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Imaging of Inflammatory Arthritis in Adults
Imaging of Inflammatory A r t h r i t i s in A d u l t s Status and Perspectives on the Use of Radiographs, Ultrasound, and MRI Alissa Jo Burge, MD*, O. Kenechi Nwawka, MD, Jennifer L. Berkowitz, MD, Hollis G. Potter, MD KEYWORDS Inflammatory arthritis Imaging Radiographs Ultrasound MRI KEY POINTS Inflammatory arthritis refers to a group of arthritides with similar, often overlapping, clinical and imaging characteristics. A variety of imaging modalities may be used for the evaluation of patients with inflammatory arthritis, with radiographs, ultrasound scan, and MRI having the widespread clinical use. These modalities tend to complement one another, each individual modality having its own set of strengths and weaknesses. Knowledge of the expected appearance of imaging findings associated with inflammatory arthritis for each of these modalities aids in the timely diagnosis and accurate monitoring of patients with these conditions.
INTRODUCTION
The term inflammatory arthritis encompasses a variety of conditions, the common feature being synovial inflammation. Chronic joint inflammation results in synovial hyperplasia, which causes the average depth of blood vessels from the synovial surface to increase, increasing the distance over which nutrients must travel and thereby decreasing the efficiency of nutrient transport to the articular cartilage. This process may stimulate angiogenesis. Local tissue damage may occur as a result of progression of this process, with the enlarging synovial pannus invading nonsynovial
Disclosures: Research support received from General Electric Healthcare (A.J. Burge, O.K. Nwawka, H.G. Potter); No relevant disclosures (J. Berkowitz). Department of Radiology and Imaging, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA * Corresponding author. E-mail address: [email protected] Rheum Dis Clin N Am 42 (2016) 561–585 http://dx.doi.org/10.1016/j.rdc.2016.07.001 0889-857X/16/ª 2016 Elsevier Inc. All rights reserved.
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tissues such as articular cartilage and bone. Vascularization of typically nonvascular tissues, such as articular cartilage, may lead to functional compromise, resulting in further tissue damage.1 Although numerous inflammatory arthropathies exist, they often share similar and overlapping basic imaging characteristics. Synovitis, cartilage wear, and osseous changes tend to be common and fairly universal imaging findings. Additional findings may include tenosynovitis, skin changes, and deposits. The individual arthropathies may often be distinguished by the pattern of joint involvement, the specific appearance of pathologic changes, and ancillary findings. Various complementary imaging modalities may be used to evaluate patients with inflammatory arthropathies. PREIMAGING PLANNING
Synovial joints comprise of a variety of tissues. These tissues include the highly vascular synovium and variably less vascular tissues such as articular cartilage, ligaments, menisci, tendons, muscles, bone, capsule, and bursae.1 Plain radiography is the conventional first-line imaging examination obtained in the evaluation of suspected inflammatory arthropathy, as it is accessible and relatively inexpensive and allows for the simultaneous evaluation of multiple joints. Radiographs provide valuable information regarding the bony manifestations of arthritis. These osseous abnormalities, however, represent the late sequelae of the disease, and, accordingly, radiographs do not allow for early detection and, consequently, treatment of these conditions. Additionally, conventional radiographs do not provide sensitive soft tissue assessment. Finally, radiography necessitates exposure to ionizing radiation and its potential stochastic effects, the risks of which increase with repeated imaging acquired to monitor for disease progression.2 Ultrasound scan (US) uses the acoustic properties of tissue to produce images. In the evaluation of inflammatory arthropathy, US can detect soft tissue abnormalities including synovial hypertrophy, joint effusion, and tenosynovitis. Doppler evaluation provides additional benefit, as it can detect hyperemia, thus, informing the user on the activity of inflammatory disease. Although US imaging of bone is limited because of its highly reflective properties, periarticular osseous erosions can be detected. The benefits of US include portability, ease of contralateral side imaging, and lack of ionizing radiation, particularly useful in young patients who are more susceptible to effects of repeated radiation. Additionally, US is relatively cost effective when compared with other imaging modalities. MRI provides excellent tissue contrast and sensitivity for mobile water, offering superior evaluation of both the synovium and nonsynovial soft tissues and of periarticular marrow edema and osseous erosions. This, along with the lack of ionizing radiation, makes MRI a superb modality for evaluation of patients with inflammatory arthropathies; however, the cost makes it inappropriate as a first-line imaging test, and contraindications, such as claustrophobia and pacemakers, preclude the use of MRI in certain patients.2,3 DIAGNOSTIC IMAGING TECHNIQUE
Radiographs of the symptomatic joints and the patient’s hands, wrists, and feet are typically obtained at the outset of the disease to provide baseline information regarding joint integrity. Follow-up radiographs of the hands and feet, regardless of symptoms, should be considered in an effort to gauge disease progression or treatment efficacy,4 as they often detect early erosions radiographically. No specific recommendations regarding the exact timeframe of serial follow-up radiographs exist.5
Imaging of Inflammatory Arthritis in Adults
US imaging in inflammatory arthropathy usually consists of extremity imaging. As such, high frequency transducers are recommended to provide high-resolution imaging of joints and surrounding soft tissues. Typically, 12- to 18-MHz transducers are used. If imaging digits, a small or “hockey-stick” transducer may be useful. Patients can be comfortably imaged seated or recumbent on a stretcher, depending on the body part. Optimal MRI technique depends on the anatomic region being imaged, but, in general, the scan should be tailored to the anatomy of interest to the extent that this is possible. Dedicated imaging coils sized appropriately for the anatomic region should be used, and imaging planes should follow anatomic planes. Field of view should be chosen to cover the area of interest without imaging an excessive amount of nonrelevant anatomy to maximize spatial resolution. At the least, some combination of sequencing incorporating fat-suppressed fluid-sensitive images (for evaluation of fluid and edema) along with high spatial resolution images (for evaluation of anatomic detail) should be obtained. At the authors’ institution, a routine clinical joint imaging protocol typically incorporates a single plane of fat-suppressed fluid-sensitive imaging (commonly an inversion recovery sequence) and 3 planes of high-resolution proton density (PD)-weighted images, which provide excellent spatial resolution and tissue contrast with fluid sensitivity. In addition, these PD sequences allow detailed evaluation of the articular cartilage, nicely depicting the normal layered chondral architecture, and providing an element of contrast of the articular cartilage against the relatively hyperintense joint fluid. Sample acquisition parameters for a routine hip MRI are listed in Table 1. Additional more specialized sequences (for example, gradient echo imaging in the setting of suspected pigmented villonodular synovitis) may be added as clinically indicated. INTERPRETATION/ASSESSMENT OF CLINICAL IMAGES Rheumatoid Arthritis
Rheumatoid arthritis (RA) (Box 1) manifests radiographically as uniform joint space narrowing with periarticular osteopenia, marginal erosions, and soft tissue swelling (Fig. 1). Metacarpophalangeal joint ulnar deviation and phalangeal swan neck and boutonniere deformities may also be present (Fig. 2). In the feet, a characteristic marginal erosion is often seen along the lateral aspect of the fifth metatarsal head (Fig. 3). Cervical spine involvement includes erosion of the odontoid process and atlantodental interval widening. The lack of associated osseous proliferative change facilitates the differentiation of rheumatoid arthritis from osteoarthritis and the seronegative spondyloarthropathies.6 The sonographic features of RA are well characterized, and the use of US is widespread in the clinical evaluation of the disease, particularly as it affects the extremities.8,9 RA on sonography most commonly appears as joint synovitis, with hypoechoic synovial thickening and joint effusion, at times accompanied by Doppler hyperemia. When synovial thickening is present, one should look carefully for concomitant osseous erosion, which presents on US as focal osseous irregularity, more commonly at the margins of the joints (Fig. 4). Tenosynovitis presents as irregular hypoechoic thickening of the tendon sheath, with or without tendon sheath effusion and Doppler hyperemia (Fig. 5). There may also be thickening of the finger flexor tendon pulleys, predisposing to finger triggering. Adventitial bursitis may be seen in subcutaneous tissues over prominent osseous structures, as in olecranon bursitis, or in regions susceptible to repeated friction (Fig. 6).
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Table 1 Acquisition parameters for routine clinical imaging of the hip at 1.5 T Parameter
Coronal Fast Inversion Recovery (Whole Pelvis)
TR (ms)
3500–5000
4000–5000
4000–5000
4000–5000
4000–5000
TE (ms)
17
34
34
34
34
TI
150
—
—
—
—
BW (Hz/pixel)
200
200
200
200
200
ETL
7–9
8–12
9–12
9–12
9–12
NEX
2
2
3
3
3
FOV (cm)
Greater intertrochanteric distance plus 2 cm
Greater intertrochanteric distance
17–18
17–18
16
512 256
Axial FSE (Whole Pelvis)
Sagittal FSE (Affected Hip)
Coronal FSE (Affected Hip)
Oblique Axial FSE (Affected Hip)
Matrix
256 192
512 256
512 384
512 384
Slice/Gap (mm)
5/0
5/0
2.5/0
4/0
3/0
NPW
Yes
Yes
Yes
Yes
Yes
Frequency
R/L
A/P
A/P
R/L
A/P
Abbreviations: A/P, anterior to posterior; BW, receiver bandwidth; ETL, echo train length; FOV, field of view; FSE, fast spin echo; NEX, number of excitations; NPW, no phase wrap; R/L, right to left; TE, echo time; TI, time to inversion; TR, repetition time.
Imaging of Inflammatory Arthritis in Adults
Box 1 Rheumatoid arthritis Rheumatoid arthritis is a classic example of an inflammatory arthropathy and typically manifests as a symmetric peripheral polyarthritis with a variety of osseous and soft tissue findings. Clinically, diagnosis is based on an established set of criteria: Polyarthritis involving 3 or more joints Positive serologic markers Duration of symptoms for more than 6 weeks Exclusion of similar diseases Additional clinical manifestations may include morning stiffness, rheumatoid nodules, and lung disease. The arthritis commonly involves the hands and wrist and results in an inflammatory synovitis with osseous erosions. Common soft tissue findings include tenosynovitis and bursitis.7
Fig. 1. Posteroanterior radiograph of the right hand shows juxta-articular demineralization with erosions, joint space narrowing, and autofusion of the radiocarpal and midcarpal joints (arrow) and erosions of the metacarpophalangeal joints, interphalangeal joint of the thumb, proximal interphalangeal joints of the second through fifth digits, and distal interphalangeal joint of the fifth digit. Chronic erosion of the distal ulna is also noted (arrowhead).
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Fig. 2. Posteroanterior (A), lateral (B), and oblique (C) radiographs of the right hand in multiple patients with rheumatoid arthritis show ulnar deviation and subluxation of the metacarpophalangeal joints (arrow), swan neck deformity with hyperextension of the proximal interphalangeal joint, and flexion of the distal interphalangeal joint (arrow) and boutonniere deformity with flexion of the proximal interphalangeal joint and extension of the distal interphalangeal joint (arrow) respectively.
MRI findings in patients with RA include inflammatory synovitis, commonly with hyperintense and thickened synovium and debris. Periarticular marrow edema may be present and may precede the development of defined osseous erosions (Fig. 7). Tenosynovitis is common in patients with RA, appearing as hyperintensity and thickening of the tendon sheath with fluid distention and tenosynovial adhesions often developing in longstanding cases. Bursitis may also be observed, commonly developing in the olecranon region and about the metatarsals.2,4
Imaging of Inflammatory Arthritis in Adults
Fig. 3. Anteroposterior radiograph of the right forefoot shows a distinctive marginal erosion of rheumatoid arthritis along the lateral aspect of the fifth metatarsal head (arrow).
SPONDYLOARTHROPATHIES Psoriatic Arthritis
Psoriatic arthritis (Box 2) manifests radiographically as marginal erosions, osseous productive change, periostitis, enthesitis, and joint subluxations (Fig. 8). “Pencilin-cup” deformities, in which one aspect of the joint projects like a pencil into a cup created by the other aspect of the joint, are caused by significant associated osseous damage (Fig. 9). Dactylitis, which is also referred to as a sausage digit and describes soft tissue swelling of an entire digit (see Fig. 8), is another feature commonly associated with the disease. Sclerosis, enthesitis, periostitis, and soft tissue swelling of the distal phalanx of the great toe, also known as the ivory phalanx, are distinctive for psoriatic arthritis. When an axial component of the disease is present, bilateral, symmetric or asymmetric, sacroiliac joint irregularities, erosions, and ultimately ankylosis may be seen.6
Fig. 4. Osseous erosion in rheumatoid arthritis. US image at the second metacarpophalangeal (MCP) joint depicts dorsal synovial thickening (arrowhead) and focal osseous erosion (arrow) at the medial margin of the metacarpal head in a 53-year-old woman with rheumatoid arthritis. MC, metacarpal head; PP, proximal phalanx.
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Fig. 5. Posterior tibial tendinosis and tenosynovitis. US images show a thickened and hypoechoic distal posterior tibial tendon surrounded by complex tenosynovitis (A, asterisks), with associated intense hyperemia (B) in a 74-year-old woman with RA. NAV, navicular; PTT, posterior tibial tendon.
US poorly evaluates axial disease in psoriatic arthritis and other spondyloarthropathies, and its use is not recommended for this purpose.12 However, peripheral manifestations of spondyloarthropathy can be assessed using sonography, including enthesitis, bursitis, and tenosynovitis. Enthesitis may appear as tendon thickening at its bony attachment, sometimes associated with mild osseous irregularity and hyperemia (Fig. 10). Osseous erosions in psoriatic arthritis have a similar sonographic appearance to that of RA, although the distribution is different. In some cases, periostitis can be seen as surface osseous irregularity on US. On MRI, joint involvement is characterized by synovitis with osseous erosions. Areas of marrow edema often occur at the capsular attachments and entheses (Fig. 11). Tenosynovitis often affects the flexor tendons more commonly than the extensors, and dactylitis may result in the characteristic sausage digit, with soft-tissue swelling and edema. Sacroiliitis is classically asymmetric, and spondylitis may manifest as areas of marrow edema, commonly along the endplates.10 Reactive Arthritis
Radiographically, the findings of reactive arthritis (Box 3) overlap with those of psoriatic arthritis and consist of joint inflammation, bony productive change, periostitis,
Imaging of Inflammatory Arthritis in Adults
Fig. 6. Adventitial bursitis. (A) US image obtained at the posterior elbow shows a fluiddistended olecranon bursa (asterisks) in a 59-year-old woman with RA. (B) US image shows an adventitial bursa (arrowheads) seen in the plantar subcutaneous tissues over the second metatarsophalangeal joint in a 33-year-old woman with RA. MT, metatarsal head; PP, proximal phalanx.
enthesitis, and dactylitis. Bilateral symmetric or asymmetric sacroiliitis may also be present.6 MRI features in patients with reactive arthritis may include synovitis (Fig. 12) with erosive arthritis and tenosynovitis and bursitis commonly involving the ankle and foot. Marrow edema and osseous remodeling may be observed at sites of enthesitis. The sacroiliac joints may also be involved, classically manifesting as an asymmetric sacroiliitis.13 Inflammatory Bowel Disease Associated Arthritis
Radiographs in patients with inflammatory bowel disease–associated arthropathy (Box 4) may demonstrate effusions and periarticular osteopenia peripherally and syndesmophytes and sacroiliac joint ankylosis axially.14 MRI findings of peripheral inflammatory arthritis in inflammatory bowel disease often include synovitis, although erosions and joint destruction are less commonly observed
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Fig. 7. Coronal inversion recovery (A), gradient echo (B), and proton density (C) images of the wrist in a 65-year-old man with rheumatoid arthritis show synovitis (white arrowhead) and osseous erosions (arrows) with adjacent periarticular marrow edema (black arrowhead).
than often seen with other inflammatory arthropathies. Axial disease tends to have a similar appearance to ankylosing spondylitis, with areas of inflammation, sclerosis, syndesmophytes, and vertebral fusion in the spine as well as bilateral symmetric sacroiliitis (Fig. 13).14
Imaging of Inflammatory Arthritis in Adults
Box 2 Psoriatic arthritis Psoriatic arthritis is an inflammatory arthropathy affecting approximately 4% to 30% of patients with psoriasis. Joint involvement is typically polyarticular or oligoarticular, and various patterns of involvement have been described, including: Distal, typically involving the distal interphalangeal joints Asymmetric oligoarthritis Symmetric polyarthritis Spondyloarthritis with sacroiliitis Additional characteristics include tenosynovitis, enthesitis, dactylitis, ivory phalanx, and periostitis.10,11
Crystalline Arthropathy
Crystalline arthropathies (Box 5) include gout and calcium pyrophosphate deposition. The typical radiographic features of gouty arthritis include periarticular punched out erosions with overhanging edges and sclerotic margins as well as soft tissue nodular
Fig. 8. Posteroanterior radiograph of the left fifth digit shows an irregular fuzzy appearance along the radial aspect of the proximal phalanx (arrow) with periarticular marginal erosions (arrowheads) and diffuse soft tissue swelling of the entire digit, which is consistent with dactylitis.
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Fig. 9. Lateral radiograph of the right hand shows pencil-in-cup deformities of the second, third, and fourth distal interphalangeal joints (arrows); third and fourth proximal interphalangeal joints; and first metacarpophalangeal joint.
tophaceous deposits (Fig. 14).15 Pseudogout manifests radiographically as chondrocalcinosis (Fig. 15) within hyaline and fibrocartilage, joint space narrowing, subchondral sclerosis, and osteophyte formation.16 The sonographic appearance of crystalline arthropathy has been well described.18,19 Most commonly seen at the first MTP, joints affected by gout or pseudogout can have characteristic echogenic aggregates within a joint effusion or along the synovial lining (Fig. 16). Capsular hyperemia is frequently detected by Doppler during acute attacks. Osseous erosions can also be seen, often adjacent to para-articular soft tissue deposits. MRI allows direct visualization of deposits in crystalline arthropathy, which appear low signal on T1-weighted images and variable signal on T2, often with areas of mineralization. These are often found in areas of marginal erosions about the joints although also occur within the soft tissues or may be intraosseous (Fig. 17). Synovitis and bursitis are also common imaging features, with the retrocalcaneal and olecranon bursae being common sites of involvement.20,21 Lupus-Associated Arthritis
Systemic lupus erythematosus–related arthropathy (Box 6) presents radiographically with nonerosive periarticular osteopenia and pericapsular soft tissue swelling.
Imaging of Inflammatory Arthritis in Adults
Fig. 10. Patellar enthesitis. US images show a thickened distal patella tendon (A, arrowheads) with associated marked hyperemia (B) in a 35-year-old woman with psoriatic arthritis.
Ligamentous laxity results in reducible metacarpophalangeal joint subluxations, which may become irreversible in Jaccoud syndrome owing to muscle atrophy and contracture (Fig. 18). Carpal instability, evidenced by scapholunate interval widening, may also be seen on radiographs of the wrist in radioulnar deviation.22
Fig. 11. (A) Coronal inversion recovery and (B) proton density images in a 45-year-old man with known psoriatic arthritis show osseous erosions (arrowheads) with associated marrow and soft tissue edema (arrow).
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Box 3 Reactive arthritis Reactive arthritis typically occurs in young adults after an infection involving certain organisms, such as: Chlamydia trachomatis Yersinia Salmonella Shigella Campylobacter Escherichia coli Clostridium difficile Chlamydophila pneumoniae Clinically, reactive arthritis manifests as a mono- or oligoarticular arthritis, which often involves the lower extremities. Additional features include fever and malaise and conjunctivitis; oral, skin, and genital lesions; nail changes; enthesitis; and dactylitis.13
Fig. 12. (A) Sagittal IR and (B) axial proton density images of the knee in a 35-year-old man with known reactive arthritis show marked inflammatory synovitis (arrows).
Box 4 Inflammatory bowel disease–associated arthritis Arthritis associated with inflammatory bowel disease may occur as: Type I: Acute pauciarticular remitting commonly involving the knees Type II: chronic polyarticular relapsing form most typically involving the metacarpophalangeal joints Additional areas of involvement may include the spine and sacroiliac joints, classically resulting in a bilateral symmetric sacroiliitis.14
Imaging of Inflammatory Arthritis in Adults
Fig. 13. Radiographs (A) in a 26-year-old woman with inflammatory bowel disease show arthritis with osteophytosis (arrow), with synovitis (arrow) on coronal inversion recovery image (B), and sacroiliitis with pronounced subchondral irregularity (arrowheads) on radiograph (A) and axial proton density image (C).
Although features are not specific, synovitis, tenosynovitis, and osseous erosions can be detected on ultrasound scan. On MRI, imaging features of SLE arthritis may include synovitis, tenosynovitis, subluxations, and osseous erosions, commonly involving the hands and wrists (Fig. 19). Although erosions are not typically a defining characteristic of SLE arthritis on
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Box 5 Crystalline arthropathies Crystalline arthropathy, the most common of which is gout, occurs secondary to the deposition of various crystals within the joints and periarticular soft tissues. In gout, longstanding hyperuricemia leads to the deposition of monosodium urate crystals, with resultant inflammatory arthritis, tophaceous deposits, and renal disease.17 Commonly involved sites include the great toe, knee, ankle, wrist, fingers, and olecranon bursa. Calcium Pyrophosphate Deposition Disease (CPPD) may result in a variety of clinical symptoms, although most joints affected by CPPD deposition tend to be asymptomatic. Joint involvement by pseudogout is more common in the knee than the toe, although definitive differentiation from gout necessitates identification of characteristic crystals within the synovial fluid.17 Pseudogout: attacks of crystal-induced synovitis clinically similar to gout but precipitated by CPPD Chondrocalcinosis: deposition of CPPD crystals within hyaline and fibrocartilage, resulting in mineralization Pyrophosphate arthropathy: joint disease related to CPPD
Fig. 14. Anteroposterior radiographs of the left foot in 2 patients with gout show a well defined punched-out erosion with sclerotic margins and overhanging edges along the medial aspect of the distal first proximal phalanx (arrow, A) and a periarticular punched out erosion along the medial aspect of the first metatarsophalangeal joint with an associated dense soft tissue tophaceous deposit (white arrow, B).
Imaging of Inflammatory Arthritis in Adults
Fig. 15. Anteroposterior radiograph of the knee shows chondrocalcinosis within both the medial and lateral menisci (arrows).
radiography, MRI may show subtle erosions not visible on radiographs, suggesting that erosion may be more common than previously suspected.22,23 Scleroderma
The radiographic evaluation of arthritis associated with systemic sclerosis (Box 7) demonstrates periarticular osteopenia, joint space narrowing, and osseous erosions with calcinosis and acro-osteolysis, particularly characteristic of the disease (Fig. 20).24 Patients with scleroderma most frequently have joint synovitis found during sonographic evaluation. Additional findings that may be detected on US include tenosynovitis, thickening of flexor tendon pulleys (Fig. 21), and calcific soft tissue deposits.27
Fig. 16. Gout in the first metatarsophalangeal joint. US image of the first metatarsophalangeal joint in a 45-year-old man with great toe pain and swelling shows a joint effusion distending the dorsal capsule (asterisk). Hyperechoic aggregates are seen in the joint (arrows) and along the capsular lining (arrowheads). Fluid sampling confirmed the diagnosis of gout. MT, metatarsal head; PP, proximal phalanx.
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Fig. 17. Coronal inversion recovery (A) and proton density (B) images of the right foot in a 68-year-old man with gout shows osseous erosions (arrowheads) and soft-tissue swelling (arrows) related to tophaceous urate deposits. Coronal inversion recovery (C) and proton density (D) images in a 70-year-old man with calcium pyrophosphate deposition disease arthropathy show synovitis (arrowhead) and osseous erosions with associated marrow edema (arrows).
Box 6 Lupus associated arthritis Joint involvement in the setting of SLE may manifest as: Deforming arthropathy with reversible subluxations (Jaccoud Arthropathy) Erosive arthritis (less common) These forms may overlap as a mild deforming arthropathy with subtle erosions, often visible only on advanced imaging.22,23
Imaging of Inflammatory Arthritis in Adults
Fig. 18. Posteroanterior radiograph of bilateral hands shows marked ulnar deviation and subluxation of the bilateral metacarpophalangeal joints (arrows).
MRI manifestations of scleroderma include skin thickening, soft tissue calcifications, flexion contractures, tenosynovitis, periarticular edema, synovitis with erosive arthropathy, and acro-osteolysis (Fig. 22). Magnetic resonance angiography may be used for evaluation of vasculitis, which is common in the hands, resulting in arterial attenuation, irregularity, beading, and areas of occlusion (Fig. 23).24–26
Fig. 19. Radiograph (A) and sagittal proton density (B) images in a 68-year-old woman with lupus show subluxations (arrowheads) involving multiple joints.
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Burge et al Box 7 Scleroderma Scleroderma is an autoimmune connective tissue disorder typically affecting women of reproductive age. Musculoskeletal involvement is common, with the hands being the site most typically affected. Clinical features include: Skin thickening Soft tissue calcifications Flexion contractures Atrophy of the fingertips Arthropathy Vasculitis, which may affect all vessel sizes but most commonly occurs as a small vessel antineutrophil cytoplasmic antibody–associated vasculitis25,26
Fig. 20. Posteroanterior radiograph of the right hand shows acro-osteolysis of the second digit (arrow), flexion contracture of the third proximal interphalangeal joint, and subcutaneous and periarticular soft tissue calcifications (arrowheads).
Fig. 21. Pulley thickening at the flexor tendon. US image shows a markedly thickened A1 pulley of the left ring finger flexor tendon (arrowheads) in a 59-year-old woman with scleroderma.
Imaging of Inflammatory Arthritis in Adults
Fig. 22. Axial proton density image (A) in a 51-year-old man with scleroderma shows marked circumferential skin thickening (calipers). Axial proton density image (B) shows inflammatory tenosynovitis (white arrow) in a 31-year-old man with scleroderma.
Fig. 23. Contrast-enhanced magnetic resonance angiogram (A) in a 59-year-old woman with scleroderma shows globally decreased perfusion to the hand with areas of arterial irregularity (arrow) and occlusion (arrowhead). Repeat magnetic resonance angiogram (B) in the same patient 1 week later after vascular intervention shows overall greatly improved perfusion, although areas of irregularity and occlusion persist.
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IMAGE-GUIDED INTERVENTION
Integral to diagnosis and treatment, image-guided interventions are commonly performed in patients with inflammatory arthritis. A fluid sample from an inflamed joint can be used to assess for the presence of crystals in suspected crystalline arthropathy or to exclude infection. Image guidance can improve the accuracy and thus efficacy of procedures, and the choice of imaging modality depends on the intervention. Large joints like the hip, knee, or glenohumeral joint can easily be targeted fluoroscopically or using US. Smaller joints in the extremity may be more difficult to target using fluoroscopy, and sonographic guidance is recommended in these cases. An additional benefit of sonography is the ability to visualize intra-articular and periarticular fluid, allowing for easier targeting of fluid for laboratory evaluation. US is an ideal modality for guidance in synovial biopsy, at times performed to help diagnose or stage inflammatory disease. Again underscored is the lack of ionizing radiation in US, yet another reason to use it for image guidance. Because of their deep location, facet and sacroiliac joint procedures are most commonly accessed under computed tomography guidance. Therapeutic injection of corticosteroids may be recommended for patients with focal inflammation. Joints (Fig. 24), tendon sheaths, and inflamed bursae are common targets for injection, all well seen using sonography. Sonographic guidance is also useful in perineural injection, as in carpal tunnel syndrome, commonly seen in RA, and in flexor tenosynovial injection for “trigger finger” (Fig. 25), also frequently seen in RA and scleroderma.
Fig. 24. US-guided injection of the first metatarsophalangeal joint. The first metatarsophalangeal joint is imaged in the sagittal plane, and the needle is inserted out-of-plane to the transducer. The needle tip is seen as an echogenic dot inside the joint (A, B; circle). Echogenic corticosteroid distends the joint after injection (B; asterisk). MT, metatarsal head; PP, proximal phalanx.
Imaging of Inflammatory Arthritis in Adults
Fig. 25. US-guided flexor tendon sheath injection in a 64-year-old woman with rheumatoid arthritis complaining of finger triggering. US images (A, B) show the needle (arrowhead) placed in the tendon sheath at the level of the A1 pulley (bracket). During the procedure, the injected material (B; asterisks) distends the flexor tendon sheath. FT, flexor tendon; MC, metacarpal head; PP, proximal phalanx.
SUMMARY
Imaging features in patients with inflammatory arthritis are related to pathologic changes in the architecture and function of synovial and nonsynovial tissues comprising the joint. A variety of imaging modalities are available for evaluation of these arthritides, each having different strengths and weaknesses and in general, are complementary to one another. Radiographs, US, and MRI are frequently used for the evaluation of patients with inflammatory arthritis, with various grading systems having been developed for use with these modalities. Knowledge of expected characteristic imaging findings is crucial in the accurate diagnosis and monitoring of patients with inflammatory arthritis. REFERENCES
1. Haywood L, Walsh DA. Vasculature of the normal and arthritic synovial joint. Histol Histopathol 2001;16(1):277–84. 2. McQueen FM. Imaging in early rheumatoid arthritis. Best Pract Res Clin Rheumatol 2013;27(4):499–522. 3. van Steenbergen HW, van Nies JA, Huizinga TW, et al. Characterising arthralgia in the preclinical phase of rheumatoid arthritis using MRI. Ann Rheum Dis 2015; 74(6):1225–32. 4. Sommer OJ, Kladosek A, Weiler V, et al. Rheumatoid arthritis: a practical guide to state-of-the-art imaging, image interpretation, and clinical implications. Radiographics 2005;25(2):381–98.
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5. Colebatch AN, Edwards CJ, Ostergaard M, et al. EULAR recommendations for the use of imaging of the joints in the clinical management of rheumatoid arthritis. Ann Rheum Dis 2013;72(6):804–14. 6. Jacobson JA, Girish G, Jiang Y, et al. Radiographic evaluation of arthritis: inflammatory conditions. Radiology 2008;248(2):378–89. 7. Venables PJW, Maini RN. Diagnosis and differential diagnosis of rheumatoid arthrtitis. Waltham (MA): UpToDate; 2014. Available at: http://www.uptodate.com/ contents/diagnosis-and-differential-diagnosis-of-rheumatoid-arthritis?source5 search_result&search5rheumatoid1arthritis&selectedTitle51%7E150. Accessed August 20, 2014. 8. Iagnocco A, Ceccarelli F, Perricone C, et al. The role of ultrasound in rheumatology. Semin Ultrasound CT MR 2011;32(2):66–73. 9. Schueller-Weidekamm C. Quantification of synovial and erosive changes in rheumatoid arthritis with ultrasound–revisited. Eur J Radiol 2009;71(2):225–31. 10. Gladman D, Ritchlin C. Clinical manifestations and diagnosis of psoriatic arthritis. Waltham (MA): UpToDate; 2014. Available at: http://www.uptodate.com/contents/ clinical-manifestations-and-diagnosis-of-psoriatic-arthritis?source=search_result& search=psoriatic+arthritis&selectedTitle=1%7E142. Accessed August 20, 2014. 11. Huynh D, Kavanaugh A. Psoriatic arthritis: current therapy and future approaches. Rheumatology (Oxford) 2015;54(1):20–8. 12. Mandl P, Navarro-Compan V, Terslev L, et al. EULAR recommendations for the use of imaging in the diagnosis and management of spondyloarthritis in clinical practice. Ann Rheum Dis 2015;74(7):1327–39. 13. Yu D. Reactive arthritis. Waltham (MA): UpToDate; 2014. Available at: http://www. uptodate.com/contents/reactive-arthritis?source=machineLearning&search= reactive+arthritis&selectedTitle=1%7E125§ionRank=1&anchor=H4#H4. Accessed August 20, 2014. 14. Arvikar SL, Fisher MC. Inflammatory bowel disease associated arthropathy. Curr Rev Musculoskelet Med 2011;4(3):123–31. 15. Jacobson JA, Girish G, Jiang Y, et al. Radiographic evaluation of arthritis: degenerative joint disease and variations. Radiology 2008;248(3):737–47. 16. Helms C, Vogler J, Simms D, et al. CPPD crystal deposition disease or pseudogout. Radiographics 1982;2(1):40–52. 17. Becker M. Clinical manifestations and diagnosis of gout. Waltham (MA): UpToDate; 2014. Available at: http://www.uptodate.com/contents/clinical-manifestationsand-diagnosis-of-gout?source=search_result&search=Gout&selectedTitle=2%7 E150. Accessed August 20, 2014. 18. Naredo E, Uson J, Jimenez-Palop M, et al. Ultrasound-detected musculoskeletal urate crystal deposition: which joints and what findings should be assessed for diagnosing gout? Ann Rheum Dis 2014;73(8):1522–8. 19. Scirocco C, Rutigliano IM, Finucci A, et al. Musculoskeletal ultrasonography in gout. Med Ultrason 2015;17(4):535–40. 20. Girish G, Glazebrook KN, Jacobson JA. Advanced imaging in gout. AJR Am J Roentgenol 2013;201(3):515–25. 21. Popovich I, Dalbeth N, Doyle A, et al. Exploring cartilage damage in gout using 3-T MRI: distribution and associations with joint inflammation and tophus deposition. Skeletal Radiol 2014;43(7):917–24. 22. Lalani TA, Kanne JP, Hatfield GA, et al. Imaging findings in systemic lupus erythematosus. Radiographics 2004;24(4):1069–86. 23. Ball EM, Tan AL, Fukuba E, et al. A study of erosive phenotypes in lupus arthritis using magnetic resonance imaging and anti-citrullinated protein
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antibody, anti-RA33 and RF autoantibody status. Rheumatology (Oxford) 2014; 53(10):1835–43. Avouac J, Clements PJ, Khanna D, et al. Articular involvement in systemic sclerosis. Rheumatology 2012;51(8):1347–56. Chitale S, Ciapetti A, Hodgson R, et al. Magnetic resonance imaging and musculoskeletal ultrasonography detect and characterize covert inflammatory arthropathy in systemic sclerosis patients with arthralgia. Rheumatology 2010;49(12): 2357–61. Abdel-Magied RA, Lotfi A, AbdelGawad EA. Magnetic resonance imaging versus musculoskeletal ultrasonography in detecting inflammatory arthropathy in systemic sclerosis patients with hand arthralgia. Rheumatol Int 2013;33(8):1961–6. Porta F, Gargani L, Kaloudi O, et al. The new frontiers of ultrasound in the complex world of vasculitides and scleroderma. Rheumatology 2012;51(Suppl 7): vii26–30.
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INTRODUCTION
The term inflammatory arthritis encompasses a variety of conditions, the common feature being synovial inflammation. Chronic joint inflammation results in synovial hyperplasia, which causes the average depth of blood vessels from the synovial surface to increase, increasing the distance over which nutrients must travel and thereby decreasing the efficiency of nutrient transport to the articular cartilage. This process may stimulate angiogenesis. Local tissue damage may occur as a result of progression of this process, with the enlarging synovial pannus invading nonsynovial
Disclosures: Research support received from General Electric Healthcare (A.J. Burge, O.K. Nwawka, H.G. Potter); No relevant disclosures (J. Berkowitz). Department of Radiology and Imaging, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA * Corresponding author. E-mail address: [email protected] Rheum Dis Clin N Am 42 (2016) 561–585 http://dx.doi.org/10.1016/j.rdc.2016.07.001 0889-857X/16/ª 2016 Elsevier Inc. All rights reserved.
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tissues such as articular cartilage and bone. Vascularization of typically nonvascular tissues, such as articular cartilage, may lead to functional compromise, resulting in further tissue damage.1 Although numerous inflammatory arthropathies exist, they often share similar and overlapping basic imaging characteristics. Synovitis, cartilage wear, and osseous changes tend to be common and fairly universal imaging findings. Additional findings may include tenosynovitis, skin changes, and deposits. The individual arthropathies may often be distinguished by the pattern of joint involvement, the specific appearance of pathologic changes, and ancillary findings. Various complementary imaging modalities may be used to evaluate patients with inflammatory arthropathies. PREIMAGING PLANNING
Synovial joints comprise of a variety of tissues. These tissues include the highly vascular synovium and variably less vascular tissues such as articular cartilage, ligaments, menisci, tendons, muscles, bone, capsule, and bursae.1 Plain radiography is the conventional first-line imaging examination obtained in the evaluation of suspected inflammatory arthropathy, as it is accessible and relatively inexpensive and allows for the simultaneous evaluation of multiple joints. Radiographs provide valuable information regarding the bony manifestations of arthritis. These osseous abnormalities, however, represent the late sequelae of the disease, and, accordingly, radiographs do not allow for early detection and, consequently, treatment of these conditions. Additionally, conventional radiographs do not provide sensitive soft tissue assessment. Finally, radiography necessitates exposure to ionizing radiation and its potential stochastic effects, the risks of which increase with repeated imaging acquired to monitor for disease progression.2 Ultrasound scan (US) uses the acoustic properties of tissue to produce images. In the evaluation of inflammatory arthropathy, US can detect soft tissue abnormalities including synovial hypertrophy, joint effusion, and tenosynovitis. Doppler evaluation provides additional benefit, as it can detect hyperemia, thus, informing the user on the activity of inflammatory disease. Although US imaging of bone is limited because of its highly reflective properties, periarticular osseous erosions can be detected. The benefits of US include portability, ease of contralateral side imaging, and lack of ionizing radiation, particularly useful in young patients who are more susceptible to effects of repeated radiation. Additionally, US is relatively cost effective when compared with other imaging modalities. MRI provides excellent tissue contrast and sensitivity for mobile water, offering superior evaluation of both the synovium and nonsynovial soft tissues and of periarticular marrow edema and osseous erosions. This, along with the lack of ionizing radiation, makes MRI a superb modality for evaluation of patients with inflammatory arthropathies; however, the cost makes it inappropriate as a first-line imaging test, and contraindications, such as claustrophobia and pacemakers, preclude the use of MRI in certain patients.2,3 DIAGNOSTIC IMAGING TECHNIQUE
Radiographs of the symptomatic joints and the patient’s hands, wrists, and feet are typically obtained at the outset of the disease to provide baseline information regarding joint integrity. Follow-up radiographs of the hands and feet, regardless of symptoms, should be considered in an effort to gauge disease progression or treatment efficacy,4 as they often detect early erosions radiographically. No specific recommendations regarding the exact timeframe of serial follow-up radiographs exist.5
Imaging of Inflammatory Arthritis in Adults
US imaging in inflammatory arthropathy usually consists of extremity imaging. As such, high frequency transducers are recommended to provide high-resolution imaging of joints and surrounding soft tissues. Typically, 12- to 18-MHz transducers are used. If imaging digits, a small or “hockey-stick” transducer may be useful. Patients can be comfortably imaged seated or recumbent on a stretcher, depending on the body part. Optimal MRI technique depends on the anatomic region being imaged, but, in general, the scan should be tailored to the anatomy of interest to the extent that this is possible. Dedicated imaging coils sized appropriately for the anatomic region should be used, and imaging planes should follow anatomic planes. Field of view should be chosen to cover the area of interest without imaging an excessive amount of nonrelevant anatomy to maximize spatial resolution. At the least, some combination of sequencing incorporating fat-suppressed fluid-sensitive images (for evaluation of fluid and edema) along with high spatial resolution images (for evaluation of anatomic detail) should be obtained. At the authors’ institution, a routine clinical joint imaging protocol typically incorporates a single plane of fat-suppressed fluid-sensitive imaging (commonly an inversion recovery sequence) and 3 planes of high-resolution proton density (PD)-weighted images, which provide excellent spatial resolution and tissue contrast with fluid sensitivity. In addition, these PD sequences allow detailed evaluation of the articular cartilage, nicely depicting the normal layered chondral architecture, and providing an element of contrast of the articular cartilage against the relatively hyperintense joint fluid. Sample acquisition parameters for a routine hip MRI are listed in Table 1. Additional more specialized sequences (for example, gradient echo imaging in the setting of suspected pigmented villonodular synovitis) may be added as clinically indicated. INTERPRETATION/ASSESSMENT OF CLINICAL IMAGES Rheumatoid Arthritis
Rheumatoid arthritis (RA) (Box 1) manifests radiographically as uniform joint space narrowing with periarticular osteopenia, marginal erosions, and soft tissue swelling (Fig. 1). Metacarpophalangeal joint ulnar deviation and phalangeal swan neck and boutonniere deformities may also be present (Fig. 2). In the feet, a characteristic marginal erosion is often seen along the lateral aspect of the fifth metatarsal head (Fig. 3). Cervical spine involvement includes erosion of the odontoid process and atlantodental interval widening. The lack of associated osseous proliferative change facilitates the differentiation of rheumatoid arthritis from osteoarthritis and the seronegative spondyloarthropathies.6 The sonographic features of RA are well characterized, and the use of US is widespread in the clinical evaluation of the disease, particularly as it affects the extremities.8,9 RA on sonography most commonly appears as joint synovitis, with hypoechoic synovial thickening and joint effusion, at times accompanied by Doppler hyperemia. When synovial thickening is present, one should look carefully for concomitant osseous erosion, which presents on US as focal osseous irregularity, more commonly at the margins of the joints (Fig. 4). Tenosynovitis presents as irregular hypoechoic thickening of the tendon sheath, with or without tendon sheath effusion and Doppler hyperemia (Fig. 5). There may also be thickening of the finger flexor tendon pulleys, predisposing to finger triggering. Adventitial bursitis may be seen in subcutaneous tissues over prominent osseous structures, as in olecranon bursitis, or in regions susceptible to repeated friction (Fig. 6).
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Table 1 Acquisition parameters for routine clinical imaging of the hip at 1.5 T Parameter
Coronal Fast Inversion Recovery (Whole Pelvis)
TR (ms)
3500–5000
4000–5000
4000–5000
4000–5000
4000–5000
TE (ms)
17
34
34
34
34
TI
150
—
—
—
—
BW (Hz/pixel)
200
200
200
200
200
ETL
7–9
8–12
9–12
9–12
9–12
NEX
2
2
3
3
3
FOV (cm)
Greater intertrochanteric distance plus 2 cm
Greater intertrochanteric distance
17–18
17–18
16
512 256
Axial FSE (Whole Pelvis)
Sagittal FSE (Affected Hip)
Coronal FSE (Affected Hip)
Oblique Axial FSE (Affected Hip)
Matrix
256 192
512 256
512 384
512 384
Slice/Gap (mm)
5/0
5/0
2.5/0
4/0
3/0
NPW
Yes
Yes
Yes
Yes
Yes
Frequency
R/L
A/P
A/P
R/L
A/P
Abbreviations: A/P, anterior to posterior; BW, receiver bandwidth; ETL, echo train length; FOV, field of view; FSE, fast spin echo; NEX, number of excitations; NPW, no phase wrap; R/L, right to left; TE, echo time; TI, time to inversion; TR, repetition time.
Imaging of Inflammatory Arthritis in Adults
Box 1 Rheumatoid arthritis Rheumatoid arthritis is a classic example of an inflammatory arthropathy and typically manifests as a symmetric peripheral polyarthritis with a variety of osseous and soft tissue findings. Clinically, diagnosis is based on an established set of criteria: Polyarthritis involving 3 or more joints Positive serologic markers Duration of symptoms for more than 6 weeks Exclusion of similar diseases Additional clinical manifestations may include morning stiffness, rheumatoid nodules, and lung disease. The arthritis commonly involves the hands and wrist and results in an inflammatory synovitis with osseous erosions. Common soft tissue findings include tenosynovitis and bursitis.7
Fig. 1. Posteroanterior radiograph of the right hand shows juxta-articular demineralization with erosions, joint space narrowing, and autofusion of the radiocarpal and midcarpal joints (arrow) and erosions of the metacarpophalangeal joints, interphalangeal joint of the thumb, proximal interphalangeal joints of the second through fifth digits, and distal interphalangeal joint of the fifth digit. Chronic erosion of the distal ulna is also noted (arrowhead).
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Fig. 2. Posteroanterior (A), lateral (B), and oblique (C) radiographs of the right hand in multiple patients with rheumatoid arthritis show ulnar deviation and subluxation of the metacarpophalangeal joints (arrow), swan neck deformity with hyperextension of the proximal interphalangeal joint, and flexion of the distal interphalangeal joint (arrow) and boutonniere deformity with flexion of the proximal interphalangeal joint and extension of the distal interphalangeal joint (arrow) respectively.
MRI findings in patients with RA include inflammatory synovitis, commonly with hyperintense and thickened synovium and debris. Periarticular marrow edema may be present and may precede the development of defined osseous erosions (Fig. 7). Tenosynovitis is common in patients with RA, appearing as hyperintensity and thickening of the tendon sheath with fluid distention and tenosynovial adhesions often developing in longstanding cases. Bursitis may also be observed, commonly developing in the olecranon region and about the metatarsals.2,4
Imaging of Inflammatory Arthritis in Adults
Fig. 3. Anteroposterior radiograph of the right forefoot shows a distinctive marginal erosion of rheumatoid arthritis along the lateral aspect of the fifth metatarsal head (arrow).
SPONDYLOARTHROPATHIES Psoriatic Arthritis
Psoriatic arthritis (Box 2) manifests radiographically as marginal erosions, osseous productive change, periostitis, enthesitis, and joint subluxations (Fig. 8). “Pencilin-cup” deformities, in which one aspect of the joint projects like a pencil into a cup created by the other aspect of the joint, are caused by significant associated osseous damage (Fig. 9). Dactylitis, which is also referred to as a sausage digit and describes soft tissue swelling of an entire digit (see Fig. 8), is another feature commonly associated with the disease. Sclerosis, enthesitis, periostitis, and soft tissue swelling of the distal phalanx of the great toe, also known as the ivory phalanx, are distinctive for psoriatic arthritis. When an axial component of the disease is present, bilateral, symmetric or asymmetric, sacroiliac joint irregularities, erosions, and ultimately ankylosis may be seen.6
Fig. 4. Osseous erosion in rheumatoid arthritis. US image at the second metacarpophalangeal (MCP) joint depicts dorsal synovial thickening (arrowhead) and focal osseous erosion (arrow) at the medial margin of the metacarpal head in a 53-year-old woman with rheumatoid arthritis. MC, metacarpal head; PP, proximal phalanx.
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Fig. 5. Posterior tibial tendinosis and tenosynovitis. US images show a thickened and hypoechoic distal posterior tibial tendon surrounded by complex tenosynovitis (A, asterisks), with associated intense hyperemia (B) in a 74-year-old woman with RA. NAV, navicular; PTT, posterior tibial tendon.
US poorly evaluates axial disease in psoriatic arthritis and other spondyloarthropathies, and its use is not recommended for this purpose.12 However, peripheral manifestations of spondyloarthropathy can be assessed using sonography, including enthesitis, bursitis, and tenosynovitis. Enthesitis may appear as tendon thickening at its bony attachment, sometimes associated with mild osseous irregularity and hyperemia (Fig. 10). Osseous erosions in psoriatic arthritis have a similar sonographic appearance to that of RA, although the distribution is different. In some cases, periostitis can be seen as surface osseous irregularity on US. On MRI, joint involvement is characterized by synovitis with osseous erosions. Areas of marrow edema often occur at the capsular attachments and entheses (Fig. 11). Tenosynovitis often affects the flexor tendons more commonly than the extensors, and dactylitis may result in the characteristic sausage digit, with soft-tissue swelling and edema. Sacroiliitis is classically asymmetric, and spondylitis may manifest as areas of marrow edema, commonly along the endplates.10 Reactive Arthritis
Radiographically, the findings of reactive arthritis (Box 3) overlap with those of psoriatic arthritis and consist of joint inflammation, bony productive change, periostitis,
Imaging of Inflammatory Arthritis in Adults
Fig. 6. Adventitial bursitis. (A) US image obtained at the posterior elbow shows a fluiddistended olecranon bursa (asterisks) in a 59-year-old woman with RA. (B) US image shows an adventitial bursa (arrowheads) seen in the plantar subcutaneous tissues over the second metatarsophalangeal joint in a 33-year-old woman with RA. MT, metatarsal head; PP, proximal phalanx.
enthesitis, and dactylitis. Bilateral symmetric or asymmetric sacroiliitis may also be present.6 MRI features in patients with reactive arthritis may include synovitis (Fig. 12) with erosive arthritis and tenosynovitis and bursitis commonly involving the ankle and foot. Marrow edema and osseous remodeling may be observed at sites of enthesitis. The sacroiliac joints may also be involved, classically manifesting as an asymmetric sacroiliitis.13 Inflammatory Bowel Disease Associated Arthritis
Radiographs in patients with inflammatory bowel disease–associated arthropathy (Box 4) may demonstrate effusions and periarticular osteopenia peripherally and syndesmophytes and sacroiliac joint ankylosis axially.14 MRI findings of peripheral inflammatory arthritis in inflammatory bowel disease often include synovitis, although erosions and joint destruction are less commonly observed
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Fig. 7. Coronal inversion recovery (A), gradient echo (B), and proton density (C) images of the wrist in a 65-year-old man with rheumatoid arthritis show synovitis (white arrowhead) and osseous erosions (arrows) with adjacent periarticular marrow edema (black arrowhead).
than often seen with other inflammatory arthropathies. Axial disease tends to have a similar appearance to ankylosing spondylitis, with areas of inflammation, sclerosis, syndesmophytes, and vertebral fusion in the spine as well as bilateral symmetric sacroiliitis (Fig. 13).14
Imaging of Inflammatory Arthritis in Adults
Box 2 Psoriatic arthritis Psoriatic arthritis is an inflammatory arthropathy affecting approximately 4% to 30% of patients with psoriasis. Joint involvement is typically polyarticular or oligoarticular, and various patterns of involvement have been described, including: Distal, typically involving the distal interphalangeal joints Asymmetric oligoarthritis Symmetric polyarthritis Spondyloarthritis with sacroiliitis Additional characteristics include tenosynovitis, enthesitis, dactylitis, ivory phalanx, and periostitis.10,11
Crystalline Arthropathy
Crystalline arthropathies (Box 5) include gout and calcium pyrophosphate deposition. The typical radiographic features of gouty arthritis include periarticular punched out erosions with overhanging edges and sclerotic margins as well as soft tissue nodular
Fig. 8. Posteroanterior radiograph of the left fifth digit shows an irregular fuzzy appearance along the radial aspect of the proximal phalanx (arrow) with periarticular marginal erosions (arrowheads) and diffuse soft tissue swelling of the entire digit, which is consistent with dactylitis.
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Fig. 9. Lateral radiograph of the right hand shows pencil-in-cup deformities of the second, third, and fourth distal interphalangeal joints (arrows); third and fourth proximal interphalangeal joints; and first metacarpophalangeal joint.
tophaceous deposits (Fig. 14).15 Pseudogout manifests radiographically as chondrocalcinosis (Fig. 15) within hyaline and fibrocartilage, joint space narrowing, subchondral sclerosis, and osteophyte formation.16 The sonographic appearance of crystalline arthropathy has been well described.18,19 Most commonly seen at the first MTP, joints affected by gout or pseudogout can have characteristic echogenic aggregates within a joint effusion or along the synovial lining (Fig. 16). Capsular hyperemia is frequently detected by Doppler during acute attacks. Osseous erosions can also be seen, often adjacent to para-articular soft tissue deposits. MRI allows direct visualization of deposits in crystalline arthropathy, which appear low signal on T1-weighted images and variable signal on T2, often with areas of mineralization. These are often found in areas of marginal erosions about the joints although also occur within the soft tissues or may be intraosseous (Fig. 17). Synovitis and bursitis are also common imaging features, with the retrocalcaneal and olecranon bursae being common sites of involvement.20,21 Lupus-Associated Arthritis
Systemic lupus erythematosus–related arthropathy (Box 6) presents radiographically with nonerosive periarticular osteopenia and pericapsular soft tissue swelling.
Imaging of Inflammatory Arthritis in Adults
Fig. 10. Patellar enthesitis. US images show a thickened distal patella tendon (A, arrowheads) with associated marked hyperemia (B) in a 35-year-old woman with psoriatic arthritis.
Ligamentous laxity results in reducible metacarpophalangeal joint subluxations, which may become irreversible in Jaccoud syndrome owing to muscle atrophy and contracture (Fig. 18). Carpal instability, evidenced by scapholunate interval widening, may also be seen on radiographs of the wrist in radioulnar deviation.22
Fig. 11. (A) Coronal inversion recovery and (B) proton density images in a 45-year-old man with known psoriatic arthritis show osseous erosions (arrowheads) with associated marrow and soft tissue edema (arrow).
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Box 3 Reactive arthritis Reactive arthritis typically occurs in young adults after an infection involving certain organisms, such as: Chlamydia trachomatis Yersinia Salmonella Shigella Campylobacter Escherichia coli Clostridium difficile Chlamydophila pneumoniae Clinically, reactive arthritis manifests as a mono- or oligoarticular arthritis, which often involves the lower extremities. Additional features include fever and malaise and conjunctivitis; oral, skin, and genital lesions; nail changes; enthesitis; and dactylitis.13
Fig. 12. (A) Sagittal IR and (B) axial proton density images of the knee in a 35-year-old man with known reactive arthritis show marked inflammatory synovitis (arrows).
Box 4 Inflammatory bowel disease–associated arthritis Arthritis associated with inflammatory bowel disease may occur as: Type I: Acute pauciarticular remitting commonly involving the knees Type II: chronic polyarticular relapsing form most typically involving the metacarpophalangeal joints Additional areas of involvement may include the spine and sacroiliac joints, classically resulting in a bilateral symmetric sacroiliitis.14
Imaging of Inflammatory Arthritis in Adults
Fig. 13. Radiographs (A) in a 26-year-old woman with inflammatory bowel disease show arthritis with osteophytosis (arrow), with synovitis (arrow) on coronal inversion recovery image (B), and sacroiliitis with pronounced subchondral irregularity (arrowheads) on radiograph (A) and axial proton density image (C).
Although features are not specific, synovitis, tenosynovitis, and osseous erosions can be detected on ultrasound scan. On MRI, imaging features of SLE arthritis may include synovitis, tenosynovitis, subluxations, and osseous erosions, commonly involving the hands and wrists (Fig. 19). Although erosions are not typically a defining characteristic of SLE arthritis on
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Box 5 Crystalline arthropathies Crystalline arthropathy, the most common of which is gout, occurs secondary to the deposition of various crystals within the joints and periarticular soft tissues. In gout, longstanding hyperuricemia leads to the deposition of monosodium urate crystals, with resultant inflammatory arthritis, tophaceous deposits, and renal disease.17 Commonly involved sites include the great toe, knee, ankle, wrist, fingers, and olecranon bursa. Calcium Pyrophosphate Deposition Disease (CPPD) may result in a variety of clinical symptoms, although most joints affected by CPPD deposition tend to be asymptomatic. Joint involvement by pseudogout is more common in the knee than the toe, although definitive differentiation from gout necessitates identification of characteristic crystals within the synovial fluid.17 Pseudogout: attacks of crystal-induced synovitis clinically similar to gout but precipitated by CPPD Chondrocalcinosis: deposition of CPPD crystals within hyaline and fibrocartilage, resulting in mineralization Pyrophosphate arthropathy: joint disease related to CPPD
Fig. 14. Anteroposterior radiographs of the left foot in 2 patients with gout show a well defined punched-out erosion with sclerotic margins and overhanging edges along the medial aspect of the distal first proximal phalanx (arrow, A) and a periarticular punched out erosion along the medial aspect of the first metatarsophalangeal joint with an associated dense soft tissue tophaceous deposit (white arrow, B).
Imaging of Inflammatory Arthritis in Adults
Fig. 15. Anteroposterior radiograph of the knee shows chondrocalcinosis within both the medial and lateral menisci (arrows).
radiography, MRI may show subtle erosions not visible on radiographs, suggesting that erosion may be more common than previously suspected.22,23 Scleroderma
The radiographic evaluation of arthritis associated with systemic sclerosis (Box 7) demonstrates periarticular osteopenia, joint space narrowing, and osseous erosions with calcinosis and acro-osteolysis, particularly characteristic of the disease (Fig. 20).24 Patients with scleroderma most frequently have joint synovitis found during sonographic evaluation. Additional findings that may be detected on US include tenosynovitis, thickening of flexor tendon pulleys (Fig. 21), and calcific soft tissue deposits.27
Fig. 16. Gout in the first metatarsophalangeal joint. US image of the first metatarsophalangeal joint in a 45-year-old man with great toe pain and swelling shows a joint effusion distending the dorsal capsule (asterisk). Hyperechoic aggregates are seen in the joint (arrows) and along the capsular lining (arrowheads). Fluid sampling confirmed the diagnosis of gout. MT, metatarsal head; PP, proximal phalanx.
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Fig. 17. Coronal inversion recovery (A) and proton density (B) images of the right foot in a 68-year-old man with gout shows osseous erosions (arrowheads) and soft-tissue swelling (arrows) related to tophaceous urate deposits. Coronal inversion recovery (C) and proton density (D) images in a 70-year-old man with calcium pyrophosphate deposition disease arthropathy show synovitis (arrowhead) and osseous erosions with associated marrow edema (arrows).
Box 6 Lupus associated arthritis Joint involvement in the setting of SLE may manifest as: Deforming arthropathy with reversible subluxations (Jaccoud Arthropathy) Erosive arthritis (less common) These forms may overlap as a mild deforming arthropathy with subtle erosions, often visible only on advanced imaging.22,23
Imaging of Inflammatory Arthritis in Adults
Fig. 18. Posteroanterior radiograph of bilateral hands shows marked ulnar deviation and subluxation of the bilateral metacarpophalangeal joints (arrows).
MRI manifestations of scleroderma include skin thickening, soft tissue calcifications, flexion contractures, tenosynovitis, periarticular edema, synovitis with erosive arthropathy, and acro-osteolysis (Fig. 22). Magnetic resonance angiography may be used for evaluation of vasculitis, which is common in the hands, resulting in arterial attenuation, irregularity, beading, and areas of occlusion (Fig. 23).24–26
Fig. 19. Radiograph (A) and sagittal proton density (B) images in a 68-year-old woman with lupus show subluxations (arrowheads) involving multiple joints.
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Fig. 20. Posteroanterior radiograph of the right hand shows acro-osteolysis of the second digit (arrow), flexion contracture of the third proximal interphalangeal joint, and subcutaneous and periarticular soft tissue calcifications (arrowheads).
Fig. 21. Pulley thickening at the flexor tendon. US image shows a markedly thickened A1 pulley of the left ring finger flexor tendon (arrowheads) in a 59-year-old woman with scleroderma.
Imaging of Inflammatory Arthritis in Adults
Fig. 22. Axial proton density image (A) in a 51-year-old man with scleroderma shows marked circumferential skin thickening (calipers). Axial proton density image (B) shows inflammatory tenosynovitis (white arrow) in a 31-year-old man with scleroderma.
Fig. 23. Contrast-enhanced magnetic resonance angiogram (A) in a 59-year-old woman with scleroderma shows globally decreased perfusion to the hand with areas of arterial irregularity (arrow) and occlusion (arrowhead). Repeat magnetic resonance angiogram (B) in the same patient 1 week later after vascular intervention shows overall greatly improved perfusion, although areas of irregularity and occlusion persist.
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IMAGE-GUIDED INTERVENTION
Integral to diagnosis and treatment, image-guided interventions are commonly performed in patients with inflammatory arthritis. A fluid sample from an inflamed joint can be used to assess for the presence of crystals in suspected crystalline arthropathy or to exclude infection. Image guidance can improve the accuracy and thus efficacy of procedures, and the choice of imaging modality depends on the intervention. Large joints like the hip, knee, or glenohumeral joint can easily be targeted fluoroscopically or using US. Smaller joints in the extremity may be more difficult to target using fluoroscopy, and sonographic guidance is recommended in these cases. An additional benefit of sonography is the ability to visualize intra-articular and periarticular fluid, allowing for easier targeting of fluid for laboratory evaluation. US is an ideal modality for guidance in synovial biopsy, at times performed to help diagnose or stage inflammatory disease. Again underscored is the lack of ionizing radiation in US, yet another reason to use it for image guidance. Because of their deep location, facet and sacroiliac joint procedures are most commonly accessed under computed tomography guidance. Therapeutic injection of corticosteroids may be recommended for patients with focal inflammation. Joints (Fig. 24), tendon sheaths, and inflamed bursae are common targets for injection, all well seen using sonography. Sonographic guidance is also useful in perineural injection, as in carpal tunnel syndrome, commonly seen in RA, and in flexor tenosynovial injection for “trigger finger” (Fig. 25), also frequently seen in RA and scleroderma.
Fig. 24. US-guided injection of the first metatarsophalangeal joint. The first metatarsophalangeal joint is imaged in the sagittal plane, and the needle is inserted out-of-plane to the transducer. The needle tip is seen as an echogenic dot inside the joint (A, B; circle). Echogenic corticosteroid distends the joint after injection (B; asterisk). MT, metatarsal head; PP, proximal phalanx.
Imaging of Inflammatory Arthritis in Adults
Fig. 25. US-guided flexor tendon sheath injection in a 64-year-old woman with rheumatoid arthritis complaining of finger triggering. US images (A, B) show the needle (arrowhead) placed in the tendon sheath at the level of the A1 pulley (bracket). During the procedure, the injected material (B; asterisks) distends the flexor tendon sheath. FT, flexor tendon; MC, metacarpal head; PP, proximal phalanx.
SUMMARY
Imaging features in patients with inflammatory arthritis are related to pathologic changes in the architecture and function of synovial and nonsynovial tissues comprising the joint. A variety of imaging modalities are available for evaluation of these arthritides, each having different strengths and weaknesses and in general, are complementary to one another. Radiographs, US, and MRI are frequently used for the evaluation of patients with inflammatory arthritis, with various grading systems having been developed for use with these modalities. Knowledge of expected characteristic imaging findings is crucial in the accurate diagnosis and monitoring of patients with inflammatory arthritis. REFERENCES
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