Arthritis and Differential Inflammatory Joint Disorders


Rheumatologic conditions in children are myriad in presentation, with overlapping imaging features that may sometimes superficially mimic infection. Rheumatologic conditions in children do not follow the typical course and presentation compared with their counterparts in adults. As a consequence, the International League of Associations for Rheumatology (ILAR) formulated a revised nomenclature to describe the various pediatric rheumatologic conditions ( Box 136.1 ). In this chapter, we discuss imaging of pediatric arthritis from the point of view of noninfectious synovial proliferation using the ILAR classification, including juvenile idiopathic arthritis (JIA) and its differentials: hemophilic arthropathy, lipoma arborescens, synovial chondromatosis, pigmented villonodular synovitis (PVNS), and reactive synovitis ( Box 136.2 ). Subtypes of JIA, enthesitis-related arthritis and psoriatic arthritis, will be discussed in their own subsections because of their unique presentation and imaging findings. Infectious arthritis is discussed in Chapter 137 .

Box 136.1
From Petty RE, Southwood TR, Manners P, et al. International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol . 2004;31:390–392.
Classification of Juvenile Idiopathic Arthritis

  • Onset <16 years

  • Duration: at least 6 weeks

  • Other known conditions are excluded

Subtypes

  • 1.

    Systemic arthritis

  • 2.

    Oligoarthritis

    • a.

      Persistent—affecting ≤4 joints throughout the disease course

    • b.

      Extended—affecting a total of >4 joints after the first 6 months of disease

  • 3.

    Polyarthritis (rheumatoid factor negative)

  • 4.

    Polyarthritis (rheumatoid factor positive)

  • 5.

    Psoriatic arthritis

  • 6.

    Enthesitis-related arthritis

  • 7.

    Other undifferentiated arthritis

    • a.

      Does not meet any criteria for categories 1–6

    • b.

      Meets criteria for more than one of the categories 1–6

Box 136.2
Differential Diagnosis of Juvenile Idiopathic Arthritis

Noninfectious Disorders

Synovial Disorders

Pauciarticular

Acute

  • Early rheumatic disease

  • Arthritis associated with chromosomal abnormalities—Down, Turner syndromes

  • Seronegative spondyloarthropathy

  • Acute transient synovitis

Chronic

  • Rheumatic diseases

  • Arthritis associated with chromosomal abnormalities—Down, Turner syndromes

  • Tenosynovial giant cell tumors (pigmented villonodular synovitis)

  • Intraarticular venous malformation

  • Lipoma arborescens

  • Synovial osteochondromatosis

Other

  • Foreign body arthritis

  • Hemophilic arthropathy

  • Sarcoidosis

  • Intraarticular osteoid osteoma

Polyarticular

Seronegative spondyloarthropathy

  • Connective tissue disorders

    • Systemic lupus erythematosus

    • Sarcoidosis

  • Inherited disorders

  • Familial hypertrophic synovitis

  • Hemophilic arthropathy

  • Immunodeficiency

Nonsynovial Disorders

Pauciarticular

Acute

  • Malignancy

  • Leukemia

  • Neuroblastoma

Chronic

  • Noninflammatory disorders

  • Avascular necrosis

  • Slipped capital femoral epiphysis and dysplasias

Other

  • Juvenile osteoporosis

  • Multifocal osteolysis

Polyarticular

  • Metabolic or inherited disorders

  • Diabetic arthropathy

  • Turner syndrome

  • Lysosomal storage disease

  • Kniest syndrome

  • Winchester syndrome

  • Chondrodysplasias

  • Frostbite

  • Goldbloom disease

Infectious Disorders

Pauciarticular

  • Infectious arthritis

  • Septic arthritis

  • Reactive arthritis

  • Tuberculous arthritis

  • Postinfectious arthritis

Polyarticular

  • Infectious arthritis

  • Lyme disease

  • Reactive arthritis

Juvenile Idiopathic Arthritis

Clinical Overview

JIA, which occurs worldwide, is the most frequent cause of chronic musculoskeletal pain in youths and the most common chronic musculoskeletal disease of childhood. It is a chronic, monoarticular or polyarticular arthropathy of childhood.

The diagnostic criteria for JIA include arthritis in one or more joints for at least 6 weeks before the age of 16 years. The onset type is defined by pattern of disease in the first 6 months of diagnosis (see Box 136.1 ) and exclusion of other forms of juvenile arthritis. JIA may be associated with systemic manifestations that include fever, erythematous rashes, nodules, leukocytosis, and, less commonly, iridocyclitis, pleuritis, pericarditis, anemia, fatigue, and growth failure. At the time of presentation, other causes of inflammation should be excluded. JIA differs from the adult type of rheumatoid arthritis because of the age of presentation, its preference for large joints, its tendency to generate joint contractures and muscle wasting, and its association with extraarticular clinical manifestations.

A new internationally accepted classification system was established in 1995 and revised in 2001 (see Box 136.1 ). The previously used terms juvenile chronic arthritis and juvenile rheumatoid arthritis were incorporated under the term JIA .

The early diagnosis of JIA is essential to interrupt or delay the course of the disease, which results in joint deformity, severe functional impairment, and chronic pain if the disease is not treated at its early stage.

The currently available clinical and laboratory tests for assessment of JIA are poor for characterization of early inflammatory, hypoxic, and vascular changes, which are the primary physiologic events involved in the disease. Therefore imaging is vitally important for early diagnosis and assessing treatment response during follow-up in persons with this disease.

Epidemiology

The incidence and prevalence of JIA in Europe varies greatly in published reports, with the incidence and prevalence, respectively, of 1.6 to 42.5 and 3.8 to 400 per 100,000. Twice as many girls as boys have JIA. Although few data are available on geographic or racial groups, studies suggest that, in the United States, proportionately fewer African American than white children have JIA. The onset of JIA before the age of 6 months is distinctly unusual; nevertheless, the age at onset is often quite young, with the highest frequency occurring between 1 and 3 years.

Radiographic changes are seen most frequently in children with JIA who have a polyarticular course. Large joints are most commonly affected in persons with this disease. The knee is the most frequently affected joint, followed by the ankle. Changes may also develop in the cervical spine or temporomandibular joint. It has been suggested that patients with JIA who have polyarthritis and wrist disease are at high risk of experiencing radiographic progression. The wrist is the most vulnerable site for early radiographic changes in patients with JIA.

Pathophysiology

Although the etiology of JIA is unknown, some investigators believe that it is multifactorial given the heterogeneity of presentations and course of the disease. JIA is characterized by an acute synovitis that leads to synovial proliferation and formation of a highly cellular pannus. The pannus erodes the adjacent articular cartilage and subchondral bone, leading to centripetal articular destruction; that is, the articular damage starts at the periphery of the joint and progresses toward its center. Inflammatory changes also can involve tendon sheaths and bursa and can give rise to periostitis. With prolonged inflammation, more extensive joint changes, including cartilage destruction, bone erosions, and joint malalignment, often are present.

Despite the fact that JIA is usually transient and self-limited, without active synovitis in adulthood, up to 10% of children become severely disabled in adulthood. Despite therapy, 28% to 54% of children have progressive disease and experience cartilage or bone erosions, with a median onset of radiographic findings between 2.2 to 5.4 years after initial presentation. The disease process may lead to joint instability, subluxation, and ankylosis. Disturbance of joint growth can be consequent to the disease itself and/or to the treatment.

Imaging

Imaging plays a key role in establishing the presence, severity, and extent of joint disease and monitors disease complications, excludes other diagnoses, and assesses treatment response. Advanced imaging allows detailed evaluation of synovitis and osteochondral damage.

Radiographs are typically the initial imaging study for the diagnosis of JIA; however, they have low sensitivity (50%) and moderate specificity (85%) for detection of cartilage destruction.

Both magnetic resonance imaging (MRI) and ultrasound can detect synovial hypertrophy, cartilage erosion, and joint effusion in peripheral joints, and clinically meaningful response to treatment in children with JIA. Ultrasound is less sensitive than MRI for assessment of both soft tissue findings (sensitivity, 62%) and superficial cartilage loss (sensitivity, 60%). Overall, MRI is the imaging modality of choice for evaluation of joints in children with JIA. However, ultrasound can be an excellent initial imaging tool for evaluation of young children who otherwise would require sedation for MRI. As expertise and standardization continues to develop, ultrasound will likely prove to be a complementary imaging method along with MRI.

Radiography

Conventional radiography is not effective in the evaluation of soft tissue abnormalities, which are precursors of cartilage degeneration in persons with JIA. Moreover, available radiographic scoring systems have poor internal consistency and poor criterion and construct validity because they do not take into consideration patients' sex and age. As mentioned earlier, there is low sensitivity (50%) and moderate specificity (85%) in the detection of cartilage destruction with radiography, hence the expanding role for ultrasound and MRI in the evaluation of JIA.

A variety of radiographic features can be encountered with joint disease. Specific joint findings will depend on the underlying abnormality, the chronicity of the disease, and the response to therapy. A systematic approach to the imaging interpretation of any joint is highly recommended. One popular approach is the “ABCDS” of joint disease, featuring assessment of joint A lignment, B one density and other bone changes, C artilage loss, D istribution of joint disease (whether monoarticular, oligoarticular, or polyarticular), and S oft tissue abnormalities ( Box 136.3 ).

Box 136.3
From Johnson K, Gardner-Medwin J. Childhood arthritis: classification and radiology. Clin Radiol . 2002;57:47–58.
Radiographic Features of Juvenile Idiopathic Arthritis

Alignment Abnormalities

  • Atlantoaxial subluxation

  • Coxa valga or varus

  • Finger deformities including boutonniere or swan neck deformity

  • Knee valgus

  • Hallux valgus

Bone Density

  • Juxtaarticular osteoporosis

  • Diffuse osteoporosis (late)

  • Metaphyseal lucent band (rarely)

  • Periosteal reaction adjacent to affected small joints

Cartilage and Joint Spaces

  • Erosions (late), may appear corticated

  • Cartilage space narrowing (late)

  • Ankylosis (especially spine, wrists)

Distribution

  • Monoarticular, oligoarticular, or polyarticular

Growth Abnormalities

  • Affected small bones are shorter than normal

  • Overgrowth (lengthening) of affected long bones

  • Advanced maturation of affected epiphyses

  • Large epiphyses

  • Micrognathia (may have mandibular notching)

  • Protrusio acetabuli

  • Small fused cervical vertebrae

  • Angular carpal bones

  • Square patella

  • Intercondylar notch widening (also a feature of hemophilia)

Soft Tissues

  • Effusions and joint distension

  • Nodules

  • Periarticular calcification (probably due to corticosteroid injections)

The earliest abnormalities include soft tissue swelling, osteopenia, and effusion. Periosteal reaction occasionally may be seen. Typically, the osteopenia is initially periarticular ( Fig. 136.1 ), becoming more diffuse with time. Osteopenia may be subtle and better recognized by comparison with the contralateral extremity (if it is unaffected). With long-standing disease, uniform bone loss may occur with a thin cortex. Uncommonly, a linear subphyseal demineralization can be observed, but this finding is nonspecific and can also be seen in persons with other conditions such as leukemia.

Figure 136.1, Juvenile idiopathic arthritis in a girl with progressive bilateral hip arthritis.

Joint effusions are encountered commonly and can be seen in inflammatory or noninflammatory joint disease. A sign of knee effusions is fullness in the suprapatellar region, which is best seen on the lateral view. In the elbow, knee, and ankle, adjacent fat lines and fat pads are displaced. Periosteal reaction, when present, is commonly seen in the phalanges, metacarpals, and metatarsals but also can occur in the long bones. Joint space narrowing may be caused by cartilage loss (see Fig. 136.1 ). In persons with JIA, the joint space narrowing is usually uniform. In some patients with rheumatoid factor positive polyarthritis or systemic arthritis, early erosive disease can occur ( Fig. 136.2 ).

Figure 136.2, Systemic juvenile idiopathic arthritis in a patient with multiple hip infections.

Bone erosions are typically located at joint margins in the bare areas but also may occur at tendinous insertions. Bone erosions also can be seen in persons with septic arthritis or hemophilic arthritis related to the inflammatory reaction caused by intraosseous hemorrhage. Large erosions can also be seen in the camptodactyly arthropathy coxa vara pericarditis syndrome ( e-Fig. 136.3 ). Deformity of the fingers, whether with boutonniere (proximal interphalangeal [PIP] flexion with distal interphalangeal [DIP] extension) or swan neck (PIP extension with DIP flexion) deformity, can be seen in a variety of disorders, including JIA ( Fig. 136.4 ), camptodactyly arthropathy coxa vara pericarditis syndrome, or systemic lupus erythematosus. Enlarged or irregular epiphyseal ossification centers can be seen in persons with hemophilia, JIA, and tuberculous arthritis. Atlantoaxial subluxation or cervical vertebrae pseudosubluxation and ankylosis ( e-Fig. 136.5 ) may be noted in persons with JIA, the arthropathy of Down syndrome, dysostosis multiplex, and systemic lupus erythematosus.

Figure 136.4, Advanced juvenile idiopathic arthritis in the peripheral skeleton in different patients.

e-Figure 136.3, Camptodactyly arthropathy coxa vara pericarditis syndrome.

e-Figure 136.5, Polyarticular juvenile idiopathic arthritis.

In contrast to adult patients with inflammatory arthritis, bone erosions are less commonly seen in children because the epiphyseal ossification center is surrounded not only by articular cartilage but also by epiphyseal cartilage and the spherical growth plate. As a result, significant cartilage loss must occur before osseous erosions are visible with radiography. Therefore the role of MRI is relatively more important in children to detect articular or epiphyseal cartilage erosions before actual bony erosions are visible on radiography.

Changes in bone growth and maturation with changes in the normal size of ossification centers and alteration of normal bone modeling can be seen in persons with JIA, and with infections and hemophilia. Enlargement of ossification centers and epiphyses (see Fig. 136.4 ), contour irregularity, trabecular changes, and squaring (typically of the patella) can be seen. Tibiotalar slant (ankle valgus) can also be seen.

Late sequelae of JIA include epiphyseal deformity, abnormal angular carpal bones, widening of the intercondylar notch of knees (see Fig. 136.4 ), and premature fusion of the growth plates. Growth disturbances are more frequent if disease onset is early. Joint space narrowing and osseous erosions are usually late manifestations. At the hip, protrusio acetabuli (see Fig. 136.1 ), premature degenerative changes, coxa magna, and coxa valga can be seen. Joint space loss can progress to ankylosis, particularly in the apophyseal joints of the cervical spine (see e-Fig. 136.5 ) and wrist. Rarely, ankylosis also can be seen in larger joints, including the hips. Subluxation of the joints, especially at the wrist, may be evident. Growth disturbance of the temporomandibular joint may lead to micrognathia and temporomandibular disk abnormality.

Although radiography should be used initially in evaluation of joints, cross-sectional imaging techniques have provided a significant improvement in anatomic delineation and diagnosis.

Magnetic Resonance Imaging

MRI is an optimal tool for evaluation of both soft tissues and osteochondral abnormalities with superb tissue contrast. Contrast-enhanced MRI is extremely sensitive for detecting active disease and for early detection of cartilage loss, bone erosions, and synovial hypertrophy in children and adolescents. MRI provides multiplanar evaluation with a combination of available imaging sequences, including T1 and fast spin echo T2-weighted sequences, gradient echo sequences, and postcontrast studies all tailored to the specific clinical problem. High cost, limited availability, and frequent need for sedation in very young patients are limitations.

Various forms of cartilage can be visualized on MRI, including articular, unossified epiphyseal, and the physeal cartilage. Gadolinium-enhanced MRI can demonstrate normal vessels present within the cartilaginous epiphysis. MRI also is helpful in detecting synovial abnormalities and can be used to assess for changes with therapy.

Without contrast material, proliferating synovium on MRI appears as soft tissue thickening, which is typically intermediate signal on T1-weighted and increased signal intensity on T2-weighted images ( Fig. 136.6 ). It may have slightly higher signal intensity than adjacent fluid on unenhanced T1-weighted images. At times, pannus may appear as intermediate to dark signal intensity on T2-weighted images outlined by bright signal joint fluid. Its variable signal intensity reflects the relative amount of fibrous tissue and hemosiderin. Intravenous administration of gadolinium-based contrast agents improves visualization of thickened synovium, especially with use of fat-suppression techniques. Proliferating synovium appears as enhancing linear, villous, or nodular tissue. Images should be obtained immediately after contrast injection because diffusion of contrast material from the synovium into joint fluid occurs over time. Hypervascular inflamed pannus enhances significantly (see Fig. 136.2E ), whereas fibrous inactive pannus shows much less enhancement. Subchondral cysts and bone erosions (see Fig. 136.2 ) appear as low signal areas on T1-weighted sequences, with overlying articular and epiphyseal cartilage loss better delineated on fluid-sensitive sequences. Meniscal hypoplasia can be seen in some cases of JIA ( e-Fig. 136.7 ).

Figure 136.6, Juvenile idiopathic arthritis and symptomatic tenosynovitis in a 14-year-old girl.

e-Figure 136.7, Juvenile idiopathic arthritis in a 13-year-old girl.

Quantitative techniques have been developed for synovial volume. MRI is more sensitive than clinical evaluation in detecting some specific joint involvement, including the temporomandibular joint, which often demonstrates inflammatory change in the absence of clinical symptoms.

With prolonged synovial inflammation, well-defined intraarticular nodules termed “rice bodies” ( Fig. 136.8 ) may be present. Rice bodies likely arise from detached fragments of hypertrophied synovial villi. On MRI, rice bodies are low signal on T2-weighted images because of their fibrous tissue composition and are associated with joint effusion, synovial hypertrophy, and synovial enhancement after gadolinium administration.

Figure 136.8, Rice bodies.

Bone marrow edema is represented by areas of low T1-weighted and high T2-weighted signal intensity ( e-Fig. 136.9 ) and should be differentiated from normal marrow speckling seen on fluid-sensitive sequences, most frequently in the ankle and foot. Studies in adults have shown an association between presence of subchondral bone marrow edema in persons with inflammatory arthritis and radiographic erosive progression.

e-Figure 136.9, Juvenile idiopathic arthritis in an 11-year-old girl with a swollen left ankle and midfoot.

Because cartilage is one of the earliest sites of damage in persons with JIA, it is an important area to be evaluated with MRI. Standard T2-weighted and proton density magnetic resonance (MR) sequences can assess articular cartilage injury, from increased signal intensity within cartilage to articular cartilage thinning, erosions, and areas of full-thickness cartilage loss. Fat-saturated fluid-sensitive sequences will also depict subchondral bone marrow edema. Advanced sequences for cartilage evaluation are discussed later.

Although MRI has been extensively investigated in JIA, standardized measures for data acquisition and interpretation are not widely used ; hence this technique is underutilized both in clinical practice and in research. Few MRI scales have been designed to specifically assess morphologic changes with JIA.

Novel Magnetic Resonance Imaging Techniques.

A number of novel MRI techniques are under evaluation for improved assessment of synovial, cartilaginous, or osseous abnormalities. These MRI techniques include diffusion-weighted imaging (DWI) and perfusion imaging, delayed gadolinium-enhanced cartilage imaging, T2 quantification, and ultra-short echo time (TE) pulse sequences. DWI evaluates the translational movement (Brownian motion) of water molecules that occurs in all tissues, including synovium and cartilage. Alteration of normal diffusion can occur in diseases including infection, inflammation, and infarction. Diffusion tensor imaging (DTI) is a variant of DWI and has been used to study the structure of ordered biologic tissue, and holds potential to delineate synovial inflammation.

Contrast-enhanced perfusion MRI assesses blood flow using intravenously administered paramagnetic contrast agents. Potential uses of this technique include recognition of epiphyseal ischemia and quantification and monitoring of synovial inflammation. The rate of synovial enhancement depends in part on tissue vascularization and capillary permeability, both of which are highly correlated with synovial inflammation. Rapid enhancement suggests active synovial inflammation, whereas gradual delayed enhancement suggests subacute/chronic synovial inflammation. Quantitative dynamic contrast-enhanced MRI based on pharmacokinetic modeling has been proposed as an objective measure of therapeutic efficacy in patients with JIA.

Delayed gadolinium-enhanced MR cartilage imaging is a sensitive technique for assessing cartilage proteoglycan content using the negative charge of the intravenously administered paramagnetic MR contrast agent. The contrast agent distributes into cartilage inversely to the fixed charge density of negatively charged glycosaminoglycan (GAG). Delayed gadolinium-enhanced MR cartilage imaging may be used to assess early cartilage injury with depletion of GAG before anatomic changes are visible by conventional cartilage sequences.

Cartilage assessment can also be provided by mapping T2 relaxation time measurements. These measurements may help characterize the structural integrity of the cartilaginous tissue and quantitatively assess the degree of cartilaginous hydration and collagen orientation. Typically there is a decrease in T2 relaxation from the cartilage surface to the deeper layers. In persons with JIA, increased cartilage T2 relaxation time is thought to be an early marker of disease progression in JIA, because it can identify microstructural changes before damage becomes visible. In a longitudinal study evaluating patients with JIA from 3-month to 2-year follow-up, the clinical assessments improved, whereas T2 maps showed increased T2 values. This increase likely represents progressive microstructural changes, even though clinical symptoms improved with treatment.

Other advanced MRI techniques for cartilage assessment include T1 rho, sodium imaging, and ultrashort TE sequences.

Ultrasonography

Recent advances in ultrasonography, including better transducers and more pediatric musculoskeletal experience, have stimulated increased use of ultrasound in the assessment of pediatric joint disease. Ultrasound is ideal for assessing the pediatric musculoskeletal system because of its ability to visualize intraarticular structures such as cartilage and thickened synovium without the need for radiation. Ultrasound is very sensitive in detecting joint effusion, even in areas where radiographs are insensitive, such as the hip (see Fig. 136.2C ) and shoulder. Intraarticular masses may be detected with ultrasound, although their appearance is often nonspecific. Tendons and ligaments also can be assessed with higher-frequency transducers. Fluid within the synovial sheath appears as an anechoic halo surrounding the tendon ( Fig. 136.10 ), whereas synovial thickening appears as a hypoechoic thickening around the tendon. Synovial hyperemia leads to increased signal on Doppler evaluation. Power Doppler has been shown to detect residual disease activity more sensitively than clinical examination and/or MRI both in active disease and when JIA is in remission and could be used to predict short-term relapse in patients with JIA who appear to be in remission clinically.

Figure 136.10, Polyarticular juvenile idiopathic arthritis in a 10-year-old girl.

Sonography can also be used to assess other periarticular soft tissue abnormalities, including popliteal cysts ( e-Fig. 136.11 ) or other soft tissue masses, and to guide aspiration or injection of joints.

e-Figure 136.11, Bakers cyst.

Disadvantages of ultrasound include lack of standardization of ultrasound techniques for assessment of growing joints and normative data, lack of capability to visualize the central aspect of some joints, and difficulty in assessing some joints such as the temporomandibular joints ( Fig. 136.12 ).

Figure 136.12, Temporomandibular joint involvement in longstanding juvenile idiopathic arthritis in a symptomatic 12-year-old girl.

Erosions and focal or diffuse thinning of the articular cartilage also can be detected but only peripherally in the joint. Color Doppler ultrasound enables the detection of perisynovial hyperemia. Studies in children have demonstrated the ability of color and power Doppler sonography, with or without intravenous injection of contrast agents, to estimate synovial activity in JIA. Resistive indices and fraction of color pixels may be used as quantitative measurements of the blood flow. Contrast-enhanced sonography holds potential for detecting active synovial inflammatory disease in persons with subclinical JIA and may help guide early treatment.

Very limited information is available about the diagnostic performance and accuracy of ultrasound compared with MRI or clinical examination (in knees, sensitivity for joint effusion is 62%, ranging between 60% and 90% for clinically active joints and approximately 70% for clinically inactive joints ; for superficial cartilage destruction, overall sensitivity is 60%). Ultrasound-determined synovial thickness of the knee seems to correlate with clinical and laboratory (sedimentation rate and C-reactive protein levels) disease activity scores and with biomarkers of disease activity. In ankles, however, very poor agreement was observed comparing clinical and ultrasound scores.

Treatment and Follow-up

A systematic review on evidence-based treatment of JIA showed that nonsteroidal antiinflammatory drugs are effective only for a minority of patients, mainly those with oligoarthritis. Intraarticular corticosteroid injections are very effective for persons with oligoarthritis. Methotrexate is effective for the treatment of persons with extended oligoarthritis and polyarthritis and less effective for persons with systemic arthritis. Sulfasalazine and leflunomide may be alternatives to methotrexate. Antitumor necrosis factor medications are highly effective for polyarticular JIA that is not responsive to methotrexate but are less effective in persons with systemic arthritis. Therefore, despite many treatment advances, evidence is still lacking for treatment of several disease subtypes.

With regard to intraarticular corticosteroids, studies have shown that as many as 70% of patients with oligoarthritis do not have reactivation of disease in the injected joint for at least 1 year, and 40% do not have reactivation for more than 2 years. Radiographic and MRI studies have shown a marked decrease in synovial volume after injection without deleterious effects on the cartilage.

Imaging in the Assessment of Response to Therapy

Once therapy has begun for patients with JIA, imaging can be a helpful adjunct to assess disease activity and response to therapy. To date, several studies have examined radiographic changes before and after initiation of therapy, whereas more recent studies have used CT and/or MRI to describe joint changes and to use more quantitative measures of disease activity.

Radiography.

Radiography is able to demonstrate epiphyseal overgrowth and osteopenia after the injection of intraarticular triamcinolone hexacetonide. Carpal length, defined as the radiometacarpal length plotted against the length of the second metacarpal bone on a chart with normal growth carpal scores, as described by Poznanski et al., is another parameter that has been used in follow-up with an interval increase in carpal length (a positive change) indicating improvement.

Ultrasound.

In a small study of 15 joints, Eich et al. used ultrasound to determine the presence of effusion, pannus, popliteal cysts, and lymphadenopathy before and after intraarticular therapy and concluded that ultrasound was as sensitive as MRI in demonstrating joint effusion and/or pannus but that differentiation between the two was difficult, particularly in the hip joint. Spârchez et al. showed power Doppler ultrasonography correlated with physician global assessment of disease activity on visual analogue scale (PhGA) and to be more sensitive than erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels in assessing disease activity.

Magnetic Resonance Imaging.

Although CT is able to demonstrate joint space narrowing, erosions, and condylar flattening, MRI is the modality of choice to document changes before and after therapy. MRI can be used to monitor cartilage and bone erosions, effusion, pannus, and synovial volumes. In studies of children with arthritis who received intraarticular steroid injections, MRI has shown a long-lasting beneficial effect, with suppression of synovial inflammation and reversion of pannus formation.

Quantitative dynamic contrast-enhanced MRI can be used to evaluate disease activity in the knee. A study of pharmacokinetic parameters and synovial volumes showed significant decreases at 12 months after intraarticular steroid therapy; however, improvement in synovial volume appeared to lag behind dynamic parameters, reflecting delay or subclinical synovitis. Of all the imaging modalities, MRI has been shown to be the most sensitive modality in the assessment of temporomandibular joint arthritis in children and has been used as a reference standard measure for comparison of clinical examination and ultrasound in clinical studies. Ultrasound has been shown to be less useful than clinical examination to exclude active temporomandibular joint arthritis in patients with JIA. Standardized and validated assessment systems are still are being developed.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here