Imaging 15:286-297 (2003)
© 2003 The British Institute of Radiology
Imaging in rheumatology
A J Grainger, MRCP, FRCR1 and
D McGonagle, FRCPI, PhD2
1 Department of Musculoskeletal Radiology, B Floor, Clarendon Wing, Leeds General Infirmary, Leeds LS1 3EX and 2 Department of Rheumatology, Leeds University, Leeds, UK
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Summary
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- Plain films continue to be central to diagnosis and monitoring of rheumatological diseases.
- Imaging has a particular role to play in identifying disease in its earliest stages.
- Ultrasound and MRI permit the detection of subclinical joint inflammation.
- Ultrasound is helpful in guiding diagnostic and therapeutic interventions.
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Clinical perspective
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The role of musculoskeletal imaging in the assessment of the rheumatic diseases is expanding such that it is playing an increasingly important role in the diagnosis, assessment and monitoring of various rheumatological conditions. Conventional radiography (CR) has traditionally been the marker for both diagnosis and disease therapeutic modification in the inflammatory and degenerative arthropathies. However at the early stages of arthritis, when therapy may have the greatest role and where structural abnormalities may be reversible, radiographically defined joint damage is not a prominent feature. The limited utility of CR has lead to the introduction of newer, multiplanar imaging modalities, such as MRI and ultrasound (US) that have the ability to image both soft tissue and bone. These have resulted in an ability to diagnose arthritis earlier, and have increased the clinical understanding of disease.
Collectively the chronic rheumatic diseases are extremely common but can be difficult to recognise in the earliest phases and need to be distinguished from an array of non specific or transient inflammatory conditions. Rheumatoid arthritis (RA) is one of the most common chronic non-infectious diseases in the world and one of the biggest causes of potentially treatable disability [1]. It has an estimated prevalence of 1% [2]. The second major category of inflammatory arthritis is the seronegative spondyloarthropathies (SpA) that includes ankylosing spondylitis (AS), reactive arthritis (ReA), psoriatic arthritis (PsA), enteropathic arthritis and undifferentiated spondyloarthropathy (USpA). AS has an estimated prevalence of between 0.6% and 1.9% in European populations and is 3 times more common in men. Osteoarthritis (OA) represents a heterogeneous group of disorders that culminate in joint failure. It is virtually universal in older subjects. The impact of OA on health services is already substantial but is set to increase sharply in the 21st century as a result of an ageing population. Crystal induced arthropathies, infectious arthropathies and an array of other conditions involving the joints also lead to arthritis. Imaging is essential in establishing the correct diagnosis and help in guiding and monitoring of therapy.
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Conventional radiographs
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Despite the advent of newer imaging modalities conventional radiographs continue to have a central role in the diagnosis of arthritis and in the monitoring of disease progression and response to therapy. When evaluating a conventional radiograph for joint related disease it is vital to consider the various aspects of the joint where changes may be seen. Often in the hand and foot the eye will be drawn to major changes such as subluxation, erosion or joint space loss in one joint but careful examination will demonstrate more subtle changes in other joints. It is useful to consider radiographic changes in four key areas when evaluating joint disease on the conventional radiographs.
Soft tissues
Swelling
Localized soft tissue swelling associated with a joint may be the earliest radiographic sign of joint disease. The finding is generally non-specific and swelling due to synovitis is indistinguishable from swelling due to an effusion. In the interphalangeal joints soft tissue swelling is often obvious due to the change in contour of the fingers. However in other joints more subtle changes must be sought. For instance while we are familiar with the displaced posterior fat pad sign as an indication of elbow joint effusion in the context of trauma, synovitis or effusion in arthritides will give a similar picture. Elsewhere joints are often surrounded by relatively radiolucent fat and the denser soft tissues of the joint can be visualized. This is the case at the metacarpophalangeal (MCP), wrist, ankle and metatarsophalgeal (MTP) joints, along with the knee joint where an effusion or synovitis may be seen as thickening of the suprapatellar stripe (Figure 1
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Figure 1. Lateral knee: patient with septic arthritis showing thickening of the suprapatellar stripe due to synovitis and effusion in the suprapatellar pouch.
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Soft tissue swelling in arthritis may not always relate to joint disease. Patients with RA may have tenosynovitis which can also be seen as a localized soft tissue swelling. In patients with RA review of the soft tissues about the ulna styloid may reveal localized swelling representing synovitis of the extensor carpi ulnaris tendon sheath, an early sign of the disease.
In the case of gout the pattern of soft tissue swelling can help in making the diagnosis. Here asymmetrical swelling as a result of subcutaneous tophus formation may be seen. Although soft tissue swelling is an important feature to recognise on CR, and may be the only feature seen in early arthritis, it is usually recognised clinically. Thus in early arthritis CR offers little that cannot be demonstrated by thorough clinical examination.
Calcification
In chronic cases of gout soft tissue calcification may be associated with the typical asymmetrical soft tissue swelling described above (Figure 2).
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Figure 2. Dorsipalmer middle finger: this patient has chronic tophaceous gout, here seen involving the distal interphalangeal joint of the middle finger. Note the asymmetrical soft tissue swelling and calcification typical of the chronic form of this disease.
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The other crystal arthropathies are also associated with periarticular soft tissue calcification. In calcium pyrophosphate deposition disease (CPPD) chondrocalcinosis (see later) is a common finding, but synovial, bursal, ligamentous and tendon crystal deposition may also be seen (Figure 3).
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Figure 3. (a) Anteroposterior (AP) and (b) lateral knee radiographs. This patient has calcium pyrophosphate deposition disease. Note the chondrocalcinosis, best seen in the lateral meniscus on the AP film and the synovial calcification seen in the suprapatellar pouch (arrow). Note that joint space loss and subchondral bony changes are most marked at the patellofemoral joint. This is a characteristic distribution for calcium pyrophosphate deposition disease involvement of the knee.
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Hydroxyapatite (HA) crystal deposition disease is a disease of unknown aetiology characterized by the deposition of calcium HA crystal deposition in para-articular soft tissues resulting in tendonitis and bursitis. Soft tissue calcification associated with this disease process may change rapidly on follow up films and may resolve completely. HA crystal deposition may also occur in an intra-articular location resulting in a synovitis and the subsequent release of destructive enzymes which over time lead to irreversible joint damage. HA crystals have a characteristic amorphous paste like appearance on CR (Figure 4).
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Figure 4. Anteroposterior shoulder. There is hydroxyapatite deposition in the supraspinatus tendon seen as smooth amorphous calcification.
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There are other causes of soft tissue calcification that can be readily seen on plain radiographs (Table 1). Systemic sclerosis may lead to widespread deposition of amorphous subcutaneous calcification which can be an early indicator of the disease (Figure 5). An indistinguishable appearance may be seen with hyperparathyroidism.
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Figure 5. Dorsipalmer hand. This patient has systemic sclerosis. Multiple foci of hydroxyapatite crystal deposition can be seen in the soft tissues of the fingers.
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Joint space
On conventional radiographs the articular cartilage can only be evaluated indirectly by assessment of joint space. As cartilage is lost from a joint so the joint space will narrow. Along with soft tissue swelling described above this is one of the early signs of arthritis, although occasionally in very early infective or inflammatory arthritis the presence of a joint effusion causes separation of the non-weight joint bearing joint resulting in apparent preservation of joint space despite underlying cartilage loss. Joint space is preserved until late in the disease process in gout, and in PsA the deposition of fibrous tissue may prevent joint space loss.
When observed it is important to establish whether the joint space loss is generalized or focal. In osteoarthritis cartilage loss is focal affecting one part of the joint more than others (Figure 6). In the hip joint space loss is most often seen superiorly as in Figure 6. However, a pattern of medial joint space loss is also well recognised. This is well seen in the interphalangeal, hip and knee joints. In contrast the inflammatory arthritides usually result in more generalized joint space loss (Figure 7).
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Figure 6. Anteroposterior hip. This shows typical features of osteoarthritis. Note the pattern of joint space loss predominantly involves the superior joint space with preservation of the joint space more medially. This is typical for osteoarthritis and should be contrasted with the appearances of inflammatory arthritis seen in Figure 7 . In addition to subchondral sclerosis a large subchondral cyst is seen in the acetabular roof.
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Figure 7. Anteroposterior hip. This patient suffers from rheumatoid arthritis, note the large erosion on the lateral aspect of the femoral neck (*). Joint space loss is seen to have occurred throughout the joint, typical of an inflammatory arthritis. Contrast with Figure 6.
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In some conditions complete joint space loss may be associated with bony ankylosis. This is a characteristic feature of AS where ankylosis of the sacroiliac joints is a feature of late stage disease. However it may be seen in the appendicular joints as a feature of other inflammatory arthritides, including RA and PsA (Figure 8). Ankylosis is a characteristic feature of the juvenile arthritides.
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Figure 8. Dorsipalmer hand. Multiple joint involvement is seen in this patient with psoriatic arthritis with characteristic erosive arthritis is a predominantly distal distribution. The proximal interphalangeal joint of the little finger is ankylosed.
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Joint space may occasionally be increased as in the case of acromegaly. Here cartilage overgrowth occurs resulting in widening of the joint spaces, best seen in the hands (Figure 9).
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Figure 9. Dorsipalmer hand. Appearances of acromegaly. There is widening of the joint spaces, particularly seen at the proximal interphalangeal joints. Other features shown on this film include hypertrophic new bone at the sites of muscle, tendon and ligament insertion and widening of the phalangeal bases. Patients with acromegaly suffer premature osteoarthritis changes.
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Calcification may be seen within the joint space in the form of chondrocalcinosis. Although this may be seen in any joint, characteristic sites are the knee and wrist. Chondrocalcinosis is seen in CPPD although the cartilage calcification is not essential for the diagnosis. Chondrocalcinosis is not a specific finding and is seen in a variety of other conditions (Table 2).
Subchondral and periarticular bone
Some of the most useful and more specific diagnostic features of arthropathies are seen in the bone on either side of the joint. These take the form of erosions, changes in the subchondral bone, osteophyte and new bone formation, and changes in bone density.
Erosions
Bone erosion is a feature of a variety of arthropathic processes, but the pattern of erosion can give useful information relating to the disease process. Erosions can be divided into central, marginal and periarticular erosions depending on their location relative to the articular surfaces. The inflammatory arthritides are characterized by marginal erosions which develop at the edge of the articular cartilage in the adjacent intra-articular bone that is not protected by cartilage, the so called "bare area" (Figures 7 and 10). As the disease progresses and cartilage is lost the underlying subchondral bone will also start to show erosions. These are seen as central erosions. The earliest sign of erosion may be a subtle loss of the bone cortex, seen before more obvious bone erosion occurs. In RA the earliest erosions are often seen on the radial aspect of the metacarpal heads and along the ulnar aspect of the wrist where erosion of the ulnar styloid along with the ulnar aspect of the triquetrum and hamate is frequently seen (Figure 11). It is important to remember that erosions are not always seen tangentially to the X-ray beam and when seen en face erosions may simulate cysts. This is particularly seen with erosions in the carpal bones.
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Figure 10. Dorsipalmer hand. Appearances of rheumatoid arthritis with multiple marginal erosions seen predominantly affecting the metacarpophalangeal joints. The proximal distribution is characteristically seen in rheumatoid arthritis.
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Figure 11. Dorsipalmer wrist. This enlarged image in a patient with rheumatoid arthritis shows early erosion of the ulnar styloid and ulnar aspect of the triquetrum. These represent early sites for the detection of erosions in rheumatoid arthritis.
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The seronegative arthritides will show erosions which simulate RA, although the distribution of the disease gives clues to the diagnosis (see later). However entheseal disease is also a characteristic feature of these conditions. The disease process involves inflammation at tendon, capsular and ligamentous bone insertions (entheses). Erosions at these sites are a feature of the seronegative arthritides and are often seen in association with fluffy new bone formation (Figures 12, 13).
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Figure 12. Dorsipalmer hand. In addition to the erosive arthritis seen in this patient with psoriatic arthropathy there is fluffy periosteal new bone formation characteristic of the entheseal disease seen in this condition and seen well along the distal shafts of the proximal phalanges.
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Figure 13. Lateral calcaneum. This patient has psoriatic arthropathy and has entheseal disease at the calcaneal insertion of the plantar fascia. A small erosion is seen (arrowhead) along with a little new bone formation (arrow).
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Gout shows a typical pattern of erosion in a periarticular location. These erosions are seen adjacent to the joints but away from the articular surfaces. The erosions characteristically have a "rat-bite" configuration with overhanging edges and sclerotic margins (Figure 14).
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Figure 14. Dorsipalmer middle finger. This shows the typical appearances of a periarticular gout erosion with overhanging margins and a well defined "punched out" appearance.
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Erosions are also seen in OA. Erosive OA has classically been described as a variant of primary generalized OA where the inflammatory component of the disease becomes particularly significant. Although the condition usually affects the joints of the hand, the wrist may occasionally be involved. Two types of erosion appear to exist: those which seem to be the result of true synovial inflammation; and those which relate to collapse or pressure atrophy of the subchondral bone. The pattern of central subchondral erosion typically seen in erosive OA gives the joint an appearance that resembles a seagull's wings (Figure 15). Adjacent periosteal new bone formation may be seen and bony ankylosis is a frequent occurrence in patients with erosive OA.
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Figure 15. Dorsipalmer fingers. A patient with erosive osteoarthritis. Central erosions at the little finger distal interphalangeal (DIP) joint result in a seagull wing configuration to the joint. Note also a small marginal erosion at the adjacent DIP joints (arrowhead).
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Subchondral bone change
Changes in the subchondral bone are a characteristic feature of OA. These changes comprise sclerosis and cyst formation. Although a controversial area there is some evidence that the subchondral bone changes are the primary event in the development of OA. It is suggested that subchondral sclerosis is the result of microfracture repair and it is postulated that these microfractures occur as a result of abnormal loading across the joint. The subsequent reduced compliance of the underlying bone is thought to lead to an increase in the stresses to be absorbed by the overlying cartilage which eventually fails.
The presence of subchondral sclerosis provides a useful distinguishing feature from those arthritic processes, such as RA, which are characterized by periarticular osteoporosis. Following cartilage loss, the opposing bone surfaces become closely applied leading to eburnation and eventual collapse. Areas of sclerosis develop, which predominate on the pressure segments of the joints, and extend vertically into the subchondral bone. In addition there is horizontal extension over a larger proportion of the adjacent bone.
Subchondral cyst formation is also typically seen in OA. The pathogenesis of this is also unclear. They may be the result trauma or avascular necrosis. An alternative hypothesis suggests that they result from encysted fluid entering the bone through the subchondral plate that has become denuded of cartilage.
Osteophyte and new bone formation
The tendency to form osteophytes is a distinctive feature of OA and represents part of the reparative process seen with this disease. Osteophytes may be classified according to their location as marginal, central, periosteal and capsular. Central osteophytes are most usually seen in the hip and knee. When seen in the hip they may cause lateral displacement of the femoral head and apparent widening of the joint space. Periosteal osteophytosis, also termed buttressing, is most typically seen in the femoral neck of the osteoarthritic hip (Figure 16). Marginal osteophytes occur at the edge of the articular cartilage. They contain bone trabeculae and marrow and are usually covered with cartilage. In the case of capsular osteophytes the bony spurs develop in reaction to capsular traction forces and develop along the direction of capsular pull at the site of the capsular insertion.
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Figure 16. Anteroposterior hip. The hip joint shows severe osteoarthritis change with loss of joint space, subchondral sclerosis and cyst formation. In addition there is periosteal osteophyte formation seen as buttressing along the femoral neck (arrowheads).
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Syndesmophytes are seen in the spine and are peculiar to the spondyloarthropathies. They are distinguished from spinal osteophytes by their vertical orientation, although the distinction can be difficult. In AS the syndesmophytes are usually symmetrical in that they occur on both sides of the spine. They have a thin gracile appearance bridging the vertebral bodies (Figure 17). This is in contrast to the syndesmophytes of PsA and Reiter's syndrome which typically have a more asymmetric distribution and a more bulky appearance. Diffuse idiopathic skeletal hyperostosis (DISH) is a hypertrophic form of OA that must be distinguished from AS. In the spine large flowing chunky and symmetrical syndesmophytes are seen along with ossification anterior to the vertebral bodies in the anterior longitudinal ligament. Coarse proliferative new bone formation is commonly seen at entheseal sites in this condition.
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Figure 17. Lateral lumbar spine. Fine syndesmophytes are seen bridging the disk spaces along the anterior aspect of the spine (arrows). Note also calcification in the disks from L1 to S1, another typical feature of ankylosing spondylitis.
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Periosteal new bone formation is also a feature of the seronegative arthritides, typically occurring at enthesis sites and seen as fluffy bone formation near joints and often along the shafts of the phalanges. The periosteal new bone may be seen in conjunction with erosions at the enthesis sites.
Heterotopic new bone formation is one of the classically described features of neuropathic arthropathy where foci of ossification along with soft tissue calcification are seen about the disordered joint. The ossific foci often give the impression of bone fragments and debris about the joint.
Change in bone density
This is perhaps the most difficult feature to assess when viewing joint radiographs. Osteopenia reflecting osteoporosis is seen in a number of inflammatory arthritides. It is a well recognised feature of RA and juvenile arthritis, but when seen infective arthritis and connective tissue diseases also need consideration. It is often easier to confidently say when osteopenia is not present and in these cases the crystal and seronegative arthritides need consideration. Neuropathic arthropathy is a further cause of arthritis with preservation of bone density. One catch for the unwary is that Reiter's syndrome, in common with the other seronegative arthritides, classically shows preservation of bone density. However if seen in the acute phase there may be periarticular osteopenia.
Joint alignment
Radiographs allow an assessment of joint alignment to be made. Joint alignment may be altered as a result of non-uniform cartilage loss as in OA. For instance OA of the knee characteristically affects the medial joint compartment more than the lateral resulting in a varus deformity.
However many arthropathic processes result in ligamentous or capsular laxity and disruption which can lead to joint dislocation. Classic hand changes in RA include swan neck and boutonniere deformities. In the former hyperextension of the proximal interphalangeal (PIP) joint and flexion of the distal interphalangeal (DIP) joint is thought to result from synovitis in the flexor tendon sheath restricting interphalangeal flexion. The boutonniere deformity occurs when the extensor tendon complex over the dorsum of the PIP joint subluxes around it resulting in hyperextension of the DIP joint with a flexion deformity of the PIP joint.
Severe dislocations and subluxations are seen in neuropathic joints in combination with joint destruction and heterotopic ossification. However in systemic lupus (SLE) subluxation and dislocation of the hand joints are seen without evidence of erosion or bone destruction (Figure 18).
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Figure 18. Dorsipalmer hand. Note the joint subluxations seen at the metacarpophalangeal joints in this patient with systemic lupus erythematosis. A characteristic feature is that there is no associated joint destruction.
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Other considerations
Despite the many radiographic features discussed above, one of the most important aids to the diagnosis of arthritides is a consideration of the distribution of joint involvement. The first question should be whether one or multiple joints are affected. If the disease is monoarticular then it is important to consider infective arthritis near the top of the differential along with the crystal arthropathies. If more than one joint is involved the distribution may be symmetrical or asymmetrical. Classically RA shows symmetrical joint involvement as do the connective tissue diseases scleroderma and SLE. In contrast the seronegative arthritides will often show a more asymmetrical distribution. An assessment of the distribution of joint involvement in the hand is also useful with RA generally showing a proximal distribution involving the wrists, MCP and PIP joints, while PsA typically shows a more distal distribution affecting the DIP joints with sparing of the MCP joints. OA typically involves the DIP and PIP joints with characteristic wrist involvement at the base of the thumb in a trapezocentric distribution.
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Ultrasound and MRI
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Imaging plays an important role in the diagnosis of rheumatological diseases and as seen above CR readily demonstrates arthropathic changes and in many cases can prove diagnostic. Plain films are also able to monitor disease progression and response to treatment and sophisticated scoring systems have been developed for assessing the severity of the disease based on features such as erosion counting. Examples of these are the scoring systems of Larsen and of Sharp and their modifications [3, 4]. However, many of the features seen on radiographs, such as joint space loss, erosions and subluxations, represent changes occurring late in the disease process. By the time these features have developed the joint is irreparably damaged. Furthermore these features take time to progress and so changes in disease status seen on plain films are relatively slow to develop.
The limitation of CR as stated above has been addressed by utilizing US and MRI in the imaging of arthritis. Both US and MRI are uniquely able to demonstrate the soft tissue components of joint disease. In addition MRI is able to provide images which show changes within the periarticular bone. MRI has multiplanar imaging capabilities ideally suited for showing both joint inflammation and joint damage and allows accurate delineation of structural and inflammatory lesions of all joint structures including tendons and tendon sheaths, ligaments, synovial membrane, cartilage and bone [5]. Although ultrasound is unable to demonstrate changes in the bone marrow and has only limited use in evaluating articular cartilage, erosions can be shown along with changes in the tendons and tendon sheaths, synovium, and ligaments.
Synovium and effusion
MRI and US are both sensitive to the detection of joint effusions and synovitis. Studies show both techniques are more sensitive than clinical examination for the detection of synovitis and so there is certainly a role for MRI and US in detecting clinically occult disease. Evidence would suggest that MRI is more sensitive than US for detecting synovitis, but, besides issues relating to cost and time, US does have the advantage of being able to screen multiple joints rapidly.
Synovium is normally not seen at US. However when thickened it appears as hypoechoic intra-articular tissue. The precise appearance varies depending on the amount of extracellular fluid in the tissue. The reflectivity decreases with more extracellular fluid and using conventional grey scale imaging it can be difficult to distinguish synovium from fluid. Techniques which can help include compression (fluid will move into a different part of the joint and so appears compressible unlike synovium) and the use of colour or power Doppler imaging to detect vascular flow in synovitis.
MRI will demonstrate thickened synovium as intra-articular intermediate signal tissue on T1 imaging which appears high signal on T2 imaging. As with US it is difficult to distinguish synovium from fluid using these techniques. However synovium enhances with intravenous gadolinium on T1 weighted imaging and pre and post gadolinium T1 weighted imaging remains the MR gold standard for demonstrating synovium and allowing its distinction from fluid. Post-processing techniques allow measures of synovial volume to be made providing a quantifiable measure of disease activity. Disease activity can also be assessed by measuring the rate of gadolinium uptake in the synovium. Faster uptake occurs in more active disease. It may be that in the future US will allow similar measurements of volume and synovial vascularity to be made using Doppler and 3D techniques.
Erosions
US and MRI are both able to demonstrate erosions with greater sensitivity than plain films. This is thought to be mainly a result of their multiplanar capabilities and increased sensitivity to the smaller erosion. One disadvantage of US over MRI is the limited access it has to some joints. This is particularly true around the lateral and medial aspects of the MCP and MTP joints along with the wrist, mid and hind foot. However US does have the advantage of being able to examine multiple joints rapidly in comparison with MRI.
In the case of US erosions are demonstrated as breaks in the bone cortex, usually containing thickened synovium (Figure 19). The definition of erosion is more complicated in the case of MRI. Although erosions are demonstrated as breaks in the bone cortex filled with synovial tissue (Figure 20), changes can be seen in the bone marrow without cortical breach or synovial invasion. These changes take the form of areas of marrow oedema (raised signal intensity on T2 imaging) which show enhancement following intravenous gadolinium. Recent work suggests that these early erosions may progress to erosions with cortical breach over a period of 12 to 18 months. With treatment erosions may become inactive at which point marrow oedema and increased T2 signal is no longer seen in association with them. These then become much harder to demonstrate on MRI.
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Figure 19. Longitudinal ultrasound of metacarpophalangeal joint. This image shows the dorsal aspect of the metacarpal head (M) and proximal phalanx (P) in a patient with rheumatoid arthritis. The joint is distended by thickened synovium (arrowheads). The synovitis fills an erosion seen as a breach in the cortex of the metacarpal head (*).
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Figure 20. Coronal T1 weighted image of the hand. The study shows an erosion (arrowhead) in the head of the middle metacarpal.
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Enthesitis
In the case of seronegative arthritides US and MRI are both able to show entheseal disease. In the case of US changes in the inserting tendon or ligament are seen in the form of low reflective change and thickening. Erosions may also be seen at the site of insertion. As discussed plain films will often show a fluffy periosteal reaction at sites of enthesitis and this is also well shown with US. MRI will also demonstrate the tendon or ligament changes of enthesitis, but is also able to demonstrate bone marrow oedema at these sites, a feature not seen with other modalities (Figure 21). MRI determined bone oedema may have a role in distinguishing early spondyloarthropathy associated synovitis from RA related disease. In the case of spondylitis MRI is readily able to show the changes of entheseal disease at the "corners" of the vertebral bodies and is a sensitive means to demonstrate sacroiliitis. Therefore, MRI is superior to US for the assessment of entheseal disease because it readily demonstrates osteitis adjacent to insertions and it is suited to imaging the spine and sacroiliac joints—the primary skeletal sites of AS.
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Figure 21. Coronal short tau inversion recovery weighted image of the knee. In a patient with psoriatic arthritis foci of marrow oedema are seen at enthesis sites of the joint capsule and ligaments including the anterior cruciate ligament origin on the lateral aspect of the femoral notch.
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Osteoarthritis
In addition to the study of inflammatory arthritis MRI and US can also be used to image OA. Osteophytes are readily shown using both modalities, although US will not show central osteophytes. As might be expected given its multiplanar capabilities MRI is very sensitive to osteophyte formation and can show subtle subchondral osteophytes which are not normally seen with other imaging modalities (Figure 22).
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Figure 22. Sagittal T2 weighted water excitation sequences through the (a) lateral and (b) medial compartments of the knee. There are small osteophytes shown in the lateral compartment on the anterior and posterior aspects of the tibia. Note also the articular cartilage which is well shown with this sequence over the femoral and tibial articular surfaces. In the medial compartment there is full thickness cartilage loss over the weight bearing portions of the femur and tibia with the exception of a small area of residual cartilage under the posterior horn of the meniscus (arrowhead). Marrow oedema is seen in the subchondral bone at the sites where it is denuded of cartilage.
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As discussed CR can show erosions in OA, but these are more easily demonstrated with MRI and it is increasingly recognised that erosions are more frequently seen in OA than originally appreciated using only CR. Similarly synovitis was once considered a classical feature of the inflammatory arthritides, but US and MRI are able to demonstrate its presence in OA.
In addition to the features of subchondral sclerosis and cyst formation shown on CR in OA, subchondral marrow oedema is also now recognised as a feature of OA. Cartilage damage has long been considered fundamental in the pathophysiology of OA. For many years it has been thought of as the primary event in the development of OA, leading to the consideration of OA as a "wear and tear" disease. Increasingly studies suggest that this is probably not the case, and a move has been made to consider OA as a disease process affecting all aspects of the joint. The damage to articular cartilage seen in OA seems likely to turn out to be a secondary phenomenon resulting from primary changes in the joint elsewhere. Nevertheless using CR cartilage loss, as measured indirectly as joint space loss, has long been used to assess the progression of OA. MRI is able to demonstrate the cartilage itself and with the increasing sophistication of MR sequences available and improved spatial resolution of modern scanners, can demonstrate changes in the morphology of articular cartilage previously impossible to show non-invasively (Figure 22). To evaluate cartilage loss in longitudinal studies sophisticated techniques have been developed to measure cartilage loss including measurements of articular volume and sensitive measures of cartilage thickness.
A number of important publications in relationship to important clinical aspects of OA have recently appeared. It is now clear that the pain in OA is associated with subchondral marrow oedema [6] as is the presence of synovitis [7]. Another recent paper showed that MRI may be of value in predicting progression of hip OA based on the pattern of subchondral bone oedema in that joint at clinical presentation [8]. It is likely that the next few years will result in further developments in OA imaging, and our understanding of the pathophysiology of this common disease.
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Conclusion
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As has been shown CR still has an important role to play in the diagnosis of many rheumatological conditions. For the foreseeable future it will also continue to be an important tool for the monitoring of disease progression and assessment of therapeutic response. However clinicians are progressively turning to US and MRI for detecting the earliest (often subclinical) changes of arthritis and it is likely that these tools will play an increasingly important role in the diagnosis of arthritis in the future. Furthermore the pharmaceutical industry is increasingly using more sophisticated imaging tools, and in particular MRI, for the assessment of the efficacy of their products. As has often been the case in other areas of medicine the tools initially developed for research are likely to be assimilated into clinical practice in the future and it is probable that MRI and US will be used for monitoring disease progression in the clinical setting in years to come.
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References
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- Lee DM, Weinblatt ME. Rheumatoid arthritis. Lancet 2001;358:903–11.[Medline]
- Markenson JA. Worldwide trends in the socioeconomic impact and long-term prognosis of rheumatoid arthritis. Semin Arthritis Rheum 1991;21(2 Suppl. 1):4–12.
- Larsen A, Dale K, Eek M. Radiographic evaluation of rheumatoid arthritis and related conditions by standard reference films. Acta Radiol Diagn (Stockh) 1977;18:481–91.[Medline]
- Sharp JT, Lidsky MD, Collins LC, Moreland J. Methods of scoring the progression of radiologic changes in rheumatoid arthritis. Correlation of radiologic, clinical and laboratory abnormalities. Arthritis Rheum 1971;14:706–20.[Medline]
- Backhaus M, Burmester GR, Sandrock D, Loreck D, Hess D, Scholz A, et al. Prospective two year follow up study comparing novel and conventional imaging procedures in patients with arthritic finger joints. Ann Rheum Dis 2002;61:895–904.[Abstract/Free Full Text]
- Felson DT, Chaisson CE, Hill CL, Totterman SM, Gale ME, Skinner KM, et al. The association of bone marrow lesions with pain in knee osteoarthritis. Ann Intern Med 2001;134:541–9.[Abstract/Free Full Text]
- Hill CL, Gale DG, Chaisson CE, Skinner K, Kazis L, Gale ME, et al. Knee effusions, popliteal cysts, and synovial thickening: association with knee pain in osteoarthritis. J Rheumatol 2001;28:1330–7.[Abstract/Free Full Text]
- Boutry N, Paul C, Leroy X, Fredoux D, Migaud H, Cotten A. Rapidly destructive osteoarthritis of the hip: MR imaging findings. AJR Am J Roentgenol 2002;179:657–63.[Abstract/Free Full Text]
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Summary
Clinical perspective
