Review ArticleHong Kong Bull Rheum Dis 2009;9:1-7

Musculoskeletal Ultrasound for Rheumatologists

Ka-Lai Lee

DEPARTMENT OF MEDICINE, PAMELA YOUDE NETHERSOLE EASTERN

HOSPITAL, 3 LOK MAN ROAD, CHAIWAN, HONG KONG

Ka-Lai Lee MRCP, FHKAM, FHKCP

Correspondence to: Ka-Lai Lee

Abstract: In the past two decades, musculoskeletal ultrasonography has become an important imaging modality inrheumatology. Musculoskeletal ultrasonography, some considered it to be the rheumatologist's stethoscope,is now routinely used by an increasing number of rheumatologists throughout Europe for proven clinicalindications in diagnosis, disease monitoring and intervention.

Keywords: Musculoskeletal ultrasonography, Rheumatology

Introduction

The application of ultrasound imaging in medical field is nowregarded as an indispensable tool, was pioneered in surgeryand obstetrics in the late 1950s and early 1960s.1 The firstreport of musculoskeletal ultrasonography (MSUS) waspublished in 1958 by Dussik et al who measured the acousticattenuation of articular and periarticular tissues including skin,adipose tissue, muscle, tendon articular capsule, articularcartilage and bone.2 However, the first clinical application ofMSUS in differentiating Baker's cyst from thrombophlebitiswas only reported in 1972.3

The Development of Musculoskeletal Ultrasound

Musculoskeletal ultrasonography began with thedemonstration of synovitis of the knee in rheumatoid arthritisin 1978.4 Its initial use was limited to investigating larger jointsand soft tissue structures. In the early 1900s, technicaladvances in ultrasound had led to higher-resolution imagingof musculoskeletal structure and allowed assess to the smallerjoints, detection of bone erosions, synovitis, tendon disease,and enthesopathy. Combined with a better understanding of

the rheumatic disease, multiplanar imaging of articularstructures in real time, low running costs, absence of radiationand excellent patient acceptability, MSUS now become anideal tool for rheumatologists. In Germany, MSUS has alreadyintergraded into their clinical practice, just like the extensionof the clinical examination. Moreover, MSUS is now astandard part of the rheumatology training curriculum inGermany and Italy.5

Indications of MSUS in Rheumatologists

Musculoskeletal ultrasonography aids the early diagnosis ofrheumatoid arthritis (RA) by demonstration the bony erosionswhich may not be present in X-ray in early disease. It can beused for assessment of the disease activities by the presenceof power Doppler signal, monitoring of disease progression,treatment response, research work, needle guidance inaspiration and injection. It also helps in diagnosing otherconnective tissue disease.

MSUS Technical Equipments

Transducer and Frequency of the Ultrasound WaveTransducer is an essential element of ultrasound equipmentwhich is responsible for the generation of ultrasound beamand the detection of returning echoes. Ultrasound waves arelongitudinal, mechanical waves which are above the hearingfrequency range of the human ear (>20 kHz). Diagnosticmusculoskeletal systems need much higher frequencies,ranging from 3-18 MHz. The higher the frequency, the greater

2 Musculoskeletal Ultrasonography

the axial and the lateral resolution of image, but at the cost ofreduced tissue penetration. Therefore, a higher-frequencytransducer is best used for superficial structures, such as thesmall joints of the hand and feet (7.5-20 MHz), and a lowfrequency transducer is used for deeper joints, such as thehip or shoulder (<7.5 MHz).6 Smaller size of transducersallows better access to the small joints of the hands and feetwith adequate angulation to reduce the chance of artifact(Figure 1).

Grey-scale ImagingThe ultrasound imaging is blank and white. Each white doton the monitor indicates a reflected sound wave. Fluid,therefore, is black as it is a good transmitter of sound, andbone and soft tissue are varying degrees of white.

Power DopplerPower Doppler is useful in the detection of vascularity byvisualized the low-velocity of blood cells within a vesselespecially the synovium tissue within a joint.7 It has a practicalvalue in distinguishing inflammatory and infectious

musculoskeletal fluid collections from those that are non-inflammatory.8 However, the interpretation of power Doppleris highly dependent on the quality of the ultrasound machine,the experience of the examiner and the technical conditionsof the examination, e.g. the temperature of the examinationroom. Although power Doppler is an exciting technique forthe diagnosis and quantification of inflammatorymusculoskeletal disease but further validation is requiredbefore it could be used as a universal assessment andmonitoring of the disease activities. Figure 2 demonstratesthe presence of power Doppler signals in a metacarpalpharyngeal joint.

Ultrasound Detectable Pathologies

Bone ErosionsBone erosion found in MSUS is defined as an intraarticulardiscontinuity of the bone surface that is visible in 2perpendicular planes (Figure 3).9 The detection of joint erosionon plain radiography is a key diagnostic criterion and outcome

Figure 1. Linear probe 12-5 MHz (left) for scanning

of larger joints. Hockey stick probe 15-7 MHz (right)

for scanning of smaller joints, e.g hands and feet.

Figure 2. Dorsal transverse scan (left) and dorsal longitudinal scan (right) of right metacarpal pharyngeal joint showing a

bone erosion and grade 3 (severe) power Doppler signal within the joint and inside the erosion.

3Lee

measure in RA, however, the sensitivity of picking up boneerosion by X-ray in early rheumatoid arthritis is low.Wakefield et al showed that MUSU is capable of detecting upto seven times more erosions than plain radiography in earlyRA.10 Early detection of bone erosion using other modalitiesincluding musculoskeletal ultrasound or MRI is of paramountimportance in early diagnosis and treatment. Thus, it has beenproposed that MSUS detection of erosion should be includedin the diagnostic criteria of RA.11

Joint EffusionJoint effusion is defined as an abnormal hypoechoic oranechoic intraarticular material that is displaceable andcompressible, but does not exhibit Doppler signal.9 Thedetection of a fluid collection in joints is a useful sign ofinflammation. High resolution MSUS is superior to clinicalexamination in the detection of minute amounts of jointeffusion in asymptomatic patient.12 However, MSUS is notable to accurately differentiate whether a fluid collection isinflammatory, infectious or haematogenous. Figure 4 belowshows a significant amount of joint effusion inside themetatarsalpharyngeal joint.

Synovitis (Synovial Hypertrophy)Synovial hypertrophy is defined as abnormal hypoechoicintraarticular tissue that is nondisplaceable and poorlycompressible, which may exhibit power Doppler signal.6

Presence of synovitis on ultrasound imaging usually signifiesinflammation. However, in the absence of joint effusion,synovitis could be difficult to detect, especially when thesynovial thickening is minimal. In an asymptomatic joint, thedetection of subclinical synovitis by MSUS may lead to a re-evaluation of the clinical classification of arthritis asoligoarticular or polyarticular.13 Figure 5 demonstrates theultrasound imaging of an active synovitis involving ametacarpalpharyngeal joint.

TenosynovitisTenosynovitis is defined as a hypoechoic or anechoicthickened tissue with or without fluid within the tendon sheath

Figure 3. Dorsal longitudinal (left) and dorsal transverse (right) scan of the

right second metacarpopharyngeal joint (MCPJ) demonstrates an intraarticular

discontinuity of bone surface in 2 perpendicular planes.

Figure 4. Dorsal longitudinal scan of right metatarsalpharyngeal

joint shows significant amount of joint effusion which is

compressible on dynamic examination.

Figure 5. Dorsal longitudinal scan of right 1st MCPJ showing synovitis (left) with positive power Doppler signal (right).

4 Musculoskeletal Ultrasonography

seen in 2 perpendicular planes, which may exhibit Dopplersignal.9 MSUS is superior to MRI in the detection oflongitudinal split tendon tear, subluxed tendon and snappingtendon,14 it also has the advantage of allowing dynamic tendonexaminations although subtle changes may be missed ormisinterpreted due to anisotropy.15 Figure 6 demonstrates thescanning of Achilles tendon.

Peripheral NeuropathyMSUS easily identifies the nerve from tendons as it ishyperechoic and speckled in transverse section. Nerve doesnot demonstrate anisotropy and has a hypoechoicfascicular pattern in longitudinal section (Figure 7). Carpaltunnel syndrome is the most common peripheral nerveproblem which could be identified by measuring themedian nerve cross-sectional diameter at the tunnel inlet,an area >0.098 cm2 signify neuropathy with sensitivity and

specificity of 89% and 83% respectively.16 Additionalinformation on the cause of nerve compression in carpaltunnel may be obtained by MSUS through imaging oftenosynovitis, tendon effusion, amyloid deposition,hypertrophied accessory muscle, increased fatty tissue,ganglion cyst or variant median artery. 17

Skin AbnormalityThe development of higher-frequency probe (13-20 MHz)allows skin thickness and edema to be visualized.Ultrasound (US) assessment of skin thickness inscleroderma showed that skin thickness was increased overthe proximal phalanx of the right second finger andforearm compared with controls.18 Therefore, US criteriaof scleroderma have been successfully used to differentiatescleroderma from other skin plaques with a diagnosticsensitivity of 92% and a specificity of 100%.19

Figure 7. Volar transverse scan (left) and volar longitudinal scan (right) at the carpel tunnel. n= median nerve; flexor tendon bound by white

arrow.

Figure 6. t=Achilles tendon; k=Kaoer's fat pad; cal=calcaneus. Left: Transverse scan of Achilles tendon demonstrates Achilles tendonitis

with presence of power Doppler signal.

5Lee

Soft Tissue PathologyOther pathologies such as panniculitis, subcutaneous edema,cellulitis, necrotizing fasciitis, subcutaneous abscess or cystic,and solid dermal masses can be depicted by MSUS (Figures8 & 9).20,21

Uses of Ultrasound on Other Connective TissueDiseases

The role of ultrasound is becoming more and more relevantin the assessment of rheumatic disease apart from the arthritis.There are still more exploring field including use of ultrasoundin scleroderma,22 polymyalgia rheumatica,23 temporal arteritis(Figure 10), Takayasu's arteritis,24 and Sjogren's syndrome.25

Ultrasound Guided InterventionUltrasound can be used for guidance of aspiration, biopsy,and injection treatment.26 In patients with inflamedmetacarpophalangeal (MCP) and proximal interphalangeal

(PIP) joints, MSUS improved accurate needle placement from59% by palpation guidance to 96% by MSUS guidance.27

A pilot study showed that using US to localize effusions andguide aspiration produced a 3-fold increase in the rate ofsuccessful aspiration when compared with conventionalaspiration of the peripheral joint.28 Figure 11 shows thetechnique of MSUS guided depomedrol injection for carpeltunnel syndrome.

Advantages of Musculoskeletal UltrasoundUltrasound has a number of distinct advantages, includingbetter patient tolerability, non invasive imaging with noradiation, ready accessibility, portability and its ability toscan mul t ip le jo in ts in a br ie f per iod of t ime.Rheumatologist, with clinical understanding of thepatient's problem, can scan in the clinic (rather thansending the patient for another appointment), therebyallowing rapid interpretation of the images and immediatedecision-making, such as starting or changing dosage of adisease-modifying anti-rheumatic agent.

Figure 8. Increase power Doppler signal over the subcutaneous tissue in panniculitis.

Figure 9. Presence of hypoechoeic fluid within

subcutaneous tissue suggests subcutaneous edema.

6 Musculoskeletal Ultrasonography

Pitfalls of Musculoskeletal UltrasoundHowever, ultrasound is often perceived as an imperfectand operator-dependent tool. There is also lack of dataregarding it validity, reproducibility, and responsivenessto change, making interpretation and comparison of studiesdifficulties. In particular, there are limited data describingstandardized scanning methodology29 and standardizeddefinitions of US pathologies. In addition, experience andproper training is required to perform consistent and highquality scanning.

Training of Musculoskeletal UltrasoundOver the last 10 years, the EULAR Working Group forMusculoskeletal Ultrasound in rheumatology and the BritishSociety of Rheumatology had been organizing basic,intermediate and advanced US courses which had beensuccessful. Rheumatologists are always encouraged to attendthese courses.30 Using the EULAR website (http://www.sameint.it/eular/ultrasound) as a training reference forobtaining a MUSU standard images is a good self-directed

learning method too.31 Of course, the best way to train isdirectly under the supervision of an expert and constantpractice is the key to success. Although, MSUS is still theinfancy in most of the Asian Countries, we hope, in the nearfuture, Hong Kong will organize a musculoskeletal ultrasoundcourse for the Asian Rheumatologists.

Conclusion

Musculoskeletal ultrasound used in rheumatology had beengetting more and more popular in recent twenty years. Severalapplications especially in the management of arthritis havebeen successful and made a great contribution to patient care.With the great quality improvement of sonographicequipments and the more training opportunities provided tothe rheumatologists, hopefully in one day, MSUS could beintegrated into our clinical practice in helping us to make anearly diagnosis, monitor the disease progression and treatmentresponse.

Figure 11. (a) Preparation before MSUS guided injection. (b) Insertion of needle towards median nerve using ultrasound guidance.

(c) MSUS confirm the needle tip touching the median nerve sheath.(d) Injection of the depomedrol.

Figure 10. (a) Longitudinal color Doppler image of the temporal

arteries in acute temporal arteritis. (b) Transverse color Doppler image

of the temporal arteries in acute temporal arteritis. The arrows points

to the edematous wall swelling "halo"

7Lee

References

1. Donald I, MacVicar J, Brown TG. Investigation of abdominalmasses by pulsed ultrasound. Lancet 1958;1:1188-95.

2. Dussik KT, Fritch DJ, Kyriazidou M, Sear RS. Measurementsof articular tissues with ultrasound. Am J Phys Med 1958;37:160-5.

3. McDonald DG, Leopold GR. Ultrasound B-scanning in thedifferentiation of Baker's cyst and thrombophlebitis. Br JRadiol 1972;45:729-32.

4. Cooperberg PL, Tsang I, Truelove L, Knickerbocker WJ.Gray scale ultrasound in the evaluation of rheumatoid arthritisof the knee. Radiology 1978;126:759-63.

5. Manger B, Kalden JR. Joint and connective tissueultrasonography-a rheumatologic bedside procedure? AGerman experience. Arthritis Rheum 1995;38:736-42.

6. Grassi W, Tittarelli E, Blasetti P, Pirani O, Cervini C. Fingertendon involvement in rheumatoid arthritis. Evaluation withhigh-frequency sonography. Arthritis Rheum 1995;38:786-94.

7. Szkudlarek M, Court-Payen M, Strandberg C, Klarlund M,Klausen T, Ostergaard M. Power Doppler ultrasonographyfor assessment of synovitis in the metacarpophalangeal jointsof patients with rheumatoid arthritis: a comparison withdynamic magnetic resonance imaging. Arthritis Rheum 2001;44:2018-23.

8. Wakefield RJ, Brown AK, O'Connor PJ, Emery P. PowerDoppler sonography: improving disease activity assessmentin inflammatory musculoskeletal disease. Arthritis Rheum2003;48:285-8.

9. Wakefield RJ, Balint PV, Szkudlarek M, et al. Musculoskeletalultrasound including definitions for ultrasoungraphicpathology. J Rheumatol 2005;32:2485-7.

10. Wakefield RJ, Gibbon WW, Conaghan PG, et al. The valueof sonography in the detection of bone erosions in patientswith rheumatoid arthritis: a comparison with conventionalradiography. Arthritis Rheum 2000;43:2762-70.

11. Schmidt WA. Value of sonography in diagnosis of rheumatoidarthritis. Lancet 2001;357:1056-7.

12. Nazarian LN, Rawool NM, Martin CE, Schweitzer ME.Synovial fluid in the hindfoot and ankle: detection of amountand distribution with US. Radiology 1995;197:275-8.

13. Karim Z, Wakefiled RJ, Conaghan PG, et al. The impact ofultrasonography on diagnosis and management of patientswith musculoskeletal conditions. Arthritis Rheum 2001;44:2932-3.

14. Grassi W, Filippucci E, Farina A, Cervini C. Sonographicimaging of tendons. Arthritis Rheum 2000;43:969-76.

15. Cambell RS, Grainger AJ. Current concepts in imaging oftendinopathy. Clin Radiol 2001;56:253-67.

16. Wong SM, Griffith JF, Hui AC, Tang A, Wong KS.Discriminatory sonographic criteria for the diagnosis of carpal

tunnel syndrome. Arthritis Rheum 2002;46:1914-21.17. Martinoli C, Bianchi S, Gandolfo N, Valle M, Simonetti S,

Derchi LE. US of nerve entrapments in osteofibrous tunnelsof the upper and lower limbs. Radiographics 2000;20:S199-S213;discussion S213-S217.

18. Scheja A, Akesson A. Comparison of high frequency (20MHz) ultrasound and palpation for the assessment of skininvolvement in systemic sclerosis (scleroderma). Clin ExpRheumatol 1997;15:283-8.

19. Cosnes A, Anglade MC, Revuz J, Radier C. Thirteen-megahertz ultrasound probe: its role in diagnosing localizedscleroderma. Br J Dermatol 2003;148:724-9.

20. Bureau NJ, Ali SS, Chhem RK, Cardinal E. Ultrasound ofmusculoskeletal infections. Semin Musculoskelet radiol1998;2:299-306.

21. Bureau NJ, Cardinal E, Chhem RK. Ultrasound of soft tissuemasses. Semin Musculoskelet Radiol 1998;2:283-98.

22. Valentini G, D'Angelo S, Della Rossa A, Bencivelli W,Bombardieri S. European Scleroderma Study Group to definedisease activity criteria for systemic sclerosis. IV. Assessmentfor Skin thickening by modified Rodnan skin score. AnnRheum Dis 2003;62:904-5.

23. Schmidt WA, Gromnica-Ihle E. Incident of temporal arteritisin patients with polymyalgia rheumatica: a prospective studyusing colour Doppler ultrasonography of the temporalarteries. Rheumatolgy 2002;41:46-52.

24. Schmidt WA, Nerenheim A, Seipelt E, Poehls C, Gromnica-Ihle E. Diagnosis of early Takayasu arteritis with sonography.Rheumatology (Oxford) 2002;41:496-502.

25. Carotti M, Salaffi F, Manganelli P, Argalia G. Ultrasonographyand colour Doppler sonography of salivary glands in primarySjogren's syndrome. Clin Rheumatol 2001;20:213-9.

26. Grassi W, Lamanna G, Farina A, Cervini C. Synovitis ofsmall joints: sonographic guided diagnostic and therapeuticapproach. Ann Rheum Dis 1999;58:595-7.

27. Raza K, Lee CY, Pilling D, et al. Ultrasound guidance allowsaccurate needle placement and aspiration from small jointsin patients with early inflammatory arthritis. Rheumatology(Oxford) 2003;42:976-9.

28. Balint PV, Kane D, Hunter J, McInnes IB, Field M, SturrockRD. Ultrasound guided versus conventional joint and softtissue fluid aspiration in rheumatology practice: a pilot study.J Rheumatol 2002;29:2209-13.

29. Lassere MN, Bird P. Measurement of RA disease activityand damage using MRI: Truth and discrimination. Does MRImake the grade? J Rheumatol 2001;28:1151-7.

30. Manger B, Kalden JR. Joint and connective tissueultrasonography - a rheumatologic bedside procedure? AGerman experience. Arthritis Rheum 1995;38:736-42.

31. Filippucci E, Unlu Z, Farina A, Grassi W. Sonographictraining in rheumatology: a self teaching approach. AnnRheum Dis 2003;62:565-7.