Backfill is a specific sign of axial spondyloarthritis seen on MRI

"Long-term MRI findings in Ankylosing spondylitis patients treated with TNF inhibitors for a decade"

OBJECTIVE

This study aims to evaluate the active and chronic lesions in sacroiliac joints and lumbar spine over a decade of TNFi therapy in patients with AS.

METHODS

The study enrolled patients with AS under treatment with a TNFi for over a decade. The patients underwent a new MRI scan of their lumbar spine and sacroiliac joint (SIJ). Two readers evaluated all images. Inflammation of SIJ (SIS), SIJ structural damage (SSS) including Fat Metaplasia, Erosions, Backfill and Ankylosis, and Spondyloarthritis Research Consortium of Canada Bone marrow edema (SPARCC) spine score were recorded.

RESULTS

In the study, 15 patients were included, with 80% being male. The mean age during their first MRI was 38.1 (± 11.9) years old, and the majority (86.7%) tested positive for HLA-B27. While TNFi improved both BASDAI and BASFI scores, there was a noticeable increase in MRI acute lesions in the SIJ over time, where the median score increased from 0 (0-4) to 3 (0-10) after ten years (p = 0.028). After a decade of treatment, the median SPARCC spine score also increased from 0 (0-9) to 5 (0-16), p = 0.093. Finally, it was observed that there was a significant positive correlation between ESR and SIS erosions in cases of chronic lesions (r = 0.819, p < 0.001).

CONCLUSIONS

While TNFi have significantly improved the treatment of AS, this study shows that acute lesions can still develop despite treatment. A personalized approach that adapts MRI assessment to each patient's specific requirements may help detect changes early and enable doctors to intervene promptly to prevent further damage.

New Bone Formation in Axial Spondyloarthritis: A Review

BACKGROUND

 Axial spondyloarthritis (axSpA) is a chronic inflammatory disease primarily affecting the sacroiliac joints (SIJs) and the spine. Imaging plays a crucial role in the diagnosis of axSpA, with magnetic resonance imaging (MRI) and radiography being the primary modalities used in clinical practice. New bone formation occurs in both the spine (non-bridging and bridging syndesmophytes, transdiscal ankylosis, and ankylosis of small joints and posterior elements) and the SIJs (backfill and ankylosis). New bone formation indicates advanced axSpA.

METHOD

 This review explores the role of imaging in the diagnosis and monitoring of axSpA, focusing on the significance of new bone formation, and provides an overview of the characteristic imaging findings of new bone formation in axSpA in each imaging modality.

CONCLUSION

 Imaging methods, such as X-ray, MRI, and CT, have different diagnostic accuracies for detecting structural lesions and new bone formation. Each modality has its strengths and weaknesses, and the choice depends on the specific clinical context. Imaging is crucial for the diagnosis and monitoring of axSpA, particularly for the detection of new bone formation. Different imaging techniques provide valuable information about disease progression and treatment response. Understanding the significance of new bone formation and its detection using imaging modalities is essential for the accurate diagnosis and effective management of patients with axSpA.

KEY POINTS

  · New bone formation is a hallmark feature of advanced axial spondyloarthritis.. · New bone formation occurs both in the spine and in the sacroiliac joints.. · Differentiation of new bone formation in axial spondyloarthritis from that in other conditions such as diffuse idiopathic skeletal hyperostosis and from osteophytes is essential.. · Imaging methods, such as X-ray, MRI, and CT, have different diagnostic accuracies for detecting new bone formation..

Evaluation of active inflammation, chronic structural damage, and response to treatment of sacroiliitis in axial spondyloarthritis using the Spondyloarthritis research consortium of Canada scoring system

Background

Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease affecting the spine and sacroiliac joints. To investigate whether there are differences in inflammatory and chronic structural damages, as assessed by a semiquantitative MRI scoring method, between non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS) patients with active inflammation at baseline, and to evaluate the treatment response in these patients after 3 months of tumor necrosis factor-alpha (TNF-α) inhibitor treatment.

Methods

Fifty-eight axSpA patients with active inflammation were included in the study. The patients were divided into nr-axSpA group and AS group. MRI examinations of the sacroiliac joints were performed before and after treatment. Inflammatory and structural damages in these patients were assessed using the established Spondyloarthritis Research Consortium of Canada (SPARCC) inflammation and sacroiliac joint structural (SSS) scoring methods, which are two MRI-based scoring methods. The SPARCC score, SSS score, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) level were compared between the two groups.

Results

At baseline, SPARCC scores for patients in the nr-axSpA and AS groups did not differ significantly (P > 0.05); however, SSS scores for fat metaplasia, erosion, and backfill for patients in the AS group were significantly higher (P < 0.001). Compared with baseline, SPARCC scores were significantly decreased in both groups after treatment (P < 0.001); however, after treatment, no statistically significant difference was found regarding SPARCC scores between the AS and nr-axSpA groups. Compared with baseline, a significant increase in the SSS scores for fat metaplasia and backfill (P < 0.001) and a significant decrease in the SSS scores for erosion (P < 0.001) were observed in all axSpA patients. Changes in the SPARCC score was inversely correlated with the changes in the SSS score for fat metaplasia (r = − 0.634, P < 0.001). Changes in the SSS score for backfill were positively correlated with the changes in the SSS score for fat metaplasia (r = 0.277, P < 0.05) and inversely correlated with those for erosion (r = − 0.443, P < 0.001).

Conclusion

The SPARCC and SSS scoring systems can be used to assess inflammatory and chronic structural damages as well as treatment responses in patients with axSpA. More severe structural damages were seen in AS patients. TNF-α inhibitor treatment for 3 months could effectively reduce inflammation in axSpA patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05609-x.

Baseline Severity of Sacroiliitis and Extensive Fat Metaplasia Predicts the Progression of Backfill at the Sacroiliac Joint in Patients With Axial Spondyloarthritis

Objectives

Fat metaplasia in an erosion cavity, also known as backfill, is an essential intermediary in new bone formation in axial spondyloarthritis (axSpA) patients; however, the predictors of backfill progression are unknown. This longitudinal study aimed to assess the predictors of backfill progression in axSpA patients on magnetic resonance imaging (MRI).

Methods

Clinical and MRI data were collected at baseline and follow-up in 52 axSpA patients. Backfill progression was defined as the new or increased T1 hyperintensity within the SI joint space. Logistic regression analyses were performed to identify the predictors of the backfill progression.

Results

A total of 19 patients had “backfill” at baseline and 30 patients exhibited the backfill progression after follow-up. The mean disease duration and SPARCC scores at baseline were significantly different between patients with and without backfill progression (P&lt;0.001, P=0.003, respectively). Patients with backfill progression had a higher frequency of backfill at baseline, a higher SSS score of fat metaplasia, and a higher SSS score of backfill than those without (P=0.001, P&lt;0.001, and P=0.002, respectively). A higher fat fraction value in the fat metaplasia area at the baseline was more frequent in patients with, than without, backfill progression (P=0.019). In the univariate logistic regression analyses, a higher SPARCC score for inflammation and a higher SSS score for fat metaplasia at baseline were associated with backfill progression.

Conclusions

Severity of sacroiliitis and extensive fat metaplasia at baseline are predictors of the backfill progression in axSpA patients.

ACR Appropriateness Criteria® Inflammatory Back Pain: Known or Suspected Axial Spondyloarthritis: 2021 Update

Inflammatory back pain is a hallmark feature of axial spondyloarthritis, a heterogeneous group of inflammatory disorders which affects the sacroiliac joints and spine. Imaging plays a key role in diagnosis of this disease and in facilitating appropriate treatment. This document provides evidence-based recommendations on the appropriate use of imaging studies during multiple stages of the clinical evaluation of patients with suspected or known axial spondyloarthritis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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 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.

Performance of magnetic resonance imaging in the diagnosis of axial spondyloarthritis: a systematic literature review

OBJECTIVES

To summarize the evidence on the performance of MRI for the diagnosis of axial SpA.

METHODS

This was a systematic literature review of all studies from January 2013 to March 2017 including adult patients with clinically suspected axial SpA undergoing MRI. Studies from a previously published systematic literature review up to January 2013 were also included.

RESULTS

Thirty-one studies were included. Six studies demonstrated good sensitivity and specificity for SI joint (SIJ) bone marrow oedema (BMO). Specificity was increased by the presence of other structural lesions alongside BMO, particularly erosions or fat infiltration. Four studies addressed the utility of SIJ fat infiltration, finding good sensitivity but poor specificity. SIJ erosions showed good specificity in five studies. Studies addressing high T1 signal in the SIJ, fluid signal in the SIJ, ankylosis, sclerosis, capsulitis, backfill and vacuum phenomenon reported limited diagnostic value. In the spine, four studies reported moderate sensitivity and specificity for corner inflammatory lesions, and four reported poor sensitivity and specificity for spinal fat infiltration. Five studies evaluated the added value of spinal MRI over SIJ MRI alone, with variable results depending on the cohort. Six studies addressed the effect of acquisition parameters on diagnostic accuracy: fat-saturated T2-weighted imaging and short tau inversion recovery (STIR) imaging showed comparable utility in identifying BMO. Three studies showed that gadolinium was of minimal added value in the detection of BMO.

CONCLUSIONS

These results confirmed the diagnostic utility of MRI in axial SpA. Performance varied according to the characteristics of the cohort and the number and combination of MRI lesions considered.

Post-traumatic arthritis of the sacroiliac joints mimicking inflammatory sacroiliitis: analysis of consecutive computed tomography examinations

AIM

To assess the presence, prevalence and characteristics of post-traumatic, inflammatory-like changes of the sacroiliac joint (SIJ) on pelvic computed tomography (CT).

MATERIALS AND METHODS

Sequential CT examinations from the acute (index) and follow-up post-traumatic periods of 24 patients that underwent pelvic trauma with SIJ involvement were evaluated and compared to 32 control patients with pelvic fractures that did not involve the SIJs. Index CT was evaluated for the presence of fracture, intra-articular step, and diastasis, whereas follow-up CT was scored for periarticular sclerosis, erosions, ankylosis, and backfill. Clinical follow-up was performed by pain provocation SIJ tests and a questionnaire (study representative subgroup, n=11, 46%) and from clinical files (control group, n=26, 31%). Pearson correlation coefficient was assessed between the index and follow-up CT variables. Linear regression was used to predict the influence of trauma variables on the development of inflammatory-like structural changes.

RESULTS

Total "structural, arthritis-like lesions' score from the follow-up CT examination was significantly higher in the study compared to the control group (3.25 versus 0.05 respectively, p<0.001). The presence of intra-articular diastasis and fracture were significant risk factors for the development of structural inflammatory-like lesions in the SIJ (1.19 and 2.1 respectively, p<0.001). Painful SIJs by physical examination were found in 50% of the clinically evaluated subgroup which was mechanical by nature in 81.8%.

CONCLUSION

Traumatic SIJ fracture or diastasis is associated with the development of post-traumatic SIJ structural inflammatory-like lesions on pelvic CT, mimicking sacroiliitis. These findings may be the result of focal, post-traumatic joint inflammation, which leads to mechanical rather than inflammatory symptoms.

Recommendations for acquisition and interpretation of MRI of the spine and sacroiliac joints in the diagnosis of axial spondyloarthritis in the UK

Objectives

To develop evidence-based recommendations on the use of MRI in the diagnosis of axial SpA (axSpA).

Methods

A working group comprising nine rheumatologists and nine musculoskeletal radiologists with an interest in axSpA was established, with support from the British Society of Spondyloarthritis (BRITSpA). Two meetings were held. In the first meeting, research questions were formulated. In the second meeting, the results of a systematic literature review designed to inform the recommendations were reviewed. An anonymized Delphi process was used to formulate the final set of recommendations. For each recommendation, the level of evidence and strength of recommendation was determined. The level of agreement was assessed using a 0–10 numerical rating scale.

Results

Two overarching principles were formulated, as follows: The diagnosis of axSpA is based on clinical, laboratory and imaging features (overarching principle 1), and patients with axSpA can have isolated inflammation of either the sacroiliac joints or the spine (overarching principle 2). Seven recommendations addressing the use of MRI in the assessment of patients with suspected axSpA were formulated, covering topics including recommended sequences, anatomical coverage, acquisition parameters and interpretation of active and structural MRI lesions. The level of agreement for each recommendation was very high (range 8.8–9.8).

Conclusion

A joint rheumatology and radiology consensus on the acquisition and interpretation of MRI in axSpA diagnosis was achieved, and a research agenda formulated. This consensus should help standardize practice around MRI and ensure a more informed, consistent approach to the diagnosis of axSpA.

Recent advances in ankylosing spondylitis: understanding the disease and management

The term spondyloarthritis refers to a group of immune-mediated diseases characterised by inflammation of the axial skeleton, peripheral joints, and entheses. Ankylosing spondylitis (AS) is the most common and characteristic of these entities and even though it was first described over two centuries ago, the understanding of the underlying disease mechanism remains incomplete. It is known that around 40% of patients with AS have subclinical bowel inflammation, suggesting that the origin of the disease could be in the gut. Also, more genes and new molecules have demonstrated a role in the pathogenesis of AS. In this review, we analyse the latest therapies for spondyloarthritis and the most relevant discoveries over the last three years, together with their implications for different aspects of the disease.

The Role of Imaging in Diagnosing Axial Spondyloarthritis

Imaging has a central role in the diagnosis, management, and follow-up of patients with axial spondyloarthritis (axSpA). For the early diagnosis of axSpA, magnetic resonance imaging is of utmost relevance. While no novel imaging techniques were developed during the past decade, improvements to the existing modalities have been introduced. This report provides an overview of the applications and limitations of the existing imaging modalities.