were evaluated using Spondyloarthritis Research Consortium of Canada (SPARCC) MRI SIJ score, and chronic changes using the Danish scoring method. Bath Ankylosing Spondylitis Disease Activity Index, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Ankylosing Spondylitis Disease Activity Scores with CRP, and ESR were used to assess disease activity. Serum levels of Dkk-1, TGF-β1, and sclerostin were significantly lower in SpA patients compared to healthy controls. The serum levels of Dkk-1 positively correlated with CRP. Dkk-1 had a significant negative correlation with Danish score. The sclerostin serum level had a weak negative correlation with the active inflammatory MRI SIJ lesions. There were positive correlations between TGF-β1 and sclerostin with Dkk-1, and negative correlation between Wnt3 and sclerostin. Dkk-1 positively correlated with CRP and negatively with chronic SIJ changes by Danish score. Sclerostin negatively correlated with the active SIJ lesions by SPARCC. This suggests that Dkk-1 and sclerostin are the most promising candidates to reveal inflammation and bone turnover in patients with SpA.

Assessing the effect of interventions for axial spondyloarthritis according to the endorsed ASAS/OMERACT core outcome set: a meta-research study of trials included in Cochrane reviews

The Assessment of SpondyloArthritis international Society (ASAS) has defined core sets for (i) symptom-modifying anti-rheumatic drugs (SM-ARD), (ii) clinical record keeping, and (iii) disease-controlling anti-rheumatic therapy (DC-ART). These include the following domains for all three core sets: “physical function,” “pain,” “spinal mobility,” “spinal stiffness,” and “patient’s global assessment” (PGA). The core set for clinical record keeping further includes the domains “peripheral joints/entheses” and “acute phase reactants,” and the core set for DC-ART further includes the domains “fatigue” and “spine radiographs/hip radiographs.” The Outcome Measures in Rheumatology (OMERACT) endorsed the core sets in 1998.

Using empirical evidence from axSpA trials, we investigated the efficacy (i.e., net benefit) according to the ASAS/OMERACT core outcome set for axSpA across all interventions tested in trials included in subsequent Cochrane reviews. For all continuous scales, we combined data using the standardized mean difference (SMD) to meta-analyze outcomes involving the same domains. Also, through meta-regression analysis, we examined the effect of the separate SMD measures (independent variables) on the primary endpoint (log [OR], dependent variable) across all trials.

Based on 11 eligible Cochrane reviews, from these, 85 articles were screened; we included 43 trials with 63 randomized comparisons. Mean (SD) number of ASAS/OMERACT core outcome domains measured for SM-ARD/physical therapy trials was 4.2 (1.7). Six trials assessed all proposed domains. Mean (SD) for number of core outcome domains for DC-ART trials was 5.8 (1.7). No trials assessed all nine domains. Eight trials (16%) were judged to have inadequate (i.e., high risk of) selective outcome reporting bias. The most responsible core domains for achieving success in meeting the primary objective per trial were pain, OR (95% CI) 5.19 (2.28, 11.77), and PGA, OR (95% CI) 1.87 (1.14, 3.07). In conclusion, selective outcome reporting (and “missing data”) should be reduced by encouraging the use of the endorsed ASAS/OMERACT outcome domains in clinical trials. Overall outcome reporting was good for SM-ARD/physical therapy trials and poor for DC-ART trials. Our findings suggest that both PGA and pain provide a valuable holistic construct for the assessment of improvement beyond more objective measures of spinal inflammation.

High prevalence of spondyloarthritis-like MRI lesions in postpartum women: a prospective analysis in relation to maternal, child and birth characteristics

OBJECTIVES

Bone 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.

METHODS

Thirty-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.

RESULTS

Seventy-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.

CONCLUSION

A 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.