eMedicine Specialties > Radiology > Musculoskeletal

Rheumatoid Arthritis, Hands: Imaging

Author: Ian Y Y Tsou, MBBS, FRCR, Clinical Lecturer, Faculty of Medicine, National University of Singapore; Consulting Staff, Department of Radiology, Mount Elizabeth Medical Centre
Coauthor(s): Wilfred CG Peh, MD, MBBS, FRCP(Glasg), FRCP(Edin), FRCR, MHSM, Clinical Professor, Faculty of Medicine, National University of Singapore; Senior Consultant Radiologist, Programme Office, Singapore Health Services; Michael A Bruno, MD, Associate Professor, Departments of Radiology and Medicine, Pennsylvania State University College of Medicine; Director, Radiology Quality Management Services, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine
Contributor Information and Disclosures

Updated: May 10, 2007

Radiography

Findings

Morphology

Usually, the earliest sign of RA is a periarticular soft-tissue swelling with a fusiform appearance (see Image 1). Normal fat planes may be obliterated, which occurs as a result of joint effusion, edema, and tenosynovitis. Juxta-articular osteopenia is another early sign, particularly during the acute inflammatory stage (see Image 2). Osteopenia subsequently becomes more generalized as the disease progresses.

Initially, joint spaces in the small joints of the hands show widening as a result of effusion; however, with cartilage destruction, joint spaces narrow. Erosions usually begin at the bare area of the joint not covered by cartilage, such as the intracapsular articular margins (see Image 3). Marginal erosions occur as a result of direct mechanical action of the hypertrophied synovium and granulation tissue (see Images 4-5).

The forces of tendon imbalance and capsular contraction result in joint subluxation and malalignment (see Image 6). Characteristic appearances include the boutonnière (flexion at the PIP joint and extension at the DIP joint) and swan-neck (extension at the PIP joint and flexion at the DIP joint) deformities at the IP joints. Ulnar deviation is also commonly present at the MCP joints. MCP joints may also dislocate and have overriding ends (main en lorgnette or telescoping joints). Subluxations are progressive and may occur with or without the presence of bony erosions (see Image 7). Tendinous involvement of RA may result in rupture of the tendon, causing increased disability. If significant involvement of the scapholunate joint is present, laxity or rupture may cause rotatory subluxation of the scaphoid.

Fusion or joint ankylosis is common in the later stages of RA (see Image 8). Fusion usually takes place in a deformed or malaligned position (see Image 9). This further reduces the functionality of the hand and affects independence in the activities of daily living. In the end stages, extensive erosions may combine to result in resorption and tapering of the ends of the bones.

Complications of therapy may be seen, such as generalized osteoporosis from steroid usage. Large bony erosions and severe osteopenia predispose patients to relatively atraumatic fractures. Long-term steroid use also predisposes patients to avascular necrosis.

Distribution

The hands are affected symmetrically, and the disease process is usually visible first at the second and third MCP joints and the third PIP joint. The disease continues in the remainder of the MCP and PIP joints. Varying stages may be seen in different joints at a single point in time. DIP joint involvement without proximal involvement is rare.

Erosions may be detected first either in the MCP and PIP joints or at the carpal bones. Erosions may also be seen at the intra-articular portion of the distal end of the radius or within the carpal bones. Carpal bone ankylosis is a common and fairly specific sign, particularly in the Asian population, in whom it tends to occur early in the disease process.

Degree of Confidence

RA is indicated on radiographs by the overall pattern and features of joint involvement. Although the presence of bony erosions is typical of RA, erosions are not specific because of the large number of other erosive arthritides. An absence of osteophyte formation and subchondral sclerosis is also indicative of RA rather than osteoarthritis.

False Positives/Negatives

In the late stage (but not in the early stage), the deformities and joint fusion of RA are usually distinguishable from other causes of erosive arthropathy. No normal variants simulate RA.

Computed Tomography

Findings

Currently, computed tomography (CT) has a minimal role in treating RA of the hands. Although CT is useful for demonstrating bony pathology, erosions in the small joints of the hands are evaluated best by using a combination of radiography and MRI. MRI also has the added advantage of being able to visualize bone marrow edema and synovial and soft-tissue involvement.

Magnetic Resonance Imaging

Findings

MRI provides images with good delineation of soft-tissue changes, cartilaginous defects, and osseous erosions associated with RA. In particular, the ability to detect synovial hypertrophy and pannus formation before the onset of bony erosions has become more valuable with the advent of disease-modifying antirheumatic drugs. The drugs, which retard the progression of RA, are most effective in the early stages of disease.

Signal intensity of the inflamed synovial lining may vary markedly on T1- and T2-weighted images. An inflamed synovial lining usually demonstrates low signal intensity on T2-weighted images, and the images may be even darker if hemosiderin or a predominantly fibrous component is present within the lining. Tenosynovitis resulting from inflammation is seen as high–signal-intensity fluid on T2-weighted sequences (see Image 10).

The intravenous (IV) administration of a gadolinium-based contrast agent allows better distinction of inflammatory soft-tissue changes and can help differentiate pannus from eburnation. In addition, rapid enhancement of proliferative inflammatory synovium has been reported, compared to minimal signal change in healthy soft tissue and bone. Fat suppression and fast dynamic scanning have also been used to increase the sensitivity of synovial imaging.

Gadolinium-based contrast agents (eg, gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. These diseases have occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography (MRA) scans. As of late December 2006, the FDA has received reports of 90 such cases. According to the FDA, over 200 cases have been reported worldwide. NSF/NFD are debilitating and sometimes fatal diseases. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of  the  eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

MRI is clearly superior to radiography in the early detection of bone erosions (see Image 11, Image 13). MRI is more sensitive to bone marrow edema. Bright lesions on T2-weighted images often do not correspond to findings on radiographs or T1-weighted images (see Image 12). These lesions are believed to represent potentially reversible pre-erosive changes.

Routine use of MRI in evaluating rheumatoid arthropathy in the hands and wrist has been limited by the relatively high cost, the difficulty in positioning disabled patients, and the inability to image several joints simultaneously.

Degree of Confidence

MRI has been shown to be more sensitive to early changes in RA, and in the appropriate clinical setting, it is more accurate than plain radiography in the diagnosis of RA.

False Positives/Negatives

Imaging of early synovial disease by MRI makes early detection possible, but the findings are not specific in differentiating RA from other causes of synovitis or joint erosions.

Ultrasonography

Findings

High-resolution sonography with a high-frequency probe is used for evaluation of the small joints in RA (see Image 14). Joint effusion is hypoechoic, while the hypertrophic synovium is more echogenic. Rheumatoid nodules are seen as fluid-filled round cavities with sharp borders. Bone erosions may be seen as irregularities in the hyperechoic cortex. Complications of RA, such as tenosynovitis and tendon rupture, can also be visualized by using ultrasonography. This is most useful in the MCP and IP joints. The carpal bones and the carpometacarpal joints are not visualized as well because of their irregular configuration and deeper location.

Sonography has been applied to the assessment of RA with the goal of improving on the current standard of conventional radiography. Ultrasonography, especially when augmented by amplitude color Doppler (ACD) imaging, has also provided clinically useful information in the assessment of RA. Originally, ACD or power Doppler scanning was developed as an improvement to existing vascular sonographic imaging techniques to delineate stenoses by imaging blood flowing in vessel lumina by virtue of higher sensitivity to flow and lack of directional dependence.

ACD imaging has been applied to RA with the goal of evaluating the manifestation of hyperemia in the inflammatory joint tissues at the symptomatic sites of disease. Synovial hyperemia is a fundamental pathophysiologic feature of RA (see Image 15). Most likely, synovial hyperemia is the principal factor underlying the hallmark x-ray observation of periarticular demineralization on radiographs of patients with RA, and it is believed to occur in proportion to joint-destructive disease activity. Hyperemia in the tendon sheath is common as well (see Image 16).

Two recent reports in the literature have explored a possible role for Doppler ultrasonography in evaluating arthritis, especially RA, on the basis of synovial hyperemia. In 1996, Newman et al¹ used a 3-level semiquantitative approach by trained radiologists to grade Doppler flow subjectively in patients with RA, psoriatic arthritis, and calcium pyrophosphate deposition disease arthritis. The investigators found that the degree of abnormal tissue hyperemia visualized correlates grossly with the severity of local disease activity as measured by synovial-fluid white blood cell (WBC) counts and patients' subjective estimates of symptoms. The report did not include joint examinations or other physical/functional measurements.

Hau et al² from the University Hospital of Würzburg, Germany, reported findings from ultrasound in the MCP and PIP joints of 34 patients with RA and 15 control subjects over a 6-month period. In the protocol, each patient was examined only once. Patients were stratified into 3 groups based on swelling and tenderness. Ultrasonography was performed by using a Siemens Doppler unit and a 5- to 13-MHz linear-array transducer operating at 12 MHz. The authors identified joint pannus on gray-scale images as hypoechoic soft tissue adjacent to the articular surfaces and described the pannus distribution as favoring the radial side of the joints. Velocity color Doppler (ie, conventional direction-sensitive Doppler) imaging was used to evaluate vascularization and blood flow in the rheumatoid pannus as a surrogate marker of inflammation.  The quantitation method used was analogous to that used by one of the coauthors of this article in preliminary studies.

A simple image-based quantification was obtained in the study by Hau et al² by summing the color pixels within all joints in each patient classification after selection of regions of interest within each joint.  The result was a unitless numerical scale that showed a greater than tenfold difference between patients with active RA and controls. From the preliminary investigations, both groups (Newman in 1996 and Hau in 1999) concluded that power Doppler ultrasonography can reflect disease activity in RA, and each group suggested further research in this area.
 
Since 1999, several research groups have gone further in their development of power Doppler ultrasonography and its application to RA.  In 2003, Teh, Stevens, and Williamson et al³ evaluated quantitative power Doppler ultrasonography for the assessment of therapeutic response in rheumatoid synovitis in 13 consecutive patients over 7 months, with correlation to serum inflammatory markers and clinical evaluation.  Quantitiative power Doppler spectra were derived within select regions of interest from each patient’s scan, both before and after treatment; essentially, the method used was an automated pixel-counting technique similar to that of Hau. There was extremely good correlation between the image-based quantitation of synovial hyperemia and the clinical and laboratory assessment of disease activity in this study. Thus, quantitative power Doppler ultrasonographywas  able to accurately depict the patients’ response to treatment. Theauthorsof the study felt that the addition of quantitative power Doppler ultrasonography to the routine assessment of therapeutic response in RA yielded more accurate findings than existing clinical and laboratory methods alone.
 
In 2004 , Strunk et al⁴ compared quantified power Doppler ultrasonography with laboratory measurement of serum vascular endothelial growth factor (VEGF level) as markers for disease activity, finding a very high correlation (p<0.0001) for ultrasound and no relation with the immediate serum VEGF level in the same patient. That same year, Salaffi et al⁵ evaluated quantified power Doppler ultrasonography augmented by the use of IV ultrasound contrasts, such as Levovist, using a quantitative time-intensity curve integration to arrive at the quantification in arbitrary units. The results showed a correlation of the Doppler signal to other measures of disease and treatment efficacy.
 
In 2005, Fiocco et al⁶ found that both C-reactive protein and Doppler findings reliably measured response to treatment with etancercept, an anti–tumor necrosis factor-alpha medication that has shown considerable efficacy in rheumatoid arthritis.
 
Research in this area is ongoing, but according to published reports, quantified power Doppler ultrasonography is a reproducible and reliable surrogate indicator of disease activity, which can predict and evaluate treatment response with a greater degree of sensitivity and specificity than other available clinical methodologies.

Degree of Confidence

Similar to MRI, ultrasonography serves as an early diagnostic tool and can help in evaluating the cause of joint swelling in a patient with RA.

False Positives/Negatives

Imaging of early synovial disease by ultrasonography makes early detection possible, but sonography is not specific in differentiating RA from other causes of synovitis or joint erosions.

Nuclear Imaging

Findings

Apart from demonstration of active disease, the results of radionuclide bone scans remain nonspecific and are used mainly to provide an overview of the distribution of disease.

Angiography

Findings

Currently, angiography has no defined role in assessing RA of the hands.

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