MUSCULOSKELETAL ULTRASOUND SYMPOSIUM
|Year : 2007 | Volume
| Issue : 4 | Page : 299-305
|Ultrasound in rheumatology
Tikka Harinder Singh Bedi, RN Bagga
Diwan Chand Satyapal Aggarwal Imaging Center, 10-B, K. G. Marg, New Delhi-100 001, India
Click here for correspondence address and email
|How to cite this article:|
Bedi TH, Bagga R N. Ultrasound in rheumatology. Indian J Radiol Imaging 2007;17:299-305
| Introduction|| |
X-rays have been the mainstay of the radiological assessment of joint disorders. However, conventional radiography is not capable of assessing early bone abnormalities, especially when the lesion is not tangential to the x-ray beam. Early periarticular soft tissue abnormalities and synovitis are also not well seen. The gold standard for the assessment of soft tissue abnormalities is MRI. However, in the last few years, musculoskeletal USG has made its presence felt among rheumatologists and radiologists as the first radiological investigation in the assessment of rheumatoid disease and during follow-up. This has been possible due to the better availability of USG equipment, transducers and softwares.  These changes have allowed USG to be used for the early detection of fluid in the joint spaces and around tendon sheaths. Due to better resolution, even normal, minute amounts of synovial fluid can be seen. Similarly, irregularities on the bone surface, such as erosions and periosteal irregularities as well as sub-periosteal collections / bleed can be now appreciated. Intraosseous abnormalities, however, cannot be appreciated as sound is not able to penetrate bone. Use can also be made of 'real-time' USG to assist in the better evaluation of these abnormalities. 
USG is often called the "rheumatologist's extended finger". However, rheumatologists are still not agreed on whether they should introduce routine USG in their clinical practices. ,, There are also issues related to the reproducibility of USG findings and though numerous training programs are available in Europe, there is still some resistance in accepting a 'new' modality, which is operator dependent.
| Imaging Requirements|| |
Since most of the joints and periarticular structure to be imaged are superficial, high-resolution and high-definition USG, with 7.5-15 MHz linear probes, is required for adequate resolution. However, lower frequency probes upto 5 MHz are often used for larger joints that require more penetration, such as the shoulders and hips.  Phased-array probes with tissue harmonic imaging and compound imaging are now routinely used. 3D and 4D usually do not significantly add value. "Extended field-of-view' is very useful, as it allows a larger area to be visualized and measured. The size of the footprint is important, since transducers with a large footprint are often inadequate for visualizing small joints such as the metacarpophalangeal joints, since they cannot be maneuvered adequately.
Power and color Doppler are extremely useful for identifying the degree of inflammation and help in increasing the confidence for diagnosing subtle changes.
USG is an operator dependent modality and it is imperative to have a sound knowledge of its principles and the musculo-skeletal anatomy.
| Indications|| |
USG was probably first used in the musculoskeletal system for the identification of Baker's cysts and to differentiate them from thrombophlebitis,  as early as 1972. The indications today are: ,,,
a) Synovial effusion
b) Synovial proliferation
c) Cartilage changes
2. Periarticular soft tissues:
a) Tendon disease
c) Bursal involvement
- Soft tissue rheumatology
- Nerve involvement assessment
- MRI contraindications
Most articular diseases affect the synovium. The presence of excess intra-articular fluid suggests the presence of synovitis. USG is capable of detecting synovial fluid in excess of 1ml [Figure - 1] and standards for diagnosing effusion are available for most joints.  This technique is therefore potentially important in the management, diagnosis, monitoring and the assessment of treatment efficacy. USG is more sensitive than physical examination for the diagnosis of synovial effusion. , This is true for the smaller joints of the hands and feet as well as the large joints such as the shoulder, hip and knee. , USG is however limited in its ability to assess the nature of the joint fluid. The synovial effusion may be due to inflammation, infection or bleed. Aspiration is usually required for confirmation and is often performed under USG guidance..
Since joint effusion usually occurs in an arthropathy and is better seen on USG, the "quantity" and distribution of disease seem to vary from the traditional disease description. The classification criteria of the American College of Rheumatologists for mono-. oligo- and polyarticular diseases may need to be re-evaluated, since more sub-clinical disease can be seen with USG. 
The hands and wrists are the commonest areas evaluated in rheumatology. The pattern and location of synovitis may be diagnostic of the disease. In rheumatoid arthritis (RA), synovitis of the metacarpophalangeal (MCP), metatarsophalangeal (MTP) and proximal interphalangeal (PIP) joints is primarily seen. The target joints in psoriatic arthritis are the distal interphalangeal (DIP) joints. [Figure - 2]. However, in early disease, such typical patterns of involvement are often not seen. As a result, in early disease, USG primarily helps in deciding the presence/absence of synovitis, its location and the number of joints involved along with any associated synovial proliferation, cartilaginous changes or erosions. The palmar and dorsal aspects of the joints both need to be assessed.
Synovial proliferation presents with thickening of the synovium [Figure - 3],[Figure - 4]. If the "fluid" in the joint cannot be compressed, that usually implies the presence of thickened synovium, , which may also show increased flow on Doppler. Though complex fluid with high protein contents may mimic synovial proliferation, it can still be easily compressed and will change its appearance on application of pressure. Severe synovial proliferation shows an irregular contour of the synovial membrane with synechiae between the walls of the articular recesses.
Areas of active disease show increased flow on Doppler [Figure - 5]. This is due to neo-vascularization in the pannus. The degree of increased flow on Doppler may be a rough indicator of the degree of active disease. A negative Doppler signal does not exclude possible active inflammation. Moreover, the same joint may show different Doppler signals on different machines, as well as with the same machine with change in the surrounding room temperature.
Studies done by Ridden et al and Hau et al, using color and spectral Doppler to assess possible changes in synovial perfusion, after treatment with anti-tumor necrosis factor alpha, in patients with RA have shown that it is possible to see reduction in the number of color pixels after treatment, correlating well with symptomatic improvement. In a few cases, USG improvement was seen even prior to symptomatic improvement. Similar improvements have been noted after steroid injections. , In a study by Filippucci et al , in 70% of patients showed improvement of grey scale and power Doppler findings, after treatment with steroids. 
In the last decade, USG has become the gold standard for tendon examination. , Tenosynovial effusion, tenosynovial proliferation and tendon tears are routinely detected by USG [Figure - 6]. Clinical examination of tendon involvement is highly inaccurate. According to Grassi et al, USG is even superior to MRI in the detection of longitudinal split tendon tears.  It is the only modality which allows real-time, dynamic assessment, which is extremely useful for identifying subluxed and snapping tendons. , USG also demonstrates focal or diffuse tendonitis, calcified tendonitis and tendon xanthomas.
Synovial involvement of the tendons is very common in seropositive arthritis and is known as tenosynovitis [Figure - 7]. Peri-articular soft tissue swelling may be due to effusion or due to tenosynovitis and USG helps in differentiating between these causes. Tendon involvement may present prior to joint involvement in RA and commonly involves the tendons of the flexor digitorum superficialis and profundus, flexor carpi ulnaris and radialis as well as the extensor digitorum [Figure - 8]. The flexor digitorum superficialis and profundus tendons are probably the most common tendons involved in psoriatic arthropathy giving a typical 'sausage digit' appearance [Figure - 9]. Areas of active disease show increased flow on Doppler application. A negative Doppler signal does not exclude the possibility of tenosynovitis.
Although USG is sensitive in identifying tendon disease, like synovitis, it is non-specific. Correlation with biochemical parameters and history is important to achieve a diagnosis.
Normal weight-bearing cartilage ranges from 1.2 - 1.9 mm in thickness. The cartilage in the wrists and hands is thinner. The earliest radiological finding is usually thinning of the cartilage, though rarely, USG may show thickening due to edema, in very early stages of arthritis. However, non-visualization of the cartilage is not necessarily an ominous sign, as the cartilage may not always be seen, depending on the site. Irregular thinning or thickening of the cartilage is usually abnormal [Figure - 10].
MRI is the gold standard for the assessment of erosions. USG has of late shown to be useful in the early diagnosis of erosions. ,,,, Radiographic detection of small erosions may be delayed due to patient positioning or technical reasons. The multiplanar capabilities of USG, allow a careful assessment of the bone surfaces on more views than those allowed by standard radiographs. This improves the sensitivity of USG in detecting small erosions, especially in areas not well seen on standard views.  Marginal erosions are seen as crater-like defects,along the edges of the articular cartilage, affecting the so-called "bare" areas [Figure - 11]. In RA, pannus is seen as hypoechoic soft tissue filling these erosions. Color and power Doppler usually show an intense increase in flow at these sites especially in active disease. In acutely inflamed joints with erosions, it is not uncommon to see a vascular pedicle supplying the pannus up to the erosion crater [Figure - 12].
USG of MCP joints with good accessibility (second and fifth) exhibit better correlation with MRI than USG of joints only accessible in two planes (third and fourth). Using USG, Szkudlarek et al, found more bone erosions in PIP joints as compared to MRI and radiographs, probably due to the use of 3 mm thick slices on MRI, which is a suboptimal slice thickness for the small PIP joints.  Backhaus and coworkers employing thinner MRI slices (1 mm) found that MRI scored over USG. Small erosions of the carpal bones are also difficult to interpret on USG, as the normal carpal bones have irregular margins. MRI is superior in the carpal bones.. Bone marrow edema and cartilaginous changes are also better seen on MRI.  Subarticular cysts are often completely missed on USG.
Crystal Deposition Disease
A few papers have described the USG appearance of articular and periarticular changes caused by calcium pyrophosphate dihydrate (CPPD) disease. In some cases, calcification detected by USG may not be found on radiographs, either because of the location of the calcium deposit or the technique used. MRI is not good for the evaluation of calcium. Frediani et al, have identified the following patterns of CPPD  calcification
- Thin hyperechoic bands, parallel to the surface of the hyaline cartilage (frequently observed in the knee).
- A "punctate" pattern composed of several thin hyperechoic spots, more common in fibrous cartilage and in tendons.
- Homogeneous hyperechoic nodular or oval deposits localized in bursae and articular recesses (frequently mobile). 
Bursitis is a common disease entity in joint diseases. Subacromial-subdeltoid bursitis is a common USG finding in RA [Figure - 13]. A Baker's cyst is often seen in chronic cases. It may be anechoic or may show calcified or non-calcified loose bodies. A ruptured Baker's cyst can be readily diagnosed on USG and can be differentiated from deep vein thrombosis [Figure - 14]. Differentiation of joint effusion from bursitis, for example in the popliteal fossa, can be easily accomplished by USG.
Enthesitis is the inflammation at the origin and insertion of ligaments and tendons and is commonly seen in seronegative spondyloarthropathy (SpA). and may be the first sign of an SpA in some cases. There is initially inflammation, followed by fibrosis in the involved ligaments and tendons. This is followed by ossification. The involved segment of bone shows erosions.
Balintz et al , found that compared with USG, clinical examination had a low sensitivity (22.6%) and moderate specificity (79.7%) for the detection of enthesitis of the lower limbs.  Acute enthesitis on USG, is seen as a tender area with increased thickness of the tendon and ligament insertion with hypoechogenicity and loss of normal echopattern. The adjoining bone may be normal or may show irregularity at the site of tendon insertion [Figure - 15]. In chronic cases, there is evidence of intratendinous and interligamentous calcification adjacent to the entheseal insertion. Various studies have identified that there is considerable sub-clinical enthesitis in SpA, which can be objectively measured by USG using standardized protocols.
The median nerve at the wrist is the most involved nerve in rheumatology practice, as part of the carpal tunnel syndrome (CTS). CTS is primarily a clinical diagnosis and imaging is used mainly to identify a secondary cause such as wrist joint effusion, tenosynovitis, amyloid deposition, hypertrophied accessory muscle, increased fatty tissue, ganglion cyst or a variant median artery  [Figure - 16].
Many investigators have attempted to define USG criteria for the diagnosis of CTS. According to Wong et al, these include volar bulging and thickening of the flexor retinaculum and focal or diffuse swelling or flattening of the nerve. A median nerve cross-sectional diameter of >0.098 cm 2 at the tunnel inlet has been reported to have a sensitivity of 89% and a specificity of 83%. 
| Conclusion|| |
USG in rheumatology has already gained acceptance in numerous clinics in Europe. Various training programs are available from time to time. Consensus is being developed for 'normal' and 'abnormal' patterns. The "operator-dependence" is an issue that rheumatologists have to overcome. With time, USG will become an important modality in the evaluation of rheumatologic conditions.
| References|| |
|1.||Kane D, Grassi W, Sturrock R, Balint PV. A brief history of musculoskeletal ultrasound: 'From bats and ships to babies and hips'. Rheumatology 2004;43:931-3. [PUBMED] [FULLTEXT]|
|2.||Backhaus M, Burmester GR, Gerber T, Grassi W, Machold KP, Swen WA, et al . Guidelines for musculoskeletal ultrasound in rheumatology. Ann Rheum Dis 2001;60:641-9. [PUBMED] [FULLTEXT]|
|3.||Grassi W, Cervini C. Ultrasonography in rheumatology: An evolving technique. Ann Rheum Dis 1998;57:268-71. [PUBMED] [FULLTEXT]|
|4.||Wakefield RJ, Gibbon WW, Emery P. The current status of ultrasonography in rheumatology. Rheumatology (Oxford) 1999;38:195-8. [PUBMED] [FULLTEXT]|
|5.||Kane D, Grassi W, Sturrock R, Balint PV. Musculoskeletal ultrasound: A state of the art review in rheumatology, Part 2: Clinical indications for musculoskeletal ultrasound in rheumatology. Rheumatology 2004;43:829-38. [PUBMED] [FULLTEXT]|
|6.||Schmidt WA, Schmidt H, Schicke B, Gromnica-Ihle E. Standard reference values for musculoskeletal ultrasonography. Ann Rheum Dis 2004;63:988-94. [PUBMED] [FULLTEXT]|
|7.||Carpenter JR, Hattery RR, Hunder GG, Bryan RS, McLeod RA. Ultrasound evaluation of the popliteal space: Comparison with arthrography and physical examination. Mayo Clin Proc 1976;51:498-503. [PUBMED] |
|8.||Kane D, Balint PV, Sturrock RD. Ultrasonography is superior to clinical examination in the detection and localization of knee joint effusion in rheumatoid arthritis. J Rheumatol 2003;30:966-71. [PUBMED] |
|9.||Szkudlarek M, Klarlund M, Narvestad E, Court-Payen M, Strandberg C, Jensen KE, et al . Ultrasonography of the metacarpophalangeal and proximal interphalangeal joints in rheumatoid arthritis: A comparison with magnetic resonance imaging, conventional radiography and clinical examination. Arthritis Res Ther 2006;8:R52. [PUBMED] [FULLTEXT]|
|10.||Backhaus M, Kamradt T, Sandrock D, Loreck D, Fritz J, Wolf KJ, et al . Arthritis of the finger joints: A comprehensive approach comparing conventional radiography, scintigraphy, ultrasound and contrast-enhanced magnetic resonance imaging. Arthritis Rheum 1999;42:1232-45. [PUBMED] [FULLTEXT]|
|11.||Ridden C, Andrι B, Marcelis S, Kaye O, Mathy L, Bonnet V, et al . Rheumatoid hand joint synovitis: Gray-scale and power Doppler US quantifications following anti-tumor necrosis factor-alpha treatment. Radiology 2003;229:562-9. |
|12.||Grassi W, Lamanna G, Farina A, Cervini C. Synovitis of small joints: Sonographic guided diagnostic and therapeutic approach. Ann Rheum Dis 1999;58:595-7. [PUBMED] [FULLTEXT]|
|13.||Grassi W, Tittarelli E, Pirani O, Avaltroni D, Cervini C. Ultrasound examination of metacarpophalangeal joints in rheumatoid arthritis. Scand J Rheumatol 1993;22:243-7. |
|14.||Hau M, Kneitz C, Tony HP, Keberle M, Jahns R, Jenett M. High resolution USG detects a decrease in pannus vascularization of small finger joints in patients with Rheumatoid Arthritis receiving treatment with soluble anti tumor necrosis factor alpha receptor. Ann Rheum Dis 2002;61:55-8. [PUBMED] [FULLTEXT]|
|15.||Filippucci E, Farina A, Carotti M, Salaffi F, Grassi W. Grey scale and power Doppler sonographic changes induced by intra-articular steroid injection treatment. Ann Rheumat Dis 2004;63:740-3. [PUBMED] [FULLTEXT]|
|16.||Grassi W, Filippucci E, Farina A, Cervini C. Sonographic imaging of tendons. Arthritis Rheum 2000;43:969-76. [PUBMED] [FULLTEXT]|
|17.||Campbell RS, Grainger AJ. Current concepts in imaging of tendinopathy. Clin Radiol 2001;56:253-67. [PUBMED] [FULLTEXT]|
|18.||Grassi W, Filippucci E, Farina A, Salaffi F, Cervini C. Ultrasonography in the evaluation of bone erosions. Ann Rheum Dis 2001;60:98-103. [PUBMED] [FULLTEXT]|
|19.||Grassi W, Tittarelli E, Pirani O, Avaltroni D, Cervini C. Ultrasound examination of metacarpophalangeal joints in rheumatoid arthritis. Scand J Rheumatol 1993;22:243-7. [PUBMED] |
|20.||Mc Gonagle D, Gibbon W, O'Connor P, Blythe D, Wakefield R, Green M, et al . A preliminary study of bone erosion in early rheumatoid arthritis. Rheumatology 1999;38:329-31. [PUBMED] [FULLTEXT]|
|21.||Wakefield RJ, Gibbon WW, O'Csonnor P. High resolution ultrasound: A superior method to radiography for detecting cortical bone erosions in rheumatoid arthritis. Br J Rheumatol 1998;7:S197. |
|22.||Szkudlarek M, Klarlund M, Narvestad E, Court-Payen M, Strandberg C, Jensen KE, et al . Ultrasonography of the metacarpophalangeal and proximal interphalangeal joints in rheumatoid arthritis: A comparison with magnetic resonance imaging, conventional radiography and clinical examination. Arthritis Res Ther 2006;8:R52. [PUBMED] [FULLTEXT]|
|23.||Frediani B, Filippou G, Falsetti P, Lorenzini S, Baldi F, Acciai C, et al . Diagnosis of calcium pyrophosphate dihydrate crystal deposition disease: Ultrasonographic criteria proposed. Ann Rheumat Dis 2005;64:638-40. [PUBMED] [FULLTEXT]|
|24.||Balint PV, Kane D, Wilson H, McInnes IB, Sturrock RD. Ultrasonography of entheseal insertions in the lower limb in spondyloarthropathy. Ann Rheumat Dis 2002;61:905-10. [PUBMED] [FULLTEXT]|
|25.||Wong SM, Griffith JF, Hui AC, Tang A, Wong KS. Discriminatory sonographic criteria for the diagnosis of carpal tunnel syndrome. Arthritis Rheum 2002;46:1914-21. [PUBMED] [FULLTEXT]|
Tikka Harinder Singh Bedi
Diwan Chand Satyapal Aggarwal Imaging Center, 10-B, K. G. Marg, New Delhi-100 001
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13], [Figure - 14], [Figure - 15], [Figure - 16]
|This article has been cited by|
||Ultrasonography of synovium in rheumatological diseases | [Ultrasonografia błony maziowej w chorobach reumatycznych]
| ||Jeka, S., Murawska, A. |
| ||Reumatologia. 2009; 47(6): 339-343 |
| Article Access Statistics|
| Viewed||8444 |
| Printed||115 |
| Emailed||4 |
| PDF Downloaded||1053 |
| Comments ||[Add] |
| Cited by others ||1 |