Standardized reporting of spine and sacroiliac joints in axial spondyloarthritis MRI: from the ESSR-Arthritis Subcommittee.

OBJECTIVES: Apply a modified Delphi-based approach and produce a practical, radiology-specific set of definitions for interpretation and standardization of the multiple MRI findings in axial spondyloarthritis (ax-SpA), specifically to aid the general radiologist with a musculoskeletal interest, working with gold standard basic MRI protocols. MATERIALS AND METHODS: We report the results of a modified Delphi-based consensus of 35 experts from 13 countries in the Arthritis Subcommittee of the European Society of Musculoskeletal Radiology (ESSR). Seventeen definitions were created (i.e., nine for the spine and eight for the sacroiliac joint) and two Delphi rounds were conducted on an electronic database, collated and revised by the project leader with agreement. Group leads were appointed for each definition following the first round. Final definitions included only those that reached a consensus > 80%; if > 50% agreed on exclusion consensus, definitions were excluded. Final results have been shared during the Arthritis meeting at the Annual ESSR Congress. RESULTS: Fourteen definitions, eight for the spine and six for the sacroiliac joint were agreed for standardized reporting. Andersson's, anterior corner sclerotic and costovertebral joint inflammatory lesions of the spine, with active and non-active erosions, and fat metaplasia of the sacroiliac joint reaching the highest consensus (≥ 95%). More than 50% of the experts agreed to exclude joint space inflammation in the sacroiliac joint and tissue backfill. Syndesmophytes reached 76% agreement. CONCLUSIONS: Agreed definitions by expert radiologists using a modified Delphi process, should allow standardized actionable radiology reports and clarity in reporting terminology of ax-SpA. CLINICAL RELEVANCE STATEMENT: The proposed definitions will support reporting from musculoskeletal and general radiologists working with gold-standard basic MRI, improve confidence in lesion assessment, and standardize terminology to provide actionable reports on MRI in patients with ax-SpA. KEY POINTS: Experts applied a modified Delphi method to optimize the definitions of MRI findings of ax-SpA. After two Delphi rounds and one in-person meeting, fourteen definitions reached the agreement threshold. These consensus-based definitions will aid in actionable reporting specifically for the general radiologist with a musculoskeletal interest.

Current Role of Conventional Radiography of Sacroiliac Joints in Adults and Juveniles with Suspected Axial Spondyloarthritis: Opinion from the ESSR Arthritis and Pediatric Subcommittees.

This opinion article by the European Society of Musculoskeletal Radiology Arthritis and Pediatric Subcommittees discusses the current use of conventional radiography (CR) of the sacroiliac joints in adults and juveniles with suspected axial spondyloarthritis (axSpA). The strengths and limitations of CR compared with magnetic resonance imaging (MRI) and computed tomography (CT) are presented.Based on the current literature and expert opinions, the subcommittees recognize the superior sensitivity of MRI to detect early sacroiliitis. In adults, supplementary pelvic radiography, low-dose CT, or synthetic CT may be needed to evaluate differential diagnoses. CR remains the method of choice to detect structural changes in patients with suspected late-stage axSpA or established disease and in patients with suspected concomitant hip or pubic symphysis involvement. In children, MRI is the imaging modality of choice because it can detect active as well as structural changes and is radiation free.

Diagnostic accuracy of high-resolution peripheral quantitative computed tomography and X-ray for classifying erosive rheumatoid arthritis.

OBJECTIVE: To investigate whether high-resolution peripheral quantitative CT (HR-pQCT) of two metacarpophalangeal (MCP) joints can more accurately classify patients as having erosive RA compared with conventional radiography (CR) of 44 joints in the hands, wrists and feet. METHODS: In this single-centre cross-sectional study, patients with established RA (disease duration ≥5 years) were investigated by HR-pQCT and CR. The second and third MCP joints of the dominant hand were assessed for erosions by HR-pQCT. CR of the hands, wrists and feet were scored according to the Sharp-van der Heijde (SHS) method. RESULTS: In total, 353 patients were included; 66 (18.7%) patients were classified as having non-erosive RA, and 287 (81.3%) had erosive RA by CR. The sensitivity and specificity (95% CI) of HR-pQCT for classifying patients as having erosive RA when standard CR of hands, wrists and feet was used as the reference was 89% (84, 92%) and 30% (20, 43%), respectively. Using HR-pQCT as the reference, the sensitivity and specificity of CR for classifying patients having erosive RA were 85% (80, 89%) and 38% (25, 52%), respectively. McNemar's χ2 test showed no significant difference between the sensitivities of patients classified as having erosive RA by HR-pQCT or by CR (2.14, P = 0.177). CONCLUSION: The diagnostic accuracy of HR-pQCT scanning of only two MCP joints and CR of 44 joints suggests the two modalities were comparable for classifying patients with established RA as having erosive disease. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (NCT03429426).

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

BACKGROUND: Pregnancy-related pain may be associated with sacroiliac joint (SIJ) changes, detectable by magnetic resonance imaging (MRI). PURPOSE: To analyze the prevalence and course of SIJ MRI and clinical findings in women referred with low back pain and relate these to pregnancy. MATERIAL AND METHODS: A retrospective follow-up study from a longitudinally collected cohort comprising 328 women. RESULTS: Women reporting debut of pain in relation to a pregnancy (PP group) tended to have a higher baseline prevalence of all investigated MRI findings, cumulated positive SIJ tests, and a potential fulfilment of the spondyloarthritis diagnosis compared to remainders. The prevalence of subchondral bone marrow edema (BME), any SIJ MRI finding, and potential fulfilment of the spondyloarthritis diagnosis were significantly higher in the PP group compared to women who had not been pregnant. In the total study group, the prevalence of ≥1 MRI finding increased over the four-year study period from 34% to 47% (P<0.001), driven by increasing prevalence of BME (25% to 32%; P=0.008) and fatty marrow deposition (FMD) (20% to 25%; P=0.020). In addition, the BME volume score increased. Over time, the PP group had persisting high prevalence of buttock pain and total MRI findings and their FMD volume score increased, but there were no between-group differences in MRI variables at follow-up. CONCLUSION: Overall, the prevalence of MRI findings increased over time. Although the PP group had different clinical and SIJ MRI characteristics cross-sectional at baseline compared to remainders, longitudinal analyses revealed that these diminished over time.

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

OBJECTIVE: To estimate the prevalence of atypical anatomical morphologies at the sacroiliac joints (SIJ) in young adults by CT and analyze the diagnostic ability of MRI to detect the variations in addition to concomitant MRI findings that could be misdiagnosed as inflammatory changes. MATERIALS AND METHODS: The study sample constituted CT examinations of 155 individuals aged 18-40 years and prospectively collected comparative SIJ MRI examinations of 49, who also filled out a questionnaire on back and buttock pain. The CT and MRIs were analyzed by two musculoskeletal radiologists regarding seven SIJ variations and additional subchondral bone marrow edema (BME) by MRI. RESULTS: CT and MRI interobserver agreements were good or very good for most variations. Mean age of the 155 individuals was 28 years, 99 (64%) were males; 88 (57%) had at least one SIJ variation, and most frequent were dysmorphic cartilaginous joint facets (n = 33, 21%), bipartite iliac bony plate (n = 27, 17%), accessory SIJ (n = 24, 16%), and iliosacral complex (n = 18, 12%), with a female predominance of all variations. The ability of MRI to detect the frequent variations was satisfying. Dysmorphic cartilaginous joint facets, accessory SIJ, and iliosacral complex were frequently observed in individuals reporting symptoms and were accompanied by BME, often located anteriorly in sacrum/inferiorly in ilium. CONCLUSION: Atypical SIJ morphology is frequent in young adults, especially females, demanding further research into the anatomical natural variation. Most of the variations were detectable by MRI and three variations warrant further exploration as they often were accompanied by symptoms and/or BME.

Prognostic value of the clinical and imaging arm of the ASAS criteria for progression of structural sacroiliac joint lesions.

OBJECTIVE: To investigate the prognostic value of the two arms of the Assessment of SpondyloArthritis international Society (ASAS) criteria regarding the progression of structural lesions in the sacroiliac joints (SIJ). METHODS: Information on baseline fulfilment of the ASAS criteria and baseline and follow-up magnetic resonance imaging of the SIJ in 603 patients aged 18-40 years, referred with low back pain to an outpatient spine were collected. MRI-positivity was defined as bone marrow oedema (BMO) in ≥2 consecutive slices or ≥2 lesions in 1 slice, as described in ASAS definition of sacroiliitis. RESULTS: Of 71 participants fulfilling the ASAS criteria at baseline, 66(93%) fulfilled the 'imaging arm' and 14(20%) the 'clinical arm'. The 'clinical arm' predicted progression of erosions with an odds ratio of 55 (compared with not fulfilling the ASAS criteria), while the 'imaging arm' predicted progression of erosions with an odds ratio of 8. Moreover, in 24% of patients in the 'imaging arm', all having BMO at the SIJ at baseline, the BMO disappeared without neither erosions nor ankylosis emerging. CONCLUSION: We found that the 'clinical arm' was a strong predictor for progression of sacroiliac joint erosion, while the 'imaging arm' had a more modest prognostic value for structural progression.

MRI of the sacroiliac joints in athletes: recognition of non-specific bone marrow oedema by semi-axial added to standard semi-coronal scans.

OBJECTIVE: Assessment of combined semi-axial and semi-coronal SI joint MRI in two cohorts of young athletes to explore frequency and topography of non-specific bone marrow oedema (BMO), its association with four constitutional SI joint features, and potential restriction of false-positive assignments of Assessment of SpondyloArthritis International Society-defined sacroiliitis on standard semi-coronal scans alone. METHODS: Combined semi-axial and semi-coronal SI joint MRI scans of 20 recreational runners before/after running and 22 elite ice-hockey players were evaluated by three blinded readers for BMO and its association with four constitutional SI joint features: vascular partial volume effect, deep iliac ligament insertion, fluid-filled bone cyst and lumbosacral transitional anomaly. Scans of TNF-treated spondyloarthritis patients served to mask readers. We analysed distribution and topography of BMO and SI joint features across eight anatomical SI joint regions (upper/lower ilium/sacrum, subdivided in anterior/posterior slices) descriptively, as concordantly recorded by ⩾2/3 readers on both MRI planes. BMO confirmed on both scans was compared with previous evaluation of semi-coronal MRI alone, which met the Assessment of SpondyloArthritis International Society definition for active sacroiliitis. RESULTS: Perpendicular semi-axial and semi-coronal MRI scans confirmed BMO in the SI joint of every fourth young athlete, preferentially in the anterior upper sacrum. BMO associated with four constitutional SI joint features was observed in 20-36% of athletes, clustering in the posterior lower ilium. The proportion of Assessment of SpondyloArthritis International Society-positive sacroiliitis recorded on the semi-coronal plane alone decreased by 33-56% upon amending semi-axial scans. CONCLUSION: Semi-axial combined with standard semi-coronal scans in MRI protocols for sacroiliitis facilitated recognition of non-specific BMO, which clustered in posterior lower ilium/anterior upper sacrum.

Imaging to Differentiate the Various Forms of Seronegative Arthritis.

Spondyloarthritis (SpA) is a group of diseases characterized by back pain, spinal inflammation, human leukocyte antigen-B27 positivity, and peripheral findings such as dactylitis, enthesitis, and uveitis. It includes ankylosing spondylitis, psoriatic arthritis, reactive arthritis, arthritis associated with inflammatory bowel disease, and undifferentiated SpA. The role of imaging in the diagnosis, management, and follow-up of patients with SpA has become dramatically more important with the introduction of new therapies such as tumor necrosis factor-α inhibitors. Although in many instances differentiating between the SpA entities is straightforward based on the clinical presentation, often such differentiation remains challenging, and categorization of an individual patient into a subset of SpA can be difficult. Imaging, mainly radiography and magnetic resonance imaging, serves as an important diagnostic tool. Diseases in the spondyloarthritis complex share common presentation but at the same time may have distinct radiographic phenotypes. We present these common and distinct imaging manifestations that may potentially help distinguish between the entities in the diagnostic work-up.

Prevalence of degenerative and spondyloarthritis-related magnetic resonance imaging findings in the spine and sacroiliac joints in patients with persistent low back pain.

OBJECTIVE: To estimate the prevalence of degenerative and spondyloarthritis (SpA)-related magnetic resonance imaging (MRI) findings in the spine and sacroiliac joints (SIJs) and analyse their association with gender and age in persistent low back pain (LBP) patients. METHODS: Degenerative and SpA-related MRI findings in the whole spine and SIJs were evaluated in Spine Centre patients aged 18-40 years with LBP. RESULTS: Among the 1,037 patients, the prevalence of disc degeneration, disc contour changes and vertebral endplate signal (Modic) changes were 87 % (±SEM 1.1), 82 % (±1.2) and 48 % (±1.6). All degenerative spinal findings were most frequent in men and patients aged 30-40 years. Spinal SpA-related MRI findings were rare. In the SIJs, 28 % (±1.4) had at least one MRI finding, with bone marrow oedema being the most common (21 % (±1.3)). SIJ erosions were most prevalent in patients aged 18-29 years and bone marrow oedema in patients aged 30-40 years. SIJ sclerosis and fatty marrow deposition were most common in women. SIJ bone marrow oedema, sclerosis and erosions were most frequent in women indicating pregnancy-related LBP. CONCLUSION: The high prevalence of SIJ MRI findings associated with age, gender, and pregnancy-related LBP need further investigation of their clinical importance in LBP patients. KEY POINTS: • The location of vertebral endplate signal changes supports a mechanical aetiology. • Several sacroiliac joint findings were associated with female gender and pregnancy-related back pain. • Sacroiliac joint bone marrow oedema was frequent and age-associated, indicating a possible degenerative aetiology. • More knowledge of the clinical importance of sacroiliac joint MRI findings is needed.

Recommendations of the ESSR Arthritis Subcommittee on Ultrasonography in Inflammatory Joint Disease.

This article presents the recommendations of the European Society of Musculoskeletal Radiology Arthritis Subcommittee on the use of ultrasonography (US) in rheumatic disease, focused on the examination of joints in the adult population. The recommended examination technique and protocols used in a radiologic work-up are discussed. The main US features that can lead to a final diagnosis in the most common rheumatic diseases are addressed. The differential diagnosis that should be considered at image interpretation is presented. The role of US in interventional procedures and clinically important recent developments is also discussed.

Glenohumeral joint kinematics during apprehension-relocation test in patients with anterior shoulder instability and glenoid bone loss.

Aims: This study aimed to quantify the shoulder kinematics during an apprehension-relocation test in patients with anterior shoulder instability (ASI) and glenoid bone loss using the radiostereometric analysis (RSA) method. Kinematics were compared with the patient's contralateral healthy shoulder. Methods: A total of 20 patients with ASI and > 10% glenoid bone loss and a healthy contralateral shoulder were included. RSA imaging of the patient's shoulders was performed during a repeated apprehension-relocation test. Bone volume models were generated from CT scans, marked with anatomical coordinate systems, and aligned with the digitally reconstructed bone projections on the RSA images. The glenohumeral joint (GHJ) kinematics were evaluated in the anteroposterior and superoinferior direction of: the humeral head centre location relative to the glenoid centre; and the humeral head contact point location on the glenoid. Results: During the apprehension test, the centre of the humeral head was 1.0 mm (95% CI 0.0 to 2.0) more inferior on the glenoid for the ASI shoulder compared with the healthy shoulder. Furthermore, the contact point of the ASI shoulder was 1.4 mm (95% CI 0.3 to 2.5) more anterior and 2.0 mm (95% CI 0.8 to 3.1) more inferior on the glenoid compared with the healthy shoulder. The contact point of the ASI shoulder was 1.2 mm (95% CI 0.2 to 2.6) more anterior during the apprehension test compared to the relocation test. Conclusion: The humeral head centre was located more inferior, and the GHJ contact point was located both more anterior and inferior during the apprehension test for the ASI shoulders than the healthy shoulders. Furthermore, the contact point displacement between the apprehension and relocation test revealed increased joint laxity for the ASI shoulder than the healthy shoulders. These results contribute to existing knowledge that ASI shoulders with glenoid bone loss may also suffer from inferior shoulder instability.

Spondyloarthritis-related and degenerative MRI changes in the axial skeleton--an inter- and intra-observer agreement study.

BACKGROUND: The Back Pain Cohort of Southern Denmark (BaPa Cohort) was initiated with the aim of evaluating the clinical relevance of magnetic resonance imaging (MRI) in the diagnosis of early spondyloarthritis (SpA). In order to facilitate the collection of MRI data for this study, an electronic evaluation form was developed including both SpA-related and degenerative axial changes. The objective of the current study was to assess the intra- and inter-observer agreement of the MRI changes assessed. METHODS: Three radiologists evaluated 48 MRI scans of the whole spine and the sacroiliac joints from a subsample of the BaPa Cohort, consisting of patients with non-specific low back pain and patients with different stages of SpA features. The spine was evaluated for SpA-related and degenerative MRI changes and the SIJ for SpA-related changes. Inter- and intra-observer agreements were calculated with kappa statistics. In the interpretation of the kappa coefficient, the standards for strength of agreement reported by Landis and Koch were followed. RESULTS: A total of 48 patients, 40% men and mean age of 31 years (range 18-40 years), were evaluated once by all three readers and re-evaluated by two of the readers after 4-12 weeks. For MRI changes in the spine, substantial to almost perfect observer agreement was found for the location and the size of vertebral signal changes and for disc degeneration and disc contour. For the sacroiliac joints, substantial or almost perfect observer agreement was found for the grading of bone marrow oedema and fatty marrow deposition, the depth of bone marrow oedema and for subchondral sclerosis. Global assessment of the SpA diagnosis had substantial to almost perfect observer agreements. CONCLUSION: The acceptable agreement for key MRI changes in the spine and sacroiliac joints makes it possible to use these MRI changes in the BaPa Cohort study and other studies investigating MRI changes in patients with non-specific low back pain and suspected SpA.

The Minimal Erosive Volume Needed for Radiographic Identification of Erosions in the Metacarpophalangeal Joints in Patients With Rheumatoid Arthritis.

OBJECTIVE: To compare in images, obtained by high-resolution peripheral quantitative computed tomography (HR-pQCT) and conventional radiography (CR) of the second and third metacarpophalangeal (MCP) joints, the minimal erosive cortical break needed to differentiate between pathological and physiological cortical breaks. METHODS: In this single-center cross-sectional study, patients with established rheumatoid arthritis (disease duration ≥ 5 yrs) had their second and third MCP joints of the dominant hand investigated by HR-pQCT and CR. Empirical estimation was used to find the optimal cut-off value for the number of erosions and total erosive volume, which were detectable between patients with and without erosions in the second and third MCP joints according to CR. RESULTS: The total erosive volume in the second and third MCP joints by HR-pQCT for CR-detected erosive disease was estimated to be 56.4 mm3 (95% CI 3.5-109.3). The sensitivity and specificity at this cutpoint were 78% and 83%, respectively, with an area under the receiver-operating characteristic curve (AUC) of 0.81. The optimal cut-off value for the number of erosions by HR-pQCT was 8.5 (95% CI 5.9-11.1) for CR-detected erosive disease in the second and third MCP joints. The sensitivity and specificity at this cutpoint were 74% and 88%, respectively, with an AUC of 0.81. CONCLUSION: Erosions by HR-pQCT were larger in patients with erosive damage in the second and third MCP joints by CR. We found that CR had poor sensitivity for detecting erosive disease when the erosive volume was < 56.4 mm3 or the number of erosions was < 8.5.

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

BACKGROUND: Early diagnostics of axial spondyloarthritis (axSpA) remains a challenge. Traditional imaging one-plane sacroiliac joint (SIJ) MRI assessment is used. By introducing a two-plane assessment system, the objective was to analyse the differences in SIJ MRI changes in early axSpA compared with changes in patients with mechanical back pain (MBP) by exploring the differences in volume and location. METHODS: MRIs in the early diagnostic state of 25 axSpA patients (mean age 31.3 years) and 59 MBP patients (mean age 32.3 years) were included. The MRIs were assessed by two readers regarding the distribution of bone marrow edema (BME) in 14 joint portions and structural changes in six joint portions in addition to SIJ anatomical variations and lumbar spine disc degeneration. RESULTS: AxSpA patients had a significantly higher overall BME sumscore (volume) of 25.1 compared to MBP patients 6.8, p < 0.005. The MBP group had the highest prevalence (66%) and sumscore (5.7) in the middle anterior sacrum. The axSpA group had significantly higher prevalence and sumscores in all joint portions except the three cartilaginous anterior sacral joint portions, including the ligamentous compartments (prevalence 40-60% compared to 8-15%, p both < 0.005). The axSpA group had also a significantly higher prevalence of erosions and fatty marrow disposition, but there were no differences in the prevalence of anatomical variations except the bipartite iliac bony plate. CONCLUSIONS: AxSpA patients demonstrated a widespread distribution of both inflammatory and structural changes, including high BME occurrence in the ligamentous joint portions whereas patients with MBP had the highest occurrence of BME in the middle anterior sacrum. These findings may help differentiate axSpA patients from other back pain conditions in the early diagnostic phase.

[A rarely diagnosed cause of acute hip and groin pain in an 86-year-old woman].

This case report illustrates a common clinical issue, where an 86-year-old woman was being referred to an emergency department because of severe hip and groin pain. The primary examination ruled out proximal femoral or pelvic fracture, and after an MRI was performed, the unusual cause of her pain was revealed: a rupture of the iliopsoas tendon at its insertion on the lesser trochanter. We present the causes and dispositions for iliopsoas tendon rupture among elderly, as well as the diagnostic order of imaging techniques and treatment for this condition.

What Level of Inflammation Leads to Structural Damage in the Sacroiliac Joints? A Four-Year Magnetic Resonance Imaging Follow-Up Study of Low Back Pain Patients.

OBJECTIVE: Sacroiliac (SI) joint bone marrow edema (BME) is considered to be pivotal in the detection of early spondyloarthritis. However, the link between BME and development of spondyloarthritis-related bone remodeling remains unclear. This study was undertaken to investigate the evolution of BME and structural lesions in the SI joints over time. METHODS: Baseline and 4-year follow-up magnetic resonance imaging scans were conducted in 604 patients ages 18-40 years who were referred with low back pain to an outpatient spine clinic. Eight SI joint regions were scored for BME and categorized as absent, limited (<25% of subcortical bone region), intermediate (25-50%), or extensive (>50%). Structural lesions including erosions and fat lesions were scored as absent or present. RESULTS: SI joint BME was seen at either time point (baseline or at 4 years) in 41% of participants but was persistent at both time points in only 16% of participants. Structural SI joint lesions developed according to the extent of BME at baseline: limited, intermediate, and extensive BME (as compared to absent BME) were independently associated with erosion at follow-up with odds ratios (ORs) of 3, 5, and 46, respectively, and with fat lesions (ORs 3, 7, and 33, respectively). In regions with limited and intermediate BME at baseline, 60% and 50% had resolved by follow-up, respectively, while only 2% and 7% had evolved into extensive BME by follow-up. CONCLUSION: While extensive SI joint BME was a strong independent predictor of development of structural lesions, limited and intermediate BME were mostly transient and only rarely evolved into extensive BME or structural lesions. These findings enhance our understanding of the natural development of SI joint lesions and indicate different progression patterns for limited/intermediate versus extensive BME, possibly due to different etiologies.

Frequency and Anatomic Distribution of Magnetic Resonance Imaging Features in the Sacroiliac Joints of Young Athletes: Exploring "Background Noise" Toward a Data-Driven Definition of Sacroiliitis in Early Spondyloarthritis.

OBJECTIVE: Low-grade bone marrow edema (BME) has been reported in the sacroiliac (SI) joints of 25% of healthy individuals and patients with nonspecific mechanical back pain, thus challenging the specificity and predictive value of magnetic resonance imaging (MRI) for the discrimination of early spondyloarthritis (SpA). It is unknown whether stress injury in competition sports may trigger BME. This study sought to explore the frequency and anatomic distribution of SI joint MRI lesions in recreational and elite athletes. METHODS: After pretest calibration, semicoronal MRI scans of the SI joints of 20 recreational runners before and after running and 22 elite ice hockey players were assessed for BME and structural lesions. Three readers assessed the MRI scans in a blinded manner, using an SI joint quadrant-based module; scans from tumor necrosis factor inhibitor-treated patients with SpA served for masking. The readers recorded subjects who met the Assessment of SpondyloArthritis international Society (ASAS) definition of active sacroiliitis. For descriptive analysis, the frequency of SI joint quadrants exhibiting BME and structural lesions, as concordantly recorded by ≥2 of 3 readers, and their distribution in 8 anatomic SI joint regions (the upper and lower ilium and sacrum, subdivided in anterior and posterior slices) were determined. RESULTS: The proportions of recreational runners and elite ice hockey players fulfilling the ASAS definition of active sacroiliitis, as recorded concordantly by ≥2 of 3 readers, were 30-35% and 41%, respectively. In recreational runners before and after running, the mean ± SD number of SI joint quadrants showing BME was 3.1 ± 4.2 and 3.1 ± 4.5, respectively, while in elite ice hockey players, it was 3.6 ± 3.0. The posterior lower ilium was the single most affected SI joint region, followed by the anterior upper sacrum. Erosion was virtually absent. CONCLUSION: In recreational and elite athletes, MRI revealed BME in an average of 3-4 SI joint quadrants, meeting the ASAS definition of active sacroiliitis in 30-41% of subjects. The posterior lower ilium was the single most affected SI joint region. These findings in athletes could help refine data-driven thresholds for defining sacroiliitis in early SpA.

Anatomy of the sacroiliac joints in children and adolescents by computed tomography.

BACKGROUND: Diagnosing sacroiliitis by magnetic resonance imaging (MRI) in children/adolescents can be difficult due to the growth-related changes. This study analyzed the normal osseous anatomy of the sacroiliac joints (SIJ) in a juvenile population using computed tomography (CT). METHODS: The anatomy of the SIJ was retrospectively analyzed in 124 trauma patients aged 9 months - <18 years by CT, based on 2 mm slices in axial, semi-axial and semi-coronal planes. The following anatomical features were recorded: intersegmental fusion of the sacral vertebral segments 1-3 (S1-S3), ossified nuclei (antero-superior at S1, lateral to the intervertebral spaces and lateral to S1 and S2) and joint facet defects larger than 3 mm. RESULTS: Fusion of S1/S2 started at the age of 6 years and was complete after the age of 13 years in most girls and after the age of 14 years in most boys. Fusion of S2/S3 started at the age of 9 years, but could remain incomplete up to 18 years in both genders. Ossified nuclei antero-lateral at S1 and/or in the joint space were observed until the age of 18 years and occurred in 77% of individuals ≥13 years with intraarticular localization in 64% of girls and 60% of boys. Joint facet defects >3 mm occurred in 21 children/adolescents (17%) located to both the iliac and sacral joint facets. CONCLUSIONS: Normal osseous SIJ structures in children and adolescents vary considerably. Attention to these normal anatomical structures during growth may help to avoid false positive findings by MRI.

Associations Between Spondyloarthritis Features and Magnetic Resonance Imaging Findings: A Cross-Sectional Analysis of 1,020 Patients With Persistent Low Back Pain.

OBJECTIVE: The Assessment of SpondyloArthritis international Society (ASAS) has previously published criteria for spondyloarthritis (SpA). In the Spines of Southern Denmark cohort, which included patients with persistent low back pain and an unknown proportion of patients with SpA, our objectives were 1) to estimate the prevalence of magnetic resonance imaging (MRI) findings and clinical features included in the ASAS criteria for SpA and 2) to explore the associations between MRI findings and clinical features. METHODS: We included patients ages 18-40 years with persistent low back pain who had been referred to the Spine Centre of Southern Denmark. We collected information on clinical features (including HLA-B27 and high-sensitivity C-reactive protein) and MRI findings in the spine and sacroiliac (SI) joints. RESULTS: Of 1,020 included patients, 537 (53%) had at least 1 of the clinical features included in the ASAS criteria for SpA. Three clinical features were common-inflammatory back pain according to the ASAS criteria, a good response to nonsteroidal antiinflammatory drugs (NSAIDs), and family history of SpA. The prevalence of these features ranged from 15% to 17%. Sacroiliitis on MRI according to the ASAS definition was present in 217 patients (21%). Of those 217 patients, 91 (42%) had the minimum amount of bone marrow edema required according to the ASAS definition (a low bone marrow edema score). The presence of HLA-B27, peripheral arthritis, a good response to NSAIDs, and preceding infection were independently positively associated with MRI findings in the SI joints (odds ratios [ORs] of 1.9-9.0). The remaining 8 clinical features were not positively associated with MRI findings. Importantly, only age was independently associated with low bone marrow edema score at the SI joints (OR of 1.1 per year). CONCLUSION: In this population, 53% had at least 1 clinical feature included in the ASAS criteria for SpA, and 21% had sacroiliitis according to the ASAS definition; furthermore, the associations between the clinical and imaging domains were inconsistent. The results indicate a need for further investigation of the importance of these findings in SpA, including investigation of the minimum requirements for defining sacroiliitis on MRI.