Imaging Ultrasound Imaging for the Rheumatologist II. Ultrasonography of the Hand and Wrist

Imaging

Ultrasound imaging for the rheumatologist II. Ultrasonography of the hand and wrist E. Filippucci1, A. Iagnocco2, G. Meenagh3, L. Riente4, A. Delle Sedie4, S. Bombardieri4, G. Valesini2, W. Grassi1

1Cattedra di Reumatologia, Università ABSTRACT pathology of the hand and wrist could Politecnica delle Marche, Jesi, Italy; The hand is one of the anatomical be approached employing high quality 2Cattedra di Reumatologia, Università regions most frequently explored by real time imaging and a new field of Roma “La Sapienza”, Roma, Italy; ultrasonography (US) in rheumatology. research started. Since then, several 3Department of Rheumatology, Musgrave Park Hospital, Belfast, UK; The last generation US systems equip- studies have demonstrated the great 4Unità Operativa di Reumatologia, ped with high frequency probes allow value of US imaging of the hand and Università di Pisa, Pisa, Italy. for a quick and accurate assessment of wrist in rheumatology (4-16). Emilio Filippucci, MD; Annamaria even minimal pathological changes in This paper provides the basic knowl- Iagnocco, MD; Gary Meenagh, MD; patients with rheumatic conditions af- edge, reviews the available evidence Lucrezia Riente, MD; Andrea Delle Sedie, fecting the small joints and the soft tiss- and discusses the potential of US in the MD; Stefano Bombardieri, MD, Professor ues of the hand and wrist. Several stud- evaluation of the hand and wrist. of Rheumatology; Guido Valesini, MD, ies have demonstrated the great value Professor of Rheumatology; Walter Grassi, of US imaging of the hand and wrist in Indications MD, Professor of Rheumatology. rheumatology but there are still contro- There are several clinical settings in Please address correspondence and reprint versial issues which yet have to be ade- which US examination of the hand and requests to: Prof. Walter Grassi, Cattedra di Reumatologia, Università Politecnica quately addressed, particularly with re- wrist may be beneficial (Table I). In delle Marche, Ospedale “A. Murri”, Via gard to US semi-quantitative evalua- early arthritis hand US is a sensitive tool dei Colli 52, 60035 Jesi (AN), Italy. tion of synovitis and bone erosions in for detecting both synovitis and bone E-mail: [email protected] patients with chronic arthritis. This erosions in small joints (13-16). It can Clin Exp Rheumatol 2006; 24: 118-122. paper provides the basic knowledge, also carefully depict sub-clinical tendon Received and accepted on March 22, 2006 reviews the available evidence and dis- involvement in patients with chronic © Copyright CLINICAL AND EXPERIMEN- cusses the potential of US in the evalu- arthritis (17). US of the hand and wrist TAL RHEUMATOLOGY 2006. ation of the hand and wrist. is also of great use in the identification of underlying pathology responsible for Key words: Ultrasonography, hand Introduction clinical scenarios such as “sausage fin- and wrist, small joints, finger tendons, The hand is one of the anatomical ger” and “carpal tunnel syndrome” (18). median nerve. regions most frequently explored by The modality can therefore add vital ultrasound (US). This is for at least two information to tricky clinical situations main reasons. The first is related to the in rheumatological practice. fact that this area is a common target in several rheumatic diseases. The second Equipment is linked to the relatively wide acoustic The availability of a very high frequen- windows available for finger joints and cy probe is a ‘sine qua non’ for a com- tendons which permit careful depiction prehensive evaluation of the entire US of critical details for rheumatological landscape of the hand. The use of linear investigation. The hand is an anatomi- probes with frequencies > 10 MHz is cally complex region but in spite of this recommended. Another important fea- it should be regarded as a friendly area ture to consider is the size and the shape for the early training of rheumatolo- of the probe: small “hockey stick” gists in the difficult art of scanning transducers allow an easier multi-planar since many pathognomonic changes of assessment of the small joints of the several important rheumatic diseases hand because they can be readily placed can be depicted at this level. The earli- among the fingers. Wide footprint and est investigations in hand US date back extended view reconstructions allow to the late 1980’s with the availability panoramic views that are particularly of probes with frequencies > 10 MHz useful while assessing the anatomical (1-3). For the first time soft tissue structures of the wrist: radio-carpal and

118 Ultrasonography of the hand and wrist / E. Filippucci et al. IMAGING

Table I. Main indications for performing an US examination of hand and/or wrist. lthy subjects, the thickness of the articular cartilage of the metacarpal head Rheumatological setting Indications for performing US examination ranges from 0.2 to 0.5 mm (5). Early arthritis To reveal bone erosions, especially at II MCP joint level. In longitudinal scan, the triangular liga- To detect synovitis (especially sub-clinical joint inflammation). ment of the carpus appears as a homo- Tendon involvement To detect tendon inflammation (especially sub-clinical involvement). geneous echoic or hyper-echoic struc- To reveal tendon ruptures. ture between the head of the ulna and Dactylitis To characterize the underlying pathologic substrate (synovitis, tenosynovi- the triquetrum bone and is best seen tis, both synovitis and tenosynovitis, enthesitis). during abduction and adduction of the Carpal tunnel syndrome To visualize pathological conditions responsible for carpal tunnel syndrome. hand (20, 21). To depict morphostructural changes of the median nerve. Tendons Wrist pain To detect calcification or ruptures of the triangular ligament. Morphostructurally, the finger flexor US guidance for To reduce risk of damage due to needle contact or steroid injection. and extensor tendons appear on longi- injection therapy To visualize correct placement of drug during injection. tudinal scans, as tightly packed echoic Therapy monitoring To assess changes in soft tissue anatomy induced by therapy. bands with thin parallel linear echoes in patients with chronic (fibrillar pattern) separated by fine ane- arthritis choic lines. On transverse view, they have an oval-to-round shape and their inter-carpal joints, carpal tunnel and readily displaced even by minimal ex- echo-texture is characterised by tightly extensor tendon compartments. ternal pressure and result in underesti- packed echoic dots with a homoge- Power Doppler sonography (PDS) and mation of joint effusion. Moreover, for neous distribution (17, 22). colour Doppler sonography are now proper PD examination of a joint, the US examination of the tendons of the essential for assessment which also patient must be asked to take a position hand and wrist is relatively easy due to includes the study of tissue perfusion. generating the lowest intra-articular the absence of acoustic barriers and pressure. For the small joints of the their relatively straight course. Active Scanning technique hand, this position corresponds to the and passive movements of the fingers Each anatomical structure must be hand resting on the bed with a mild are very helpful when examining the explored through all the available degree of flexion of the joints. carpal tunnel or the IV compartment of acoustic windows using a multi-planar the wrist where more than four tendons scanning technique. In particular, the US anatomy lie next to one another. articular cartilage of the metacarpal Joints The flexor and extensor tendons of the head requires maximal flexion of the The articular surfaces of the small joints fingers are enveloped by a synovial metacarpophalangeal (MCP) joint to of the hand represent the landmarks to sheath for the majority of their course. expose the maximal extent of its sur- be visualised during US examination. A subtle anechoic layer, indicating syn- face to the US beam. US examination In all cases the bone profile appears as a ovial fluid surrounding tendons with of the II MCP joint must include evalu- sharp, continuous and hyperechoic line synovial sheath, can be visualized with ation of the lateral aspect of the joint generating an acoustic shadow. Particu- very-high frequency transducers (>13 where bone erosions, undetectable by lar attention should be paid during the MHz). The size of this virtual space for conventional antero-posterior hand evaluation of the anatomical neck of the the finger flexor tendons is 0.3 mm at radiography, are most frequently dis- metacarpal bone as it may be misinter- the level of the MCP joints. The ten- covered. preted as bone erosion. dons and their tracts with synovial The tendons must be assessed from In healthy subjects the joint space is sheaths are listed in Table II (17). Mild their musculo-tendinous origin to their filled by the intra-articular fat pad tendon sheath widening on the dorsal distal insertion into bone. Dynamic real which appears as an inverted triangular aspect of the IV compartment of the time examination is recommended for area with homogeneous echogenicity wrist, proximal to the extensor retinac- assessing the hand and wrist and is par- (19). ulum ligament is detectable in healthy ticularly true for the tendons and the Normal articular cartilage appears as a subjects. median nerve. Active and passive ten- homogeneous anechoic band delimited don movement during US examination by sharply defined hyperechoic mar- Median nerve can confirm the presence of a tendon gins. The superficial chondro-synovial At the entrance to the carpal tunnel the tear in cases where an intra-tendineous margin corresponds to the interface median nerve is located between the anechoic or hypoechoic area are found. between the synovial fluid and the car- tendon of flexor carpi radialis and the Both greyscale US and PDS mode re- tilage surface. This margin is thinner tendons of the flexor digitorum superfi- quire very low compression of the than the deeper one and its visualisa- cialis, deep to the tendon of palmaris probe on the tissues under examination. tion is optimised by perpendicular longus, when present, and superficial Fluid collection in small joints can be insonation of the US beam. (5). In hea- to the flexor pollicis longus tendon.

119 IMAGING Ultrasonography of the hand and wrist / E. Filippucci et al.

The median nerve is similar in shape to Table II. Tendons of the hand and wrist with synovial sheath. a tendon on both longitudinal and tran- Tendons Site where tendons are surrounded by synovial sheath sverse views. It can however, be recog- nised by its typical echo-texture with Abductor pollicis longus and extensor I compartment of the wrist discrete hyper-echoic bundles on a pollicis brevis hypo-echoic background delimited by Extensor carpi radialis longus and brevis II compartment of the wrist a hyper-echoic margin (23). It is distin- Extensor pollicis longus III compartment of the wrist guished from tendons on real-time US Extensor digitorum IV compartment of the wrist examination where they run during finger flexion-extension movements in Extensor minimi V compartment of the wrist longitudinal views and change their Extensor carpi ulnaris VI compartment of the wrist echogenicity according to the angle of Flexor carpi radialis At the level of the distal epiphysis of the radius and insonnation because of anisotropy on scaphoid bone transverse scans. Flexor pollicis longus Carpal tunnel, thenar eminence, thumb In healthy subjects, the cross-sectional Finger flexor tendons superficialis and There are two synovial sheaths: a common synovial area of the median nerve can extend up profundus sheath within the carpal tunnel and a single digitalis to 10 mm2 when measured at the level synovial sheath for each finger from the II to the V. of the pisiform bone (24, 25). Flexor carpi ulnaris Guyon canal

joint space can be related to joint effu- multi-planar examination to assess its US pathology sion and/or synovial proliferation. PDS full extent. With the advent of the three- Joints is of value in the evaluation of synovial dimensional US, PDS interpretation Joint cavity widening is the US hall- perfusion which may be patchy in its will become simpler since a single mark of synovitis. Enlargement of the distribution, requiring an accurate three-dimensional image is able to con-

Fig. 1. Representative examples of hand and wrist US pathological findings. A-B. Rheuma- toid arthritis. Prolifera- tive synovitis (s) of a MCP joint on dorsal longitudinal (A) and transverse (B) views. C. Hed- erden node. Dorsal longitudinal scan showing osteophytes (arrow- heads). D. Rheumtoid arthritis. Partial rupture (arrow) of the extensor carpi ulnaris tendon (t). E-F. Carpal tunnel syndrome. Marked thicken- ing of the median nerve (n) at the proximal entrance of the carpal tunnel both on tranverse (E) and longitudinal (F) views. m = metacarpus; pp = proximal phalanx; mp = mid- dle phalanx; dp = distal phalanx; u = ulna; lu = lunate bone; ca = capitate bone; r = radius.

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120 Ultrasonography of the hand and wrist / E. Filippucci et al. IMAGING vey the full extent of PDS assessed by with hand arthritis including: diffuse Controversial issues the US beam (26). Both greyscale and tendon swelling with multiple small In spite of the wealth of available evi- PDS findings of synovitis can be semi- anechoic areas, focal anechoic and/or dence supporting the value of US in the quantitatively assessed using a scale of hypo-echoic loss of substance sur- detection of synovitis and bone erosion 0-3 (8, 11, 27). Bone erosion appears as rounded by an area of fibrillar derange- in patients with RA, quantitative ass- an intra-articular discontinuity of the ment and subtotal tendon rupture (17). essment of these specific entities re- bone surface which is visible on at least In patients with RA, US can show pan- mains a matter of debate. Agreement two perpendicular scanning planes nus within the synovial sheath breach- on these US parameters of inflamma- (19). In early rheumatoid arthritis ing and invading the integrity of the tion will be the topic of future research (RA), US is more sensitive than X-ray tendon. particularly in terms of therapeutic in the detection of bone erosions espe- In chronic gout, tophaceous deposits monitoring. Currently, a four point sco- cially on the lateral aspect of the sec- can be depicted in the peri-articular soft ring system appears to be the most ond MCP joint (13, 14). Scoring of bo- tissues both surrounding or within the widely used and appropriate method ne erosion has not been formally stan- tendons. Intra-tendineous monosodium for semi-quantitative evaluation of dardised to date but currently the most urate crystalline deposits appear as cir- both greyscale and PDS findings in commonly used approach is to measure cumscribed areas of loss of normal fib- synovitis. Consensus upon the quanti- the maximal distance between the free rillar echotexture replaced by inhomo- tative assessment of bone erosion still edges of the erosion (13, 14). geneous echoic material covered with has to be reached. In hand osteoarthritis, US demonstrates bright hyper-echoic spots. Depending It seems likely that the hand and wrist both inflammatory and degenerative on their size and/or density, tophaceous will continue to be one of the main anato- changes. Osteophytes appear as single deposits may or may not generate an mical targets for research and develop- or multiple characteristic irregularities acoustic shadow (29). ment in the field of US worldwide. of the bone profile, located at the edges of the joint surfaces (28-30). Median nerve Link In chronic gout, US can detect deposi- The most relevant pathological finding For further ultrasound images, go to www.clinexprheumatol.org/ultrasound tion of urate crystals on the cartilage relating to the median nerve is the surface which appears as hyper-echoic change of its cross-sectional area. An References enhancement of the superficial margin. increment of the transverse area of the 1. FORNAGE BD: Soft-tissue changes in the Calcification of the triangular ligament nerve at the proximal entrance to the hand in rheumatoid arthritis: evaluation with of the wrist can be depicted as focal carpal tunnel is the most frequent and US. Radiology 1989; 173: 735-7. hyper-echoic areas, without acoustic non-specific sign of high pressure 2. VINCENT LM: Ultrasound of soft tissue abnormalities of the extremities. Radiol Clin shadow, which can be best visualised within the tunnel. North Am 1988; 26: 131-44. with dynamic evaluation. US can also identify secondary causes 3. 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