Inter- and intrareader variability in the interpretation of two radiographic classification systems for juvenile rheumatoid arthritis

Tocilizumab may slow radiographic progression in patients with systemic or polyarticular-course juvenile idiopathic arthritis: post hoc radiographic analysis from two randomized controlled trials

Background

Few clinical trials have investigated the prevention of radiographic progression in children with juvenile idiopathic arthritis treated with antirheumatic drugs. This study aimed to investigate radiographic progression in patients with systemic juvenile idiopathic arthritis (sJIA) and patients with polyarticular-course juvenile idiopathic arthritis (pcJIA) treated with the anti–interleukin-6 receptor antibody tocilizumab for 2 years in the TENDER and CHERISH randomized controlled trials, respectively.

Methods

Standard radiographs of both wrists and both hands in the posteroanterior view were obtained within 4 weeks of baseline and were repeated at weeks 52 ± 4 and 104 ± 4 in both trials. All films were scored by two independent readers using the adapted Sharp–van der Heijde (aSH) and Poznanski scoring methods. Although the Poznanski score indicates bone growth limitation or cartilage growth decrease, which are not the same as joint space narrowing in rheumatoid arthritis, its change reflects damage to cartilage. Therefore, impairment in the Poznanski score as well as the aSH score was considered as a measure of structural joint damage. Radiographic progression was defined as worsening of radiographic scores beyond the smallest detectable difference.

Results

Poznanski and aSH scores were available at baseline and at one or more postbaseline time points for 33 and 47 of 112 sJIA patients and 61 and 87 of 188 pcJIA patients, respectively, providing a representative subset of the study populations. The inter-reader and intra-reader agreement intra-class correlation coefficient was > 0.8. Median baseline Poznanski and aSH scores, respectively, were − 2.4 and 24.6 for sJIA patients and − 1.5 and 8.0 for pcJIA patients. Compared with baseline, aSH scores remained stable for all sJIA patients at week 52, whereas 9.4% of sJIA patients had radiographic progression according to Poznanski scores at week 52; at 104 weeks, radiographic progression according to aSH and Poznanski scores was observed in 5.4% and 11.5%, respectively. In pcJIA patients, radiographic progression from baseline at 52 weeks and at 104 weeks was 12.5% and 2.9%, respectively, using aSH scoring and 6.5% and 4%, respectively, using Poznanski scoring.

Conclusion

Tocilizumab may delay radiographic progression in children with sJIA and children with pcJIA.

Trial registration

Trial registration numbers and dates: TENDER, NCT00642460 (March 19, 2008); CHERISH, NCT00988221 (October 1, 2009)

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.

KEY POINTS

• CR is a valuable imaging technique in selected indications. • CR is routinely recommended for peripheral joints, when damage risk is high. • CR is recommended according to the damage risk, depending on JIA subtype. • CR is not the first-line technique for imaging of the axial skeleton.

Quantifying Temporomandibular Joint Synovitis in Children With Juvenile Idiopathic Arthritis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) frequently affects the temporomandibular joints (TMJs) and is often undetected by history, examination, and plain imaging. Qualitative assessment of gadolinium-enhanced magnetic resonance images (MRIs) is currently the standard for diagnosis of TMJ synovitis associated with JIA. The purpose of this study is to apply a quantitative analysis of synovial enhancement to MRIs of patients with and without JIA to establish a disease threshold and sensitivity and specificity for the technique.

METHODS

This is a retrospective case-control study of children (age ≤16 years) who had MRIs with gadolinium including the TMJs. Subjects were divided into a JIA group and a control group. From a coronal T1-weighted image, a ratio (enhancement ratio [ER]) of the average pixel intensity within three 0.2-mm² regions of interest (ROIs) in the TMJ synovium to that of a 50-mm² ROI of the longus capitis muscle was calculated. Receiver operating characteristic curves were used to determine the sensitivity and specificity. The inter- and intraexaminer reliability was evaluated with Bland-Altman plots and 2-way mixed, absolute agreement intraclass correlation coefficients.

RESULTS

There were 187 and 142 TMJs included in the JIA and control groups, respectively. An ER threshold of 1.55 had a sensitivity and specificity for detecting synovitis of 91% and 96%, respectively. The inter- and intraexaminer reliability was excellent.

CONCLUSION

Calculating a ratio of pixel intensity between the TMJ synovium and the longus capitis muscle is a reliable way to quantify synovial enhancement. An ER of 1.55 differentiates normal TMJs from those affected by inflammatory arthritis.

Juvenile Idiopathic Arthritis: Diagnosis and Treatment

Juvenile idiopathic arthritis is a broad term that describes a clinically heterogeneous group of arthritides of unknown cause, which begin before 16 years of age. This term encompasses several disease categories, each of which has distinct presentation, clinical manifestations, and, presumably, genetic background and etiopathogenesis. Although none of the available drugs has curative potential, prognosis has greatly improved as a result of substantial progresses in disease management. The most important new development has been the introduction of the biologic medications, which constitute a valuable treatment option for patients who are resistant to conventional antirheumatic agents. Further insights into the disease pathogenesis and treatment will be provided by the continuous advances in understanding of the mechanisms related to the immune response and inflammatory process, and by the development of new drugs that are capable of selectively inhibiting single molecules or pathways.

Imaging of juvenile idiopathic arthritis: a multimodality approach

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases characterized by synovial inflammation and is the most common rheumatic complaint in children. To facilitate research and treatment, JIA has been further classified on the basis of the number of joints involved, additional symptoms, family history, and serologic findings. Imaging in patients with JIA has historically relied on radiography, which allows the accurate assessment of chronic changes of JIA, including growth disturbances, periostitis, and joint malalignment. However, radiographic findings of active inflammation are nonspecific, and, in the past, clinical evaluation has taken precedence over imaging of acute disease. Recent advances in disease-modifying therapeutic agents that can help prevent long-term disability in patients with JIA have led to greater emphasis on the detection of early joint-centered inflammation that cannot be accurately assessed radiographically and may not be evident clinically. Both contrast material-enhanced magnetic resonance (MR) imaging and Doppler ultrasonography (US) are well suited for this application and are playing an increasingly important role in diagnosis, risk stratification, treatment monitoring, and problem solving. Contrast-enhanced MR imaging is the most sensitive technique for the detection of synovitis and is the only modality that can help detect bone marrow edema, both of which indicate active inflammation. US is more sensitive than radiography for the detection of synovial proliferation and effusions and is particularly useful in the evaluation of small peripheral joints. The complexity of the temporomandibular and sacroiliac joints limits the usefulness of radiographic or US evaluation, and contrast-enhanced MR imaging is the preferred modality for evaluation of these structures.

Frequency of radiographic damage and progression in individual joints in children with juvenile idiopathic arthritis

OBJECTIVE

To evaluate the presence and progression of radiographic joint damage, as assessed with the adapted Sharp/van der Heijde score (SHS), in individual joints in the hand and wrist in patients with juvenile idiopathic arthritis (JIA) and to compare progression of damage among different JIA categories.

METHODS

A total of 372 radiographs of both wrists and hands obtained at first observation and at last followup visit (after 1-10 years) in 186 children with polyarticular-course JIA were evaluated. All radiographs were scored using the adapted SHS by 2 independent readers. Radiographic assessment included evaluation of joint space narrowing (JSN) and erosions on baseline and last followup radiographs and of progression of radiographic changes from baseline to last followup radiographs.

RESULTS

Both JSN and erosions occurred in all adapted SHS areas. Overall, radiographic damage and progression were more common in the wrist and less common in metacarpophalangeal (MCP) joints. The hamate and capitate areas appeared particularly vulnerable to cartilage loss. Erosions were identified most frequently in the hamate and capitate bones as well as in the second and third metacarpal bases. Patients with extended oligoarthritis were distinctly less susceptible to JSN in hand joints, whereas patients with polyarthritis showed a greater tendency to developing erosions in hand joints.

CONCLUSION

Radiographic joint damage and progression in our patients with JIA were seen most commonly in the wrist and less commonly in MCP joints. The frequency and localization of structural abnormalities differed markedly across disease categories.

Agreement among musculoskeletal pediatric specialists in the assessment of radiographic joint damage in juvenile idiopathic arthritis

OBJECTIVE

To evaluate agreement among musculoskeletal pediatric specialists in assessing radiographic joint damage in juvenile idiopathic arthritis (JIA).

METHODS

Two pediatric rheumatologists, 2 pediatric radiologists, and 2 pediatric orthopedic surgeons evaluated independently 60 radiographs of both wrists and hands of children with polyarticular-course JIA. Films were scored using an adapted and simplified version of the Larsen score, ranging from 0-5. Study radiographs were selected from 568 films used in a previous study aimed to validate an adapted pediatric version of the Sharp/van der Heijde (SHS) score. To enable comparison of specialists' scores with the adapted SHS score, the 60 radiographs were divided into 6 classes of severity of damage based on quintiles of the adapted SHS score. Agreement was evaluated in terms of absolute agreement and through weighted kappa statistics.

RESULTS

The pediatric radiologists tended to assign lower scores and to provide more frequently scores of 0 than did the other specialists. Weighted kappa for the 3 pairs of specialists ranged from 0.67-0.69, indicating substantial agreement. Absolute agreement ranged from 51.3-55.7%, depending on the pair of specialists examined. Both absolute and weighted kappa concordance between specialists' scores and the adapted SHS score were poorer for the pediatric radiologist than for the other specialists.

CONCLUSION

We observed fair agreement in the assessment of radiographic damage among pediatric specialists involved in the care of children with JIA. The radiologists tended to be more reserved than the rheumatologists and orthopedic surgeons in labeling radiographs as damaged or in considering changes as important.

The diagnostic accuracy of unenhanced MRI in the assessment of joint abnormalities in juvenile idiopathic arthritis

OBJECTIVES

To assess the diagnostic accuracy and reliability of MRI without contrast enhancement in the evaluation of JIA knee joint abnormalities.

METHODS

JIA patients with clinically active knee involvement were prospectively studied using an 1-T open-bore magnet. MRI features were independently evaluated by two readers using the JAMRIS system. The first reading included unenhanced images, whereas complete image sets were available for the second reading.

RESULTS

Imaging findings from 73 patients were analysed. Agreement between Gd-enhanced (+Gd) and Gd-unenhanced (-Gd) MRI scores of bone marrow changes, cartilage lesions and bone erosions was good concerning sensitivity, specificity, negative predictive value and positive predictive value. Inter-observer agreement was good for both -Gd and +Gd scores (ICC = 0.91-1.00, 0.93-1.00, respectively). Regarding the assessment of synovial hypertrophy, specificity of -Gd was high (0.97), but the sensitivity of unenhanced MRI was only 0.62. Inter-reader agreement for +Gd MRI was ICC = 0.94; however, omitting post-Gd acquisitions increased inter-reader variation (ICC = 0.86).

CONCLUSIONS

If Gd-enhanced MRI is the reference standard, omitting Gd contrast medium is irrelevant for the assessment of bone marrow changes, cartilage lesions and bone erosions as joint abnormalities in JIA. Omitting intravenous Gd in the MRI assessment of joints in JIA is inadvisable, because it decreases the reliability of detecting synovial disease.

KEY POINTS

• Magnetic resonance imaging is increasingly used to assess juvenile idiopathic arthritis. • Synovial hypertrophy, a marker of JIA activity, is well shown by MRI. • Omitting intravenous contrast medium decreases the reliability of synovial hypertrophy scores. • Bone marrow, cartilage and erosions can be reliably evaluated without contrast enhancement. • In the evaluation of JIA disease activity, unenhanced MRI is inadvisable.

Epidemiology, pathogenesis, and imaging of arthritis in children

Juvenile idiopathic arthritis is a broad term used to describe a series of chronic arthritis occurring in children younger than 16 years of age. Even though the cause is not fully understood, several clues regarding the pathogenesis have been found. Diagnosis of the different types of juvenile idiopathic arthritis is made clinically, and imaging plays a role in answering specific questions pertaining to disease classification, staging, and outcome of treatment options.

Advances and challenges in imaging in juvenile idiopathic arthritis

Imaging assessments of the joints of children with juvenile idiopathic arthritis (JIA) are challenging, owing to the unique features of the growing skeleton. Traditionally, imaging studies in childhood arthritis have been based on conventional radiography. However, in the past few years, interest in the use of MRI and ultrasonography has increased. As a result, imaging has become a main area of clinical and research investigation in paediatric rheumatology. The chief advance in the field of conventional radiography has been the development and validation of paediatric scoring systems for the assessment of radiographic progression. Several studies have shown that MRI provides a precise quantification of synovitis in children with JIA. Furthermore, a high frequency of bone marrow oedema and bone erosions has been found early in the disease course. Ultrasonography has been proven to be superior to clinical examination in detecting synovitis, tenosynovitis and enthesitis. A high frequency of subclinical synovitis has been demonstrated in patients with JIA who have clinically inactive disease using both MRI and ultrasonography. However, more information from healthy children is needed to enable differentiation of the bone and cartilage abnormalities that reflect damage from those that are part of normal development using MRI or ultrasonography. This Review provides a summary of the current information on conventional radiography, ultrasonography and MRI in JIA and highlights the advantages and limitations of each imaging modality.

Synovial and inflammatory diseases in childhood: role of new imaging modalities in the assessment of patients with juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) represents a group of heterogeneous diseases characterized by a chronic inflammatory process primarily targeting the synovial membrane. A persistent synovitis is associated with an increased risk of osteocartilaginous damage.With the advent of effective structure-modifying treatment for JIA, it may be possible to significantly reduce or even completely prevent structural damage and associated functional disability. The trend towards early suppression of inflammation, in order to prevent erosive disease, shifts the emphasis away from conventional radiographic detectable structural damage to the slightest traces of early joint damage, and drives the need for alternative imaging techniques more sensitive in detecting early signs of disease activity and damage. In this regard MRI and US are playing an increasing role in the evaluation of arthritic joints.This article will review the key aspects of the current status and recent important advances of imaging techniques available to investigate the child with rheumatic disease, briefly discussing conventional radiography, and particularly focusing on MRI and US. In this era of advancing imaging technology, knowledge of the relative values of available imaging techniques is necessary to optimize the management of children with JIA.

Quantitative MR in multi-center clinical trials

MRI has a wide variety of applications in the clinical trials process. MR has shown particular utility in the early phases of clinical development, when trial sponsors are interested in demonstrating proof of concept and must make decisions about allocation of resources to a particular compound based on the results from a small number of experimental subjects. This utility is largely due to the many different imaging endpoints that can be measured using MR, ranging from structural (tumor burden, hippocampal volume) to functional (blood flow, vascular permeability) to molecular (hepatic fat fraction, glycosaminoglycan content). The unique flexibility of these systems has proven to be both a blessing and a curse to those attempting to deploy MR in multi-center clinical trials, however, as differences among scanner manufacturers and models in pulse sequence implementation, hardware capabilities, and even terminology make it increasingly difficult to ensure that results obtained at one center are comparable to those at another. These problems are compounded by the differences between the procedures used in clinical trials and those used in routine clinical practice, which make trial-specific training for site technologists and radiologists a necessity in many cases. This article will briefly review the benefits of including quantitative MR imaging in clinical trials, then explore in detail the challenges presented by the need to develop and deploy a detailed MR protocol that is both effective and implementable across many different MR systems and software versions.

Development and Initial Validation of a Radiographic Scoring System for the Hip in Juvenile Idiopathic Arthritis

Objective.

To develop and validate a radiographic scoring system for the assessment of radiographic damage in the hip joint in patients with juvenile idiopathic arthritis (JIA).

Methods.

The Childhood Arthritis Radiographic Score of the Hip (CARSH) assesses and scores these radiographic abnormalities: joint space narrowing (JSN), erosion, growth abnormalities, subchondral cysts, malalignment, sclerosis of the acetabulum, and avascular necrosis of the femoral head. Score validation was accomplished by evaluating reliability and correlational, construct, and predictive validity in 148 JIA patients with hip disease who had a total of 381 hip radiographs available for study.

Results.

JSN was the most frequently observed radiographic abnormality, followed by erosion and sclerosis of the acetabulum. The least common abnormalities were avascular necrosis, growth abnormalities, and malalignment. Interobserver and intraobserver reliability on baseline and longitudinal score values and on score changes was good, with intraclass correlation coefficients ranging from 0.76 to 0.98. Early score changes, but not absolute baseline score values, were moderately correlated (rs > 0.4) with clinical indicators of disease damage at last followup observation, thereby demonstrating that the CARSH has good construct and predictive validity. The amount of structural damage in the hip radiograph at last followup observation was predicted better by baseline to 1-year score change (rs = 0.66; p < 0.0001) than by absolute baseline score values (rs = 0.40; p = 0.002).

Conclusion.

Our results show that the CARSH is reliable and valid for the assessment of radiographic hip damage and its progression in patients with JIA.

MRI in juvenile idiopathic arthritis and juvenile dermatomyositis

The use of MRI in the assessment of the musculoskeletal system in children has important differences from its use in adults. Growth in children has significant impact on the epiphysis and growth plate, which are important structures in the growing child, and there are radiological features that differ from those in adults: disease may alter structures during a period of growth; the pathologies themselves are a distinct group of diseases at variance with adult arthritis and myositis, with a different spectrum of differential diagnoses; and many technical issues are different when imaging a child. These are important considerations in choosing the appropriate imaging. MRI is a powerful and valuable imaging technique in pediatric musculoskeletal pathologies, with considerable potential for future developments to enhance its role in diagnosis, management, and therapeutic intervention for these children.

US findings of metacarpophalangeal joints in children with idiopathic juvenile arthritis

BACKGROUND

Juvenile idiopathic arthritis (JIA) is the most common cause of chronic arthritis in children, with frequent involvement of the metacarpophalangeal joints (MCPJ).

OBJECTIVE

To compare US findings with those of radiography and clinical examination.

MATERIALS AND METHODS

All MCPJs in 20 children with JIA (17 females, median age 9.7 years, range 3.6 to 16.8 years) were evaluated clinically and imaged with gray-scale and color Doppler US, and 90 MCPJs were also imaged radiographically. Each MCPJ was graded on physical examination from 0 (normal) to 4 (severe) by the patient's rheumatologist.

RESULTS

US demonstrated abnormalities in 64 of 200 MCPJs (32.0%), including pannus vascularity and/or tenosynovitis in 55 joints (27.5%) (pannus vascularity in 43, tenosynovitis in 40) and bone destruction in 25 joints (12.5%). Overall, US abnormalities and physical examination scores were significantly associated (P < 0.001). However, interobserver agreement between US and clinical evaluation was poor (kappa 0.1) and between US and radiography was only fair (kappa 0.4).

CONCLUSION

US of the MCPJ in children with JIA can demonstrate cartilage thinning, bone erosions, and pannus vascularity. Abnormal US findings are significantly correlated with severity of disease as evaluated clinically.

Adapted versions of the Sharp/van der Heijde score are reliable and valid for assessment of radiographic progression in juvenile idiopathic arthritis

OBJECTIVE

To develop adapted versions of the Sharp/van der Heijde radiographic scoring system for use in juvenile idiopathic arthritis (JIA), and to investigate their validity in JIA patients with polyarticular disease.

METHODS

The study group comprised 177 patients with polyarticular JIA. Radiographs of the wrist/hand of each patient were obtained at baseline (first observation) and then at 1, 3, 5, 7/8, and 10 years and were assessed independently by 2 pediatric rheumatologists according to different adaptations of the Sharp/van der Heijde method. To facilitate score assignment, the radiograph for each patient was compared with a bone age-related standard. Validation procedures included analysis of reliability, construct validity, and score progression over time.

RESULTS

Interobserver and intraobserver agreement on longitudinal score values and score changes was good for all of the adapted scoring versions (intraclass correlation coefficient >0.85). Score changes over time were moderately to strongly correlated with the clinical indicators of long-term joint damage and with the amount of long-term radiographic damage as measured with the carpo:metacarpal ratio, thereby demonstrating good construct validity. A steady increase in scores over time was observed, with joint space narrowing being the most common form of damage throughout the disease course. The inclusion of 5 new areas appeared to increase the overall construct validity of erosion scores.

CONCLUSION

Our results show that the adapted versions of the Sharp/van der Heijde score are reliable and valid for the assessment of radiographic progression in patients with JIA.

High-Frequency Sonographic Patterns of the Spleen in Children

PURPOSE

To retrospectively evaluate the normal sonographic appearance of splenic parenchyma in children of various ages with high-frequency transducer sonography.

MATERIALS AND METHODS

Research ethics committee board approval was obtained, with waiver of informed consent. We evaluated in vivo sagittal and transverse sonograms of spleens obtained with 13-MHz linear-array transducers in 100 children (age range, 1 day to 17 years) with clinically diagnosed disease that did not affect the lymphoid system. Three radiologists working in consensus defined the grading system for the splenic parenchyma. Thereafter, these same radiologists graded the sonographic reticulonodular pattern independently as granular, mild, or marked. These grades were cross correlated with clinical data by using logistic regression analysis and chi(2) tests. Sonographic measurements of the splenic parenchyma in nine pediatric cadavers separate from the in vivo cohort of the study were compared with those of corresponding histologic slices by means of linear correlation.

RESULTS

Both grade 2 and grade 3 patterns occurred more frequently in children older than 1 year but no older than 5 years, whereas grade 1 pattern occurred most frequently in neonates (P < .001). As patients' age (odds ratio, 1.6; P < .001) and splenic dimensions (odds ratio, 3.1; P < .001) increased, the frequency with which the reticulonodular pattern was classified as either grade 2 or grade 3 increased. No association was noted between sonographic patterns and body mass index (P = .85) or sex (P = .07). The parenchymal nodules graded as 2 or 3 on sonograms correlated well with the presence of lymphoid follicles (white pulp) at histologic analysis (r = .71, P = .03).

CONCLUSION

High-frequency transducer sonography of the spleen in children can demonstrate normal echo patterns that should not be misinterpreted as indicative of disease.

Imaging of juvenile idiopathic arthritis

Over the past decade there have been considerable changes in the classification and imaging of juvenile idiopathic arthritis (JIA). Radiology now has a considerable role in the management of JIA, the differential diagnosis, monitoring disease progression and detecting complications. The different imaging modalities available, their role and limitations are discussed in this article and the various disease features that the radiologist should be aware of are described. An approach to the imaging of the child with joint disease and in the monitoring of disease complications are also discussed.

A critical appraisal of radiographic scoring systems for assessment of juvenile idiopathic arthritis

Assessing structural damage to joints over time is essential for evaluating the effectiveness of therapeutic interventions for patients with inflammatory arthritis. Although radiography is able to quantify joint damage, the changes found with conventional radiography early in the disease course are nonspecific, and late radiographic changes are often irreversible. Although many clinical trials on drug development for children still use radiographic scales as endpoints for the study, more specific therapies have been developed for juvenile idiopathic arthritis (JIA) that would enable imaging to "fine-tune" patients to placement into specific treatment algorithms. As a result, new imaging scales to identify early abnormalities are clearly needed. Many pediatric rheumatology centers around the world persistently apply adult-designed radiographic scoring systems to evaluate the progression of JIA. Few pediatric-targeted radiographic scales are available for assessment of progression of JIA in growing joints, and the clinimetric and psychometric properties of such scales have been poorly investigated. We present a critique to the evaluative, discriminative, and predictive roles of the van der Heijde modification of Sharp's radiographic method, a scale originally designed to assess damage to joints of adults with rheumatoid arthritis, when it is applied to a pediatric population. We discuss the advantages and drawbacks of this radiographic scoring system for assessing growing joints and the ability of MRI to overcome inadequacies of conventional radiography.