Conventional radiography in juvenile idiopathic arthritis: Joint recommendations from the French societies for rheumatology, radiology and paediatric rheumatology

Background Juvenile idiopathic arthritis (JIA) can cause structural damage. However, data on conventional radiography (CR) in JIA are scant. Objective To provide pragmatic guidelines on CR in each non-systemic JIA subtype. Methods A multidisciplinary task force of 16 French experts (rheumatologists, paediatricians, radiologists and one patient representative) formulated research questions on CR assessments in each non-systemic JIA subtype. A systematic literature review was conducted to identify studies providing detailed information on structural joint damage. Recommendations, based on the evidence found, were evaluated using two Delphi rounds and a review by an independent committee. Results 74 original articles were included. The task force developed four principles and 31 recommendations with grades ranging from B to D. The experts felt strongly that patients should be selected for CR based on the risk of structural damage, with routine CR of the hands and feet in rheumatoid factor-positive polyarticular JIA but not in oligoarticular non-extensive JIA. Conclusion These first pragmatic recommendations on CR in JIA rely chiefly on expert opinion, given the dearth of scientific evidence. CR deserves to be viewed as a valuable tool in many situations in patients with JIA.

# Introduction
Juvenile idiopathic arthritis (JIA) is a heterogeneous group of chronic inflammatory joint conditions that can cause structural damage [bib_ref] Juvenile idiopathic arthritis, Prakken [/bib_ref]. Seven mutually exclusive subtypes of JIA are defined in the 2001 Edmonton classification developed by the International League Against Rheumatism (ILAR) [bib_ref] International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second..., Petty [/bib_ref]. This classification has been challenged and modifications suggested, such as exclusion of systemic-onset JIA (sJIA) due to its similarity to autoinflammatory diseases [bib_ref] It is time to rethink juvenile idiopathic arthritis classification and nomenclature, Martini [/bib_ref] [bib_ref] Juvenile idiopathic arthritis: Definition and classification, Deslandre [/bib_ref].
The prevalence of joint damage among patients with JIA has been estimated at 8-27 % in extended oligoarticular JIA (oJIA), 35-67 % in polyarticular JIA (pJIA) and up to 80 % in rheumatoid factor (RF)-positive pJIA [bib_ref] Radiographic progression in children with polyarticular juvenile rheumatoid arthritis: a pilot study, Mason [/bib_ref] [bib_ref] Early predictors of outcome in juvenile idiopathic arthritis, Ravelli [/bib_ref]. The main treatment objectives in JIA are to control the pain and to prevent structural damage. Joint space narrowing (JSN), bone erosions and demineralization are radiographic findings shared between JIA and adult rheumatoid arthritis (RA). Changes specific to the paediatric population are early growth plate closure, epiphyseal deformity and growth asymmetry [bib_ref] Juvenile idiopathic arthritis: clinically relevant imaging in diagnosis and monitoring, Southwood [/bib_ref].
Conventional radiography (CR), magnetic resonance imaging (MRI) and ultrasound (US) are the imaging modalities most often used to evaluate joint inflammation or structural damage [bib_ref] Imaging approaches for evaluating peripheral joint abnormalities in juvenile idiopathic arthritis, Breton [/bib_ref]. MRI and US hold considerable promise but are still under evaluation in JIA. CR remains the most readily available imaging technique for detecting and monitoring structural damage. However, potential limitations of CR in JIA include the risk of radiationinduced harm to the patient, interpretation difficulties raised by skeletal immaturity, and the delayed development of structural joint damage. Furthermore, because JIA is rare, little is known about the potential effects of synthetic or biological disease-modifying anti-rheumatic drugs (DMARDs) on structural joint damage [bib_ref] Preliminary evidence that etanercept may reduce radiographic progression in juvenile idiopathic arthritis, Nielsen [/bib_ref] [bib_ref] Effects of methotrexate on radiologic progression in juvenile rheumatoid arthritis, Harel [/bib_ref] [bib_ref] Radiologic progression in patients with juvenile chronic arthritis treated with methotrexate, Ravelli [/bib_ref]. Thus, whereas recommendations based on large studies are available for the radiographic assessment of chronic inflammatory joint disease in adults [bib_ref] Ability of oblique foot radiographs to detect erosions in early arthritis: results..., Devauchelle-Pensec [/bib_ref] [bib_ref] Recommendations of the French Society for Rheumatology for managing rheumatoid arthritis, Gaujoux-Viala [/bib_ref] , no similar guidelines have been developed for JIA. A task force was recently convened by the European League Against Rheumatism (EULAR) -Paediatric Rheumatology European Society (PReS) to develop recommendations about imaging studies for diagnosing and managing JIA [bib_ref] EULAR recommendations for the use of imaging of the joints in the..., Colebatch [/bib_ref]. Although this undertaking acknowledged, for the first time, that an assessment of imaging studies in JIA was needed, the task force neither focussed on CR nor provided specific guidance for everyday practice.
We established a multidisciplinary task force to develop guidelines on the use of CR for the diagnosis and follow-up of each JIA subtype in everyday practice. Our project was supported by the French Society for Rheumatology (SFR), French Society for Paediatric Rheumatology and Internal Medicine (SOFREMIP), French Society for Paediatric and Prenatal Imaging (SFIPP), French Society for Radiology (SFR), and largest non-profit paediatric rheumatology patient organisation in France (KOURIR).

# Methods

## Field of research
We considered the following situations, at diagnosis and during follow-up, in each of the following five subtypes of JIA (oJIA, pJIA with and without RF and/or anti-citrullinated peptide antibody (ACPA), juvenile psoriatic arthritis (jPsA), and enthesitis-related arthritis (ERA)) Undifferentiated arthritis, as a heterogeneous subset related to one or several subtypes, and systemic JIA, having a peculiar articular course and structural prognosis, were left aside. Experts also focused on juvenile monoarthritis. Special attention was directed to the cervical spine, hip and temporo-mandibular joints (TMJs).

## Recommendation development process
The task force comprised 16 JIA experts (eight rheumatologists, five paediatricians, two paediatric radiologists experienced in skeletal disease and one patient organisation representative). We used the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) method [bib_ref] Grading quality of evidence and strength of recommendations in clinical practice guidelines..., Brozek [/bib_ref] for elaborating, evaluating, disseminating and implementing recommendations elaborated by the EULAR and the Outcome Measures in Rheumatology (OMERACT) group [bib_ref] EULAR standardised operating procedures for the elaboration, evaluation, dissemination, and implementation of..., Dougados [/bib_ref] [bib_ref] Update of the EULAR standardised operating procedures for EULARendorsed recommendations, Van Der Heijde [/bib_ref] , and the Population, Intervention, Comparison, Outcome (PICO) process to frame the research questions.
We considered structural radiographic abnormalities: JSN, erosions, pseudo-joint space widening for sacro-iliac joint [bib_ref] Spondyloarthritis in a pediatric population: risk factors for sacroiliitis, Stoll [/bib_ref] [bib_ref] Early predictors of juvenile sacroiliitis in enthesitis-related arthritis, Pagnini [/bib_ref] and ankylosis [bib_ref] Ability of oblique foot radiographs to detect erosions in early arthritis: results..., Devauchelle-Pensec [/bib_ref]. A research fellow (PM) assisted by two experts in systematic review methodology (CGV, methodologist; and VDP, convenor) performed a systematic literature review by searching PubMed, Scopus/Elsevier, and the Cochrane Library. Original articles including clinical trials, retrospective cohort studies, other retrospective studies, and case-control studies published between 1980 and December 2016 were identified. The following indexing was used: 'juvenile idiopathic arthritis' OR 'juvenile rheumatoid arthritis' OR 'juvenile chronic arthritis' OR 'juvenile psoriatic arthritis' O R ' e n t h e s i t i s -r e l a t e d a r t h r i t i s ' O R ' j u v e n i l e spondyloarthritis' AND 'radiography' OR 'X-ray' (see Appendix 1 for details). The quality of evidence and grades of recommendation were determined according to the standards of the Oxford Centre for Evidence-Based Medicine . Recommendations were graded A to D depending on the level of the underlying evidence (from 1A to 4) [bib_ref] Update of the EULAR standardised operating procedures for EULARendorsed recommendations, Van Der Heijde [/bib_ref].
The task force debated and formulated a preliminary set of recommendations based on the systematic literature review supplemented, when necessary, by their expert opinion. This set was then evaluated by a panel of 14 independent Frenchspeaking experts. Modifications were debated by the task force. The final recommendations were then rated on a 10point scale by the task force and independent panel through a Delphi process.

# Results

## Systematic literature review
Of the 118 publications identified by the literature search, 74 original articles, as well as one abstractand one online recommendation, were included .

## Recommendations
The experts elaborated four overarching principles and 31 recommendations. [fig_ref] Table 2: Routine CR of the wrists, hands, and forefeet is strongly recommended at... [/fig_ref] lists the recommendations.

## Overarching principles
Radiation exposure was taken into account (principle B), according to French Society for Radiology recommendations(Appendix 2). Much of the cartilage is still radiotransparent in children younger than 5 years of age. In this age group, the need for CR must be evaluated with great care (principle C) [bib_ref] Development of the long bones in the hands and feet of children:..., Laor [/bib_ref].
Other imaging modalities such as US and MRI are increasingly used in JIA. Although promising, they are not discussed herein. They will be the focus of specific recommendations (principle D).
Oligoarticular JIA (oJIA) 1. CR should not be performed routinely as a diagnostic investigation in oJIA. The literature review identified ten studies in which CR was performed, even in patients younger than 4 years. Among them, one focussed specifically on oJIA [bib_ref] Longterm outcome and prognosis in oligoarticular-onset juvenile idiopathic arthritis, Guillaume [/bib_ref] and nine investigated several JIA subtypes but reported data separately for oJIA . The usefulness of CR is limited by the incomplete ossification of the epiphyses, most notably in the youngest age groups [bib_ref] Use of the Sharp and Larsen scoring methods in the assessment of..., Rossi [/bib_ref]. Therefore, when the diagnosis is definitive, CR is not recommended.
2. and 3. During follow-up, CR should be performed on affected joint(s) that remain symptomatic after 3 months. By 'symptomatic joints'*, we mean painful and/or swollen joints and/or joints that are limited in motion. In patients with persistently symptomatic* joints, the reiteration of CR during follow-up is at the discretion of the physician. Several studies showed evidence of radiographic progression early in the natural history of oJIA [bib_ref] Antinuclear antibody-positive patients should be grouped as a separate category in the..., Ravelli [/bib_ref] [bib_ref] Anticitrullinated protein antibodies and radiological progression in juvenile idiopathic arthritis, Lipinska [/bib_ref] [bib_ref] Longterm outcome and prognosis in oligoarticular-onset juvenile idiopathic arthritis, Guillaume [/bib_ref] [bib_ref] Radiologic outcome and its relationship to functional disability in juvenile rheumatoid arthritis, Oen [/bib_ref]. [bib_ref] Juvenile idiopathic arthritis: Definition and classification, Deslandre [/bib_ref]. In patients with clinically inactive disease (CID), CR should not be performed routinely. The diagnosis of CID relies on physician judgement, aided by validated tools [bib_ref] American College of Rheumatology provisional criteria for defining clinical inactive disease in..., Wallace [/bib_ref] [bib_ref] Validity of a three-variable Juvenile Arthritis Disease Activity Score in children with..., Mcerlane [/bib_ref] [bib_ref] Development and validation of a composite disease activity score for juvenile idiopathic..., Consolaro [/bib_ref]. No data are available on radiographic disease progression in clinically silent joints in patients with oJIA. [bib_ref] Radiographic progression in children with polyarticular juvenile rheumatoid arthritis: a pilot study, Mason [/bib_ref]. In patients with extended oJIA, the recommendations for pJIA should be applied. The number of affected joints is strongly associated with structural damage in oJIA [bib_ref] Longterm outcome and prognosis in oligoarticular-onset juvenile idiopathic arthritis, Guillaume [/bib_ref]. [bib_ref] Early predictors of outcome in juvenile idiopathic arthritis, Ravelli [/bib_ref]. In patients with structural damage, the selection and timing of specific imaging techniques to further assess the damaged joint during follow-up is guided by clinical considerations.
Joints with structural damage must undergo specific CR evaluations during the patient's growth.
Polyarticular JIA (pJIA) 7. and 8. Routine CR of the wrists, hands and forefeet is strongly recommended at the diagnosis of polyarticular JIA with positive RF/ACPA. CR of other joints than wrists, hands and forefeet, is recommended at the diagnosis for symptomatic joints*only. Prospective studies were reviewed, with special attention to early pJIA. Erosions and JSN occurred preferentially at the hands, wrists and feet [bib_ref] Radiologic progression in patients with juvenile chronic arthritis treated with methotrexate, Ravelli [/bib_ref] [bib_ref] Radiologic features in juvenile idiopathic arthritis: a first step in the development..., Van Rossum [/bib_ref] , joints that were sometimes asymptomatic [bib_ref] Radiologic features in juvenile idiopathic arthritis: a first step in the development..., Van Rossum [/bib_ref] CR at the diagnosis provides a reference for assessing disease progression. It is supported by 'adult' recommendations [bib_ref] Recommendations of the French Society for Rheumatology for managing rheumatoid arthritis, Gaujoux-Viala [/bib_ref] for rheumatoid arthritis, which has a similar structural evolution. 9. and 10. In new-onset RF/ACPA-negative pJIA with adverse prognostic factors, CR at diagnosis should be performed as for RF/ACPA-positive pJIA. Box 1 lists the factors of adverse prognostic significance in pJIA [bib_ref] Radiologic features in juvenile idiopathic arthritis: a first step in the development..., Van Rossum [/bib_ref]. These factors are associated with a pattern of joint damage over time similar to that seen in RF/ACPA-positive pJIA [bib_ref] Radiologic outcome and its relationship to functional disability in juvenile rheumatoid arthritis, Oen [/bib_ref].
Box 1: Factors of adverse prognostic significance in polyarticular juvenile idiopathic arthritis (pJIA) Early involvement of wrists Symmetric arthritis Distal, small-joint arthritis Elevated ESR/CRP Pre-existing radiographic abnormalities ESR, erthrocyte sedimentation rate; CRP, serum C-reactive protein level [bib_ref] Radiologic progression in patients with juvenile chronic arthritis treated with methotrexate, Ravelli [/bib_ref]. In new-onset, RF/ACPA-negative pJIA without adverse prognostic factors, at diagnosis, CR should be confined to symptomatic* joints. This recommendation is based on expert opinion.
12. In RF/ACPA-positive pJIA, CR of the hands, wrists and forefeet is strongly recommended 1 year after disease onset, and when transitioning from paediatric to adult healthcare. At other time points, the use of CR during follow-up is at the discretion of the physician. Prospective studies found evidence of joint damage even in asymptomatic joints [bib_ref] Radiologic features in juvenile idiopathic arthritis: a first step in the development..., Van Rossum [/bib_ref]. Patients with long-standing disease had high prevalences of joint erosions (30-70 % in historical studies) [bib_ref] Radiographic progression in children with polyarticular juvenile rheumatoid arthritis: a pilot study, Mason [/bib_ref] [bib_ref] Radiographic and clinical outcome in early juvenile rheumatoid arthritis and juvenile spondyloarthropathy:..., Selvaag [/bib_ref] [bib_ref] Radiologic outcome and its relationship to functional disability in juvenile rheumatoid arthritis, Oen [/bib_ref] [bib_ref] Health status of patients with juvenile rheumatoid arthritis at 1 and 5..., Bowyer [/bib_ref] , close to those in adults with RA [48]. In RA, joint destruction at asymptomatic sites is a major predictor of adverse outcomes [bib_ref] Recommendations of the French Society for Rheumatology for managing rheumatoid arthritis, Gaujoux-Viala [/bib_ref] [bib_ref] Presence of significant synovitis in rheumatoid arthritis patients with diseasemodifying antirheumatic drug-induced..., Brown [/bib_ref]. However, radiographic progression with erosions in asymptomatic joints is not well documented in JIA and may have been underestimated. In a study of 471 joints in 67 patients with polyarticular JIA, radiographs showed erosions at the hands and feet in 36 % and 39 % of [bib_ref] Radiologic features in juvenile idiopathic arthritis: a first step in the development..., Van Rossum [/bib_ref]. Our literature review identified some data on the best times for CR. One study suggested a higher risk of radiographic progression within the first year after disease onset . The experts felt that CR contributed to ease the transition from paediatric to adult healthcare [bib_ref] EULAR/PReS standards and recommendations for the transitional care of young people with..., Foster [/bib_ref]. [bib_ref] Recommendations of the French Society for Rheumatology for managing rheumatoid arthritis, Gaujoux-Viala [/bib_ref]. Routine CR of other joints is not recommended. No data were found on which to base specific recommendations.
14. During the follow-up of RF/ACPA-negative pJIA with adverse prognostic factors, CR should be performed as for RF/ACPA-positive pJIA (see recommendation #12). [bib_ref] Grading quality of evidence and strength of recommendations in clinical practice guidelines..., Brozek [/bib_ref]. During the follow-up of RF/ACPA-negative pJIA without adverse prognostic factors, the use of CR is at the discretion of the physician. No scientific data were available on which to base specific recommendations.. and 17. CR can be repeated in patients who remain symptomatic* longer than 3 months. In patients with structural damage, the selection and timing of specific imaging techniques during follow-up is guided by clinical considerations. The experts emphasised the need for careful attention to joints with active disease. In prospective studies, the time interval separating CR assessments of the same joints ranged from 8 months to 24 years. The 3-month interval in this recommendation was based on expert opinion.

# Enthesitis-related arthritis (era)
18. In patients with axial ERA, CR of the spine and hip joints should be performed only when needed for the differential diagnosis. Axial manifestations may arise at the spine, hips and sacro-iliac joints. A radiographic view specifically designed to assess the sacro-iliac joints is not recommended, as the results are not interpretable in skeletally immature patients and radiation exposure is significant [bib_ref] Early predictors of juvenile sacroiliitis in enthesitis-related arthritis, Pagnini [/bib_ref]. In patients with axial inflammatory pain, MRI (for both sacro-iliac and hip joints) and US (for the hip joint) may be more relevant [bib_ref] Assessment of Sacroiliitis at Diagnosis of Juvenile Spondyloarthritis by Radiography, Magnetic Resonance..., Weiss [/bib_ref]. [bib_ref] Spondyloarthritis in a pediatric population: risk factors for sacroiliitis, Stoll [/bib_ref]. During the follow-up of axial ERA, CR should be considered only for the hip joints, depending on the clinical course and availability of US and/or MRI. ERA is associated with a high prevalence of hip joint arthritis [bib_ref] The influence of patient characteristics, disease variables, and HLA alleles on the..., Flat [/bib_ref]. MRI or US are non-irradiating methods capable of detecting hip joint effusion; in addition, MRI can detect bone oedema. Therefore, in the future, MRI and US may deserve consideration as first-line imaging techniques. CR, however, is appropriate for monitoring known structural damage and deformities.
20. and 21. CR is not recommended for multifocal enthesitis. In patients with isolated enthesitis, CR can be JIA juvenile idiopathic arthritis, CR conventional radiography, oJIA oligoarticular juvenile idiopathic arthritis, pJIA polyarticular juvenile idiopathic arthritis, RF rheumatoid factor, ACPA anti-citrullinated protein antibody, ERA enthesitis-related arthritis, TMJ temporo-mandibular joint *Symptomatic joints: swollen and/or painful joints, and/or joints with motion range limitation considered as a tool for establishing the differential diagnosis. When isolated enthesitis is suspected, CR may contribute to the differential diagnosis (e.g. with post-traumatic changes or osteochondritis); otherwise, CR is unhelpful for assessing peri-articular manifestations.
Psoriatic juvenile arthritis (jPsA)

## 22.
No specific recommendation can be made about CR in juvenile psoriatic arthritis. Scientific data are scarce [bib_ref] Comparison of patients with juvenile psoriatic arthritis and nonpsoriatic juvenile idiopathic arthritis:..., Butbul [/bib_ref] [bib_ref] Juvenile psoriatic arthritis: longterm outcome and differentiation from other subtypes of juvenile..., Flat [/bib_ref] [bib_ref] Patterns of joint involvement at onset differentiate oligoarticular juvenile psoriatic arthritis from..., Huemer [/bib_ref] [bib_ref] Clinical comparison of early-onset psoriatic and non-psoriatic oligoarticular juvenile idiopathic arthritis, Stoll [/bib_ref] [bib_ref] Psoriatic juvenile idiopathic arthritis: a tale of two subgroups, Stoll [/bib_ref] [bib_ref] Positive family history of psoriasis does not affect the clinical expression and..., Tsitsami [/bib_ref]. The definition of this entity is still debated [bib_ref] Positive family history of psoriasis does not affect the clinical expression and..., Tsitsami [/bib_ref]. Traditionally, two subtypes are described, an axial inflammatory disease resembling axial ERA and a peripheral joint disease resembling oJIA [bib_ref] Psoriatic juvenile idiopathic arthritis: a tale of two subgroups, Stoll [/bib_ref]. 23. Guidance may be taken from the recommendations above, depending on the clinical presentation, or from recommendations issued for adults.

## Situations of specific interest
Monoarthritis 24. At the diagnosis of acute monoarthritis, CR of the involved joint should be performed, with two perpendicular views. The French Society for Radiologystrongly recommends CR of any site of focal bone pain in paediatric patients, with the goal of excluding a tumour, osteomyelitis, or a haematological malignancy [bib_ref] Predictive plain X-ray findings in distinguishing early stage acute lymphoblastic leukemia from..., Tafaghodi [/bib_ref] [bib_ref] Monoarthritis; remember to ask the child, Rayen [/bib_ref]. [bib_ref] Radiographic Progression of Patients With Psoriatic Arthritis Who Achieve Minimal Disease Activity..., Kavanaugh [/bib_ref]. At the diagnosis of acute monoarthritis, comparative CR of the contralateral joint is unnecessary. Because cartilage thickness varies within individuals, comparison to the healthy contra-lateral joint is uninformative [bib_ref] Useful measurements in the evaluation of hand radiographs, Poznanski [/bib_ref] [bib_ref] Use of the Sharp and Larsen scoring methods in the assessment of..., Rossi [/bib_ref].
Cervical spine 26. In patients with persistent neck pain related to JIA, MRI is preferable over CR.
27. When MRI is unavailable, CR is recommended only for the cervical spine and should consist only of a lateral view.
28. In patients with JIA who have neurological symptoms of spinal cord compression and neck pain, cervical MRI must be performed, on an emergency basis.
In a cohort study of oJIA, 2.4 % of patients had cervical spine damage at the diagnosis [bib_ref] Longterm outcome and prognosis in oligoarticular-onset juvenile idiopathic arthritis, Guillaume [/bib_ref]. Cervical spine erosions and ankylosis are common in advanced pJIA [bib_ref] Disease course, outcome, and predictors of outcome in a populationbased juvenile chronic..., Bertilsson [/bib_ref] [bib_ref] Subaxial cervical vertebrae in patients with juvenile idiopathic arthritis-something special?, Enden [/bib_ref]. Evidence-based data are too scarce to recommend any specific pattern of radiological follow-up. Atlanto-axial diastasis may be normal in paediatric patients, and dynamic CR is therefore irrelevant. MRI is the most sensitive imaging technique, and is mandatory when spinal cord compression is suspected [bib_ref] Radiological evaluation of cervical spine involvement in rheumatoid arthritis, Joaquim [/bib_ref].
Temporomandibular joints 29. CR of the TMJs is not recommended when cross-sectional imaging is available.
TMJ damage is common in JIA, with the prevalence ranging across studies from 17 % to 87 % [bib_ref] Temporomandibular involvement in juvenile idiopathic arthritis, Twilt [/bib_ref]. The TMJ cartilage is thin and condylar erosions therefore develop early. The panoramic radiograph is often normal at disease onset.
Cross-sectional imaging offers better diagnostic performance. Imaging of the TMJs is not usually performed on a routine basis but is required in the event of pain, mouth-opening limitation or audible cracking of the TMJs . MRI is considered the best imaging technique, although distinguishing the normal appearance from abnormal changes can be challenging [bib_ref] Contrastenhanced MRI of the temporomandibular joint: findings in children without juvenile idiopathic..., Kottke [/bib_ref] [bib_ref] MRI thresholds for discrimination between normal and mild temporomandibular joint involvement in..., Ma [/bib_ref]. Cone-beam computed tomography allows three-dimensional reconstructions [bib_ref] Change in condylar and mandibular morphology in juvenile idiopathic arthritis: Cone Beam..., Farronato [/bib_ref]. The usefulness of US TMJ imaging is under debate [bib_ref] Early diagnosis of temporomandibular joint involvement in juvenile idiopathic arthritis: a pilot..., Muller [/bib_ref] [bib_ref] Sonographic evaluation of the temporomandibular joints in juvenile idiopathic arthritis(, Melchiorre [/bib_ref].
Hip joint 30. Routine CR of the hip joint is not recommended in patients with pJIA.
31. When CR of a symptomatic hip joint is performed, a single view should be obtained, i.e. either an antero-posterior view or a frog leg view.
In RF/ACPA-positive pJIA, hip joint damage is common [48] but CR of the hip joint is associated with a high level of ionising radiation exposure, so the hip is not among the joints for which routine CR is recommended .When available, MRI should be performed instead of, or in addition to, CR. If CR is performed, either an antero-posterior or a frog leg view is recommended, to visualise both hip joints and to allow the detection of bone erosions and/or avascular necrosis.

# Discussion
CR is the most widely available imaging procedure worldwide. In paediatric patients, this advantage should be weighed against the heightened risks of radiation exposure and difficulty in interpreting joint radiographs before skeletal maturity is achieved. In addition, in JIA, radiographically visible joint damage takes time to develop, limiting the usefulness of CR. Specific recommendations about CR in paediatric patients are therefore needed, a fact that prompted the present work.
Obstacles to the development of recommendations about CR in JIA included the paucity of strong evidence about structural disease progression in JIA and the pooling of JIA subtypes in many studies. The low incidence of JIA contributes to explain the dearth of data. To maximise the usefulness of our recommendations to all physicians caring for patients with JIA, we focussed on CR and separated the five non-systemic, nonundifferentiated subtypes of JIA. Importantly, these recommendations are based not only on recently published data, but also, in many cases, on expert opinion, due to the paucity of paediatric studies. As a result, many of our recommendations are low grade, and in some cases obtaining guidance from recommendations for adults would seem to be the only option. However, the level of agreement among the multidisciplinary experts sitting on our panel was high.
Structural damage requires evaluation in JIA, especially in pJIA and extended oJIA, which carry the highest risk of adverse outcomes. In the treatment plans for pJIA developed by the CARRA, CR changes are considered an important outcome and their yearly assessment is suggested . However, the risk associated with exposure to ionising radiation during CR is of major concern, as pointed out by the representative of the patient organisation during our study. Little evidence is available on which to base an objective quantification of this risk. Our experts considered that the risk was substantial for CR of the pelvis and lumbar spine but was too small at peripheral sites to constitute an argument against using CR. To minimise radiation exposure, the experts recommended having CR performed at centres with expertise in paediatric radioprotection.
Research is needed in a broad range of areas to fill the knowledge gaps we identified when developing our recommendations (Box 2). More specifically, most paediatric clinical trials failed to assess potential treatment effects on structural damage. Also, data on structural damage just before the transition to adult healthcare are needed, since treatment recommendations for adults are based on structural damage.
Box 2: Research agenda
We considered neither MRI nor US, both of which are under evaluation in JIA. Both are non-irradiating, and US is also widely available and inexpensive, although it requires specific training. US is now performed almost routinely in adults with joint disease. In paediatric patients, however, differentiating normal from abnormal findings by MRI and US can be challenging [bib_ref] MRI thresholds for discrimination between normal and mild temporomandibular joint involvement in..., Ma [/bib_ref] [bib_ref] MRI of the wrist in juvenile idiopathic arthritis: erosions or normal variants?..., Muller [/bib_ref]. Furthermore, very few physicians are specifically trained in paediatric US. The OMERACT and Health-e-Child Radiology groups are currently working together to standardise MRI protocols and interpretation in JIA [bib_ref] MRI Protocol for the Assessment of Juvenile Idiopathic Arthritis of the Wrist:..., Nusman [/bib_ref] [bib_ref] Current Status of Efforts on Standardizing Magnetic Resonance Imaging of Juvenile Idiopathic..., Nusman [/bib_ref] [bib_ref] Preliminary definitions for the sonographic features of synovitis in children, Roth [/bib_ref].
In conclusion, CR still appears relevant in many situations in patients with JIA. CR is a widely available and inexpensive investigation that has an acceptable safety profile and can provide essential information about the structural course of the disease. Until validation studies of other imaging techniques, such as MRI and US, are completed, CR will remain the investigation of reference for assessing structural joint damage in patients with JIA.
Statistics and biometry No complex statistical methods, were necessary for this paper.
Ethical approval Institutional Review Board approval was not required; the methodology entirely relies on literature review and expert opinion.
Informed consent Informed consent was not required because no human subjects were involved.
[table] Table 2: Routine CR of the wrists, hands, and forefeet is strongly recommended at the diagnosis of polyarticular JIA with positive RF/ACPA. CR of other joints than wrists, hands, and forefeet, is recommended at the diagnosis for symptomatic* joints only. In new-onset RF/ACPA-negative pJIA with adverse prognostic factors, CR at diagnosis should be performed as for RF/ACPA-positive pJIA (recommendation #7). At other time points, the use of CR during follow-up is at the discretion of the physician. During the follow-up of RF/ACPA-negative pJIA with adverse prognostic factors, CR should be performed as for RF/ACPA-positive pJIA (recommendation #12). [/table]