Interpreting neonatal hip sonography: intraobserver and interobserver variability.

The purpose of this study is to state the reliability of neonatal hip ultrasound interpretation, defining the intra and interoperator variability in the evaluation of the scans. We considered a sample of 2071 scans (coming from 798 patients who attended the screening programme for hip dysplasia), which were interpreted by the operator who obtained and read the images at the screening time and then by a different operator who saw the images for the first time. Both the intra and interoperator variability of α and ß angles' values resulted statistically not significative (intraclass correlation coefficient > 0.8) and determining a class shift (according to the Graf's classification) in a nonstatistically significative number of cases (agreement percentage >91% and Cohen's κ >0.8). Hip sonography can reliably detect hip dysplasia and the intra and interoperator variability in the interpretation of the exam is NS when the examination is correctly executed.

Imaging diagnosis for chronic lateral ankle ligament injury: a systemic review with meta-analysis.

BACKGROUND: Various imaging techniques have been utilized for the diagnosis of chronic lateral ankle ligament injury. This systemic review will explore the effectiveness of different imaging techniques in diagnosing chronic lateral ankle ligament injury. METHODS: Relative studies were retrieved after searching 3 databases (MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trails). Eligible studies were summarized. Data were extracted to calculate pooled sensitivity and specificity of magnetic resonance imaging (MRI), ultrasonography (US), stress radiography, and arthrography. RESULTS: Fifteen studies met our inclusion and exclusion criteria. A total of 695 participants were included. The pooled sensitivities in diagnosing chronic ATFL injury were 0.83 [0.78, 0.87] for MRI, 0.99 [0.96, 1.00] for US, and 0.81 [0.68, 0.90] for stress radiography. The pooled specificities in diagnosing chronic ATFL injury were 0.79 [0.69, 0.87] for MRI, 0.91 [0.82, 0.97] for US, and 0.92 [0.79, 0.98] for stress radiography. The pooled sensitivities in diagnosing chronic CFL injury were 0.56 [0.46, 0.66] for MRI, 0.94 [0.85, 0.98] for US, and 0.90 [0.73, 0.98] for arthrography. The pooled specificities in diagnosing chronic CFL injury were 0.88 [0.82, 0.93] for MRI, 0.91 [0.80, 0.97] for US, and 0.90 [0.77, 0.97] for arthrography. CONCLUSION: This systematic review with meta-analysis investigated the accuracy of imaging for the diagnosis of chronic lateral ankle ligament injury. Ultrasound manifested high diagnostic accuracy in diagnosing chronic lateral ankle ligament injury. Clinicians should be aware of the limitations of MRI in detecting chronic CFL injuries.

Adult Inflammatory Arthritides: What the Radiologist Should Know.

Developments and improvements in knowledge are rapid and ongoing in both the radiologic and rheumatologic fields. During the past decade, the roles of imaging and the radiologist in the assessment and management of many inflammatory rheumatologic diseases have undergone several changes. To remain effective in patient care, the radiologist needs to be aware of these changes when recommending and interpreting imaging examinations for the referring physician. The goal of contemporary rheumatoid arthritis (RA) management is to redefine RA as a disease that is no longer characterized by erosions, which reflect established or long-standing untreated disease. Most cases of RA are now diagnosed clinically, but imaging increases diagnostic confidence, is superior to clinical examination for the detection of joint inflammation, and plays an important role in patient management. The concept of the seronegative spondyloarthritides has recently been redefined by the Assessment of SpondyloArthritis International Society (ASAS). This new set of ASAS classification criteria divides the spectrum of spondyloarthritis on the basis of predominantly axial skeletal clinical manifestations or predominantly peripheral skeletal clinical manifestations. For axial spondyloarthritis, magnetic resonance imaging and radiography play crucial roles for classification and diagnosis. For both peripheral spondyloarthritis and psoriatic arthritis, the radiologist can provide important information that influences classification and diagnosis, including documenting radiologic evidence of juxta-articular new bone formation, diagnosing sacroiliitis, or delineating the presence and extent of enthesitis and dactylitis. The radiologist's familiarity with recent classification criteria, in addition to the traditional diagnostic characteristics of the individual inflammatory arthritides, maximizes the productive interface between the radiologist and the rheumatologist. ©RSNA, 2016.

A Practical Approach to Determining the Center of the Femoral Head in Subluxated and Dislocated Hips.

BACKGROUND: Mistaking the ossific nucleus as the surrogate for the center of the femoral head affects treatment decisions in hip dysplasia. Previous studies of ossific nucleus position within the femoral head have been qualitative, or, have not included both subluxated and dislocated hips. The purpose of this study was, first, to determine the most accurate radiographic landmark to define the center of the immature femoral head in hip dysplasia, and, second, to quantitatively analyze the position of the ossific nucleus relative to the center of the femoral head. METHODS: The center of the femoral head was determined from hip arthrograms for 19 consecutive patients with untreated hip dysplasia. Three radiographic proxies for the center were defined on each film: (1) the center of the proximal physis; (2) the center of the ossific nucleus; and (3) a modification of Mose's concentric circles. Each point was compared with the true center of the head on an arthrogram. RESULTS: Nineteen patients of an average age of 35.5 months (range, 9 to 76 mo) yielded 22 dysplastic hips. Modified Mose circle was the most accurate technique. In subluxated hips, the center of the femoral physis was equally accurate. The ossific nucleus was the poorest estimation of the center of the femoral head. All of the ossific nuclei were located cephalad and lateral to the center of the femoral head as determined on arthrogram. CONCLUSIONS: The modified Mose technique is the most accurate technique for determining the center of the femoral head. In subluxated hips, the center of the physis is a practical, equivalent, technique. The ossific nucleus is a poor proxy for the center of the head in hip dysplasia. CLINICAL RELEVANCE: A modification of Mose's technique is the most accurate assessment of the center of the femoral head in both subluxated and dislocated hips. The center of the physis is a practical, reliable, surrogate for the center of the head in subluxated hips without requiring an arthrogram.

Validation of a standardized mapping system of the hip joint for radial MRA sequencing.

OBJECTIVE: Intraarticular gadolinium-enhanced magnetic resonance arthrography (MRA) is commonly applied to characterize morphological disorders of the hip. However, the reproducibility of retrieving anatomic landmarks on MRA scans and their correlation with intraarticular pathologies is unknown. A precise mapping system for the exact localization of hip pathomorphologies with radial MRA sequences is lacking. Therefore, the purpose of the study was the establishment and validation of a reproducible mapping system for radial sequences of hip MRA. MATERIALS AND METHODS: Sixty-nine consecutive intraarticular gadolinium-enhanced hip MRAs were evaluated. Radial sequencing consisted of 14 cuts orientated along the axis of the femoral neck. Three orthopedic surgeons read the radial sequences independently. Each MRI was read twice with a minimum interval of 7 days from the first reading. The intra- and inter-observer reliability of the mapping procedure was determined. RESULTS: A clockwise system for hip MRA was established. The teardrop figure served to determine the 6 o'clock position of the acetabulum; the center of the greater trochanter served to determine the 12 o'clock position of the femoral head-neck junction. The intra- and inter-observer ICCs to retrieve the correct 6/12 o'clock positions were 0.906-0.996 and 0.978-0.988, respectively. CONCLUSIONS: The established mapping system for radial sequences of hip joint MRA is reproducible and easy to perform.

Shoulder arthroscopy remains superior to direct MR arthrography for diagnosis of subtle rotator interval lesions.

PURPOSE: To assess the sensitivity, specificity and accuracy of MR arthrography, as opposed to shoulder arthroscopy, in diagnosing individual rotator interval (RI) structures lesions at different levels of severity. MATERIALS AND METHODS: Seventy-five patients were enrolled in a prospective study. All the patients were diagnosed with full-thickness rotator cuff tendon tears on unenhanced MRI and had complimentary MR arthrography to search for obscure RI lesions. All the patients then underwent shoulder arthroscopy. The arthroscopist was blinded about the MR arthrography results. RESULTS: At arthroscopy, 42 patients (56 %) were found to have RI lesion(s) and represented the study group. The remaining 33 patients represented the control group. The sensitivity, specificity and accuracy of MR arthrography for detecting individual RI lesions varied widely depending on the location and severity of the lesions. MR arthrography showed intermediate sensitivity of 67-80 %, specificity of 83-89 % and accuracy of 89-92 % for diagnosing subtle RI lesions; and perfect (100 %) sensitivity, specificity and accuracy for diagnosing biceps long head tendon dislocation. For the rest of RI lesions, MR arthrography showed high sensitivity, specificity and accuracy. Inter-observer agreement was found to be almost perfect (K = 0.81-1.0). CONCLUSION: Shoulder arthroscopy remains the gold standard for diagnosing subtle RI lesions. Although MR arthrography has proved to be a valuable tool for diagnosing established RI lesions, it is of intermediate sensitivity for diagnosing subtle RI lesions resulting in early insufficiency of the biceps pulley system.

A double-blind, randomized controlled trial to compare the effect of biannual peripheral magnetic resonance imaging, radiography and standard of care disease progression monitoring on pharmacotherapeutic escalation in rheumatoid and undifferentiated inflammatory arthritis: study protocol for a randomized controlled trial.

BACKGROUND: Permanent joint damage is a major consequence of rheumatoid arthritis (RA), the most common and destructive form of inflammatory arthritis. In aggressive disease, joint damage can occur within 6 months from symptom onset. Early, intensive treatment with conventional and biologic disease-modifying anti-rheumatic drugs (DMARDs) can delay the onset and progression of joint damage. The primary objective of the study is to investigate the value of magnetic resonance imaging (MRI) or radiography (X-ray) over standard of care as tools to guide DMARD treatment decision-making by rheumatologists for the care of RA. METHODS: A double-blind, randomized controlled trial has been designed. Rheumatoid and undifferentiated inflammatory arthritis patients will undergo an MRI and X-ray assessment every 6 months. Baseline adaptive randomization will be used to allocate participants to MRI, X-ray, or sham-intervention groups on a background of standard of care. Prognostic markers, treating physician, and baseline DMARD therapy will be used as intervention allocation parameters. The outcome measures in rheumatology RA MRI score and the van der Heijde-modified Sharp score will be used to evaluate the MRI and X-ray images, respectively. Radiologists will score anonymized images for all patients regardless of intervention allocation. Disease progression will be determined based on the study-specific, inter-rater smallest detectable difference. Allocation-dependent, intervention-concealed reports of positive or negative disease progression will be reported to the treating rheumatologist. Negative reports will be delivered for the sham-intervention group. Study-based radiology clinical reports will be provided to the treating rheumatologists for extra-study X-ray requisitions to limit patient radiation exposure as part of diagnostic imaging standard of care. DMARD treatment dose escalation and therapy changes will be measured to evaluate the primary objective. A sample size of 186 (62 per group) patients will be required to determine a 36% difference in pharmacological treatment escalation between the three groups with intermediate dispersion of data with 90% power at a 5% level of significance. DISCUSSION: This study will determine if monitoring RA and undifferentiated inflammatory arthritis patients using MRI and X-ray every 6 months over 2 years provides incremental evidence over standard of care to influence pharmacotherapeutic decision-making and ultimately hinder disease progression. TRIAL REGISTRATION: This trial has been registered at ClinicalTrials.gov: NCT00808496 (registered on 12 December 2008).

The influence of hip rotation on femoral offset in plain radiographs.

BACKGROUND AND PURPOSE: Adequate restoration of femoral offset (FO) is critical for successful outcome after hip arthroplasty or fixation of hip fracture. Previous studies have identified that hip rotation influences the projected femoral offset (FOP) on plain anteroposterior (AP) radiographs, but the precise effect of rotation is unknown. PATIENTS AND METHODS: We developed a novel method of assessing rotation-corrected femoral offset (FORC), tested its clinical application in 222 AP hip radiographs following proximal femoral nailing, and validated it in 25 cases with corresponding computed tomography (CT) scans. RESULTS: The mean FORC was 57 (29-93) mm, which differed significantly (p < 0.001) from the mean FOP 49 (22-65) mm and from the mean femoral offset determined by the standard method: 49 (23-66) mm. FORC correlated closely with femoral offset assessed by CT (FOCT); the Spearman correlation coefficient was 0.94 (95% CI: 0.88-0.97). The intraclass correlation coefficient for the assessment of FORC by AP hip radiographs correlating the repeated measurements of 1 observer and of 2 independent blinded observers was 1.0 and 1.0, respectively. INTERPRETATION: Hip rotation affects the FOP on plain AP radiographs of the hip in a predictable way and should be adequately accounted for.

Plain radiographs fail to reflect femoral offset in total hip arthroplasty.

Successful biomechanical reconstruction is a major goal in total hip arthroplasty (THA). We measured leg length (LL), global (GO) and femoral offset (FO) change on anteroposterior pelvis radiographs and on three-dimensional computed-tomography (3D-CT) with fiducial landmarks after cementless THA on 18 hips of cadaveric specimens. Measurements on radiographs were performed twice by four examiners and showed high interobserver (mean CCC ≥0.79) and intraobserver agreements (mean ICC ≥0.88). Mean differences between radiographic and 3D-CT measurements were 1.0 (SD 2.0) mm for LL, 0.6 (SD 3.6) mm for GO and 1.4 (SD 5.2) mm for FO. 1% of radiographic LL-, 15% of GO- and 35% of FO measurements were outside a tolerance limit of 5mm. Radiographs seem acceptable for measuring LL/GO change but fail to reflect FO change in THA.

Optimizing success with lumbar disc arthroplasty.

PURPOSE: This study aimed at determining the variables that may prove useful in predicting clinical outcomes following lumbar disc arthroplasty. METHODS: Pre- and post-operative imaging assessments were obtained for 99 single-level lumbar disc arthroplasty patients from a prospective IDE study. The assessments and patient demographics were tested to identify variables that were significantly associated with clinical outcomes. RESULTS: Clinical outcome data were available for 85 % of patients at the 5-year follow-up. Numerous assessments made from the pre-operative imaging were found to have statistically significant associations with clinical outcomes at 2 and 5 years. The most notable factors were related to the amount of degeneration at the index level, with patients achieving better outcome scores at 5 years if they have higher grades of degeneration preoperatively. CONCLUSIONS: Several variables may prove effective at optimizing clinical outcomes including a preoperative disc height <8 mm, Modic type 2 changes adjacent to the target disc, a low amount of lordosis present at the treatment level, low levels of fatty replacement of the paraspinal musculature, a prominent amount of facet joint or disc degeneration, and the presence of flat or convex vertebral endplates. There were also post-operative findings associated with better patient outcomes including a larger percent of the endplate covered with the implant, larger implant heights, greater increases in disc space heights, and a larger increase in index level lumbar lordosis. These variables could be explored in other clinical studies to facilitate meta-analyses that could identify effective strategies to optimize clinical outcomes with lumbar disc arthroplasty.

Assessment of accuracy of marker ball placement in pre-operative templating for total hip arthroplasty.

We report the accuracy of positioning of the calibration ball in the process of pre-operative templating for total hip arthroplasty (THA). The ball should be placed in the coronal plane of the hip to provide suitable accuracy. We reviewed 112 post-operative THA radiographs where a calibration ball had been placed. We templated the femoral head size of the implant after calibrating the templating system from the ball. The calibrated femoral head diameter was compared to the known prosthetic head size. A percentage error was calculated. Overall, incorrect placement of the calibration ball resulted in a mean percentage error in templating of 6.8% (median 5.7%; range 0-26%). Such error carries implications with the templating process and may result in incorrect component sizes, leg lengths and offset.

Diagnostic utility of magnetic resonance imaging and radiography in juvenile spondyloarthritis: evaluation of the sacroiliac joints in controls and affected subjects.

OBJECTIVE: To compare the utility of radiography and magnetic resonance imaging (MRI) for the diagnosis of juvenile-onset spondyloarthritis in pediatric patients presenting with low back and/or sacroiliac (SI) pain of potentially inflammatory etiology. METHODS: Radiographs and MRI studies of the SI joints in 26 patients with juvenile spondyloarthritis (JSpA) and 35 controls were assessed independently by 2 radiologists, with discrepancies arbitrated by a third. Radiographs and MRI were blinded and read in separate batches in random order. RESULTS: Erosion was common and was the most useful diagnostic feature on radiography [positive likelihood ratio (LR) = 3.5] and was especially diagnostic of SpA on MRI (LR = 6.7). Subchondral sclerosis was common but was the least specific feature for both modalities. Joint space narrowing had some utility on radiography (LR = 2.0) and MRI (LR = 2.7) but was uncommon and had poor reader reliability. Bone marrow edema (LR = 3.1) and subarticular fat infiltration (LR = 4.5), detectable only on MRI, were both useful features. Global diagnostic impression of MRI (LR = 9.4) had very high utility for the diagnosis of JSpA, exceeding radiography (LR = 4.4) because of superior specificity. In addition, global diagnosis of SpA is much more reliably made on MRI (κ = 0.80) compared to radiography (κ = 0.30). CONCLUSION: Specificity and reliability of MRI of the SI joints are superior to radiography for the diagnosis of juvenile-onset SpA and, where available, MRI should replace radiography as the first line of investigation.

Reproducibility of radiographic assessment of femoral implant position after hip resurfacing arthroplasty: a pilot study.

To determine whether femoral implant position can be reproducibly measured on plain digital radiographs, we prospectively studied 40 patients after hip resurfacing arthroplasty. Three observers performed double blinded randomized analysis of calibrated digital radiographs meeting strict quality criteria. The implant stem-shaft angle and femoral anteversion angle were measured by the trapezoid method of axis determination using OsiriX software. The upper and lower offset and the anterior and posterior offset were measured. The statistical analysis was performed using Pearson correlation tests (intra-observer reproducibility) and Fisher F tests (inter-observer reproducibility). Intra-observer reproducibility was very good for all parameters and all observers. Inter-observer reproducibility was excellent except for superior offset measurement. Thus, this study validates a radiographic method for assessing the femoral implant position in hip resurfacing. We believe this could be useful for future studies on hip resurfacing devices.

Carbon dioxide gas arthrography for the evaluation of pediatric hip conditions: what is the risk and reliability?

BACKGROUND: Various pediatric conditions often necessitate a morphologic examination of the hip joint in infancy or childhood, and multiple imaging options have been employed to achieve this goal. Arthrography is one such modality. Different types of contrast media have been utilized and include pharmacologic contrast agents, air, and carbon dioxide. There are scattered reports of complications related to the typical various media used during arthrography. Some of the most concerning are related to gas emboli following the use of air or carbon dioxide. This study assesses the potential complications of carbon dioxide hip arthrography in a series of children over a 12-year period. METHODS: A retrospective review of the medical records of children between the ages of 0 and 3 years who underwent hip arthrography using carbon dioxide gas as the contrast medium was conducted. Outcome measures analyzed included volume of CO2 injected, vital signs, and perioperative and postoperative end-tidal CO2. RESULTS: Our study population was comprised of 118 hips in 90 children. We found no correlation between the volume of CO2 injected and the patient's vital signs or end-tidal CO2 at any point during the perioperative or postoperative period. None of the children exhibited any evidence for cardiopulmonary compromise or clinical signs of embolism. DISCUSSION: To our knowledge, there have been no large studies reporting on carbon dioxide arthrography and its potential complications. There were no gas embolisms and/or cardiopulmonary complications in our patients in the perioperative, postoperative, or 1-year follow-up period. Utilizing carbon dioxide gas as the contrast media for hip arthrography in children is safe and can help aid in the treatment of pediatric hip conditions. LEVEL OF EVIDENCE: Therapeutic Level IV.

Are the new automated methods for bone age estimation advantageous over the manual approaches?

Bone Age Assessment (BAA) is performed worldwide for the evaluation of endocrine, genetic and chronic diseases, to monitor response to medical therapy and to determine the growth potential of children and adolescents. It is also used for consultation in planning orthopedic procedures, for determination of chronological age for adopted children, youth sports participation and in forensic settings. The main clinical methods for skeletal bone age estimation are the Greulich and Pyle (GP) and the Tanner and Whitehouse (TW) methods. Seventy six per cent (76%) of radiologists or pediatricians usually use the method of GP, 20% that of TW and 4% other methods. The advantages of using the TW method, as opposed to the GP method, are that it overcomes the subjectivity problem and results are more reproducible. However, it is complex and time consuming; for this reason its usage is just about 20% on a world-wide scale. Moreover, there are some evidences that bone age assignments by different physicians can differ significantly. Computerized and Quantitative Ultrasound Technologies (QUS) for assessing skeletal maturity have been developed with the aim of reducing many of the inconsistencies associated with radiographic investigations. In spite of the fact that the volume of automated methods for BAA has increased, the majotity of them are still in an early phase of development. QUS is comparable to the GP based method, but there is not enough established data yet for the healthy population. The Authors wish to stimulate the attention on the accuracy, reliability and consistency of BAA and to initiate a debate on manual versus automated approaches to enhance our assessment for skeletal matutation in children and adolescents.

Subsidence of SB Charité total disc replacement and the role of undersizing.

PURPOSE: A possible complication after total disc replacement (TDR) is subsidence, presumably caused by asymmetric implantation, implant undersizing or reduced bone quality. This study aims to quantify the degree of subsidence of an SB Charité TDR, and investigate whether undersizing is related to subsidence. METHODS: A custom developed software package (Mathworks) reconstructed 3D bone-implant geometry. A threshold for subsidence was determined by comparing penetrated bone volume (PBV) and rotation angles. Inter- and intra-observer reproducibilities were calculated. Subsidence was correlated to undersizing. RESULTS: High inter- and intra-observer correlation coefficients were found for the method (R > 0.92). Subsidence was quantified as PBV 700 mm(3) combined with a rotation angle >7.5°. A reduced risk of subsidence was correlated to >60 and >62 % of the bony endplate covered by the TDR endplate for L4 and L5, respectively. CONCLUSIONS: A reproducible method to determine undersizing was developed. Thresholds were determined related to a reduced risk of subsidence.

The relationship of patient-reported joints with active synovitis detected by power Doppler ultrasonography in rheumatoid arthritis.

OBJECTIVES: This paper aims to evaluate the relationship of patient-reported tender and swollen joints with active inflammation as detected by power Doppler (PDUS) and whether this relationship is affected by significant joint damage. METHODS: Fifty rheumatoid arthritis patients self-assessed 28 tender and swollen joints and were followed by PDUS assessment. Relationship of tender and swollen joints with active synovitis (PDUS 'gold standard') was assessed at the joint level by: a) percentage agreement at each PDUS semiquantitative grade (grade 1 to 3), b) positive likelihood ratio (LR) of agreement with PDUS, and c) LR of agreement with PDUS according to radiographic damage (significant erosive disease vs. non-erosive disease). Correlation of tender and swollen joint counts with disease activity markers was analysed by Spearman's. Sensitivity analyses examined the influence of disease activity or global pain on level of agreement at the joint level. RESULTS: Of joints with significant active inflammation (e.g. grade 3 PDUS), patients identified 75% as tender and 63% as swollen. Swollen joints showed strong association at the joint level with active synovitis when there was no significant radiographic damage (LR 2.54, 95%CI 1.93-3.34), but with no significant radiographic damage (LR 1.32, 95%CI 0.75-2.32). Swollen joint counts were statistically correlated with PDUS-DAS28 and CRP, but not PDUS score. Sensitivity analysis showed better agreement of tender and swollen joints with active synovitis when DAS28 was ≤ 3.2 and when patient global pain was <50mm on visual analogue scale. CONCLUSIONS: The relationship between patient-reported joints and active synovitis is stronger in the setting of low disease activity without erosive disease, affected also by degree of reported global pain. Further longitudinal studies of patient-reported joints are needed.

Defining erosive disease typical of RA in the light of the ACR/EULAR 2010 criteria for rheumatoid arthritis; results of the data driven phase.

BACKGROUND: According to the 2010 criteria, rheumatoid arthritis (RA) can be classified in the presence of ≥6 points on the criteria or 'typical' erosive disease. RA-specific erosiveness however has not been defined yet. This study reports the results of the data driven phase of a European League Against Rheumatism (EULAR) taskforce aiming to define RA-specific erosiveness. METHODS: Baseline radiographs of hands and feet of 980 Dutch and 811 French early arthritis patients were studied on the number and site of erosive joints. Test characteristics were determined, with the outcome measures being initiation of methotrexate (MTX) therapy or any disease modifying antirheumatic drug (DMARD) therapy within the first year of disease and arthritis persistency over 5 years. Analyses were repeated in the patients with <6 points on the American College of Rheumatology/EULAR 2010 criteria. RESULTS: In both cohorts comparable test characteristics were observed for the outcomes MTX therapy, any DMARD therapy and arthritis persistency. Test characteristics were not influenced by the site of erosiveness. The specificity observed was >50% for ≥1 erosive joint, >80% for ≥3 erosive joints and >90% for ≥5 erosive joints. When analysing the patients not fulfilling the 2010 criteria (n=308 and 149), specificity was >60% for ≥1 erosive joint, >90% for ≥3 erosive joints and >95% for ≥5 erosive joints. Few of these patients fulfilled the radiological criterion; 27-36 patients had ≥3 erosive joints and 13-14 patients had ≥5 erosive joints. CONCLUSIONS: RA-specific erosiveness can be defined with high specificity at several cut-offs for the number of erosive joints in two independent cohorts with multiple different outcomes. The final radiological criterion will be established in the next phase.