pediatric imaging 1253 imaging of juvenile idiopathic...

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1253PEDIATRIC IMAGING

Elizabeth F. Sheybani, MD2 • Geetika Khanna, MD, MS • Andrew J. White, MD, MSc • Jennifer L. Demertzis, MD

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases characterized by synovial inflammation and is the most common rheu-matic 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 dis-turbances, 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 accu-rately 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 im-aging 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 radiogra-phy for the detection of synovial proliferation and effusions and is par-ticularly useful in the evaluation of small peripheral joints. The complex-ity 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. ©RSNA, 2013 • radiographics.rsna.org

Imaging of Juvenile Idiopathic Arthritis: A Multimodality Approach1

Abbreviations: ERA = enthesitis-related rheumatoid arthritis, ILAR = International League of Associations for Rheumatology, JIA = juvenile idiopathic arthritis, OMERACT = Outcome Measures in Rheumatology Clinical Trials, RAMRIS = rheumatoid arthritis MR imaging score, RF = rheumatoid factor, STIR = short inversion time inversion-recovery, TMJ = temporomandibular joint

RadioGraphics 2013; 33:1253–1273 • Published online 10.1148/rg.335125178 • Content Codes: 1From the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, Campus Box 8131, St Louis, MO 63110. Recipient of a Certificate of Merit award for an education exhibit at the 2011 RSNA Annual Meeting. Received August 17, 2012; revi-sion requested November 14 and received February 8, 2013; accepted February 13. For this journal-based SA-CME activity, the authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to E.F.S. (e-mail: [email protected]).

2Current address: The Hospital for Sick Children, Toronto, Ontario, Canada.

©RSNA, 2013

INVITED COMMENTARY

See discussion on this article by Rao (pp 1273–1275).

SA-CME

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LEARNING OBJECTIVES FOR TEST 2

After completing this journal-based SA-

CME activity, partic-ipants will be able to:

■ Describe the clinical features and classification of juvenile idiopathic arthritis.

■ Discuss the role of different imaging modalities in the evaluation of com-plex joints in pa-tients with juvenile idiopathic arthritis.

■ Identify the char-acteristic imaging findings of juvenile idiopathic arthritis.

1254 September-October 2013 radiographics.rsna.org

IntroductionJuvenile idiopathic arthritis (JIA) includes all forms of arthritis that develop before the age of 16 years, persist for at least 6 weeks, and have no identifiable cause. JIA is the most common rheumatic disease in children, with a reported prevalence of 16–150 per 100,000 children (1). JIA remains a clinical diagnosis with varied manifestations and is influenced by genetic and environmental factors. Historically, imaging evaluation for known or suspected JIA has relied primarily on radiography. However, radiographic findings such as bone erosions, joint space nar-rowing from cartilage destruction, and growth disturbances are irreversible findings that occur late in the course of disease. The development of improved therapeutic agents whose use can pre-vent joint destruction, especially when treatment is initiated early, highlights the importance of early (preradiographic) detection of inflamma-tion. The potentially serious side effects of these newer therapeutic agents in the pediatric popu-lation underscore the importance of accurately assessing disease activity, disease progression, and treatment response. As a result, manage-ment of JIA has evolved to include greater utili-zation of advanced imaging techniques such as contrast material–enhanced magnetic resonance (MR) imaging and Doppler ultrasonography (US), either of which can help in (a) detecting inflammatory lesions before permanent joint destruction occurs, and (b) monitoring disease progression and treatment response to more ef-fectively guide therapy (2).

In this article, we review the most recently de-veloped classification system for JIA and describe a rational approach for imaging of this disease entity, with emphasis on MR imaging and US. In addition, we discuss the imaging of peripheral joints in patients with JIA, as well as special con-siderations in the imaging of complex structures such as the cervical spine, temporomandibular joint (TMJ), and sacroiliac joints.

JIA ClassificationJIA is a diagnosis of exclusion that encompasses a broad range of disease manifestations and prog-noses. The most recent JIA classification system was proposed by the International League of As-sociations for Rheumatology (ILAR) (Table 1) in an attempt to facilitate disease management, pre-dict outcomes, and refine research populations (3). Although portions of this classification sys-tem have been brought under scrutiny and clas-

sification may continue to evolve, the radiologist should be familiar with the manifestations of the various JIA subtypes, possess a rational approach for imaging affected joints, and recognize findings related to disease prognosis to guide differential diagnosis and management in patients with JIA.

Oligoarthritis, which by definition affects from one to four joints within 6 months of onset, is the most common JIA subtype and classically in-volves the knees or ankles of preschool-aged girls (4). Iridocyclitis is a characteristic feature of oli-goarthritis that affects up to 30% of patients and necessitates routine ophthalmologic screening (1). Polyarthritis, which involves more than five joints within 6 months of onset, is further clas-sified on the basis of serologic test results. RF-positive polyarthritis classically entails symmetric involvement of the small joints of the hands in adolescent girls. It can be thought of as early-on-set, adult rheumatoid arthritis with erosive joint destruction, an uncommon finding in other JIA subtypes (Fig 1) (4). RF-negative polyarthritis may manifest at any age throughout childhood, is heterogeneous in terms of presentation and prog-nosis, and does not have a characteristic pattern of joint involvement. Systemic arthritis is a poten-tially fatal subtype of JIA and includes recurrent daily fevers in its definition. Systemic findings may include characteristic rash, lymphadenopa-thy, and hepatosplenomegaly. The classically symmetric and polyarticular joint involvement in systemic arthritis may not develop until late in the disease course. A subset of patients with systemic arthritis develop macrophage activation syndrome, an acute, life-threatening condition that is characterized by pancytopenia, dissemi-nated intravascular coagulation, liver dysfunc-tion, and sustained fever resulting in multiorgan failure. The paradoxically decreased erythrocyte sedimentation rate helps distinguish macrophage activation syndrome from a rheumatologic dis-ease flare (1). ERA predominantly affects boys over 6 years of age and is characterized by en-thesitis, most commonly of the Achilles tendon insertion, plantar fascia, and tarsus, frequently with asymmetric arthritis of the lower extremities. Unlike in other subtypes of JIA, hip involvement is common at the time of presentation in ERA (1). Spinal involvement usually does not manifest until adulthood (4). Juvenile psoriatic arthritis, like RF-negative polyarthritis, is heterogeneous in terms of presentation and prognosis (1,4). Patients with psoriatic arthritis can have large or small joint involvement and may pre sent with dactylitis before developing typical skin changes of psoriasis (Fig 2).

RG • Volume 33 Number 5 Sheybani et al 1255

Figure 1. RF-positive polyarticular JIA in an 18-year-old woman. Anteroposterior radiographs of the left (a) and right (b) hands show extensive bilateral erosive changes in the carpal and metacarpal bones (arrows) and erosions with associated periosteal reaction and soft-tissue swelling at the proximal phalan-ges of the left third finger, right fourth finger, and right little finger (arrowheads). There is marked joint space loss in both wrists and at several metacarpophalangeal and interphalangeal joints. This pattern of involvement is reminiscent of adult rheumatoid arthritis.

Table 1 ILAR Classification of JIA

Category Definition

Systemic arthritis One or more joints affected with or preceded by at least 2 weeks of fevers that have been daily for at least 3 days, with at least one of the following: transitory rash, generalized lymphadenopathy, hepato- or splenomegaly, or serositis

Oligoarthritis One to four joints affected within 6 months of onsetPolyarthritis (RF negative) Five or more joints affected within 6 months of onset, with a negative RF test

resultPolyarthritis (RF positive) Five or more joints affected within 6 months of onset, with two positive RF test

results at least 3 months apart within 6 months of disease onsetPsoriatic arthritis Arthritis and psoriasis, or arthritis and two or more of the following: dactylitis, nail

pitting or onycholysis, or psoriasis in a first-degree relativeERA Arthritis and enthesitis, or arthritis or enthesitis with two or more of the following:

presence or history of sacroiliac joint tenderness or inflammatory low back pain; positive HLA-B27 antigen; male over 6 years of age at onset; acute (symptom-atic) anterior uveitis; or a history of ankylosing spondylitis, ERA, sacroiliitis with IBD, Reiter syndrome, or acute anterior uveitis in a first-degree relative

Undifferentiated Fits into none or at least two of the other categories

Source.—Adapted from reference 3.Note.—ERA = enthesis-related arthritis, HLA = human leukocyte antigen, IBD = inflammatory bowel disease, RF = rheumatoid factor.


Figure 2. Psoriatic arthritis in a 10-year-old girl who presented with dactylitis. (a) Clinical photograph demonstrates swelling and erythema of the right second toe. (Courtesy of Dana Toib, MD.) (b) Antero-posterior radiograph of the right forefoot shows diffuse soft-tissue swelling with overgrowth of the sec-ond toe, a finding of chronic inflammation that is unique to the pediatric skeleton.

Figure 3. Acute radiographic changes in an 8-year-old boy with systemic JIA and left knee pain. (a) Clinical photograph demonstrates marked soft-tissue swelling of the left knee compared with the unaffected right knee. (Courtesy of Dana Toib, MD.) (b, c) Frontal (b) and lateral (c) radiographs of the left knee demonstrate nonspecific findings of active inflammation, including soft-tissue swelling (arrows) with a suprapatellar effusion or synovial thickening (*). Note the absence of erosions or joint space loss.


Imaging EvaluationImaging in JIA may be indicated to aid in di-agnosis, evaluate the extent and severity of dis-ease, assess treatment response, detect potential complications, and direct the administration of intraarticular therapeutic agents. Unlike the sys-tematic protocols for monitoring adult patients with rheumatoid arthritis, there are no defined imaging protocols for JIA (5). The timing and utilization of imaging in JIA must be tailored to the individual patient, with consideration given to the strengths and weaknesses of each avail-able modality in evaluating the joints in question and directing therapeutic decision making.

RadiographyRadiography has traditionally been the mainstay of imaging in JIA. Radiographs play an impor-tant role in initial diagnosis by excluding other

causes of joint pain and swelling and providing a baseline standard for follow-up. Radiographs are also useful for identifying late complications of JIA such as accelerated bone growth, premature physeal fusion, and limb length discrepancy. However, routine surveillance radiographs are not predictive of disease course and should be obtained during follow-up only when there is a change in symptoms or management (6).

For rheumatoid arthritis in adults, there are well-defined radiographic scoring systems, and radiographically defined structural damage has traditionally been a key outcome in clinical trials for new therapies (5,7). The largely cartilaginous composition of the pediatric skeleton limits ra-diographic detection of early erosive changes in children. Preerosive signs of inflammation such as synovitis and osteitis are undetectable on radiographs. In addition, the complexities of the maturing skeleton limit standardization of radiographic scoring for JIA (8). Although mul-tiple radiographic scoring systems for JIA have been proposed, none has been widely accepted for routine clinical use, in part due to significant inter- and intraobserver variation (9,10). Because of these limitations, clinical assessment of joint function and disability takes precedence over ra-diographic findings.

Radiographic findings in early-stage JIA are often nonspecific. The most commonly encoun-tered radiographic findings include soft-tissue swelling, joint effusion, and osteopenia (Fig 3). Osteopenia tends to be periarticular in the early stages of disease secondary to joint inflammation (Fig 4), whereas in advanced-stage JIA it can be diffuse due to decreased physical activity or ste-roid administration (9,11).

Persistent synovial inflammation can result in erosions, although these are less common in JIA than in adult rheumatoid arthritis because chil-dren have a large amount of epiphyseal cartilage, and significant cartilage destruction must occur before the bone is affected and erosions become radiographically apparent. In addition, the vascularization of immature cartilage provides some reparative capacity not found in adults.

Figure 4. RF-negative polyarticular JIA in a 10-year-old girl. Anteroposterior radiograph of the right hand demonstrates periarticular osteopenia (arrows) and soft-tissue swelling, which is most marked at the proximal interphalangeal and meta-carpophalangeal joints of the index finger (arrow-heads), findings that are indicative of active disease.


The prevalence of erosions and joint space loss has been shown to be higher in children with poly-articular JIA than in those with oligoarticular JIA (12). Although erosions can occur anywhere along the articular surface, they are most common at the sites of synovial reflection and ligament insertion, where there is less overlying protective cartilage. Joint space narrowing occurs due to thinning and gradual loss of the articular cartilage and is an ir-reversible finding (Fig 5). For evaluation of the lower extremities, weight-bearing radiographs are recommended over supine images for detecting joint space loss, limb length discrepancy, or joint malalignment, a particularly important consider-ation given that the knee is the most commonly involved joint in JIA.

Periostitis is more common in JIA than in adult rheumatoid arthritis (6). It most commonly occurs along the metacarpal and metatarsal bones, giving the bones an enlarged, squared-off appearance (6,13). Periostitis should not be confused with intraarticular, capsular, or periar-ticular calcifications, which can occur following therapeutic steroid injection (Fig 6). The cause of these periarticular calcifications is unknown. They most commonly occur around the knee, are composed of hydroxyapatite, and may be related to trauma and tissue necrosis (14,15).

Radiographic findings of advanced JIA include ankylosis, growth disturbances, and joint malalign-ment. Ankylosis, a feature of severe, long-standing disease in adults, has been reported to occur

Figure 5. Disease progression in a 12-year-old girl with a 7-year history of systemic JIA. (a) An-teroposterior radiograph of the right hip shows uniform joint space narrowing with small erosions of the femoral head. (b) Radiograph obtained 2 years later shows severe joint space loss (arrow) due to progressive, irreversible cartilage destruction. Acetabular and femoral head erosions (ar-rowhead) have also increased.

Figure 6. Iatrogenic periarticular calcification in a 9-year-old girl with a 2-year history of oligoar-thritis who was treated with multiple intraarticu-lar injections of triamcinolone. Anteroposterior radiograph of the proximal interphalangeal joint of the right fourth finger shows extraarticular calcifications along the ulnar aspect of the joint. Joint-centered soft-tissue swelling is also present.

within 3–5 years of disease onset in JIA. It is most commonly seen in the carpal and tarsal bones and the apophyseal joints of the upper cervical spine (Fig 7) (16,17). Growth disturbances are distinct radiographic findings of JIA as opposed to adult


Figure 8. Accelerated bone maturation in a 4-year-old girl with a 1-year history of oligoarticular JIA. Posteroanterior radiographs of the left (a) and right (b) wrists show asymmetric, advanced maturation and overgrowth of the carpal bones and distal radial epiphysis on the right side; the left side is unaffected. Note that the trapezoid ossification center is present on the right side (ar-row) but has not yet appeared on the left side.

arthritis (13). These changes reflect unique features of the immature skeleton, including growth potential, high cartilaginous content, and epiphyseal vascularization. Growth dis-turbances are more likely in patients who are young at the time of disease onset. Localized hyperemia may result in epiphyseal enlargement, accelerated maturation, and osseous overgrowth. Around the knee joint, epiphyseal enlargement causes widening of the intercondylar notch with squaring of the lower pole of the patella, find-ings that are classic for JIA but are also seen with hemophiliac arthropathy. During the early stages of disease, the accelerated growth results in a relative increase in the length of the affected

limb. In the hands, premature ossification of the carpal bones can result in a bone age greater than the chronologic age (Fig 8). In long-standing disease, accelerated maturation results in premature physeal fusion and epiphyseal de-struction with resultant limb shortening or joint malalignment. Joint malalignments such as sub-luxation, dislocation, and flexion and extension deformities can occur in any joint but are most commonly seen in the hands and feet. In con-tradistinction to the ulnar deviation seen at the wrist in adult rheumatoid arthritis, radial devia-tion at the wrist is typically seen in JIA (6).

Figure 7. Chronic radiographic changes in a 21-year-old woman in whom a diagnosis of poly-articular JIA had been made at 2 years of age. Posteroanterior radiograph of the right wrist shows erosions (arrows) at the radial articular surface and metacarpal bases and along the carpal bones, result-ing in crenated margins. There is diffuse joint space loss with ankylosis (arrowheads) of the second meta-carpal, trapezium, trapezoid, capitate, and scaphoid bones. Note the periarticular osteopenia and severe negative ulnar variance caused by premature closure of the ulnar physis.


Figure 9. Radiographically occult active inflammation in an 8-year-old girl with RF-negative poly-arthritis. (a) Anteroposterior radiograph of the left wrist shows normal findings, with the exception of an incidental lunotriquetral coalition. (b) Coronal contrast-enhanced fat-suppressed T1-weighted MR image demonstrates diffuse carpal bone marrow edema (*), a finding that is consistent with osteitis, as well as enhancing synovitis of the distal radioulnar (arrow) and intercarpal joints.

Despite the role of radiography as the standard of reference for joint evaluation in JIA, radio-graphic detection of inflammatory preerosive changes is limited (Fig 9) (9,11). Long-standing synovitis may lead to osteocartilaginous damage and permanent functional impairment, affecting up to one-third of JIA patients into adulthood (11). Early detection of synovial inflammation, cartilage damage, and erosive changes is essen-tial to initiating disease-modifying therapy and preventing long-term disability. MR imaging and US are uniquely suited to this goal. Both modali-ties are superior to radiography in the evaluation of synovial and cartilaginous changes and are increasingly being used in disease classification, prognosis, and treatment monitoring.

MR ImagingWith its multiplanar capability and excellent bone and soft-tissue contrast resolution, MR imaging is well-suited for imaging patients with JIA. MR imaging allows comprehensive evaluation of the synovium, articular cartilage, growth cartilage, bone marrow, cortical bone, and soft tissues. Contrast-enhanced MR imaging is the most sen-sitive imaging technique for detecting synovitis (9). In early JIA, MR imaging can help detect synovitis before it is apparent at physical examina-tion, a potentially important prognostic indicator (18,19). MR imaging is the only imaging modality that can demonstrate bone marrow edema (6,9),

and, although its prognostic significance in JIA has not been clearly defined, in adult rheumatoid arthritis bone marrow edema is a predictor of future erosions (20). Therefore, the presence of bone marrow edema in the setting of JIA is con-sidered a preerosive abnormality and an indication for initiating therapy to prevent permanent joint damage (11). MR imaging has been shown to help detect more than twice as many bone erosions in the wrist as either US or radiography (Fig 10) (21) and more than twice as many cases of sacroiliitis as radiography in a pediatric population (22). It can also help identify radiographically occult extraar-ticular inflammatory lesions such as tenosynovitis and enthesitis (9). MR imaging is nonirradiating, an important consideration in this radiosensitive population, although when a joint is being evalu-ated with MR imaging, correlative radiographs should be obtained to document findings and for future reference during treatment monitoring.

As with radiography, there are no fully vali-dated systems for monitoring JIA with MR im-aging (11). In adults, the Outcome Measures in Rheumatology Clinical Trials (OMERACT) study group has developed a semiquantitative scoring system and imaging protocol for the as-sessment of synovitis, bone marrow edema, and bone erosions in the wrist and metacarpophalan-geal joints of rheumatoid arthritis patients (rheu-matoid arthritis MR imaging score [RAMRIS]) (5). RAMRIS has been shown to have acceptable applicability to children despite differences in the pediatric and adult skeletons, and the three


principal scored findings are often extrapolated to joints other than the wrist and hand (23).

MR imaging should be performed on a high-field-strength magnet with a local coil closely matched in size to the affected area to achieve an acceptable signal-to-noise ratio. Spin-echo or fast spin-echo (T1-weighted) MR images (short repetition time, short echo time) are used to assess bone marrow and erosions. Wa-ter-sensitive fat-suppressed (fast spin-echo or short inversion time inversion-recovery [STIR] T2-weighted) MR images are used to evaluate joint and tenosynovial fluid, cartilage, marrow

Figure 10. Improved detection of erosions with MR imaging of the wrist in a 16-year-old girl with poly-articular JIA. (a) Posteroanterior radiograph through the left wrist demonstrates diffuse osteopenia with a well-defined erosion at the base of the hamate bone (arrow). Additional erosions are present but are difficult to delineate. (b) Coronal T1-weighted MR image demonstrates the erosion of the hamate bone (arrow) and reveals erosions in the scaphoid bone and the base of the second metacarpal bone (arrowheads). Ad-ditional images demonstrated erosions in nearly all of the carpal bones. (c) Sagittal contrast-enhanced fat-suppressed T1-weighted MR image shows uniform enhancement of the erosions involving the capitate bone and the base of the third metacarpal bone (arrowheads), and tenosynovitis in the extensor tendons (arrow), findings that are consistent with active inflammation.

edema, and tendons. The administration of gadolinium-based contrast material is essential for distinguishing active synovial inflammation from nonenhancing joint effusions or fibrotic (noninflamed) pannus; normal synovium dem-onstrates minimal to no enhancement. Contrast-enhanced fat-suppressed T1-weighted images (short repetition time, short echo time) should be obtained within 5–10 minutes of injection. Beyond this time, diffusion of contrast mate-rial into the joint limits differentiation between enhancing synovium and adjacent joint fluid (24). A combination of water-sensitive and post-contrast sequences (short repetition time, short echo time) performed in at least two orthogonal planes is essential for complete evaluation of any joint in the setting of JIA. This may be achieved


by either imaging in perpendicular planes with two-dimensional sequences or performing a three-dimensional sequence with isometric vox-els that can be reconstructed in other planes.

Assessment of articular cartilage with MR im-aging has traditionally relied on a morphologic description of detected abnormalities. A relatively recent innovation in the evaluation of JIA is T2 relaxation time cartilage mapping, which reflects biochemical changes in water and collagen con-tent and in tissue anisotropy in the extracellular matrix of articular cartilage. T2 mapping of artic-ular cartilage in the knee has been shown to help detect microstructural changes caused by inflam-mation before morphologic changes can be de-tected at conventional MR imaging (25). Kim et al (26) reported a progressive increase in T2 re-laxation time for distal femoral articular cartilage during follow-up of children with recently diag-nosed JIA, despite improving clinical assessment. More recently, T2 relaxation mapping techniques have been successfully applied in studying the cartilage of the small joints of the hands (27).

Despite these benefits, MR imaging examina-tions are lengthy, require the intravenous admin-istration of contrast material to maintain sensi-tivity, and frequently entail sedation of pediatric patients to obtain a diagnostic study. Moreover, imaging is restricted to a single joint or area of the body to achieve adequate contrast and spatial resolution. Because of these limitations, MR im-aging is presently reserved for critical therapeutic decision making and problem solving in unusual cases, with the exception of the evaluation of complex structures such as the TMJ and sacro-iliac joints, for which MR imaging is the current standard of reference (11).

UltrasonographyUS is a versatile modality for imaging patients with JIA. It is nonionizing, relatively inexpensive, and readily accessible; allows a survey of multiple joints; and does not require sedation. Although US is operator dependent, in experienced hands it provides reliable assessment of synovial pro-liferation, joint effusion, cartilage thickness, car-tilage and cortical erosions, and tenosynovitis. US allows direct visualization of the articular cartilage, which is normally seen as a hypoechoic structure with a smooth outline over the bone surface. US can also be used to facilitate joint as-piration or therapeutic injection.

There are no standardized US protocols for evaluating patients with JIA, but abnormalities such as erosions, tenosynovitis, and enthesi-tis must be documented in two perpendicular

planes. Therefore, orthogonal imaging of each area of concern is recommended. US evalua-tion of joints should be performed with high-frequency (12–15-MHz) linear transducers that provide sufficient resolution for evaluation of articular cartilage and intraarticular diseases such as erosions (6). Incorporation of color or power Doppler imaging provides diagnostic information regarding synovial vascularity and hyperemia (6,28). The availability of US con-trast agents may further improve detection and assessment of synovial proliferation and hyper-emia (29).

Compared with radiography, US is more sen-sitive for detecting joint effusions and synovial thickening and has been shown to be particularly helpful in evaluating the small joints of the hands and feet (30,31). Several studies have also demon-strated that US helps accurately detect subclini-cal synovitis and, in conjunction with physical examination, is useful in evaluating response to intraarticular therapy (32–35). Timely detection of subclinical synovitis is particularly important in JIA, not only because early detection and treat-ment may prevent long-term disability, but also because the ILAR subtypes are classified on the basis of the number of joints involved within 6 months of disease onset (3). Additionally, identifi-cation of subclinical joint involvement at US may allow patient inclusion in clinical trials for newer biologic agents in which polyarticular disease and active inflammation are required for enrollment (13,36). It has been suggested that, given the low sensitivity of physical examination for active syno-vitis, asymptomatic joints should be screened with US in patients with at least one actively inflamed joint. However, the prognostic implications of US-identified synovitis in the absence of clinically ac-tive disease are not well established. In one study in which patients were followed up for 6 months, only 35.7% of patients with US-identified synovi-tis went on to develop clinically apparent disease. In the remaining patients, mild hyperemia was the only abnormal US finding, which suggests that mild hyperemia alone is not sufficient to diagnose active synovitis (37).

US evaluation does have its disadvantages. Operator variability and the scarcity of data re-garding standardized imaging protocols limit the reproducibility, interpretation, and comparison of studies. In large joints, visualization of the en-tire articular surface may be limited by adjacent shadowing bone, and sound beam attenuation limits the amount of anatomic detail seen at im-aging of deeper structures. US cannot be used to evaluate complex joints such as the sacroiliac joints and the TMJ, and it has high false-negative rates in the detection of subtalar disease (3,37).


Joint-specific Findings and Recommendations

Peripheral JointsAlthough the patterns of peripheral joint in-volvement vary with JIA subtype, the imaging findings in active and chronic disease are simi-lar throughout the large and small joints of the appendicular skeleton. In the setting of JIA, the primary goal of imaging is to detect active inflammation that may be amenable to the ad-ministration of either site-specific or systemic therapy to prevent irreversible joint damage. Generally, both US and MR imaging will help make this determination in the large and small joints of the extremities. With either modality, important findings to document include the presence or absence of synovitis and synovial hy-pertrophy, joint effusion, tenosynovitis, periar-ticular inflammation such as enthesitis and peri-ostitis, and bone erosions. Bone marrow edema

can be detected with MR imaging, whereas US is not helpful in this regard. Because there are no standardized, validated definitions for these findings in the pediatric population, the defini-tions for these findings in adults that have been proposed by the OMERACT study group for both US and MR imaging are extrapolated to the pediatric population (Table 2) (11,23).

At MR imaging, synovitis is defined as thick-ened synovium with avid enhancement on early postcontrast images (Fig 11) (40). Synovitis can-not be reliably distinguished from adjacent joint fluid on nonenhanced images; both entities are hypointense with T1-weighted sequences and hyperintense with water-sensitive sequences. Al-though synovitis in isolation is a nonspecific find-ing, in the setting of inflammatory arthritis it rep-resents active joint inflammation even in patients who are in clinical remission (5,41,42).

Table 2 US and MR Imaging Definitions for Joint and Soft-Tissue Disease in Inflammatory Arthritis

Abnormality MR Imaging Definition US Definition

Synovitis Increased synovial enhancement with synovial thick-ness greater than the width of normal synovium

No standardized definition; see “Syno-vial hypertrophy”

Synovial fluid Nonenhancing T1-hypointense and T2-hyperintense intraarticular fluid

Abnormal, generally hypoechoic dis-placeable or compressible intraar-ticular material that exhibits no Dop-pler signal

Synovial hyper-trophy

No standardized definition; see “Synovitis” Abnormal, generally hypoechoic non-displaceable and poorly compressible intraarticular tissue that may exhibit Doppler signal

Tenosynovitis Increased water content or abnormal en hancement of a tendon sheath

Hypo- or anechoic thickened tissue with or without fluid within the tendon sheath that is visible in two perpendicular planes and may ex-hibit Doppler signal

Periarticular inflammation

Increased water content or abnormal enhancement at extraarticular sites including periosteum (peri-ostitis) and entheses (enthesitis), but not tendon sheaths (tenosynovitis)

See “Enthesopathy”

Enthesopathy See “Periarticular inflammation” Abnormally hypoechoic or thickened tendon or ligament at its bone attachment that is visible in two per-pendicular planes and may exhibit Doppler signal or bone changes

Bone edema Ill-defined lesion in trabecular bone with signal characteristics consistent with increased water content (low T1 and high T2 signal)

Not seen at US

Bone erosion Sharply marginated, juxtaarticular, T1-hypointense and T2-hyperintense bone lesion that disrupts the cortical surface in at least one plane

Intraarticular discontinuity of the bone surface that is visible in two perpen-dicular planes

Source.—Adapted from references 38 and 39.


Figure 12. Rice bodies in a 3-year-old girl with oligoarticular JIA. (a) Sagittal fat-suppressed T2-weighted MR image of the knee demonstrates a large joint effusion with hypointense debris layering dependently within the effusion. (b) Contrast-enhanced fat-suppressed T1-weighted MR image shows enhancing synovitis but no enhancement of the layering debris; the latter finding is consistent with rice bodies secondary to chronic inflammation.

Figure 11. Synovitis in a 17-year-old girl with RF-negative polyarticular JIA. (a) Coronal fat-suppressed T2-weighted MR image demonstrates hyperintense synovial fluid (*) and thickening (arrow), with bone marrow edema (arrowhead) in the lateral tibial plateau. (b) Coronal contrast-enhanced fat-suppressed T1-weighted MR image more clearly depicts nodular enhancing synovitis (arrow). Contrast enhancement is essential for differentiating between nonenhancing joint effu-sion and enhancing synovitis.


Figure 14. Tenosynovitis. (a) Sagittal fat-suppressed T2-weighted MR image of the third metacarpal bone and third finger of the right hand in a 5-year-old girl with oligoarticular JIA demonstrates fluid signal intensity within the flexor tendon sheath (arrows), a finding that is consistent with tenosynovitis. There is also edema in the subcutaneous fat along the volar aspect of the hand and finger. (b) Longitudinal color Doppler US image of the flexor tendon of the right third finger in a different patient demonstrates tenosynovitis, with hyperemic, hypoechoic noncompressible tissue within the tendon sheath, and tendinopathy (*) with a thickened tendon and loss of normal fibrillar echotexture.

Figure 13. Synovial hypertrophy in a 20-year-old woman in whom polyarticular JIA was diagnosed in child-hood. (a) Longitudinal gray-scale US image through the dorsal aspect of the wrist demonstrates thickened, hypoechoic, noncompressible intraarticular tissue consistent with synovial hypertrophy (*) deep to the nor-mal-appearing extensor tendon (arrowheads). (b) Color Doppler US image through the same region demon-strates marked synovial hypervascularity, a finding that is indicative of inflammation.

With progressive inflammation, the synovium can proliferate to form pannus that can be seen on precontrast T2-weighted images as hypointense frondlike material outlined by high-signal-intensity joint fluid. Small fragments of the hypertrophic synovium may undergo fibrinoid necrosis and slough into the joint, resulting in the formation of “rice bodies” (Fig 12), a term that reflects the macroscopic resemblance of these fragments to grains of polished rice. Rice bodies are indicators of chronic synovial inflammation when seen in JIA and can also be found in chronic low-grade infec-tions such as tuberculous arthritis and nonpig-mented villonodular synovitis.

Synovial hypertrophy at US is defined by poorly compressible intraarticular tissue that is most frequently hypoechoic relative to subcutaneous fat and may demonstrate Doppler signal (Fig 13) (38). Although the presence of Doppler signal is not required for the US diagnosis of synovitis, the significance of isolated synovial hypertrophy with-

out Doppler signal has not been validated, and the disappearance of Doppler signal may indicate resolving or inactive disease (11).

At MR imaging, periarticular inflammation (which includes both periostitis and enthesitis) and tenosynovitis demonstrate signal inten-sity consistent with increased water content or increased contrast enhancement. Unlike with synovitis, however, the presence of abnormally in-creased water content alone (high signal intensity on water-sensitive T2-weighted and STIR images, low signal intensity on unenhanced T1-weighted images) is sufficient for the diagnosis of tenosyno-vitis (Fig 14) (39). Although there are only limited data on the MR imaging findings of tenosynovitis in children, the literature on adult patients sug-gests that postcontrast images are crucial to evalu-ation for early tenosynovitis, since fluid-sensitive sequences alone have fairly low sensitivity in the


acute and subacute stages of disease (43). At US, tenosynovitis manifests with hypoechoic or an-echoic thickening of the tendon sheath (Fig 14) (38). Doppler signal may be present but is not required for diagnosis, and fluid within the tendon sheath is a variable finding. Tenosynovitis is most commonly seen around the ankle joint and along the extensor tendons of the wrist. Tenosynovitis of the ankle tendons is often clinically occult or may

mimic an ankle joint effusion at physical examina-tion (Fig 15) (44).

The term enthesitis refers to inflammation of tendons or ligaments at the site of bone attach-ment. It is most commonly seen at the insertion of the Achilles tendon on the posterior calcaneus. MR imaging findings may include soft-tissue edema, increased T2 signal or thickening of the tendon or ligament at its insertion, subjacent bone marrow edema, and distention of adjacent bursae. At US, enthesitis is characterized by hypoechoic

Figure 15. Tenosynovitis in a 6-year-old girl with psoriatic arthritis. (a) Clinical pho-tograph of the left ankle demonstrates soft-tissue swelling, a finding that was thought to be secondary to an effusion. (Courtesy of Dana Toib, MD.) (b) Anteroposterior radiograph demonstrates medial soft-tissue swelling of the ankle. (c) Coronal contrast-enhanced fat-suppressed T1-weighted MR image reveals that the soft-tissue swelling is secondary to marked tenosynovitis (arrows) of the posterior tibialis, flexor digitorum lon-gus, and flexor hallucis longus tendons and periarticular inflammation (*) with synovitis of the ankle and subtalar joints (arrowheads).


thickening or loss of the normal fibrillar structure of the tendon or ligament at its insertion. Addi-tional US features include calcifications and bone changes (eg, enthesophytes, erosions, or cortical ir-

regularity). Hyperemia seen at Doppler evaluation may be associated with these findings (38).

Bone marrow edema is visible only at MR imaging. It is an ill-defined enhancing lesion in trabecular bone that demonstrates increased signal intensity with water-sensitive sequences and decreased signal intensity with T1-weighted sequences. Histologically, the term edema is a misnomer. The MR imaging findings reflect true osteitis with an inflammatory cellular infiltrate in bone, rather than increased water content (5).

Like bone marrow edema, erosions have low T1 and high T2 signal at MR imaging; however, erosions demonstrate well-defined margins (Fig 16). At both US and MR imaging, erosions must be juxtaarticular, visible in two planes, and dem-onstrate cortical disruption in at least one plane. Although erosions may be a chronic finding, enhancement following contrast material admin-istration suggests the presence of active, hyper-vascularized pannus within the bone defect (5). MR imaging is more sensitive than radiography for the detection of erosions.

Unresolved joint inflammation can result in irreversible cartilage degradation and destruction. In the skeletally immature child, a “spoke-wheel” pattern of enhancement may be seen in growth cartilage at MR imaging secondary to hyperemia caused by long-standing inflammation (Fig 17), resulting in epiphyseal overgrowth. It is unusual to see cartilage erosions in young children due to thick, reparative cartilage with a robust blood

Figure 16. Erosions and edema in the elbow of a 15-year-old boy with polyarticular JIA. (a) Sagittal contrast-enhanced fat-suppressed T1-weighted MR image through the right elbow demonstrates severe synovitis (arrows) with erosions and osteitis. The margins of the capitellar erosion (arrowhead) are well defined and disrupt the articular surface, whereas trochlear osteitis (*) is more ill defined without corti-cal destruction. (b) Lateral radiograph demonstrates erosions of the radial head and capitellum (arrow-heads), uniform radiocapitellar joint space narrowing, and displacement of the anterior and posterior fat pads (arrows) owing to proliferative synovitis.

Figure 17. Epiphyseal cartilage hyperemia in a 4-year-old girl with oligoarticular JIA. Sagittal con-trast-enhanced fat-suppressed T1-weighted MR image through the right knee demonstrates cartilage hyper-emia in the distal femoral epiphysis with a spoke-wheel pattern of vascular enhancement (arrows). Synovitis and a joint effusion are also present.


Figure 18. Cervical spine changes in a 14-year-old patient with long-standing polyarticular JIA. Lateral radiograph demonstrates ankylosis of the posterior ele-ments of the cervical spine (*). The small, narrow ver-tebral bodies and disk space narrowing seen at the lev-els affected by ankylosis are characteristic findings in JIA, as is antegonial notching of the mandible (upward curving of the inferior surface of the mandible anterior to the angular process) (arrowhead).

supply, although with increasing age and persis-tent or progressive inflammation, cartilage thin-ning and erosions may occur.

Cervical SpineThe cervical spine shows characteristic changes in children with JIA. The prevalence of clinical find-ings of cervical inflammation in affected patients has been reported to be approximately 60% (45). The cervical spine is more commonly involved in children with polyarticular or systemic JIA than in those with oligoarticular JIA (45,46). Clinical symptoms of cervical spine involvement include neck stiffness and limited range of motion, espe-cially upon extension and lateral flexion.

The characteristic radiographic finding of JIA in the cervical spine is ankylosis of the apophyseal joints (47). The ankylosis usually involves C2–3, although it often involves multiple levels. The vertebral bodies are commonly hypoplastic in both anteroposterior and transverse dimensions (“juvenile cervical vertebrae”) with concomitant narrowing of the intervertebral disk space, typi-cally seen at the same level as the apophyseal joint ankylosis (Fig 18).

Odontoid process erosions due to atlantoaxial synovial proliferation can be seen in polyarticular JIA. Inflammation at the atlantoaxial articula-tion with subsequent ligamentous insufficiency can result in widening of the atlantodental in-terval (the normal interval in children is 5 mm or less) and atlantoaxial instability, which is best evaluated on flexion and extension radiographs. Patients with polyarticular JIA are also at risk for atlantoaxial impaction, which is generally seen in young adulthood. Atlantoaxial impaction is diagnosed if the tip of the dens lies more than 4.5 mm above the McGregor line (the “line” con-necting the posterior margin of the hard palate to the undersurface of the occipital bone) (48–50).

Temporomandibular JointsThe TMJ can be involved in any of the JIA sub-types and is affected in 17%–87% of this patient population (51–53). Given the morphogenesis and complex anatomy of the TMJ, this joint is at especially high risk for growth disturbances when affected by inflammatory arthritis, and long-term involvement may result in both poor aesthetic and functional outcomes (54–56). It is well documented that clinical symptoms, such as pain, may not be present even in the setting of severe erosive TMJ disease, and subjective symp-

toms may lead to underestimation of the degree of early inflammation (57–59). In one study, a pediatric rheumatologist who examined affected patients for signs of synovitis, including swelling, tenderness, and limited range of motion, was able to accurately diagnose active TMJ inflammation in only 58% of cases. Orthodontic examination, including a detailed questionnaire, measurements of mouth opening and deviation, and evaluation for crepitus and pain, allowed identification of only 39% of patients with active inflammation without bone deformity (60).

As with other joints, radiography can demon-strate chronic erosions of the TMJ but is unable to help identify active synovial inflammation, osteitis, or joint effusion (Fig 19) (61). Although technically appealing, US is not recommended for diagnosis or surveillance of TMJ inflammation.


Müller et al (60) demonstrated that although US is the most specific imaging modality for confirm-ing TMJ involvement, its level of sensitivity (33%) is unacceptable. US is able to help detect only the late changes of TMJ arthritis, such as destruction and disk dislocation, and is therefore not recom-mended for TMJ surveillance in patients with JIA.

Contrast-enhanced MR imaging is the stan-dard of reference for evaluation of the TMJ. Cer-tain patients, such as those who present at a very young age (<4 years), are at exceptionally high risk for TMJ involvement. These patients should undergo screening MR imaging of the TMJs at the time of diagnosis, and some authors have advocated screening with MR imaging any time the result may change treatment decisions in JIA (60,62). Contrast-enhanced MR imaging find-ings of joint effusion, synovial enhancement, and bone marrow edema indicate active inflammation and should prompt escalation of systemic therapy or site-specific steroid injection (61). Therapeu-tic injection of the TMJ is frequently imaging guided, since up to 18% of injections given with use of landmarks alone are extraarticular (63). Computed tomography (CT) and fluoroscopy are the most widely used modalities for imaging-

Figure 19. Limitations of radiographic evaluation of the TMJs in a 12-year-old girl with oligoarticular JIA. (a) Open-mouth radiographs show flattening and irregularity of the left mandibular condyle (arrow). No erosions are seen on the contralateral side. (b) Coronal contrast-enhanced fat-suppressed T1-weighted MR image helps confirm flattening of the left mandibular condyle. Actively inflamed synovitis (arrowhead) and osteitis (black arrow) are also seen. Note the erosions of the right mandibular condyle (white arrows), which were not evident radiographically, and the pres-ence of synovitis.

guided injection of the TMJ, although the use of MR imaging– and US-guided techniques has also been reported (63,64).

Sacroiliac JointsSacroiliitis affects approximately 30% of children with the ERA subtype of JIA (65). Early identifi-cation of this subset of patients is crucial because several of the first-line treatments for JIA have been shown to have minimal effectiveness in the management of axial (spine and sacroiliac joint) inflammation, and the presence of sacroiliitis is associated with increased long-term disability, including reduced spinal mobility (66–69). Even in the presence of active sacroiliitis, inflammatory back pain may be a relatively late development in the pediatric population. Therefore, routine screening MR imaging of the sacroiliac joints in children with features of juvenile spondylo-arthropathy (including male gender, late age at disease onset, acute anterior uveitis, and hip ar-thritis) has been proposed, although the optimum timing of this screening is not clear (70).

The complex orientation of the sacroiliac joints makes radiographic evaluation challenging. Several radiographic projections have been used to evalu-ate the sacroiliac joints, including standard antero-posterior, bilateral oblique, and anteroposterior views with the tube angled 30° cephalad (Fergu-son view). However, radiographic evaluation of the sacroiliac joints remains limited, with significant intra- and interobserver variation.


MR imaging allows cross-sectional imaging of the complex anatomy of the sacroiliac joints with-out exposing the young pelvis to ionizing radia-tion. MR imaging can help identify acute sacro-iliac joint inflammation earlier than radiography, which may demonstrate changes only 5–10 years after the onset of clinical symptoms (22,71). In one cohort study of children with inflammatory back pain, 80% demonstrated acute inflam-mation of the sacroiliac joints at MR imaging, whereas none had positive radiographic changes (65). In addition, MR imaging can help detect bone marrow edema, which cannot be seen at radiography or CT (72).

MR imaging findings of sacroiliitis include T2 hyperintensity of the sacroiliac joint with adjacent subarticular bone marrow edema or osteitis (best seen on fluid-sensitive images), erosions (best seen on T1-weighted images), and synovial en-hancement (seen on contrast-enhanced images) (Fig 20). These findings must be either subchon-dral or periarticular in location, and, if there is only a single lesion, it must be present on at least two consecutive sections. Despite studies dem-onstrating that STIR sequences alone are highly sensitive in the detection of active sacroiliitis, the intravenous administration of gadolinium-based contrast agents is recommended for initial evalu-

ation of sacroiliac joint disease, since secondary findings including synovitis, capsulitis, and en-thesitis are more reliably demonstrated on con-trast-enhanced T1-weighted images (73,74). It is important to note that anti-inflammatory treat-ment of sacroiliitis can result in fatty conversion of the juxtaarticular bone marrow, which should not be confused with active disease. Because the hips are commonly affected in ERA, they should be included in the field of view during imaging of the pelvis for sacroiliac joint disease. Although typically bilateral, sacroiliitis in JIA can be asym-metric. Sacroiliac joint ankylosis is a late manifes-tation and is unusual in the pediatric population.

ConclusionsAlthough JIA remains a clinical diagnosis, imag-ing plays a critical role in excluding other causes of joint swelling, monitoring disease progression and treatment response, and evaluating poten-tial complications. With the advent of newer therapeutic agents, the goal of JIA treatment is complete suppression of synovitis before the development of irreversible joint abnormalities. Although radiography remains the most com-monly used imaging modality in the evaluation of JIA, contrast-enhanced MR imaging and Dop-pler US have greater sensitivity for the detection of synovitis and other inflammatory lesions and, as a result, are increasingly being used to guide

Figure 20. Sacroiliitis in a 16-year-old boy with ERA. (a) Radiograph (Ferguson view) of the sacroiliac joints demonstrates symmetric erosions and joint space widening with iliac sclerosis, findings that are con-sistent with chronic sacroiliitis. (b) Coronal oblique contrast-enhanced fat-suppressed T1-weighted MR image obtained parallel to the sacrum shows erosions (arrows) in both iliac bones (worse on the left than on the right). Note the relative sparing of the sacrum. The enhancement of these erosions, the synovium, and osteitis in the right iliac bone (arrowhead) is consistent with ongoing active inflammation.


clinical management. For the evaluation of more complex joints affected by JIA (eg, the TMJs and sacroiliac joints), contrast-enhanced MR imaging is the preferred imaging modality.

Acknowledgment.—The authors would like to thank Dana Toib, MD, for providing the clinical photographs for this article.

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This journal-based SA-CME activity has been approved for AMA PRA Category 1 CreditTM. See www.rsna.org/education/search/RG.

Teaching Points September-October Issue 2013

Imaging of Juvenile Idiopathic Arthritis: A Multimodality ApproachElizabeth F. Sheybani, MD2 • Geetika Khanna, MD, MS • Andrew J. White, MD, MSc • Jennifer L. Demertzis, MD

RadioGraphics 2013; 33:1253–1273 • Published online 10.1148/rg.335125178 • Content Codes:

Page 1257The largely cartilaginous composition of the pediatric skeleton limits radiographic detection of early erosive changes in children.

Page 1260Contrast-enhanced MR imaging is the most sensitive imaging technique for detecting synovitis.

Page 1262Compared with radiography, US is more sensitive for detecting joint effusions and synovial thickening and has been shown to be particularly helpful in evaluating the small joints of the hands and feet.

Page 1269Contrast-enhanced MR imaging is the standard of reference for evaluation of the TMJ.

Page 1270MR imaging can help identify acute sacroiliac joint inflammation earlier than radiography, which may demonstrate changes only 5–10 years after the onset of clinical symptoms.

pediatric imaging 1253 imaging of juvenile idiopathic...

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