Magnetic Resonance Imaging of Lesions in the Sacroiliac Joints for Differentiation of Patients With Axial Spondyloarthritis From Control Subjects With or Without Pelvic or Buttock Pain: A Prospective, Cross‐Sectional Study of 204 Participants

Spine and Sacroiliac Joint Involvement in Newly Diagnosed Patients With Inflammatory Bowel Disease: Clinical and MRI Findings From a Population-Based Cohort

INTRODUCTION

In patients with inflammatory bowel disease (IBD), co-occurring spondyloarthritis (SpA) leads to poorer outcomes and impaired quality of life, highlighting the importance of early detection and effective treatment. This is the first study to assess the prevalence and distribution of axial symptoms and magnetic resonance imaging (MRI)-detected involvement of the spine and sacroiliac joints (SIJs) in early IBD.

METHODS

Newly diagnosed patients with IBD from a prospective, population-based cohort were consecutively recruited. Rheumatological interview, clinical, ultrasound, and MRI assessment for SIJ and spine inflammatory and structural lesions were made using validated scoring methods and consensus definitions of axial SpA (axSpA).

RESULTS

Of 110 patients (ulcerative colitis: 70, Crohn's disease: 40, mean age of 42 years, and 40% male), 48 (44.9%) reported back and/or buttock pain, and 10 (9.1%) had inflammatory back pain. Seventeen (16.7%) patients had MRI findings indicative of axSpA; only 10 of these patients had axial symptoms. Inflammatory MRI lesions were present in SIJs and the spine of 27 (26.5%) and 30 (30.3%) patients, respectively. The Assessment of SpondyloArthritis International Society classification criteria for axSpA were met in 11 (10%) cases. MRI findings typical of axSpA were associated with peripheral joint and entheseal inflammation detected by ultrasound ( P = 0.04). No differences in clinical or imaging findings were found between patients with ulcerative colitis and Crohn's disease.

DISCUSSION

One-in-6 newly diagnosed patients with IBD had MRI findings indicative of axSpA. As 40% of these patients were asymptomatic, this suggests that axSpA is underdiagnosed in early IBD. Multidisciplinary collaboration is essential to ensure early detection of axial inflammation and to enable optimal therapy preventing future structural damage and disability.

The sacroiliac joint across ages - what is normal?

The anatomy of the sacroiliac joint (SIJ) is complex with wide variations inter-individually as well as intra-individually (right versus left) and a frequent occurrence of anatomical variants. Besides, the joints are subject to strain, which may elicit non-inflammatory subchondral changes such as bone marrow edema (BME), sclerosis, and fat deposition simulating inflammatory SIJ changes. Furthermore, normal physiological changes during skeletal maturation can make interpretation of SIJ magnetic resonance imaging in children challenging. Knowledge about the wide range of normal findings is therefore important to avoid misinterpretation of findings as pathological. This review describes the current knowledge about normal SIJ findings across all ages.

Automatic segmentation of fat metaplasia on sacroiliac joint MRI using deep learning

OBJECTIVE

To develop a deep learning (DL) model for segmenting fat metaplasia (FM) on sacroiliac joint (SIJ) MRI and further develop a DL model for classifying axial spondyloarthritis (axSpA) and non-axSpA.

MATERIALS AND METHODS

This study retrospectively collected 706 patients with FM who underwent SIJ MRI from center 1 (462 axSpA and 186 non-axSpA) and center 2 (37 axSpA and 21 non-axSpA). Patients from center 1 were divided into the training, validation, and internal test sets (n = 455, 64, and 129). Patients from center 2 were used as the external test set. We developed a UNet-based model to segment FM. Based on segmentation results, a classification model was built to distinguish axSpA and non-axSpA. Dice Similarity Coefficients (DSC) and area under the curve (AUC) were used for model evaluation. Radiologists' performance without and with model assistance was compared to assess the clinical utility of the models.

RESULTS

Our segmentation model achieved satisfactory DSC of 81.86% ± 1.55% and 85.44% ± 6.09% on the internal cross-validation and external test sets. The classification model yielded AUCs of 0.876 (95% CI: 0.811-0.942) and 0.799 (95% CI: 0.696-0.902) on the internal and external test sets, respectively. With model assistance, segmentation performance was improved for the radiological resident (DSC, 75.70% vs. 82.87%, p < 0.05) and expert radiologist (DSC, 85.03% vs. 85.74%, p > 0.05).

CONCLUSIONS

DL is a novel method for automatic and accurate segmentation of FM on SIJ MRI and can effectively increase radiologist's performance, which might assist in improving diagnosis and progression of axSpA.

CRITICAL RELEVANCE STATEMENT

DL models allowed automatic and accurate segmentation of FM on sacroiliac joint MRI, which might facilitate quantitative analysis of FM and have the potential to improve diagnosis and prognosis of axSpA.

KEY POINTS

• Deep learning was used for automatic segmentation of fat metaplasia on MRI. • UNet-based models achieved automatic and accurate segmentation of fat metaplasia. • Automatic segmentation facilitates quantitative analysis of fat metaplasia to improve diagnosis and prognosis of axial spondyloarthritis.

Identification of patient endotypes and adalimumab treatment responders in axial spondyloarthritis using blood-derived extracellular matrix biomarkers

OBJECTIVE

To explore the potential of a panel of ECM remodelling markers as endotyping tools for axial spondyloarthritis (axSpA) by separating patients into subtypes and investigate how they differ among each other in disease activity scores and response to treatment with adalimumab.

METHODS

In three axSpA studies, a panel of 14 blood-based ECM biomarkers related to formation of collagen (PRO-C2, PRO-C3, PRO-C6), degradation of collagen by metalloproteinases (C1M, C2M, T2CM, C3M, C4M, C6M, C10C), matrix metalloproteinase (MMP)-degraded prolargin (PROM), MMP-degraded and citrullinated vimentin (VICM), basement membrane turnover (PRO-C4) and neutrophil activity (CPa9-HNE) were assessed to enable patient clustering (endotyping). MASH (n=41) was a cross-sectional study, while Adalimumab in Axial Spondyloarthritis study (ASIM,n=45) and Danish Multicenter Study of Adalimumab in Spondyloarthritis (DANISH, n=49) were randomised, double-blind placebo-controlled trials of adalimumab versus placebo every other week for 6 or 12 weeks, respectively, followed by active treatment. Biomarker data were log-transformed, standardised by mean centering and scaled by the SD prior to principal component analysis and K-means clustering.

RESULTS

Based on all three studies, we identified two orthogonal dimensions reflecting: (1) inflammation and neutrophil activity (driven by C1M and CPa9-HNE) and (2) collagen turnover (driven by PRO-C2). Three endotypes were identified: high inflammation endotype (Endotype1), low inflammation endotype (Endotype 2) and high collagen turnover endotype (Endotype3). Endotype1 showed higher disease activity (Ankylosing Spondylitis Disease Activity Score (ASDAS)) at baseline compared with Endotype2 and Endotype3 and higher percentage of patients responding to adalimumab based on ASDAS clinical improvement at week 24. Endotype3 showed higher percentage of patients with 50% improvement in Bath Ankylosing Spondylitis Disease Activity Index response at week 24 compared with Endotype2.

CONCLUSION

These endotypes differ in their tissue remodelling profile and may in the future have utility for patient stratification and treatment tailoring.

Changes of inflammation in patients with psoriatic arthritis after high intensity interval training assessed by ultrasound and MRI, a randomized controlled trial

BACKGROUND

In psoriatic arthritis (PsA) there is a theoretical risk of increased disease activity related to strenuous physical activity, including exercise. We evaluated the effect of high intensity interval training (HIIT) on objective measures of inflammation in PsA assessed by ultrasound (US) of peripheral joints and entheses, and by bone marrow edema (BME) on MRI of the sacroiliac joints (SIJ) and spine.

METHODS

We randomly assigned 67 PsA patients to an intervention group that performed structured HIIT for 11 weeks, or to a control group instructed not to change their physical exercise habits. Outcome measures included US evaluation of the total cohort and MRI in a subgroup of 41; both assessed at 3 months. We calculated the proportions with an increased US B-mode and power-doppler (PD) signal of joints and entheses and Spondyloarthritis-Research-Consortium-of-Canada (SPARCC)-BME score of the SIJ and spine for both groups.

RESULTS

Proportions with an increased US B-mode score of the joints were 32% and 28% in HIIT and control groups, respectively. Corresponding proportions of PD scores of the joints were 7% and 10% and PD scores of entheses were 32% and 31%. The proportions with increased MRI BME of the SIJ were 6% in the HIIT group and 10% in the control group. Corresponding proportions were 6% and 5% for the MRI BME of the spine.

CONCLUSION

In PsA patients with a low to moderate disease activity, there was no clear evidence of objectively measured increased inflammation after HIIT, as evaluated by US and MRI.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02995460 (16/12/2016).

Diagnostics of Sacroiliac Joint Differentials to Axial Spondyloarthritis Changes by Magnetic Resonance Imaging

The diagnosis of axial spondyloarthritis (axSpA) is usually based on a pattern of imaging and clinical findings due to the lack of diagnostic criteria. The increasing use of magnetic resonance imaging (MRI) of the sacroiliac joints (SIJ) to establish the diagnosis early in the pre-radiographic phase has resulted in a shift in the paradigm with an increasing frequency of axSpA diagnoses and a changed sex distribution. Non-radiographic axSpA affects males and females nearly equally, whereas ankylosing spondylitis predominantly occurs in males. The MRI-based increasing frequency of axSpA in women is mainly due to the presence of subchondral bone marrow edema (BME) on fluid-sensitive MR sequences, which may be a non-specific finding in both women and men. Due to the somewhat different pelvic tilt and SIJ anatomy, women are more prone than men to develop strain-related MRI changes and may have pregnancy-related changes. Awareness of non-specific subchondral BME at the SIJ is important as it can imply a risk for an incorrect SpA diagnosis, especially as the clinical manifestations of axSpA may also be non-specific. Knowledge of relevant MRI and clinical features of differential diagnoses is needed in the diagnostic workout of patients with suspected axSpA considering that non-SpA-related SIJ conditions are more common in patients with low back or buttock pain than axSpA sacroiliitis. The purpose of this review was to present current knowledge of the most frequent differential diagnoses to axSpA sacroiliitis by MRI taking the clinical characteristics into account.

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.

[CME Rheumatology 26: Bone Marrow Edema of the Sacro-Iliac Joint = Spondyloarthritis? What the General Practicioner Should Know]

CME Rheumatology 26: Bone Marrow Edema of the Sacro-Iliac Joint = Spondyloarthritis? What the General Practicioner Should Know Abstract. Axial spondyloarthritis is a chronic inflammatory joint disease mainly involving the sacroiliac joints (ISG) and the spine. The diagnosis can be made early due to acute inflammatory changes in the ISG on magnetic resonance imaging (MRI). Radiographs of the ISG do not help in early diagnosis because structural damage is not apparent on radiographs until an advanced stage. In recent years, however, several studies have shown that bone marrow edema - hyperintense signals (= bright spots) as a possible MRI correlate for inflammation - does not specifically occur in axial spondyloarthritis, but can also be seen in healthy people, athletes, people with high mechanical stress (e.g. military recruits) and postpartum women. The diagnosis of axial spondyloarthritis should therefore never be based solely on an MRI finding, but must always include the overall clinical context.

Frequency and anatomic distribution of magnetic resonance imaging lesions in the sacroiliac joints of spondyloarthritis and non-spondyloarthritis patients

Background

Lesions detected by magnetic resonance imaging (MRI) of the sacroiliac joints are critical to the diagnosis of non-radiographic axial spondyloarthritis. However, inflammatory and structural lesions may be encountered in other conditions.

Objectives

The objective of this study was to evaluate and compare the frequency and localization of inflammatory and structural lesions on MRIs of the sacroiliac joint of spondyloarthritis (SpA) and non-spondyloarthritis (non-SpA) patients.

Design

This is a retrospective study including 200 patients, each having undergone an MRI of the sacroiliac joints.

Methods

Two experienced readers evaluated the whole set of images to detect erosions, subchondral sclerosis, fatty lesions, bone marrow edema (BME) and ankylosis according to the definitions established by the ASAS MRI working group. We divided sacroiliac joints into five segments: upper, antero-middle, intermediate-middle, postero-middle and lower.

Results

A total of 96 subjects with SpA (mean age 37.4 ± 11.8 years) and 104 without SpA (mean age 39.9 ± 11.6 years) were included. Of the 96 SpA patients, 65% had inflammatory buttock pain compared with 25% in the non-SpA group. BME was seen in 65% of SpA patients, mainly in the intermediate-middle segment, and in 20% of non-SpA patients, predominantly in the antero-middle segment. Subchondral sclerosis occurred in 44% of non-SpA patients, mostly in the antero-middle segment, and in 36% of SpA patients. Fatty lesions were present in 34% of SpA and in 21% of non-SpA patients. Erosions were seen in 25% of non-SpA and in 60% of SpA patients. BME and structural lesions were minimally observed in the postero-middle segment in non-SpA patients.

Conclusion

Inflammatory and structural lesions were observed in all segments of the joint in SpA, mainly in the middle segments, while lesions predominantly affected the antero-middle segment in non-SpA, and were uncommon in the postero-middle segment.

Extracellular matrix protein turnover markers are associated with axial spondyloarthritis-a comparison with postpartum women and other non-axial spondyloarthritis controls with or without back pain

Background

Axial spondyloarthritis (axSpA) is a common chronic inflammatory disease, associated with extracellular matrix (ECM) remodeling of the cartilage, bone, and connective tissues. The primary symptom of axSpA is back pain, caused by inflammation. However, there is a medical need to truly identify patients with axSpA from other subjects with buttock or low back pain attributable to other reasons. We aimed to investigate circulating biomarkers of ECM/inflammation (MMP-degraded type I (C1M), II (C2M, T2CM), III (C3M), IV (C4M), VI (C6M), and X (C10C, COL10NC) collagens, CRPM, PROM and VICM) and ECM formation of type II (PRO-C2), III (PRO-C3), IV (PRO-C4), and VI (PRO-C6) collagens as potential biomarkers to identify patients with axSpA.

Methods

We measured biomarkers from a cross-sectional study with 204 participants by enzyme-linked immunosorbent assay (ELISA). The study included axSpA patients (N = 41), women with postpartum buttock/pelvic pain (N = 46), disc herniation (N = 25), and a group of healthy subjects (including women without postpartum pelvic pain (N = 14), subjects with various types of physical strain (cleaning staff (N = 26) long-distance runners (N = 23)), and healthy men (N = 29)). Differences between the groups were calculated by ANCOVA and AUC, while Spearman’s correlations were performed with ECM biomarkers and clinical scores.

Results

Patients with axSpA expressed significantly higher levels of C1M, C4M, and VICM (p < 0.05-p < 0.0001) compared to all the non-axSpA control groups. Further, C6M and PRO-C4 were significantly higher in patients with axSpA (both p < 0.0001) compared to women with postpartum pelvic pain and healthy subjects, whereas PRO-C3 was significantly lower compared to healthy subjects (p = 0.01). The best ECM common biomarker to differentiate between axSpA and the non-axSpA control groups was PRO-C4 (AUC ≥ 0.75; specificity ≥ 0.79, sensitivity = 0.65). Mild correlations were observed between collagen turnover and inflammation biomarkers and CRP and MRI (ρ ≥ 0.3; p < 0.05-p < 0.001).

Conclusions

Biomarkers of type I, IV, and VI collagen and biomarkers of inflammation showed an altered turnover in patients with axSpA compared with the non-axSpA control groups. Such biomarkers may be useful in combination with MRI or independently to separate patients with axSpA from other back pain conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02839-1.

Pregnancy-related sacroiliac joint findings in females with low back pain: a four-year magnetic resonance imaging follow-up study

BACKGROUND

Pregnancy-related pain may be associated with sacroiliac joint (SIJ) changes, detectable by magnetic resonance imaging (MRI).

PURPOSE

To analyze the prevalence and course of SIJ MRI and clinical findings in women referred with low back pain and relate these to pregnancy.

MATERIAL AND METHODS

A retrospective follow-up study from a longitudinally collected cohort comprising 328 women.

RESULTS

Women reporting debut of pain in relation to a pregnancy (PP group) tended to have a higher baseline prevalence of all investigated MRI findings, cumulated positive SIJ tests, and a potential fulfilment of the spondyloarthritis diagnosis compared to remainders. The prevalence of subchondral bone marrow edema (BME), any SIJ MRI finding, and potential fulfilment of the spondyloarthritis diagnosis were significantly higher in the PP group compared to women who had not been pregnant. In the total study group, the prevalence of ≥1 MRI finding increased over the four-year study period from 34% to 47% (P<0.001), driven by increasing prevalence of BME (25% to 32%; P=0.008) and fatty marrow deposition (FMD) (20% to 25%; P=0.020). In addition, the BME volume score increased. Over time, the PP group had persisting high prevalence of buttock pain and total MRI findings and their FMD volume score increased, but there were no between-group differences in MRI variables at follow-up.

CONCLUSION

Overall, the prevalence of MRI findings increased over time. Although the PP group had different clinical and SIJ MRI characteristics cross-sectional at baseline compared to remainders, longitudinal analyses revealed that these diminished over time.

Improving the design of RCTs in non-radiographic axial spondyloarthritis

Concerns have been raised that randomized placebo-controlled trials (RCTs) in non-radiographic axial spondyloarthritis (nr-axSpA) might be failing to identify patients that best show differences in clinical response rates between those receiving active drug and those receiving placebo therapies; in addition, some studies might even be showing spurious differences in responses to TNF and IL-17 inhibitor therapies. In particular, the most recent phase III RCTs in nr-axSpA have reported variable and generally lower response rates than observed in phase III trials of patients with ankylosing spondylitis and in trials conducted a decade ago in patients with early axSpA who were selected on the basis of axial inflammation evident on MRI scans. We argue that these observations at least partly reflect an RCT design that does not take full advantage of MRI to select patients who are responsive to therapy because the current MRI-based inclusion criteria cannot identify patients with axSpA with sufficient specificity. We propose that future studies should be designed using revised patient inclusion criteria based on expanded MRI evaluation and the application of data-driven definitions of a positive MRI for inflammatory and structural lesions typical of axSpA reported in an international multicentre analysis of MRI scans from the Assessment of SpondyloArthritis International Society (ASAS) classification cohort.

Progressive increase in sacroiliac joint and spinal mri lesions in healthy individuals in relation to age

OBJECTIVES

MRI plays a pivotal role in spondyloarthritis (SpA) diagnosis. However, detailed description of MRI findings of the sacroiliac joints (SIJ) and spine in healthy individuals is currently lacking. We therefore sought to evaluate the occurrence of MRI-SIJ/spine lesions in healthy individuals in relation to age.

METHODS

Ninety-five healthy subjects (20-49 years) underwent MRI-SIJ and -spine. BME and structural lesions of the SIJ were scored using the SPARCC method. Spinal inflammatory and structural lesions were evaluated using the SPARCC MRI spine inflammation index and the CANDEN MRI scoring system, respectively. Fulfillment of the ASAS definition of a positive MRI for sacroiliitis/spondylitis was reviewed. Findings were compared with MRI of axial SpA patients from the Be-GIANT cohort.

RESULTS

17.2% of subjects aged ≥30 fulfilled the definition of a positive MRI for sacroiliitis, but this occurred rarely in younger subjects. SIJ erosions (20.0%) and fat metaplasia (13.7%) were detected across all age groups. Erosions were more frequently visualized in subjects aged ≥40 (39.3%). Spinal BME (35.7%) and fat metaplasia (28.6%) were common in subjects older than 40 years. Nonetheless, only one subject had ≥3 corner inflammatory lesions. SIJ and spinal SPARCC scores and total structural lesions scores increased progressively with age.

CONCLUSION

Contrary to what is commonly believed, structural MRI-SIJ lesions are frequently seen in healthy individuals. Especially in older subjects, the high occurrence of inflammatory and structural MRI lesions impacts their specificity for SpA, which has important implications for the interpretation of MRI in patients with clinical suspicion of SpA.

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.

Anatomical variation at the sacroiliac joints in young adults: estimated prevalence by CT and concomitant diagnostics by MRI

OBJECTIVE

To estimate the prevalence of atypical anatomical morphologies at the sacroiliac joints (SIJ) in young adults by CT and analyze the diagnostic ability of MRI to detect the variations in addition to concomitant MRI findings that could be misdiagnosed as inflammatory changes.

MATERIALS AND METHODS

The study sample constituted CT examinations of 155 individuals aged 18-40 years and prospectively collected comparative SIJ MRI examinations of 49, who also filled out a questionnaire on back and buttock pain. The CT and MRIs were analyzed by two musculoskeletal radiologists regarding seven SIJ variations and additional subchondral bone marrow edema (BME) by MRI.

RESULTS

CT and MRI interobserver agreements were good or very good for most variations. Mean age of the 155 individuals was 28 years, 99 (64%) were males; 88 (57%) had at least one SIJ variation, and most frequent were dysmorphic cartilaginous joint facets (n = 33, 21%), bipartite iliac bony plate (n = 27, 17%), accessory SIJ (n = 24, 16%), and iliosacral complex (n = 18, 12%), with a female predominance of all variations. The ability of MRI to detect the frequent variations was satisfying. Dysmorphic cartilaginous joint facets, accessory SIJ, and iliosacral complex were frequently observed in individuals reporting symptoms and were accompanied by BME, often located anteriorly in sacrum/inferiorly in ilium.

CONCLUSION

Atypical SIJ morphology is frequent in young adults, especially females, demanding further research into the anatomical natural variation. Most of the variations were detectable by MRI and three variations warrant further exploration as they often were accompanied by symptoms and/or BME.

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.

Main Diagnostic Pitfalls in Reading the Sacroiliac Joints on MRI

Magnetic resonance imaging of the sacroiliac joints is now frequently performed to help identify patients with early axial spondyloarthritis. However, differential diagnoses exist and should be recognized. The aim of this article is to review the most frequent differential diagnoses that may mimic inflammatory sacroiliitis in clinical practice.

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.

Pathogenesis of Axial Spondyloarthritis - Sources and Current State of Knowledge

Scientific breakthroughs have culminated in the development of the spondyloarthritis (SpA) concept as a family of rheumatic diseases, distinct from rheumatoid arthritis. The demonstration of inflammatory lesions in the sacroiliac joints and spine of patients with axial symptoms of SpA who lacked radiographic features of ankylosing spondylitis (AS) helped refine the SpA concept. Axial SpA includes patients with AS and patients with axial symptoms previously categorized as undifferentiated SpA. This review examines the sources of knowledge that inform axial SpA pathogenesis, highlighting current limitations, and a basic working model of axial SpA pathogenesis.

Frequency of pertinent MRI abnormalities of the sacroiliac joints of patients without spondyloarthropathies: a systematic review of the literature

INTRODUCTION

MRI criteria are central to the diagnosis of non-radiographic axial spondyloarthropathy (nr-axSpA). The cardinal feature of nr-axSpa is inflammatory low back pain, which may be difficult to distinguish from highly prevalent non-specific low back pain. This study aims to determine the frequency of relevant MRI findings in the sacroiliac joints (SIJ) of patients without Spondyloarthropathy (SpA), and therefore estimate the specificity of MRI scans for SpA.

METHODS

EMBASE and Medline were searched and limited to English. Titles were screened for relevance, with studies that included primary MRI findings in patients without SpA triggering retrieval. Retrieved papers were reviewed, data extracted by two authors and quality criteria (QUADAS 2) were applied. Findings were considered for asymptomatic and symptomatic individuals.

RESULTS

The search recovered 2172 articles. Abstracts of 117 were reviewed for full text retrieval, 11 papers met eligibility criteria. These papers described MRI findings of 1180 asymptomatic patients and 1318 with low back symptoms but without SpA. In relevant populations, bone marrow oedema was found in 22% (95% CI 19-25) of asymptomatic and 20% (95% CI 18-22) of asymptomatic individuals. In all non-Spa patients, sclerosis was found in 13.4% and erosions in 6.5%.

CONCLUSIONS

There is a significant frequency of diagnostically pertinent MRI abnormalities in the SIJ of patients without SpA. These are present in both asymptomatic and symptomatic individuals. Findings, such as oedema and sclerosis, lack specificity and should be interpreted with caution. Erosions are less frequent and are likely more specific for SpA.

Diagnosing axial spondyloarthritis by multidiciplinary team conference at 3.5 years' follow-up in a cohort of patients with disease features according to the ASAS criteria

OBJECTIVES

During the past two decades, magnetic resonance imaging (MRI) has increasingly been used diagnostically in axial spondyloarthritis (axSpA), and in 2009 MRI was introduced in the Assessment of SpondyloArthritis Society (ASAS) classification criteria. In clinical practice, there is a risk of overdiagnosis if MRI findings are not related to clinical and biochemical findings. The aim of this study was to provide an estimate of the prevalence of axSpA in a cohort of clinical patients with low back pain and findings suggestive of axSpA according to ASAS through consensus diagnosis at a multi-disciplinary team (MDT) conference, and to describe the performance of the features included in the ASAS criteria.

METHOD

Consensus diagnoses of axSpA at MDT conferences were retrospectively established at 3.5 years' follow-up in a cohort of 84 patients, initially referred with disease features according to the ASAS criteria. Patients were examined clinically regarding spondyloarthritis features, and biochemical tests and MRI of the sacroiliac joints and entire spine were performed at baseline and after a mean of 3.5 years.

RESULTS

According to the MDT consensus, 25 patients (30%) of the total cohort had axSpA at follow-up; 40% of individuals who fulfilled the ASAS criteria at baseline had axSpA, and 37% at follow-up; 96% of axSpA patients according to the MDT consensus met the ASAS criteria at baseline and 92% at follow-up.

CONCLUSION

Approximately one-third of the included patients had axSpA when evaluated at the MDT conference. The ASAS criteria had low predictive value, but high sensitivity at both baseline and follow-up.

MRI contributes to accurate and early diagnosis of non-radiographic HLA-B27 negative axial spondyloarthritis

Background

Nonradiographic axial spondyloarthropathies (nr-axSpA) are diagnosed by the absence of radiographic sacroiliitis and the presence of bone marrow edema (BME) on magnetic resonance imaging (MRI). According to the classification criteria of the international Assessment of Spondyloarthritis Society (ASAS), structural changes to sacroiliac joints (SIJs) on MRI cannot be used as criteria in the absence of BME. However, less than half the Asian patients with clinically active axSpA show BME. The incidence of human leukocyte antigen (HLA)-B27 is low in Asian populations, which makes it more difficult to identify nr-axSpA. We used MRI to evaluate the structural damage to SIJs in patients with nr-axSpA with and without BME with the aim of identifying the best methodology for accurate diagnosis, especially in populations with less common BME and HLA-B27.

Methods

One hundred three patients with inflammatory back pain were included in this prospective study. No patient’s radiograph met the definition of positive modified New York criteria. BME and structural damage to SIJ including sclerosis and erosion were assessed independently on coronal and axial short-tau inversion recovery and T1-weighted spin echo MRI scans by two well-trained musculoskeletal radiologists using the Spondyloarthritis Research Consortium of Canada (SPARCC) score. Demographics of patients were collected. Disease characteristics and structural damage were analyzed in patients with and without BME on SIJ MRI. Receiver operating characteristic (ROC) curve analysis was used to assess the diagnostic performance of structural damage.

Results

All individuals in the cohort had at least one abnormal finding on SIJ MRI, including BME or structural damage; 36 of 103 patients had BME. We identified a significant positive correlation between SPARCC scores and severe erosion assessed by focal joint space widening (fJSW) (p = 0.001) in these 36 patients. Fifty-eight of the 103 enrolled patients fulfilled the ASAS criteria for nr-axSpA in the either absence or presence of BME. Of these 58 patients, 57 and 19 had erosions or fJSW, respectively, and the presence of BME was significantly correlated with fJSW (phi score of 0.319 and p = 0.015). We demonstrated a significant positive correlation between fJSW and either the presence or the severity of BME in patients with nr-axSpA who met the ASAS definition. There was a positive correlation between BME and fJSW across the whole study cohort (phi score of 0.389; p < 0.001). The area under the ROC curve (AUC) for fJSW on SIJ MRI was 0.736, p < 0.001. In both HLA-B27-positive and -negative groups, BME was more common in the presence of fJSW (phi scores of 0.370 and 0.377, p = 0.018 and 0.003, respectively) and SPARCC scores were higher in patients with fJSW (p < 0.001 and p = 0.005). We also identified a positive correlation between fJSW and BME in patients with nr-axSpA and normal serum levels of C-reactive protein (phi score of 0.362 and p = 0.001).

Conclusion

Structural damage detected on SIJ MRI, sclerosis, erosions and fJSW may be present in patients without detectable inflammation on SIJ MRI. However, fJSW is significantly correlated with the severity of inflammation seen on SIJ MRI, which contributes to the accurate diagnosis of nr-axSpA, and it could be used as an alternative diagnostic test for nr-axSpA in the general population, especially for those who do not carry the HLA-B27 gene, Asian patients without BME, or patients with normal serum inflammatory biomarkers.

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.

Morphological characteristics of sacroiliac joint MRI lesions in axial spondyloarthritis and control subjects

OBJECTIVES

To investigate sacroiliac joint(SIJ) MRI inflammation, structural and degenerative lesion characteristics in patients with axial spondyloarthritis(axSpA) and various control groups.

METHODS

Patients with axSpA(n = 41) and lumbar disc herniation(n = 25), women with(n = 46) and without(n = 14) post-partum(childbirth within 4-16 months) buttock/pelvic pain, cleaning assistants(n = 26), long-distance runners(n = 23) and healthy men(n = 29) had MRI of the SIJs prospectively performed. MRI lesions were assessed on 9 slices covering the cartilaginous compartment by two experienced readers according to the definitions of the Spondyloarthritis Research Consortium of Canada(SPARCC) SIJ inflammation and structural scores, and were evaluated according to depth and extent. Other morphological characteristics were also analysed.

RESULTS

Total depth scores for bone marrow oedema(BME) and fat lesion(FAT) and total extent score for erosion were statistically significantly highest in axSpA, while scores for sclerosis were numerically highest in women with post-partum pain. Maximum BME depth > 10mm was frequently and exclusively found in axSpA and post-partum women(39% vs 14-17%) while FAT depth > 5mm was predominantly found in axSpA(76% vs 0-10%). Erosions were primarily seen in axSpA, especially when extensive(≥4 or confluent; 17% vs 0%). Capsulitis was absent in non-axSpA groups. BME and FAT in the ligamentous compartment were primarily found in axSpA(17/22% vs 0/2% in non-axSpA groups). In non-axSpA, osteophytes(axSpA vs non-axSpA: 0% vs 3-17%) and vacuum phenomenon(7% vs 30-66%) were more frequent, and the joint space was wider(mean(SD) 1.5(0.9)mm vs 2.2(0.5)mm).

CONCLUSIONS

FAT depth > 5mm, but not BME depth > 10mm, could almost differentiate axSpA patients from all other groups. When excluding post-partum women, BME >5mm and erosion were highly specific for axSpA.

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 Value of Active Sacroiliitis in MRI for Flare Among Chinese Patients with Axial Spondyloarthritis in Remission

INTRODUCTION

In recent axSpAx patients with remission lasting at least 3 months and later followed-up monthly for a median of 8 months, we compared the predictive value of baseline MRI of sacroiliac joints and constructed a nomogram model for predicting flare.

METHODS

This study included 251 patients with axial spondyloarthritis, according to the ASAS axSpA classification criteria, who achieved Low Disease Activity (ASDAS) and underwent MRI examination. A total of 144 patients from the First Affiliated Hospital of Xiamen University were used as the nomogram training set; 107 from the First Affiliated Hospital of Fujian Medical University were for external validation.

RESULTS

The median time of relapse was 8.705 months (95% CI 8.215-9.195) and 7.781 months (95% CI 7.075-8.486) for MRI-positive patients and 9.8 months (95% CI 9.273-10.474) for MRI negative patients, respectively. Both active sacroiliitis on MRI (HR 1.792, 95% CI 1.230-2.611) and anti-TNF-α treatments (HR 0.507, 95% CI 0.349-0.736) were significantly associated with disease flares. Gender, disease duration, HLA-B27, MRI, and anti-TNF-α treatment were selected as predictors of the nomogram. The areas under the ROC curve (AUROCs) of the 1-year remission probability in the training and validation groups were 0.71 and 0.729, respectively. Nomogram prediction models present better AUROCs, C-indices, and decision curve analysis cure than the clinical experience model.

CONCLUSIONS

Active sacroiliitis in MRI requires weighting in order to estimate remission and disease flares, when axSpA patients achieve low disease activity. The simple nomogram might be able to discriminate and calibrate in clinical practice.

TRIAL REGISTRATION

ClinicalTrials, NCT03425812, Registered 8 February 2018, https://clinicaltrials.gov.

Data-driven definitions for active and structural MRI lesions in the sacroiliac joint in spondyloarthritis and their predictive utility

Objectives

To determine quantitative SI joint MRI lesion cut-offs that optimally define a positive MRI for inflammatory and structural lesions typical of axial SpA (axSpA) and that predict clinical diagnosis.

Methods

The Assessment of SpondyloArthritis international Society (ASAS) MRI group assessed MRIs from the ASAS Classification Cohort in two reading exercises where (A) 169 cases and 7 central readers; (B) 107 cases and 8 central readers. We calculated sensitivity/specificity for the number of SI joint quadrants or slices with bone marrow oedema (BME), erosion, fat lesion, where a majority of central readers had high confidence there was a definite active or structural lesion. Cut-offs with ≥95% specificity were analysed for their predictive utility for follow-up rheumatologist diagnosis of axSpA by calculating positive/negative predictive values (PPVs/NPVs) and selecting cut-offs with PPV ≥ 95%.

Results

Active or structural lesions typical of axSpA on MRI had PPVs ≥ 95% for clinical diagnosis of axSpA. Cut-offs that best reflected a definite active lesion typical of axSpA were either ≥4 SI joint quadrants with BME at any location or at the same location in ≥3 consecutive slices. For definite structural lesion, the optimal cut-offs were any one of ≥3 SI joint quadrants with erosion or ≥5 with fat lesions, erosion at the same location for ≥2 consecutive slices, fat lesions at the same location for ≥3 consecutive slices, or presence of a deep (i.e. &gt;1 cm depth) fat lesion.

Conclusion

We propose cut-offs for definite active and structural lesions typical of axSpA that have high PPVs for a long-term clinical diagnosis of axSpA for application in disease classification and clinical research.

Influence of pregnancy/childbirth on long-term bone marrow edema and subchondral sclerosis of sacroiliac joints

OBJECTIVE

To investigate long-term effects of pregnancy/childbirth on bone marrow edema (BME) and subchondral sclerosis of sacroiliac joints (SIJ) in comparison to MRI changes caused by spondyloarthritis (SpA) and assess the influence of birth method and number of children on SIJ-MRI changes.

MATERIALS AND METHODS

This is a retrospective cohort study with 349 women (mean age 47 ± 14 years) suffering low back pain. Four subgroups were formed based on SpA diagnosis and childbirth (CB) history. Two musculoskeletal radiologists scored the presence of BME and sclerosis on SIJ-MRI using the Berlin method. Further, an 11-point "global assessment score" representing the overall confidence of SpA diagnosis based on MRI was evaluated in addition to the ASAS (Assessment of Spondyloarthritis International Society) criterion of "positive MRI" for sacroiliitis.

RESULTS

CB did not correlate with BME score (p = 0.38), whereas SpA diagnosis was associated with a higher BME score (r = 0.31, p < 0.001). Both CB (r = 0.21, p < 0.001) and SpA diagnosis (r = 0.33, p < 0.001) were correlated with a higher sclerosis score. CB was not associated with a higher confidence level in diagnosing SpA based on MRI (p = 0.07), whereas SpA diagnosis was associated with a higher score (r = 0.61, p < 0.001). Both CB (phi = 0.13, p = 0.02) and SpA diagnosis (phi = 0.23, p < 0.001) were significantly associated with a positive ASAS criterion for sacroiliitis. In non-SpA patients with CB, number of children (p = 0.001) was an independent predictor of sclerosis score, while birth method yielded no significant effect (p = 0.75).

CONCLUSION

Pregnancy/CB has no impact on long-term BME on SIJ, however, may cause long-term subchondral sclerosis-similar to SpA-associated sclerosis. Number of children is positively correlated with SIJ sclerosis. Birth method yields no effect on SIJ sclerosis.

Axial spondyloarthritis: concept, construct, classification and implications for therapy

The axial spondyloarthritis (axSpA) disease concept has undergone substantial change from when the entity ankylosing spondylitis was defined by the modified New York criteria in 1984. Developments in imaging, therapy and genetics have all contributed to changing the concept of axSpA from one of erosions in the sacroiliac joints to a spectrum of disease with and without changes evident on plain radiographs. Changes to the previously held concept and construct of the disease have also necessitated new classification criteria. The use of MRI, primarily of the sacroiliac joints, has substantially altered the diagnosis and differential diagnosis of axSpA. Many in the axSpA community believe that the current classification criteria lack specificity, and the CLASSIC study is underway to examine this area. Although much about the evolving axSpA disease concept is universally agreed, there remains disagreement about operationalizing aspects of it, such as the requirement for the objective demonstration of axial inflammation for the classification of axSpA. New imaging technologies, biomarkers and genetics data will probably necessitate ongoing revision of axSpA classification criteria. Advances in our knowledge of the biology of axSpA will settle some differences in opinion as to how the disease concept is applied to the classification and diagnosis of patients.

MRI-based Synthetic CT in the Detection of Structural Lesions in Patients with Suspected Sacroiliitis: Comparison with MRI

Background Evaluation of structural lesions in the sacroiliac (SI) joints can improve the accuracy for diagnosis of spondyloarthritis. However, structural lesions, such as erosions, are difficult to assess on routine T1-weighted MRI scans. Purpose To determine the diagnostic performance of MRI-based synthetic CT (sCT) in the depiction of erosions, sclerosis, and ankylosis of the SI joints compared with T1-weighted MRI, with CT as the reference standard. Materials and Methods A prospective study (clinical trial registration no. B670201837885) was performed from February 2019 to November 2019. Adults were referred from a tertiary hospital rheumatology outpatient clinic with clinical suspicion of inflammatory sacroiliitis. MRI and CT of the SI joints were performed on the same day. SCT images were generated from MRI scans using a commercially available deep learning-based image synthesis method. Two readers independently recorded if structural lesions (erosions, sclerosis, and ankylosis) were present on T1-weighted MRI, sCT, and CT scans in different reading sessions, with readers blinded to clinical information and other images. Diagnostic performance of sCT and T1-weighted MRI scans were analyzed using generalized estimating equation models, with consensus results of CT as the reference standard. Results Thirty participants were included (16 men, 14 women; mean age, 40 years ± 10 [standard deviation]). Diagnostic accuracy of sCT was higher than that of T1-weighted MRI for erosion (94% vs 86%, P = .003), sclerosis (97% vs 81%, P < .001), and ankylosis (92% vs 84%, P = .04). With sCT, specificity for erosion detection (96% [95% CI: 90, 98] vs 89% [95% CI: 81, 94], P = .01] and sensitivity for detection of sclerosis [94% [95% CI: 87, 97] vs 20% [95% CI: 10, 35], P < .001] and ankylosis (93% [95% CI: 78, 98] vs 70% [95% CI: 47, 87], P = .001) were improved. Conclusion With CT as the reference standard, synthetic CT of the sacroiliac joints has better diagnostic performance in the detection of structural lesions in individuals suspected of having sacroiliitis compared with routine T1-weighted MRI. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Fritz in this issue.

Update of imaging in the diagnosis and management of axial spondyloarthritis

Imaging of the spine and sacroiliac joints has acquired a central role in the diagnosis and classification of axial spondyloarthritis (axSpA) in the earliest phases of the disease. New definitions of specific imaging lesions, particularly in magnetic resonance imaging (MRI), have been recently updated and revised by the ASAS MRI working group to reach a standardized understanding and diagnosis of axSpA among rheumatologists. Recognizing the misleading pitfalls of MRI lesions and differential diagnosis also represents an essential issue in clinical practice to avoid false-positive findings and establish the diagnosis of axSpA with careful regard to the clinical context, clinical signs, and biological tests. This review summarizes the current evidence on the different imaging modalities of the sacroiliac joints and the spine with their application in the clinical setting of SpA and their main pitfalls; it also highlights the newest emerging imaging techniques.

MRI of sacroiliac joints for the diagnosis of axial SpA: prevalence of inflammatory and structural lesions in nulliparous, early postpartum and late postpartum women

OBJECTIVES

To determine the prevalence of bone marrow oedema (BME) at the sacroiliac joint (SIJ) in early postpartum (EPP), nulliparous (NP) and late postpartum (LPP) women, and to identify factors associated with BME presence at the SIJ.

METHODS

Three groups were obtained: NP (never given birth), EPP (given birth within 12 months) and LPP (given birth more than 24 months). The primary outcome was the presence of BME and/or structural lesions (erosions, osteophytes, ankylosis and sclerosis) at the SIJ MRI.

RESULTS

BME prevalence was greater among EPP (33%) than NP (14%, p=0.001), but was not different to LPP (21%, p=0.071). The Assessment of SpondyloArthritis international Society (ASAS) MRI criteria for sacroiliitis were positive in 75%, 71% and 80%, respectively, of EPP, NP and LPP women with BME. EPP (38%) had similar prevalence of sclerosis than LPP (28%, p=0.135), but greater than NP (18%, p=0.001). Lastly, EPP (28%) had similar prevalence of osteophytes than LPP (42%) and NP (27%), although there was a difference between LPP and NP (p=0.006).

CONCLUSIONS

EPP have higher BME prevalence at the SIJ than NP, EPP tend to have higher BME prevalence compared with LPP and BME presence decreases with time from delivery. Three-quarters of women with BME at the SIJ had a positive ASAS MRI criteria for sacroiliitis, indicating that BME presence as the main criterion for a positive diagnosis can lead to false-positive results. SIJ MRIs should not be interpreted in isolation, since age, time from delivery and other factors may outweigh the pertinence of MRI findings. Trial registration number NCT02956824.

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.

The semi-automated algorithm for the detection of bone marrow oedema lesions in patients with axial spondyloarthritis

The aim of the study was to create the efficient tool for semi-automated detection of bone marrow oedema lesions in patients with axial spondyloarthritis (axSpA). MRI examinations of 22 sacroiliac joints of patients with confirmed axSpA-related sacroiliitis (median SPARCC score: 14 points) were included into the study. Design of our algorithm is based on Maksymowych et al. evaluation method and consists of the following steps: manual segmentation of bones (T1W sequence), automated detection of reference signal region, sacroiliac joint central lines and ROIs, a division of ROIs into quadrants, automated detection of inflammatory changes (STIR sequence). As a gold standard, two sets of manual lesion delineations were created. Two approaches to the performance assessment of lesion detection were considered: pixel-wise (detections compared pixel by pixel) and quadrant-wise (quadrant to quadrant). Statistical analysis was performed using Spearman's correlation coefficient. Correlation coefficient obtained for pixel-wise comparison of semi-automated and manual detections was 0.87 (p = 0.001), while for quadrant-wise analysis was 0.83 (p = 0.001). The correlation between two sets of manual detections was 0.91 for pixel-wise comparison (p = 0.001) and 0.88 (p = 0.001) for quadrant-wise approach. Spearman's correlation between two manual assessments was not statistically different from the correlation between semi-automated and manual evaluations, both for pixel- (p = 0.14) and quadrant-wise (p = 0.17) analysis. Average single slice processing time: 0.64 ± 0.30 s. Our method allows for objective detection of bone marrow oedema lesions in patients with axSpA. The quantification of affected pixels and quadrants has comparable reliability to manual assessment.

The incidence of bone marrow oedema at the sacroiliac joints in a non-rheumatological population - a retrospective cohort study

BACKGROUND

The purpose of this study is to determine the incidence of bone marrow oedema (BME) at magnetic resonance imaging (MRI) of the sacroiliac joints (SIJ) in a non- rheumatological population, and to explore whether patient-reported outcome measures are suitable for predicting BME at the SIJ at referral. Furthermore, to investigate the final clinical diagnoses three months after initial SIJ MRI.

METHODS

This study was a retrospective cohort study consisting of patients 18-45 years of age that were referred for a SIJ MRI between 1 July 2016 to 30 June 2017 at the Department of Radiology in Lillebaelt Hospital, Denmark. The SIJ MRI radiological reports were evaluated for signs of BME. Principal and secondary diagnoses according to the 10th version of International Classification of Diseases (ICD-10)-three months after the initial MRI-were identified in the electronic patient record system. For a subgroup of patients, patient- reported outcome measures, such as the 23-item Roland Morris Disability Questionnaire, quality of life and pain intensity in the back and leg were included from the local SpineData database.

RESULTS

In total, 333 patients were included, and 187 (56.2%) of those patients received a final diagnosis within three months after the SIJ MRI. BME was detected in 63 (18.9%) patients; 17 (9.1%) patients had both BME at SIJ MRI and were diagnosed with spondyloarthritis (M45/M46). There was no statistically significant difference between patients with and without BME regarding demographics, quality of life, pain descriptions or function.

CONCLUSIONS

The incidence of BME in the cohort correlates well to previous studies regarding the incidence of SIJ MRI changes in non-rheumatological populations in Denmark. Patient-reported outcome measures do not seem to contribute to identifying patients with early-phase BME in a non-rheumatological population.