Low-dose computed tomography for axial spondyloarthritis: update on use and limitations.

PURPOSE OF REVIEW: Recent developments in low-dose computed tomography (ldCT) have greatly reduced radiation exposure levels. This article reviews what a ldCT is and its use and limitations for imaging axial spondyloarthritis. RECENT FINDINGS: Detection of structural damage in bone with CT is far superior to radiography and ldCT of the sacroiliac joints (SIJ) can now be done at radiation exposure levels equivalent to, or even less than, conventional radiography. ldCT should be considered a 'first-choice' test for arthritis imaging, and wherever available, SIJ ldCT may completely replace conventional radiography. Radiation exposure in the spine with ldCT is lower than conventional CT. However, it is unclear whether the additional information regarding structural damage changes in the spine provided by ldCT will alter patient management sufficiently often to merit switching from spinal radiography to ldCT in routine clinical practice. In addition, ldCT cannot assess osteitis disease activity for which MRI remains the best test. SUMMARY: ldCT of the sacroiliac joints (SIJ) can be done at radiation exposure levels equivalent to, or less than, radiography and ldCT may completely replace SIJ radiography. However, the role of spinal ldCT for spondyloarthritis is not clear and MRI is far superior for detecting disease activity.

Normal subchondral high T2 signal on MRI mimicking sacroiliitis in children: frequency, age distribution, and relationship to skeletal maturity.

OBJECTIVES: To determine patterns of variation of subchondral T2 signal changes in pediatric sacroiliac joints (SIJ) by location, age, sex, and sacral apophyseal closure. METHODS: MRI of 502 SIJ in 251 children (132 girls), mean age 12.4 years (range 6.1-18.0), was obtained with parental informed consent. One hundred twenty-seven out of 251 had asymptomatic joints and were imaged for non-rheumatologic reasons, and 124 had low back pain but no sign of sacroiliitis on initial clinical MRI review. After calibration, three subspecialist radiologists independently scored subchondral signal changes on fat-suppressed fluid-sensitive sequences from 0 to 3 in 4 locations, and graded the degree of closure of sacral segmental apophyses. Associations between patient age, sex, signal changes, and apophyseal closure were analyzed. RESULTS: Rim-like subchondral increased T2 signal or "flaring" was much more common at sacral than iliac SIJ margins (72% vs 16%, p < 0.001) and was symmetrical in > 90% of children. Iliac flaring scores were always lower than sacral, except for 1 child. Signal changes decreased as sacral apophyses closed, and were seen in < 20% of subjects with fully closed apophyses. Signal changes were more frequent in boys, and peaked in intensity later than for girls (ages 8-12 vs. 7-10). Subchondral signal in iliac crests was high throughout childhood and did not correlate with other locations. CONCLUSIONS: Subchondral T2 "flaring" is common at SIJ of prepubertal children and is generally sacral-predominant and symmetrical. Flaring that is asymmetrical, greater in ilium than sacrum, or intense in a teenager with closed apophyses, is unusual for normal children and raises concern for pathologic bone marrow edema. KEY POINTS: • A rim of subchondral high T2 signal is commonly observed on MRI at pediatric sacroiliac joints, primarily on the sacral side before segmental apophyseal closure, and should not be confused with pathology. • Unlike subchondral signal changes elsewhere, high T2 signal underlying the iliac crest apophyses is a near-universal normal finding in children that usually persists throughout adolescence. • The following patterns are unusual in normal children and are suspicious for pathology: definite iliac flaring, iliac flaring more intense than sacral flaring, left-right difference in flaring, definite flaring of any pattern in teenagers after sacral apophyseal closure.

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.

Magnetic resonance imaging findings in the normal pediatric sacroiliac joint space that can simulate disease.

BACKGROUND: Magnetic resonance imaging (MRI) features of active sacroiliac joint inflammation include joint space fluid and enhancement, but it is unclear to what extent these are present in normal children. OBJECTIVE: To describe normal MRI appearances of pediatric sacroiliac joint spaces in boys and girls of varying ages. MATERIALS AND METHODS: In this ethics-approved prospective study, 251 children (119 boys, 132 girls; mean age: 12.4 years, range: 6.1-18.0 years), had both oblique-coronal T1-weighted and short tau inversion recovery (STIR) sacroiliac joint MRI. Of these, 127 were imaged for other reasons and had asymptomatic sacroiliac joints ("normal cohort") while 124 had low back pain with no features of sacroiliitis on initial clinical MRI review ("low-back-pain cohort"). Post-gadolinium T1-weighted sequences were available in 16/127 normal and 124/124 low-back-pain subjects. Three experienced radiologists scored high signal in the sacroiliac joint space on STIR (score 0=absent; 1=high signal compared to normal bone marrow present anywhere in the joint but not as bright as fluid [compared to vessels, cerebrospinal fluid]; 2=definite fluid signal in part of the joint; 3=definite fluid signal, entire vertical height, majority of slices) and, when available, joint space post-contrast enhancement (0=no high signal/enhancement; 1=thin, symmetrical, mildly increased linear high signal present in the joint space; 2=focal, thick or intense enhancement). Associations between joint signal scores, age, gender and sacral apophyseal closure were analysed. RESULTS: Increased signal on STIR (score 1-3) was present in 74.7% of pediatric sacroiliac joint spaces, as intense as fluid in 18.4%. There was no significant difference in proportion by gender, side or cohort, but girls showed peak signal earlier than boys (10 years old vs. 12 years old, respectively). On post-gadolinium T1-weighted sequences, a thin rim of increased signal was nearly universally seen in sacroiliac joint spaces without focal, intense or thick post-contrast enhancement. CONCLUSION: Sacroiliac joint spaces of most children demonstrate mildly increased signal on STIR, compared to normal bone marrow, and thin rim-like enhancement on post-contrast T1 images, likely related to cartilage. These findings should not be confused with sacroiliitis.

Development of a technique for MRI gold-standard direct volumetric measurement of complex joint effusion, and validation at the hip.

OBJECTIVE: Accurate joint fluid quantification on MRI cannot simply rely on measuring the maximum fluid depth or using an ellipsoid approximation as this does not fully characterize the complex shape of a fluid-filled joint. As per the Outcome Measurement in Rheumatology (OMERACT) filter, we sought to evaluate the feasibility, reliability, and validity of a semi-automated supervised technique to quantify hip effusion volume. MATERIALS AND METHODS: Ninety-three hip osteoarthritis patients were imaged with coronal short TI inversion recovery (STIR) and sagittal intermediate weighted fat-suppressed (IWFS) sequences at two time points (Fig. 1). Volumetric quantitative measurement (VQM) of joint fluid and measurement of the largest femoral neck fluid thickness (FTM) was performed using the custom MATLAB software. Self-reported Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and clinical measures of pain, stiffness, and function were recorded. RESULTS: Inter-observer reliability was significantly higher for VQM than FTM (ICC = 0.96 vs. 0.85, p < 0.05). VQM and FTM correlated moderately (r = 0.76, p < 0.0001). There was significantly more articular fluid in symptomatic than asymptomatic hips at baseline (mean = 9.8 vs. 5.9 mL). Volumetric quantitative measurement generally displayed more frequent and stronger correlations to clinical parameters than FTM. Volumetric quantitative measurement required 3.9 min/hip vs. < 1 min/hip for femoral neck fluid thickness. CONCLUSION: Volumetric quantitative measurement of joint effusion can serve as an MRI gold-standard, could apply to other joints and collections, and is highly suited to future automation.

Central reader evaluation of MRI scans of the sacroiliac joints from the ASAS classification cohort: discrepancies with local readers and impact on the performance of the ASAS criteria.

OBJECTIVES: The Assessment of SpondyloArthritis international Society (ASAS) MRI working group conducted a multireader exercise on MRI scans from the ASAS classification cohort to assess the spectrum and evolution of lesions in the sacroiliac joint and impact of discrepancies with local readers on numbers of patients classified as axial spondyloarthritis (axSpA). METHODS: Seven readers assessed baseline scans from 278 cases and 8 readers assessed baseline and follow-up scans from 107 cases. Agreement for detection of MRI lesions between central and local readers was assessed descriptively and by the kappa statistic. We calculated the number of patients classified as axSpA by the ASAS criteria after replacing local detection of active lesions by central readers and replacing local reader radiographic sacroiliitis by central reader structural lesions on MRI. RESULTS: Structural lesions, especially erosions, were as frequent as active lesions (≈40%), the majority of patients having both types of lesions. The ASAS definitions for active MRI lesion typical of axSpA and erosion were comparatively discriminatory between axSpA and non-axSpA. Local reader overcall for active MRI lesions was about 30% but this had a minor impact on the number of patients (6.4%) classified as axSpA. Substitution of radiography with MRI structural lesions also had little impact on classification status (1.4%). CONCLUSION: Despite substantial discrepancy between central and local readers in interpretation of both types of MRI lesion, this had a minor impact on the numbers of patients classified as axSpA supporting the robustness of the ASAS criteria for differences in assessment of imaging.

Radiation Exposure to the Sacroiliac Joint From Low-Dose CT Compared With Radiography.

OBJECTIVE: The primary objective of this study was to estimate the effective dose delivered to the sacroiliac joint (SIJ) from low-dose (LD) CT compared with that from radiography. Secondary objectives included evaluation of diagnostic quality of LD CT of the SIJ and development of a clinical protocol for LD CT of the SIJ. MATERIALS AND METHODS: Data from 36 patients (19 women, 17 men) undergoing LD CT for suspected renal colic were analyzed. Two effective dose estimates were calculated: one for the SIJ and another for an extended region from the iliac crest to 1 cm below the SIJ. Thirty-six anteroposterior pelvic and 36 SIJ view radiographs were age-, sex-, and body width-matched to CT scans. Effective dose from radiography was estimated using the method described in International Commission on Radiologic Protection Publication 60. RESULTS: Maximum effective dose to the SIJ from LD CT was less than 1 mSv in all cases, with a mean ± SD of 0.42 ± 0.18 mSv (range, 0.14-0.83 mSv), whereas mean dose to the extended region was 0.57 ± 0.24 mSv (range, 0.19-1.11 mSv). Mean dose from SIJ radiographs was 0.15 ± 0.10 mSv (range, 0.07-1.38 mSv), and mean dose from a single pelvic radiograph was 0.09 ± 0.06 mSv (range, 0.04-0.37 mSv). All CT studies were of diagnostic quality for assessment of the SIJ. CONCLUSION: LD CT of the SIJ can be consistently performed with an effective radiation dose of less than 1 mSv. Because reliability and sensitivity of radiography for sacroiliitis is poor, we recommend that LD CT replace radiography for dedicated evaluation of the SIJ.

Defining active sacroiliitis on MRI for classification of axial spondyloarthritis: update by the ASAS MRI working group.

OBJECTIVES: To review and update the existing definition of a positive MRI for classification of axial spondyloarthritis (SpA). METHODS: The Assessment in SpondyloArthritis International Society (ASAS) MRI working group conducted a consensus exercise to review the definition of a positive MRI for inclusion in the ASAS classification criteria of axial SpA. Existing definitions and new data relevant to the MRI diagnosis and classification of sacroiliitis and spondylitis in axial SpA, published since the ASAS definition first appeared in print in 2009, were reviewed and discussed. The precise wording of the existing definition was examined in detail and the data and a draft proposal were presented to and voted on by the ASAS membership. RESULTS: The clear presence of bone marrow oedema on MRI in subchondral bone is still considered to be the defining observation that determines the presence of active sacroiliitis. Structural damage lesions seen on MRI may contribute to a decision by the observer that inflammatory lesions are genuinely due to SpA but are not required to meet the definition. The existing definition was clarified adding guidelines and images to assist in the application of the definition. CONCLUSION: The definition of a positive MRI for classification of axial SpA should continue to primarily depend on the imaging features of 'active sacroiliitis' until more data are available regarding MRI features of structural damage in the sacroiliac joint and MRI features in the spine and their utility when used for classification purposes.

Imaging in Spondyloarthritis: Controversies in Recognition of Early Disease.

Advanced imaging has become essential for recognition of clinically suspected early spondyloarthritis. This report summarizes recent progress towards a data-driven comprehensive definition of a positive sacroiliac joint MRI in axial spondyloarthritis, which incorporates contextual information provided by structural lesions alongside with active changes. A focus is on emerging limitations and challenges with increasing use of imaging in spondyloarthritis. We discuss the ongoing controversy as to whether sacroiliac joint MRI due to its superior reliability and ability to depict both structural and active lesions should be the preferred imaging modality in early disease over the traditional approach with pelvic radiographs. Another challenge is transferring the expanding knowledge about imaging evaluation in spondyloarthritis to the community of rheumatologists and radiologists. Advanced imaging modalities will not become the gold standard for diagnosis of spondyloarthritis, which remains a process of composite deduction based on complementary information obtained from clinical, laboratory, and imaging assessment.

Does spinal MRI add incremental diagnostic value to MRI of the sacroiliac joints alone in patients with non-radiographic axial spondyloarthritis?

OBJECTIVE: To assess the incremental diagnostic value of spine MRI evaluated separately from and combined with sacroiliac joint (SIJ) MRI in non-radiographic axial spondyloarthritis (nr-axSpA) compared with SIJ MRI alone. METHODS: The study sample comprised two independent cohorts A/B of 130 consecutive patients aged ≤50 years with back pain, newly referred to two university clinics, and 20 healthy controls. Patients were classified according to clinical examination and pelvic radiographs as having nr-axSpA (n=50), ankylosing spondylitis (n=33), or non-specific back pain (n=47). Four readers assessed SIJ and spine MRI separately 6 months apart, and 1-12 months later both scans simultaneously using standardised modules. Readers recorded presence/absence of SpA and their level of confidence in this conclusion on a 0-10 scale (0=definitely not; 10=definite). We analysed differences between SIJ MRI versus spine MRI alone, and SIJ MRI alone versus combined MRI, descriptively by the number/percentage of subjects according to the mean of four readers. RESULTS: In cohorts A/B, 15.8%/24.2% of patients with nr-axSpA having a negative SIJ MRI were reclassified as being positive for SpA by global evaluation of combined scans. However, 26.8%/11.4% of non-specific back pain controls and 17.5% of healthy volunteers with a negative SIJ MRI were falsely reclassified as having SpA by combined MRI. Low confidence in a diagnosis of SpA by SIJ MRI increased to high confidence by combined MRI in 6.6%/7.3% of patients with nr-axSpA. CONCLUSIONS: Combined spine and SIJ MRI added little incremental value compared with SIJ MRI alone for diagnosing patients with nr-axSpA and enhancing confidence in this diagnosis.

Candidate lesion-based criteria for defining a positive sacroiliac joint MRI in two cohorts of patients with axial spondyloarthritis.

OBJECTIVE: To determine candidate lesion-based criteria for a positive sacroiliac joint (SIJ) MRI based on bone marrow oedema (BMO) and/or erosion in non-radiographic axial spondyloarthritis (nr-axSpA); to compare the performance of lesion-based criteria with global evaluation by expert readers. METHODS: Two independent cohorts A/B of 69/88 consecutive patients with back pain aged ≤50 years, with median symptom duration 1.3/10.0 years, were referred for suspected SpA (A) or acute anterior uveitis plus back pain (B). Patients were classified according to rheumatologist expert opinion based on clinical examination, pelvic radiography and laboratory values as having nr-axSpA (n=51), ankylosing spondylitis (n=34) or non-specific back pain (n=72). Four blinded readers assessed SIJ MRI, recording the presence/absence of SpA by concomitant global evaluation of T1-weighted spin echo (T1SE) and short τ inversion recovery (STIR) scans and, thereafter, whether BMO and/or erosion were present/absent in each SIJ quadrant of each MRI slice. We derived candidate lesion-based criteria based on the number of SIJ quadrants with BMO and/or erosion and calculated mean sensitivity and specificity for SpA. RESULTS: For both cohorts A/B, global assessment showed high specificity (0.95/0.83) compared with the Assessment in SpondyloArthritis international Society (ASAS) definition (0.76/0.74). BMO ≥3 (0.89/0.84) or ≥4 (0.92/0.87) showed comparably high specificity to global assessment. Erosion ≥2 and/or BMO ≥3 or ≥4 were associated with comparably high sensitivity to global assessment without affecting specificity. These combined criteria showed both higher sensitivity and specificity than the ASAS definition. CONCLUSIONS: Lesion-based criteria for a positive SIJ MRI based on both BMO and/or erosion performed best for classification of axial SpA, reflecting the contextual information provided by T1SE and STIR sequences.

Percutaneous vertebroplasty for osteoporotic vertebral compression fracture.

BACKGROUND: Percutaneous vertebroplasty is widely used to treat acute and subacute painful osteoporotic vertebral fractures although recent placebo-controlled trials have questioned its value. OBJECTIVES: To synthesise the available evidence regarding the benefits and harms of vertebroplasty for treatment of osteoporotic vertebral fractures. SEARCH METHODS: We searched CENTRAL, MEDLINE and EMBASE up to November 2014. We also reviewed reference lists of review articles, trials and trial registries to identify any other potentially relevant trials. SELECTION CRITERIA: We included randomised and quasi-randomised controlled trials (RCTs) including adults with painful osteoporotic vertebral fractures of any duration and comparing vertebroplasty with placebo (sham), usual care, or any other intervention. As it is least prone to bias, vertebroplasty compared with placebo was the primary comparison. Major outcomes were mean overall pain, disability, disease-specific and overall health-related quality of life, patient-reported treatment success, new symptomatic vertebral fractures and number of other serious adverse events. DATA COLLECTION AND ANALYSIS: At least two review authors independently selected trials for inclusion, extracted data, performed 'Risk of bias' assessment and assessed the quality of the body of evidence for the main outcomes using GRADE. MAIN RESULTS: Eleven RCTs and one quasi-RCT conducted in various countries were included. Two trials compared vertebroplasty with placebo (209 randomised participants), six compared vertebroplasty with usual care (566 randomised participants) and four compared vertebroplasty with kyphoplasty (545 randomised participants). Trial size varied from 34 to 404 participants, most participants were female, mean age ranged between 63.3 and 80 years, and mean symptom duration varied from a week to more than six months.Both placebo-controlled trials were judged to be at low overall risk of bias while other included trials were generally considered to be at high risk of bias across a range of criteria, most seriously due to lack of participant and study personnel blinding.Compared with placebo, there was moderate quality evidence based upon two trials that vertebroplasty provides no demonstrable benefits with respect to pain, disability, disease-specific or overall quality of life or treatment success. At one month, mean pain (on a scale 0 to 10, higher scores indicate more pain) was 5 points with placebo and 0.7 points better (1.5 better to 0.15 worse) with vertebroplasty, an absolute pain reduction of 7% (15% better to 1.5% worse) and relative reduction of 10% (21% better to 2% worse) (two trials, 201 participants). At one month, mean disability measured by the Roland Morris Disability Questionnaire (scale range 0 to 23, higher scores indicate worse disability) was 13.6 points in the placebo group and 1.1 points better (2.9 better to 0.8 worse) in the vertebroplasty group, absolute improvement in disability 4.8% (12.8% better to 3.3% worse), relative change 6.3% better (17.0% better to 4.4% worse) (two trials, 201 participants).At one month, disease-specific quality of life measured by the QUALEFFO (scale 0 to 100, higher scores indicating worse quality of life) was 2.4 points in the placebo group and 0.40 points worse (4.58 better to 5.38 worse) in the vertebroplasty group, absolute change: 0.4% worse (5% worse to 5% better), relative change 0.7% worse (9% worse to 8% better (based upon one trial, 73 participants). At one month overall quality of life measured by the EQ5D (0 = death to 1 = perfect health, higher scores indicate greater quality of life at one month was 0.27 points in the placebo group and 0.05 points better (0.01 worse to 0.11 better) in the vertebroplasty group, absolute improvement in quality of life 5% (1% worse to 11% better), relative change 18% better (4% worse to 39% better) (two trials, 201 participants). Based upon one trial (78 participants) at one month, 9/40 (or 225 per 1000) people perceived that treatment was successful in the placebo group compared with 12/38 (or 315 per 1000; range 150 to 664) in the vertebroplasty group, RR 1.40 (95% CI 0.67 to 2.95), absolute risk difference 9% more reported success (11% fewer to 29% more); relative change 40% more reported success (33% fewer to 195% more).Based upon moderate quality evidence from three trials (one placebo, two usual care, 281 participants) with up to 12 months follow-up, we are uncertain whether or not vertebroplasty increases the risk of new symptomatic vertebral fractures (28/143 observed in the vertebroplasty group compared with 19/138 in the control group; RR 1.47 (95% CI 0.39 to 5.50).Similary, based upon moderate quality evidence from two placebo-controlled trials (209 participants), we are uncertain about the exact risk of other adverse events (3/106 were observed in the vertebroplasty group compared with 3/103 in the placebo group; RR 1.01 (95% CI 0.21 to 4.85)). Notably, serious adverse events reported with vertebroplasty included osteomyelitis, cord compression, thecal sac injury and respiratory failure.Our subgroup analyses provided limited evidence that the effects did not differ according to duration of pain ≤ 6 weeks versus > 6 weeks. Including data from the six trials that compared vertebroplasty with usual care in a sensitivity analyses inconsistently altered the primary results, with all combined analyses displaying substantial to considerable heterogeneity. AUTHORS' CONCLUSIONS: Based upon moderate quality evidence, our review does not support a role for vertebroplasty for treating osteoporotic vertebral fractures in routine practice. We found no demonstrable clinically important benefits compared with a sham procedure and subgroup analyses indicated that results did not differ according to duration of pain ≤ 6 weeks versus > 6 weeks. Sensitivity analyses confirmed that open trials comparing vertebroplasty with usual care are likely to have overestimated any benefit of vertebroplasty. Correcting for these biases would likely drive any benefits observed with vertebroplasty towards the null, in keeping with findings from the placebo-controlled trials.Numerous serious adverse events have been observed following vertebroplasty. However due to the small number of events, we cannot be certain about whether or not vertebroplasty results in a clinically important increased risk of new symptomatic vertebral fractures and/or other serious adverse events. Patients should be informed about both the lack of high quality evidence supporting benefit of vertebroplasty and its potential for harm.

Blurring and Irregularity of the Subchondral Cortex in Pediatric Sacroiliac Joints on T1 Images: Incidence of Normal Findings That Can Mimic Erosions.

OBJECTIVE: To determine prevalence of variations of subchondral bone appearance that may mimic erosions on T1-weighted magnetic resonance imaging (MRI) of pediatric sacroiliac (SI) joints according to age and sex. METHODS: With ethics committee approval and informed consent, SI joint MRIs of 251 children (132 girls), mean age 12.4 years (range 6.1-18.0 years), were obtained in 2 cohorts: 127 children imaged for nonrheumatic reasons, and 124 children with low back pain but no features of sacroiliitis at initial clinical MRI review. MRIs were reviewed by 3 experienced radiologists, blinded from each other, for 3 features of the cortical black line representing the subchondral bone plate on T1-weighted MRI: visibility, blurring, and irregularity. RESULTS: Based on agreement from 2 or more readers, the cortical black line was partially absent in 88.4% of the children, blurred in 34.7%, and irregular in 41.4%. All these features were most common on the iliac side of SI joints and at the first sacral vertebra level. Clearly visualized, sharply delineated SI joints with none of these features were seen in only 8.0% of children, or in 35.1% if we conservatively required agreement of all 3 readers to consider a feature present. There was no significant difference between sexes or cohorts; findings were similar across pediatric age groups. CONCLUSION: Understanding the normal MRI appearance of the developing SI joint is necessary to distinguish physiologic findings from disease. At least two-thirds (65%) of normal pediatric SI joints showed at least 1 feature that is a component of the adult definition of SI joint erosions, risking overdiagnosis of sacroiliitis.

Focal fat lesions at vertebral corners on magnetic resonance imaging predict the development of new syndesmophytes in ankylosing spondylitis.

OBJECTIVE: Focal fat infiltration is frequently visible on magnetic resonance imaging (MRI) of the spine in patients with ankylosing spondylitis (AS) and likely reflects postinflammatory tissue metaplasia. To support the concept of coupling between inflammation and new bone formation, we tested the hypothesis that focal fat infiltration at a vertebral corner is more likely to evolve into a de novo syndesmophyte. METHODS: MRI scans were obtained at baseline and radiographs were obtained at baseline and 2 years in 100 AS patients from 2 cohorts: a clinical trial cohort (n = 38) and an observational cohort (n = 62). In the clinical trial cohort, patients were randomized to receive anti-tumor necrosis factor (anti-TNF) therapy or placebo for 12-24 weeks and then open-label treatment for 2 years. In the observational cohort, patients received either standard therapy (n = 36) or anti-TNF therapy (n = 26) for 2 years. Vertebral corner inflammation and fat infiltration were assessed independently by pairs of readers who were blinded with regard to the radiographic findings. RESULTS: New syndesmophytes developed significantly more frequently in vertebral corners with fat in both the clinical trial (10.2%) and the observational (6.5%) cohort as compared to those without either feature on baseline MRI (3.1% [P = 0.008] and 1.4% [P = 0.0002], respectively). Adjusting for within-patient variations in baseline syndesmophytes/ankylosis, vertebral corners that were fat-positive/inflammation-positive significantly predicted new syndesmophytes, with an odds ratio (OR) of 7.6 (95% confidence interval [95% CI] 1.5-38.5 [P = 0.01]), while a model that included baseline variations in both fat and inflammation showed an OR of 5.8 (95% CI 2.2-15.3 [P < 0.001]) for inflammation and an OR of 1.9 (95% CI 0.9-4.1 [P = 0.1]) for fat. CONCLUSION: Our data lend support to the hypothesis that inflammatory lesions evolve into new bone through a process of tissue metaplasia that includes fat infiltration.

Radiographic progression is associated with resolution of systemic inflammation in patients with axial spondylarthritis treated with tumor necrosis factor α inhibitors: a study of radiographic progression, inflammation on magnetic resonance imaging, and circulating biomarkers of inflammation, angiogenesis, and cartilage and bone turnover.

OBJECTIVE: To investigate the relationship of circulating biomarkers of inflammation (C-reactive protein [CRP], interleukin-6 [IL-6], and YKL-40), angiogenesis (vascular endothelial growth factor), cartilage turnover (C-terminal crosslinking telopeptide of type II collagen [CTX-II], total aggrecan, matrix metalloproteinase 3 [MMP-3], and cartilage oligomeric matrix protein [COMP]), and bone turnover (CTX-I and osteocalcin) to inflammation on magnetic resonance imaging (MRI) and radiographic progression in patients with axial spondylarthritis (SpA) beginning tumor necrosis factor α (TNFα) inhibitor therapy. METHODS: MRIs were evaluated according to the Berlin sacroiliac (SI) joint and spine inflammation scoring method at baseline, week 22, and week 46. Radiographs were evaluated using the modified Stoke Ankylosing Spondylitis Spine Score at baseline and week 46. Patients with new syndesmophytes were identified. Biomarker levels in patients were compared to levels in healthy subjects. RESULTS: Higher pretreatment MRI inflammation scores for SI joints and/or lumbar spine were associated with higher baseline CTX-II levels, but not with higher levels of biomarkers of inflammation and bone turnover. During treatment with TNFα inhibitors, a decrease in MRI inflammation scores from baseline to week 22 was associated with larger percentage decreases in and a normalization of CRP and IL-6 levels as compared to an increase or no change in MRI scores. Development of new syndesmophytes was associated with larger percentage decreases in CRP and IL-6 levels and an increase in osteocalcin level, and with normalization of CRP and IL-6 levels from baseline to week 22. Persistent systemic inflammation was associated with radiographic nonprogression. CONCLUSION: Our findings indicate that inflammation on baseline MRI is associated with higher CTX-II levels. Radiographic progression is associated with decreased systemic inflammation, as assessed by IL-6 and CRP levels and MRI, supporting the notion of a link between the resolution of inflammation and new bone formation in SpA patients during anti-TNFα therapy.

Advanced imaging of the axial skeleton in spondyloarthropathy: techniques, interpretation, and utility.

The development of available treatments for spondyloarthritis increases the need for accurate diagnosis and objective monitoring of response to therapy. Advances in MRI technology are improving the effectiveness of imaging of the sacroiliac joints and spine in spondyloarthritis. We discuss best practice techniques for MR image acquisition and interpretation with a view to optimizing the diagnostic utility of MRI in spondyloarthritis.

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.

The diagnostic utility of magnetic resonance imaging in spondylarthritis: an international multicenter evaluation of one hundred eighty-seven subjects.

OBJECTIVE: To systematically assess the diagnostic utility of magnetic resonance imaging (MRI) to differentiate patients with spondylarthritis (SpA) from patients with nonspecific back pain and healthy volunteers, using a standardized evaluation of MR images of the sacroiliac joints. METHODS: Five readers blinded to the patients and diagnoses independently assessed MRI scans (T1-weighted and STIR sequences) of the sacroiliac joints obtained from 187 subjects: 75 patients with ankylosing spondylitis (AS; symptom duration ≤ 10 years), 27 patients with preradiographic inflammatory back pain (IBP; mean symptom duration 29 months), 26 patients with nonspecific back pain, and 59 healthy control subjects; all participants were age 45 years or younger. Bone marrow edema, fat infiltration, erosion, and ankylosis were recorded according to standardized definitions using an online data entry system. We calculated sensitivity, specificity, and positive and negative likelihood ratios (LRs) for the diagnosis of SpA based on global assessment of the MRI scans. RESULTS: Diagnostic utility was high for all 5 readers, both for patients with AS (sensitivity 0.90, specificity 0.97, positive LR 44.6) and for patients with preradiographic IBP (sensitivity 0.51, specificity 0.97, positive LR 26.0). Diagnostic utility based solely on detection of bone marrow edema enhanced sensitivity (67%) for patients with IBP but reduced specificity (88%); detection of erosions in addition to bone marrow edema further enhanced sensitivity (81%) without changing specificity. A single lesion of the sacroiliac joint on MRI was observed in up to 27% of control subjects. CONCLUSION: This systematic and standardized evaluation of sacroiliac joints in patients with SpA showed that MRI has much greater diagnostic utility than has been documented previously. We present for the first time a data-driven definition of MRI-visualized positivity for SpA.

The impact of MRI on the clinical management of inflammatory arthritides.

In the past two decades, MRI has gained a major role in research and clinical management of patients with inflammatory arthritides, particularly in spondyloarthritis (SpA), rheumatoid arthritis (RA), and osteoarthritis (OA). MRI is regarded as the most sensitive imaging modality for detecting early SpA in young patients with inflammatory back pain and normal radiographs of the sacroiliac joints. The recently published Assessment of SpondyloArthritis International Society classification criteria for axial SpA include for the first time a positive MRI demonstrating sacroiliitis as an imaging criterion indicative of SpA together with at least one clinical feature of SpA. Recent data show that systematic assessment of sacroiliitis displayed on MRI has much greater diagnostic utility than previously reported and highlight the diagnostic relevance of structural lesions. In RA, MRI has predictive value for the development of disease in new onset undifferentiated arthritis, and MR pathology at disease onset is a highly significant predictor of radiographic erosions. Consequently MRI has been credited with an important role in the new ACR/EULAR 2010 classification criteria for RA. In OA, bone marrow edema (BME) and synovitis may serve as biomarkers in interventional trials. Treatment interventions targeting BME and synovitis observed on MRI in inflammatory arthritides may have a disease-modifying effect as these lesions are potentially reversible and have been shown to be associated with structural progression. Research should focus on the prognostic significance of MRI lesions in larger cohorts and whether adding MRI to routine care improves clinical and radiographic outcome in patients with inflammatory arthritides.

Volumetric quantitative measurement of hip effusions by manual versus automated artificial intelligence techniques: An OMERACT preliminary validation study.

OBJECTIVE: Preliminary assessment, via OMERACT filter, of manual and automated MRI hip effusion Volumetric Quantitative Measurement (VQM). METHODS: For 358 hips (93 osteoarthritis subjects, bilateral, 2 time points), 2 radiologists performed manual VQM using custom Matlab software. A Mask R-CNN artificial-intelligence (AI) tool was trained to automatically compute joint fluid volumes. RESULTS: Manual VQM had excellent inter-observer reliability (ICC 0.96). AI predicted hip fluid volumes with ICC 0.86 (status), 0.58 (change) vs. 2 human readers. CONCLUSION: Hip joint fluid volumes are reliably assessed by VQM. It is feasible to automate this approach using AI, with promising initial reliability.