Magnetresonanztomographie der Sakroiliitis: Anatomie, Pathohistologie, MR-Morphologie und Graduierung

Assessment of axial spondyloarthritis activity using a magnetic resonance imaging-based multi-region-of-interest fusion model

BACKGROUND

Identifying axial spondyloarthritis (axSpA) activity early and accurately is essential for treating physicians to adjust treatment plans and guide clinical decisions promptly. The current literature is mostly focused on axSpA diagnosis, and there has been thus far, no study that reported the use of a radiomics approach for differentiating axSpA disease activity. In this study, the aim was to develop a radiomics model for differentiating active from non-active axSpA based on fat-suppressed (FS) T2-weighted (T2w) magnetic resonance imaging (MRI) of sacroiliac joints.

METHODS

This retrospective study included 109 patients diagnosed with non-active axSpA (n = 68) and active axSpA (n = 41); patients were divided into training and testing cohorts at a ratio of 8:2. Radiomics features were extracted from 3.0 T sacroiliac MRI using two different heterogeneous regions of interest (ROIs, Circle and Facet). Various methods were used to select relevant and robust features, and different classifiers were used to build Circle-based, Facet-based, and a fusion prediction model. Their performance was compared using various statistical parameters. p < 0.05 is considered statistically significant.

RESULTS

For both Circle- and Facet-based models, 2284 radiomics features were extracted. The combined fusion ROI model accurately differentiated between active and non-active axSpA, with high accuracy (0.90 vs.0.81), sensitivity (0.90 vs. 0.75), and specificity (0.90 vs. 0.85) in both training and testing cohorts.

CONCLUSION

The multi-ROI fusion radiomics model developed in this study differentiated between active and non-active axSpA using sacroiliac FS T2w-MRI. The results suggest MRI-based radiomics of the SIJ can distinguish axSpA activity, which can improve the therapeutic result and patient prognosis. To our knowledge, this is the only study in the literature that used a radiomics approach to determine axSpA activity.

Sacroiliac joint beyond sacroiliitis-further insights and old concepts on magnetic resonance imaging

The sacroiliac joint (SIJ) is an amphiarthrosis composed of a posterior syndesmosis and an anterior cartilaginous portion, with limited yet present mobility. Its main function is to transmit the load from the axial skeleton to the lower limbs and vice-versa; it is susceptible to early mechanical and degenerative changes which are much more common than inflammatory sacroiliitis. Magnetic resonance imaging (MRI) has increasingly been used to evaluate these changes, and while subchondral bone marrow edema (BME) is a common finding related to both, care must be taken when applying the ASAS research MRI definition for sacroiliitis without considering lesion BME topography, size and depth, concomitant structural damage and, of course, the clinical picture. In this review, we will discuss the anatomy and biomechanics of the SIJ, the noninflammatory causes of SIJ subchondral BME, and how these concepts combined can be used to increase our diagnostic confidence.

Computed tomography versus fluoroscopic guided-sacroiliac joint injection: a prospective comparative study

Background

There are limited data discussing long-term pain relief and comparability of different image-guided sacroiliac joint (SIJ) injection. This study compared CT and fluoroscopic-guided SIJ injections regarding statistically and clinically significant differences in numeric pain reduction, radiation doses, and patient’s satisfaction.

Methods

A prospective study conducted on 52 patients who met specific inclusion criteria of SIJ pain. A mixture of 1 ml of 40 mg methylprednisolone acetate diluted in 2 ml of lidocaine 2% was injected under either CT or fluoroscopic guidance. Numeric rating score (NRS) and Oswestry disability index (ODI) were assessed and recorded for each patient before procedure and one-week, and one-, three-, six-, and 12-months after procedure. The results were compared between both groups.

Results

Analysis of NRS one-month post-procedure showed a significant decrease from baseline in both groups: 12.5% in CT group (p = 0.002) and 9.5% in fluoroscopic group (p = 0.006). No significant difference in NRS between two groups at one- and three-months post-procedure (p = 0.11 and 0.1, respectively). There was a significant difference in NRS between two groups at six- and 12-months post-procedure (p = 0.001 and < 0.0001, respectively). Comparison of ODI at six-month post-procedure revealed that both groups had a statistically significant improvement (p < 0.0001). There was a significant difference in ODI between two groups at six-months post-procedure (p = 0.01).

Conclusions

CT-guided SIJ injection compares favorably with fluoroscopic guidance and offers statistically and clinically significant long-term pain relief. The use of dose reduction protocol in CT is important for decreasing the radiation dose.

Loss and gain of bone in spondyloarthritis: what drives these opposing clinical features?

The breadth of bone lesion types seen in spondyloarthritis is unprecedented in medicine and includes increased bone turnover, bone loss and fragility, osteitis, osteolysis and erosion, osteosclerosis, osteoproliferation of soft tissues adjacent to bone and spinal skeletal structure weakness. Remarkably, these effects can be present simultaneously in the same patient. The search for a potential unifying cause of effects on the skeleton necessarily focuses on inflammation arising from the dysregulation of immune response to microorganisms, particularly dysregulation of T_H17 lymphocytes, and the dysbiosis of established gut and other microbiota. The compelling notion that a common antecedent pathological mechanism affects existing bone and tissues with bone-forming potential (entheses), simultaneously with variable effect in the former but bone-forming in the latter, drives basic research forward and focuses our awareness on the effects on these bone mechanisms of the increasing portfolio of targeted immunotherapies used in the clinic.

Metabolites of type I, II, III, and IV collagen may serve as markers of disease activity in axial spondyloarthritis

Local inflammation in axial spondyloarthritis (axSpA) leads to the release of collagen metabolites from the disease-affected tissue. We investigated whether collagen metabolites were associated with disease activity and could distinguish non-radiographic(nr)-axSpA from ankylosing spondylitis (AS). A total of 193 axSpA patients (nr-axSpA, n = 121 and AS, n = 72) and asymptomatic controls (n = 100) were included. Serum levels of metalloproteinase (MMP)-degraded collagen type I (C1M), type II (C2M), type III (C3M) and type IV (C4M2) were quantified by enzyme-linked immunosorbent assay (ELISA). All metabolites were higher in axSpA than in controls (all p < 0.001). Serum levels of C1M, C3M, and C4M2 were increased in AS compared to nr-axSpA (43.4 ng/mL vs. 34.6; p < 0.001, 15.4 vs. 12.8; p = 0.001, and 27.8 vs. 22.4; p < 0.001). The best metabolite to differentiate between axSpA and controls was C3M (AUC 0.95; specificity 92.0, sensitivity 83.4). C1M correlated with ASDAS-CRP in nr-axSpA (ρ = 0.37; p < 0.001) and AS (ρ = 0.57; p < 0.001). C1M, C3M, and C4M2 were associated with ASDAS-CRP in AS and nr-axSpA after adjustment for age, gender, and disease duration. Serum levels of collagen metabolites were significantly higher in AS and nr-axSpA than in controls. Moreover, the present study indicates that collagen metabolites reflect disease activity and are useful biomarkers of axSpA.

Diagnostic Accuracy of MRI-Based Sacroiliitis Scoring Systems: A Systematic Review

OBJECTIVE. Accurate and reproducible MRI assessment of the sacroiliac joint (SIJ) is challenging. Numerous scoring systems have been proposed to facilitate consistent SIJ assessment. The purpose of this article is to evaluate the diagnostic accuracy and reliability of existing MRI-based SIJ scoring systems for the evaluation of spondyloarthropathy. CONCLUSION. Among existing methods, there is fair (grade B) evidence to recommend the Spondyloarthropathy Research Consortium of Canada scoring systems as tools for MRI evaluation of the SIJ. However, limited data on criterion validity limit assessment of scoring system accuracy.

Spondyloarthritis Research Consortium of Canada Scoring System for Sacroiliitis in Juvenile Spondyloarthritis/Enthesitis-related Arthritis: A Reliability, Validity, and Responsiveness Study

OBJECTIVE

Intra- and interreader reliability, construct validity, and responsiveness of the Spondyloarthritis Research Consortium of Canada (SPARCC) magnetic resonance imaging (MRI) scoring system were investigated for scoring sacroiliitis in patients with juvenile spondyloarthritis (JSpA)/enthesitis-related arthritis (ERA) who have received biologic and/or nonbiologic treatment.

METHODS

Ninety whole-body MRI examinations with dedicated oblique coronal planes of the sacroiliac joints in 46 patients were independently reviewed and scored by 2 pediatric musculoskeletal radiologists, blinded to clinical details, using the SPARCC system. Intra- and interreader reliability was assessed by intraclass correlation coefficients (ICC). Construct validity testing was done by (1) correlating the SPARCC MRI scores of sacroiliitis with clinical disease activity indicators (cross-sectional validity), and (2) correlating the change in the MRI score with the change in clinical indicators before and after treatment (longitudinal validity). Responsiveness of the MRI and clinical indicators was also evaluated, grouped by biologic and nonbiologic treatment.

RESULTS

When applied in children with JSpA/ERA, the SPARCC showed almost perfect intra- and interreader reliability (ICC 0.79-1.00). There was poor cross-sectional and longitudinal correlation between clinical assessment indicators and MRI scoring. SPARCC scores showed higher responsiveness to treatment-related change than most clinical outcome measures. Three clinical outcome measures correlated longitudinally with SPARCC score in nonbiologic treatment: active joint count (r = 0.72, p < 0.001), FABER (Flexion, Abduction, External Rotation) test (r = 0.58, p = 0.012), and physician's global assessment (r = 0.61, p = 0.034).

CONCLUSION

The SPARCC MRI scoring system is a reliable tool with relatively higher responsiveness than clinical indicators and is suitable for objective quantification of sacroiliitis when applied to pediatric patients with JSpA/ERA.

Detection of Sacroiliitis by Short-tau Inversion Recovery and T2-weighted Turbo Spin Echo Sequences: Results from the SIMACT Study

Objective.

To compare proton density–weighted short-tau inversion recovery (PD-STIR) and T2-weighted fat-suppressed turbo spin echo (T2-FS) sequences for detecting osteitis lesions of the sacroiliac joints (SIJ) in patients with chronic low back pain (CLBP).

Methods.

This prospective study included 110 patients with CLBP and suspected spondyloarthritis and 18 healthy controls. All 128 participants (age range: 19–57 yrs) underwent 3.0 Tesla magnetic resonance imaging (MRI) of the SIJ including PD-STIR and T2-FS. Two readers independently scored PD-STIR and T2-FS images for osteitis in separate sessions. Sum scores and signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Images were further analyzed as to whether they fulfilled the Assessment of SpondyloArthritis international Society (ASAS) criterion of a positive MRI (MRI+). Interreader agreement was calculated using intraclass correlation coefficients.

Results.

Average osteitis sum scores were higher for T2-FS images (mean sum score of 4.10 in T2-FS vs 2.55 in PD-STIR, p = 0.017). Mean SNR was 16.54 for PD-STIR and 37.30 for T2-FS (p = 0.0289). Mean CNR was 4.14 for PD-STIR and 20.20 for T2-FS (p = 0.0212). For both readers, the ASAS MRI+ definition was more often fulfilled by T2-FS than by PD-STIR images, resulting in more patients being classified as having axial spondyloarthritis (axSpA): 68 patients using T2-FS versus 58 patients using PD-STIR. Interreader intraclass correlation coefficients were very good for both PD-STIR (0.91) and T2-FS (0.86).

Conclusion.

T2-FS sequences improve image quality and hence the detection of osteitis compared to the PD-STIR sequence. More patients were classified as axSpA based on a positive MRI by T2-FS.

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.

High prevalence of hidradenitis suppurativa symptoms in axial spondyloarthritis patients: A possible new extra-articular manifestation

BACKGROUND

Spondyloarthritis (SpA), a chronic inflammatory, rheumatic disease, and hidradenitis suppurativa (HS), a chronic, debilitating, inflammatory skin disease, share several clinical and pathophysiological features, such as the association with inflammatory bowel disease and elevated cytokine levels IL-17 and TNF-α. Recently, SpA was reported to be more prevalent (2.3-28.2%) in patients with HS than in the general population. Conversely, the prevalence of HS in SpA is not exactly known.

OBJECTIVE

To determine the prevalence of HS in patients with axial SpA, a subtype of SpA primarily of the axial skeleton. Secondly, to identify patient characteristics associated with the presence of HS in axial SpA.

METHODS

In this cross-sectional study, a self-screening questionnaire based on validated diagnostic HS questions was sent to all participating axial SpA patients from the Groningen Leeuwarden Axial Spondyloarthritis (GLAS) cohort fulfilling the ASAS axial SpA criteria. Self-reported HS symptoms were confirmed by previous medical diagnosis or verification by phone using highly specific validated questions.

RESULTS

In total, 75.6% (449/592) questionnaires were eligible for analyses. Included patients had a mean age of 50 ± 13 years, 64% was male, mean symptom duration was 23 ± 13 years, and 79% was HLA-B27 positive. HS diagnosis could be confirmed in 41 patients, resulting in an estimated prevalence of 9.1%. In comparison to patients without a positive history of HS, these patients were more often female (54% vs. 35%, P = 0.02), showed higher axial SpA disease activity (mean BASDAI 4.5 vs. 3.6, p = 0.01 and ASDAS_CRP 2.6 vs. 2.2, P = 0.003) and worse quality of life (QoL) (median ASQoL 9.0 vs. 4.0, P < 0.001). Also, a history of heel enthesitis and dactylitis was more prevalent (34% vs. 19%, P = 0.03 and 15% vs. 6%, P = 0.05, respectively). Multivariable analysis showed that a higher score on ASDAS was independently associated with HS (OR: 1.639, 95% CI: 1.176-2.284).

CONCLUSION

In our cohort of axial SpA patients, HS is more prevalent than in the general population (9.1% versus 0.053-4.1%). HS is associated with female gender, lower QoL, and especially higher axial SpA disease activity.

Imaging Scoring Methods in Axial Spondyloarthritis

Inflammatory and chronic structural changes are objective signs of axial spondyloarthritis. In the sacroiliac joints (SIJs), inflammation (sacroiliitis) can be visualized as bone marrow edema, whereas chronic structural changes are visualized as fat metaplasia, erosions, sclerosis, or ankylosis in the area of the SIJ. In the spine, bone marrow edema in the vertebral bodies represents spondylitis but can also affect the facet and the costovertebral and costotransverse joints (arthritis), whereas structural changes are visualized as fat metaplasia, sclerosis or syndesmophytes and ankylosis at the vertebral edges.

Dual-phase hybrid 18 F-Fluoride Positron emission tomography/MRI in ankylosing spondylitis: Investigating the link between MRI bone changes, regional hyperaemia and increased osteoblastic activity

INTRODUCTION

Focal ¹⁸ F-Fluoride uptake on blood-pool phase PET represents regional hyperaemia, while it indicates osteoblastic activity on mineralization phase PET. This study investigates the link between regional hyperaemia and osteoblastic activity in inflammatory and chronic lesions of ankylosing spondylitis (AS) of the sacroiliac joints (SIJ) using dual-phase ¹⁸ F-Fluoride PET/MRI.

METHODS

Thirteen patients (six men, seven women, age: 37 ± 10 years) with active AS prospectively underwent dual-phase ¹⁸ F-Fluoride PET/MRI. Blood-pool phase PET was acquired 6 min and mineralization phase PET 40 min after injection of 158 ± 8 MBq ¹⁸ F-Fluoride. SIJ quadrants (SQ) were assessed regarding inflammatory lesions represented by bone marrow oedema (BME), chronic AS lesions such as erosion, fat deposition (FD), sclerosis and ankylosis on MRI, and regarding focal ¹⁸ F-Fluoride uptake on both PET datasets. Image quality (IQ) of both PET datasets and MRI was evaluated using a 4-point Likert scale.

RESULTS

Of 104 SQ, there were 63.4% SQ with FD, 42.3% SQ with BME, 26.9% SQ with erosions, 26% SQ with sclerosis and 10.6% SQ with ankylosis. BME alone was associated with focal ¹⁸ F-Fluoride uptake in 63.6% SQ on blood-pool phase and 90.9% SQ on mineralization phase ¹⁸ F-Fluoride PET/MRI. Instead, FD, erosion, sclerosis, ankylosis were not associated with focal ¹⁸ F-Fluoride uptake on either blood-pool or mineralization phase ¹⁸ F-Fluoride PET/MRI. SQ showing BME alone or a combination of BME and chronic AS lesions had a significantly higher percentage of focal ¹⁸ F-Fluoride uptake on blood-pool phase and mineralization phase PET/MRI than SQ showing AS lesions without BME (P < 0.001). Both ¹⁸ F-Fluoride PET datasets provided high IQ, albeit IQ of mineralization phase PET was superior to blood-pool phase PET (P < 0.001).

CONCLUSION

Dual-phase ¹⁸ F-Fluoride PET/MRI of the SIJ showed that inflammatory rather than chronic AS lesions are associated with regional hyperaemia and osteoblastic activity.

Magnetic Resonance Imaging of the Axial Skeleton in Patients With Spondyloarthritis: Distribution Pattern of Inflammatory and Structural Lesions

Purpose:

Spondyloarthritis is a chronic inflammatory disorder of the musculoskeletal system driven by systemic enthesitis and typically involving the axial skeleton, ie, the spine and the sacroiliac joints. The purpose of this study was to assess the distribution pattern of inflammatory and structural magnetic resonance imaging (MRI) findings in spondyloarthritis.

Methods:

Retrospective study of 193 patients with axial spondyloarthritis who received MRI of the spine and the sacroiliac joints. We quantitatively assessed inflammatory and structural lesions using established MRI-based scoring methods. The significance of the differences between gender, HLA-B27 status, and spine and sacroiliac involvement was determined.

Results:

In total, 174 patients (90.2%) showed a sacroiliac involvement and 120 patients (62.2%) a combined involvement of the sacroiliac joints and the spine. An isolated sacroiliac involvement was found in 54 patients (28.0%) and an isolated spine involvement in 19 patients (9.8%). The sacroiliac joint was significantly more involved in men than in women (P < .01), and men had significantly higher scores for structural lesions (P < .001). The subgroup of HLA-B27–positive patients showed a significantly higher percentage of sacroiliac involvement compared with HLA-B27–negative patients (P < .05).

Conclusions:

Spondyloarthritis is a systemic disorder predominantly involving the sacroiliac joints. However, the entire axial skeleton may be affected. In particular, HLA-B27–negative women show atypical manifestations without sacroiliac involvement. Magnetic resonance imaging in spondyloarthritis should cover the entire axial skeleton, ie, sacroiliac joints and the spine to meet the pathophysiology of this disorder and capture the true extent of inflammatory and structural lesions.

MRI assessment of sacroiliitis for the diagnosis of axial spondyloarthropathy: comparison of fat-saturated T2, STIR and contrast-enhanced sequences

OBJECTIVE

To evaluate whether there are significant differences between contrast-enhanced fat-saturated T₁ weighted imaging and non-enhanced fat-suppression imaging for diagnosing sacroiliitis in patients with inflammatory back pain.

METHODS

92 patients, consisting of 46 males and 46 females (mean age: 34 years; range: 15-63 years), who met at least 4 out of 5 Assessment in SpondyloArthritis international Society criteria for inflammatory low back pain were enrolled in this study. All patients underwent MRI consisting of a coronal short tau inversion recovery (STIR) sequence, axial fat-saturated T₂ weighted imaging (T2FS), and coronal and axial contrast-enhanced fat-saturated T₁ weighted imaging (c & a T1CE). Two observers independently reviewed an image set of coronal STIR with axial T2FS, and an image set of c & a T1CE, at separate times. The degree of bone marrow edema and osteitis was evaluated from each image set. A decision for sacroiliitis positivity for each image set was made based on the findings. The presence of additional active inflammatory findings of spondyloarthropathy such as synovitis, enthesitis and capsulitis were also evaluated.

RESULTS

Interobserver and intersequence agreement for the degree of bone marrow edema and osteitis were good or excellent in all quadrants. Cohen's kappa coefficients for sacroiliitis positivity between the two observers were 0.978 and 0.956, and Cohen's kappa coefficients between the two image sets for each observer were 0.892 and 0.870, respectively. The intersequence agreement of additional active inflammatory findings was substantial, and the interobserver agreement was almost perfect or substantial.

CONCLUSION

STIR with T2FS image is comparable to T1CE image for diagnosing spondyloarthropathy. T1CE images may have a role in evaluating additional active inflammatory findings of spondyloarthropathy such as synovitis, enthesitis and capsulitis. Advances in knowledge: Coronal STIR with axial T2FS may be sufficient for diagnosis spondyloarthropathy without use of contrast administration.

Does evaluation of the ligamentous compartment enhance diagnostic utility of sacroiliac joint MRI in axial spondyloarthritis?

Introduction

Inflammation of the sacroiliac joints (SIJ) is a fundamental clinical feature of axial spondyloarthritis (SpA). The anatomy of the irregularly shaped SIJ is complex with an antero-inferior cartilaginous compartment containing central hyaline and peripheral fibrocartilage, and a dorso-superior ligamentous compartment. Several scoring modules to systematically assess SIJ magnetic resonance imaging (MRI) in SpA have been developed. Nearly all of them are based on the cartilaginous joint compartment alone. However, there are only limited data about the frequency of inflammatory lesions in the ligamentous compartment and their potential diagnostic utility in axial SpA. We therefore aimed to evaluate the ligamentous compartment on sacroiliac joint MRI for lesion distribution and potential incremental value towards diagnosis of SpA over and above the traditional assessment of the cartilaginous compartment alone.

Methods

Two independent cohorts of 69 and 88 consecutive back pain patients ≤50 years were referred for suspected SpA (cohort A) or acute anterior uveitis plus back pain (cohort B). Patients were classified according to rheumatologist expert opinion based on clinical, radiographic and laboratory examination as having nonradiographic axial SpA (nr-axSpA; n = 51), ankylosing spondylitis (n = 34), or nonspecific back pain (NSBP; n = 72). Five blinded readers assessed SIJ MRI globally for presence/absence of SpA. Bone marrow edema (BME) and fat metaplasia were recorded in the cartilaginous and ligamentous compartment. The incremental value of evaluating the ligamentous additionally to the cartilaginous compartment alone for diagnosis of SpA was graded qualitatively. We determined the lesion distribution between the two compartments, and the impact of the ligamentous compartment evaluation on diagnostic utility.

Results

MRI bone marrow lesions solely in the ligamentous compartment in the absence of lesions in the cartilaginous compartment were reported in just 0–2.0/0–4.0 % (BME/fat metaplasia) of all subjects. Additional assessment of the ligamentous compartment was regarded as essential for diagnosis in 0 and 0.6 %, and as contributory in 28.0 and 7.7 % of nr-axSpA patients in cohorts A and B, respectively. Concomitant BME in both compartments was evident in 11.6–42.0 % of nr-axSpA and 2.1–2.4 % of NSBP patients.

Conclusion

Assessing the ligamentous compartment on SIJ MRI provided no incremental value for diagnosis of axial SpA. However, concomitant BME in both compartments may help discriminate nr-axSpA from NSBP.

Sacroiliac indicis increase the specificity of bone scintigraphy in the diagnosis of sacroiliitis

Objective: Bone scintigraphy is a highly sensitive method in the evaluation of sacroiliitis. Aim of this study is firstly to evaluate interobserver variation of partial and whole sacroiliac indicis, secondly investigation of clinical importance of these indicis in the diagnosis of sacroiliitis.

Methods: Fourty-six subjects (24 female: 35.4±11.9; 22 male: 43.1±12.4) without sacroiliitis 45 subjects with low back pain (33 female: 43.3±11.5, 11 male: 35.5±17.2) were included in the study. For right (R) and left (L) whole indices (WSI) irregular region of interest (ROI), for partial indices superior (S) and inferior (I) rectangular ROI were used. For background activity, rectangular ROI was drawn from the sacral region. Indices were calculated from ratio of average counts of sacroiliac and background regions. Two independent observers calculated sacroiliac indices. Interobserver agreement was evaluated by Pearson analysis.

Results: There was no significant interobserver difference (p>0.05). Significant correlation existed between all calculated indices. Among 45 patients with suspicion of sacroiliitis 15 had final diagnosis of sacroiliitis and all of the Tc-99m methilenediphosphonate planar and SPECT bone scintigraphy results of these patients were concordant with sacroiliitis. There were 8 false positive results in other 30 patients. Seven of these eight patients had normal index values. If the scintigraphy would be evaluated in conjuction with indicis the specificity would increase from 73% to 97% but sensitivity decreases from 100% to 80%. There was significant correlation between the observers calculated indicis (p<0.001).

Conclusion: Superior and inferior sacroiliac index values can be used with confidence. If we use sacroiliac index values to confirm positive results; index values can increase the specificity of bone scintigraphy.

[Imaging modalities in psoriatic arthritis]

This review presents an overview of the range of imaging modalities used in the diagnostic evaluation of patients with psoriatic arthritis (PsA). Conventional radiography is used to detect structural changes of the joints and tendon attachments. These changes occur late in the course of PsA hence conventional radiography contributes little to the early detection of PsA; however, the detection of periosteal proliferations on radiographs allows a relatively specific diagnosis of PsA. Skeletal scintigraphy and computed tomography are rarely used in PsA. Arthrosonography (ultrasound of the joints) is gaining increasing importance in the early identification of inflammatory soft tissue signs of PsA in the peripheral joints. Sonography enables early detection of synovitis and tenosynovitis as well as superficial erosions and also inflammatory processes of the tendon attachments. Magnetic resonance imaging (MRI) is indispensable for identifying possible involvement of the axial skeleton. Moreover, it allows good visualization of periostitis and arthritis. High resolution microcomputed tomography is an interesting novel diagnostic tool which allows highly sensitive evaluation of the bone structure and can detect very tiny bone lesions where typical signs of PsA are omega-shaped erosions and small corona-like spikes. Another interesting new diagnostic technique is fluorescence optical imaging (FOI) with the Xiralite system which is highly sensitive for detecting inflammatory processes of the hands.

Erosions and fatty lesions of sacroiliac joints in patients with axial spondyloarthritis: evaluation of different MRI techniques and two scoring methods

OBJECTIVE

Assessment of structural damage of sacroiliac joints (SIJ) in patients with axial spondyloarthritides (axSpA) has been discussed as a useful outcome measure in clinical trials. The aim of our study was to evaluate different magnetic resonance imaging (MRI) scoring methods and pulse sequences with a focus on fatty lesions and bony erosions.

METHODS

Seventy-five patients with the diagnosis of axSpA underwent MRI at 3 timepoints as part of the ESTHER trial, which compared 2 groups of patients treated with etanercept or sulfasalazine. Two MRI sequences [unenhanced T1-weighted (T1w) turbo spin-echo (TSE) and unenhanced T1w opposed-phase gradient-echo sequences (opGRE)] and 2 different scoring systems (simple and comprehensive Berlin method) were used for the evaluation of fatty lesions and erosions of the SIJ. Differences between techniques and methods were evaluated by intraclass correlation coefficients (ICC) and standardized response means (SRM).

RESULTS

Applying the simple Berlin method, mean fatty lesion scores for etanercept-treated patients were 4.59 and 5.19 at baseline and Week 48, respectively, while the comprehensive Berlin method revealed mean fatty lesion scores of 6.59 and 7.64, respectively. Corresponding SRM were 0.59 and 0.86 for simple and comprehensive methods, respectively, while ICC dropped from 0.76-0.77 to 0.59-0.62. Scoring of erosions on T1w opGRE images resulted in a higher interreader agreement (ICC of 0.65) compared to T1w TSE sequences (ICC of 0.18).

CONCLUSION

Better characterization of fatty lesion changes within 1 year was achieved by the comprehensive Berlin scoring method; however, more reader variation has to be taken into account. The delineation of erosions is markedly improved when using T1w opGRE pulse sequences.

Effects of etanercept versus sulfasalazine in early axial spondyloarthritis on active inflammatory lesions as detected by whole-body MRI (ESTHER): a 48-week randomised controlled trial

PURPOSE

To evaluate the potential of etanercept versus sulfasalazine to reduce active inflammatory lesions on whole-body MRI in active axial spondyloarthritis with a symptom duration of less than 5 years.

METHODS

Patients were randomly assigned to etanercept (n=40) or sulfasalazine (n=36) treatment over 48 weeks. All patients showed active inflammatory lesions (bone marrow oedema) on MRI in either the sacroiliac joints or the spine. MRI was performed at weeks 0, 24 and 48 and was scored for active inflammatory lesions in sacroiliac joints and the spine including posterior segments and peripheral enthesitis by two radiologists, blinded for treatment arm and MRI time point.

RESULTS

In the etanercept group, the reduction of the sacroiliac joint score from 7.7 at baseline to 2.0 at week 48 was significantly (p=0.02) larger compared with the sulfasalazine group from 5.4 at baseline to 3.5 at week 48. A similar difference in the reduction of inflammation was found in the spine from 2.2 to 1.0 in the etanercept group versus from 1.4 to 1.3 in the sulfasalazine group between baseline and week 48, respectively (p=0.01). The number of enthesitic sites also improved significantly from 26 to 11 in the etanercept group versus 24 to 26 in the sulfasalazine group (p=0.04 for difference). 50% of patients reached clinical remission in the etanercept group versus 19% in the sulfasalazine group at week 48.

CONCLUSION

In patients with early axial spondyloarthritis active inflammatory lesions detected by whole-body MRI improved significantly more in etanercept versus sulfasalazine-treated patients. This effect correlated with a good clinical response in the etanercept group.

The Ankylosing Spondylitis Disease Activity Score is a highly discriminatory measure of disease activity and efficacy following tumour necrosis factor-α inhibitor therapies in ankylosing spondylitis and undifferentiated spondyloarthropathies in China

OBJECTIVE

To validate the clinical value of the new Ankylosing Spondylitis Disease Activity Scores (ASDASs) in assessing the disease activity and efficacy of TNF-α inhibitor in AS and uSpA patients in China.

METHODS

Two hundred and thirty patients were included in our study. They consisted of patients with active AS (n = 87) and uSpA (n = 30) participating in a double-blind placebo-controlled randomized clinical trial of etanercept and patients with active AS (n = 58) and uSpA (n = 55) treated with infliximab. The disease activity and treatment effects were assessed by ASDAS, BASDAI, patient global and the acute inflammation score of lumbar and SI joints by MRI. Discriminatory ability of all the measures was analysed by standardized mean difference and t-score.

RESULTS

In both the AS and uSpA groups, ASDAS correlated well with patient global score (AS group: r = 0.65-0.72; uSpA group: r = 0.52-0.62), ESR (AS group: r = 0.57-0.81; uSpA group: r = 0.63-0.85) and CRP (AS group: r = 0.51-0.70; uSpA group: r = 0.61-0.76) both at baseline and in changes from baseline to 6 weeks after TNF-α inhibitor treatment. The ASDAS scores outperformed BASDAI, patient global score, ESR, CRP and the acute inflammation score by MRI in differentiating patients with different levels of disease activity and patients with different levels of change in both AS and uSpA groups. There was little difference in performance between the two versions of the ASDAS.

CONCLUSION

The new ASDAS is a highly effective measure in assessing disease activity and a great discriminatory measurement to assess the efficacy of TNF-α inhibitor in Chinese AS patients and uSpA patients.

Magnetic resonance imaging of active sacroiliitis: do we really need gadolinium?

INTRODUCTION

Magnetic resonance imaging (MRI) of active inflammatory changes of the sacroiliac joint (SIJ) in spondyloarthritis (SpA) is performed with short tau inversion recovery (STIR) sequences and fat-saturated T1-weighted fast spin-echo (FSE) sequences after administration of gadolinium-based contrast medium (T1/Gd). The aim of the present study was to compare these two pulse sequences in terms of diagnosis, diagnostic confidence, and quantification of inflammatory changes.

MATERIALS AND METHODS

The study included 105 patients with suspected SpA; 72 patients developed clinical SpA over time. All patients were examined with STIR and T1/Gd and each of the two sequences was analyzed separately in conjunction with unenhanced T1 FSE images. For quantitative estimation of inflammatory changes, each sacroiliac joint (SIJ) was divided into 4 quadrants (and severity per quadrant was assigned a score of 0-4, resulting in a maximum sum score of 16 per SIJ). Diagnostic confidence was assessed on a visual analogue scale ranging from 0 to 10.

RESULTS

Active sacroiliitis was diagnosed in 46 patients and ruled out in 34 using STIR, whereas findings were inconclusive in 25 patients. The corresponding numbers for T1/Gd were 47, 44, and 14. Diagnostic confidence was significantly lower for STIR (7.3+/-2.6) compared with T1/Gd (8.7+/-1.9) (p<0.001). The sum scores were 2.5 (+/-3.3) for STIR and 2.2 (+/-3.2) for T1/Gd for the right SIJ and 2.2 (+/-2.9) (STIR) and 1.9 (+/-3.1) (T1/Gd) for the left SIJ. Agreement was high with intraclass correlation coefficient (ICC) values of 0.86 for the right SIJ and 0.90 for the left SIJ and positive correlation (r=0.62 right, 0.60 left).

SUMMARY

STIR sequences alone are sufficient for establishing a reliable diagnosis and quantify the amount of inflammation in active sacroiliitis. A contrast-enhanced study is dispensable in patients with established disease or in the setting of clinical follow-up studies. However, a contrast-enhanced MR sequence is beneficial to ensure maximum diagnostic confidence when patients with early sacroiliitis are examined.

Whole-body MR imaging for patients with rheumatism

WB-MRI in rheumatic diseases is still an emerging imaging tool. So far, WB-MRI in rheumatism is mainly used in seronegative spondyloarthropathies. In these diseases it has the ability to visualize the majority of involved joints and soft tissue structures (both active inflammatory changes and chronic structural abnormalities) in one examination, making it suitable for imaging of different forms of spondylopathies, allowing different types of joint involvement to be recognized and assessing both the acute symptoms of disease and the longer-term consequences. Its role in daily practice is not yet clear. WB-MRI is not recommended as a first line investigation in every patient suffering from a form of spondyloarthropathy, but may add important information in difficult cases. Moreover, WB-MRI might obtain a stronger role in the early diagnosis of spondyloarthritides and in the assessment of treatment response. Other rheumatic diseases where WB-MRI may play a role in the future are polymyositis/dermatomyositis, CRMO and certain forms of systemic vasculitis. WB-MRI in rheumatism is a promising tool with great potential, however further systematic evaluation of its abilities and limitations in different forms of rheumatic diseases is awaited.

[Ankylosing spondylitis--current state of imaging including scoring methods]

Conventional radiography and magnetic resonance imaging (MRI) are currently the most widely used imaging methods for the initial diagnostic evaluation and follow-up of patients with ankylosing spondylitis (AS). Scintigraphy, computed tomography (CT), and positron emission tomography (PET) only play minor roles, although some are being further developed. AS is characterized by inflammatory changes to the sacroiliac joints (SIJs) and spine, as well as asymmetrical arthritis of the peripheral joints and joints near the trunk. The diagnosis of AS is based on clinical parameters and the presence of chronic inflammatory changes to the SIJs on conventional radiographs. Typical radiographic changes also involve the spine. MRI depicts not only chronic changes, but also active inflammatory lesions, which are important for the diagnosis of early disease and precursors of AS. The scoring system of choice for quantifying spinal changes depicted by conventional radiography is the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). MRI allows the quantitative evaluation of changes involving the SIJs and the spine. Various MRI scoring systems have been proposed to quantify these changes, but they require further validation. This review article presents the imaging modalities used in AS patients, typical findings, and relevant methods of analysis. The most recent developments are discussed.

Magnetic resonance imaging of the axial skeleton in rheumatoid disease

The axial skeleton is a target for both spondyloarthritis and rheumatoid arthritis. While conventional radiography allows the clear documentation of the late stages of inflammatory changes, magnetic resonance imaging (MRI) is sensitive enough to depict early inflammatory lesions. It is, therefore, of particular importance for radiologists and clinicians to know the MRI appearances of inflammatory changes of the axial skeleton in rheumatoid diseases. Typical lesions in ankylosing spondylitis and related conditions comprise spondylitis (Romanus lesion), spondylodiscitis (Andersson lesion), arthritis of the apophyseal joints, the costovertebral and costotransverse joints, and insufficiency fractures of the ankylosed vertebral spine (non-inflammatory type of Andersson lesion). Sacroiliitis is associated with chronic changes such as sclerosis, erosions, transarticular bone bridges, periarticular accumulation of fatty tissue and ankylosis. In addition, acute findings include capsulitis, juxta-articular osteitis and the enhancement of the joint space after contrast medium administration. Another important sign of spondyloarthritis is enthesitis, which affects the interspinal and supraspinal ligaments of the vertebral spine and the interosseous ligaments in the retroarticular space of the sacroiliac joints. The main site of manifestation of spinal involvement in rheumatoid arthritis is the cervical spine. Typical changes are the destruction of the atlantoaxial complex by pannus tissue with subsequent atlantoaxial subluxation, basilar impression and erosion of the dens axis. Changes in the lower segments of the cervical spine are destruction of the apophyseal joints resulting in the so-called stepladder phenomenon. Because of the uniform response of the discovertebral complex to different noxae, a number of different conditions must be distinguished on the basis of the patient's clinical findings and history in combination with their imaging appearance. These conditions comprise degenerative disc disease, septic spondylodiscitis, Scheuermann's disease, Paget's disease and diffuse idiopathic skeletal hyperostosis (DISH).