Ultrasound of the Hand and Wrist

Abstract

Ultrasound evaluation of the hand and wrist may be helpful to the rheumatologist for evaluation of causes of pain and swelling as well as for determination of the degree of inflammation, disease activity, structural joint damage, nerve impingement, crystal deposition, and response to therapy. Ultrasound examination of the hand and wrist is approached in a systematic manner and should include standardized views, which are based on anatomical and/or sonographic landmarks. The following chapter will review these standard sonographic views of the hand and wrist and the pathology commonly encountered in this anatomical region.

FormalPara Key Points

• Hand and wrist ultrasound can help in both identifying the source of symptoms and establishing the diagnoses in patients with hand and wrist pain.

• The most common pathologies that can be identified by ultrasound in hand and wrist region include synovitis and tenosynovitis, bony erosions, osteophytes, chondrocalcinosis, gouty tophi, ligamentous injury, tendinitis, retinacular pathology (e.g., DeQuervain’s), and nerve impingement (e.g., median nerve).

• Hand and wrist ultrasound can be used in rheumatology practice to aid in the assessment of subclinical synovitis and treatment response.

• Hand and wrist ultrasound has been shown to increase both physician and patient confidence in therapeutic decision-making in rheumatoid arthritis.

• The use of ultrasound for procedural purposes can help with diagnostic synovial fluid aspiration and targeted corticosteroid injections.

General Principles

Ultrasound evaluation of the hand and wrist is the most commonly performed ultrasound in rheumatology practice. It is especially valuable for the rheumatologist to better characterize structural damage caused by inflammation and can increase confidence in clinical decision-making [1]. Gray-scale and power Doppler ultrasound modalities, when used in conjunction, provide very sensitive and specific means to identify subclinical synovial abnormalities, assess disease activity, localize inflammation or other types of pathology to a particular tissue compartment, and determine the degree of damage that has been done to the soft tissues and to the underlying bone.

Proper scanning techniques and patient positioning are the key for accurate and reliable image acquisition. The following are hand and wrist ultrasound scanning tips.

Begin scanning by placing the hand, wrist, and forearm on a supportive surface between the examiner and the ultrasound screen. To avoid motion-related artifacts, the extremity should be relaxed and fully rested on the supporting surface.

The wrist should be kept in neutral position for scanning, as flexion or extension of the wrist will affect the appearance of the synovium—more prominent dorsally with wrist extension, less prominent with wrist flexion.

Lister’s tubercle is a key anatomical landmark for obtaining standard proximal transverse view and identifying and scanning extensor tendon compartments and the distal radioulnar joint.

The pisiform and scaphoid tuberosity are the anatomical landmarks that help to identify the carpal tunnel on a volar transverse view of the wrist.

Synovial reflections should be evaluated fully by following them proximally or distally to the joint cleft depending on the joint being scanned. This is particularly important in scanning MCPs (metacarpophalangeal joints) because the dorsal synovial recesses of the MCPs continue far proximal to the joint cleft.

Localizing Doppler signal to synovial tissue identified during gray-scale scanning will help avoid mistaking feeding vessels for synovial hyperemia (or active inflammation).

Ligamentous structures such as the triangular fibrocartilage complex can be assessed for hyperechoic densities of calcium deposition such as chondrocalcinosis.

Soft tissue nodules can be differentiated based on their location and their echotexture: anechoic vs. isoechoic and homogeneous vs. isoechoic to hyperechoic and heterogeneous.

All pathology should be imaged in orthogonal planes for confirmation of abnormality.

The diagnosis of nerve impingement can be established by whether the nerve is swollen just proximal to the point of impingement in comparison to the nerve caliber further proximally.

Transducer “rocking” maneuver can be used to avoid artifacts caused by tendon and nerve anisotropy, which makes structures appear dark (hypoechoic or even anechoic), mimicking effusion.

One should avoid excessive compression of the tissues with the transducer (especially of the dorsal wrist and MCPs); otherwise, effusions and power Doppler signal could be missed. “Floating the transducer” by keeping a 1–3-mm layer of the gel between the transducer and the skin will prevent unintended tissue compression.

It is essential to perform scanning in a logical and routine progression to avoid missing/forgetting to scan any relevant structures. Slide the transducer from one view to the next, rather than picking up the transducer and setting it down in a different location. Doing the latter could result in missing pathology in the interval tissues. Table 3.1 shows recommended standard scans and corresponding common pathology that can be seen with hand and wrist ultrasound.

Table 3.1 Standard scans, indications, and key features

Dorsal Wrist

Figure 3.1 shows schematic representation of extensor tendon compartments of the dorsal wris t.

Fig. 3.1

Schematic representation of the anatomical landmarks and extensor tendon compartments of the proximal dorsal wrist. (1) Lister’s tubercle, (DRUJ) distal radioulnar joint. Extensor compartments are numbered by roman numerals: (I) first extensor compartment contains abductor pollicis longus and extensor pollicis brevis; (II) second extensor compartment contains extensor carpi radialis longus and brevis; (III) third extensor compartment contains extensor pollicis longus; (IV) fourth extensor compartment contains extensor indices and extensor digitorum tendons; (V) fifth extensor compartment contains extensor digiti minimi; (VI) sixth extensor compartment contains extensor carpi ulnaris tendon

Lister’s tubercle , the bony prominence on the distal radius, is the key to scanning the dorsal wrist (Figs. 3.1 and 3.2). The extensor pollicis longus tendon can be followed proximally to this prominence and uses it as a pulley. All of the extensor tendon compartments of the wrist can be identified relative to Lister’s tubercle. The extensor pollicis longus (third compartment) is just ulnar to the tubercle at the distal radius, and just radial to the tubercle is the extensor carpi radialis brevis and the extensor carpi radialis longus (both in the second compartment) and then the extensor pollicis brevis and the abductor pollicis longus (both in the first compartment). So, the progression from ulnar to radial is longus, brevis, longus, brevis, longus. Ulnar to the extensor pollicis longus is the fourth compartment containing the extensor indicis and the extensor digitorum. Further ulnar, in the space between the radius and ulnar, is the extensor digiti minimi (fifth compartment). These tendons can best be identified and evaluated in the transverse/short axis view. This view is also useful for evaluation of the distal radioulnar joint in a plane just deep to the extensor digiti minimi. Take care not to misidentify the extensor digiti minimi as radioulnar synovium due to anisotropic artifact making the tendon hypoechoic.

Fig. 3.2

Dorsal wrist . (a) shows a transverse ultrasound image through the radius (R) and ulna (U). Second, third, fourth, and fifth refer to the extensor compartments. Lister’s tubercle (Lis) is the most important landmark used for orientation in this view. (b) shows a transverse view through the scaphoid (S) and lunate (L). The hyperechoic ligament connecting these two bones is clearly visible, and the hypoechoic radiocarpal synovium (Syn) is just superficial to the ligament. Note the normal retinaculum (asterisk) over the fourth compartment extensors at this level. (c) shows a transverse view at the level of the capitate (C). (d) is a photographic depiction of the transducer scanning position required to obtain images (a–c). (e) shows the transducer scanning position that should be used to obtain the wrist dorsal longitudinal view. (f) is a longitudinal view of the wrist with the transducer positioned over the radius (R), lunate (L), and capitates (C). The orange lines show where the transverse images were obtained relative to the longitudinal view. Radiocarpal synovium fold (Syn) and extensor retinaculum (asterisk) can also be appreciated on this image

Sliding the transducer distally to Lister’s tubercle will result in imaging the scaphoid bone and the scapholunate ligament (Fig. 3.2b). The radiocarpal joint capsule and synovium will fold distally over this region, while sliding slightly further distally will bring the capitate bone and the overlying intercarpal synovium into view (Fig. 3.2c). Note that the head of the capitate is more rounded than the lunate in the dorsal transverse view. In addition, notice that there is a dorsal feeding vessel that emerges from the lunate [2], which could be confused with a small erosion and synovial hyperemia.

The longitudinal view to the wrist can be obtained in the midline by positioning the proximal edge of the transducer just ulnar to Lister’s tubercle and the distal end pointed at the third MCP (Figs. 3.2e, f). With this transducer position, the radius, lunate, and capitate bones should be visible, as well as the folds of the radiocarpal and intercarpal synovium. The normal extensor tendon retinaculum should be identified to avoid mistaking it for swollen tenosynovium. Sliding radially will bring the scaphoid into view. Note the effect that wrist flexion and extension have on the appearance of the synovium: extension of the wrist will make the synovial folds appear more prominent and could be mistaken for synovial hypertrophy. Power Doppler views in this plane will normally show signal from the dorsal carpal arch, superficial to the capitate, and should not be mistaken for acute synovitis/hyperemia.

Radial Wrist

The most common reason to scan the radial wrist is to evaluate for DeQuervain’s tendinitis —retinacular thickening of the first compartment tendons (Fig. 3.3). The term DeQuervain’s tenosynovitis, while classically used, is a misnomer as the flexor retinaculum (not tenosynovium) is the anatomic structure found surrounding the first compartment tendons at the distal radius. Normally this retinaculum is barely visible at less than a millimeter of thickness. Retinacular abnormalities are most easily appreciated in transverse view, while structural abnormalities of the tendon fibers are more easily seen in longitudinal view. The radial artery passes through the anatomic snuff box distal to the radius and should not be confused with synovial hyperemia. Slightly more distally, the first carpal-metacarpal joint can be seen, just deep to the abductor pollicis longus tendon.

Fig. 3.3

Radial wrist . (a) is a transverse ultrasound image through the distal radius at the level of the orange line in (b), the longitudinal view through the radial wrist. The arrows point to the thin retinaculum normally seen over the first compartment tendons. (c, d) depict transducer scanning position over the radial wrist to obtain images (a, b). (EPB) extensor pollicis brevis, (APL) abductor pollicis longus, (R) radius

Scanning the radial wrist in longitudinal view can sometimes result in mistakenly positioning the transducer over the second compartment instead of the first. Avoid this mistake by first identifying the first and second compartments in transverse section and then scanning the intended tendons in longitudinal plane.

Ulnar Wrist

The ulnar wrist scan is performed to evaluate the extensor carpi ulnaris (ECU), the distal ulna, and the triangular fibrocartilage complex (TFCC) (Fig. 3.4). This view is especially important to the rheumatologist, given the frequency of ECU involvement in rheumatoid arthritis (RA) and the specificity of ulnar styloid erosions to RA [3]. Additionally, calcifications in the TFCC can help to evaluate for calcium pyrophosphate dihydrate (CPPD) arthropathy. In fact, ultrasound was shown to be highly specific and slightly superior to conventional X-rays in detecting chondrocalcinosis of TFCC [4]. Degenerative tears of the TFCC can also be found and commonly seen in people over 50.

Fig. 3.4

Ulnar wrist . (a) shows a longitudinal ultrasound image for the ulnar wrist, with a focus on the extensor carpi ulnaris (ECU), and triangular fibrocartilage complex (TFCC). (b) shows the transverse view through the ECU and ulna (U) taken at the level of the orange line in (a). (c, d) show the transducer scanning position needed to achieve the images in (a, b). (U) ulna, (L) lunate, (T) triquetrum, (ECU) extensor carpi ulnaris, (TFCC) triangular fibrocartilage complex

To make the examination comfortable for the patient, have the patient sit across from the examiner, and bend the elbow to 90°, which will expose the ulnar wrist to the examiner. In finding proper transducer positioning, it will be helpful to remember that the ECU is dorsolateral to the styloid, rather than just lateral. Slight radial deviation of the wrist will help pull the ECU tight and reduce anisotropic artifact due to tendon curvature in a relaxed position.

Volar/Palmar Wrist

The volar view is most often used to assess for median nerve compression/carpal tunnel syndrome and flexor tendon “tenosynovitis” or retinaculitis. Schematic representation of the carpal tunnel at the level of scaphoid and pisiform is shown in Fig. 3.5. Flexor carpi radialis , palmaris longus, and flexor carpi ulnaris lay outside of the carpal tunnel, which is enclosed by the flexor retinaculum (Fig. 3.5). Ulnar artery and ulnar nerve lay within Guyon’s canal, a separate compartment.

Fig. 3.5

Schematic representation of the volar wrist and carpal tunnel at the level of scaphoid-pisiform. (1) superficial flexor tendons, (2) deep flexor tendons, (3) flexor pollicis longus, (4) median nerve, (5) ulnar nerve

The volar view is also used for the assessment of the radiocarpal and intercarpal joints. For proper transducer placement, find the pisiform bone and the scaphoid tuberosity (Fig. 3.6)—each should be visible at the edge of the ultrasound image as these bones mark the carpal tunnel inlet with the flexor retinaculum stretching between them and the median nerve usually abuts the retinaculum and is surrounded by flexor tendons that are encased in thin tendon sheaths.

Fig. 3.6

Volar wrist . (a) shows a transverse view through the inlet to the carpal tunnel taken at the level of the orange line on the longitudinal view shown in (b). The pisiform (P) and scaphoid tuberosity (S) create the sides of the carpal tunnel, the lunate (L) is the bottom, and the retinaculum (arrow) is the top. The median nerve has a coarser, slightly more hypoechoic internal architecture than the surrounding tendons, and has a bright epineurium that the tendons lack. The probe scanning position necessary to achieve the images in (a, b) are illustrated in (c, d). (P) pisiform, (L) lunate, (S) scaphoid, (f) flexor tendon, (M) median nerve, (FCR) flexor carpi radialis, (u) ulnar nerve, (arrow) retinaculum, (R) radius, (C) capitate

Typically in obtaining this view, the tendons in the tunnel are very anisotropic and can be made bright by rocking the transducer—pointing it more toward the elbow. As a more proximal slice of the wrist is obtained with this transducer position, the transducer should be slid distally at this new angle until the proper bone landmarks are once again visible. Making the tendons bright will help assess for tenosynovitis and synovitis deep to the palmar radiocarpal ligaments. Both synovitis and palmar carpal erosions are more easily identified on longitudinal views of the palmar wrist (Fig. 3.6b, d). The median nerve can be distinguished from the tendons by the bright epineurium surrounding it, which appears as hyperechoic “tram-track” lines on both sides of the nerve on longitudinal view and as a bright oval on transverse view. The fibers of the nerve itself are slightly hypoechoic relative to the tendons and do not have the fibrillar pattern typical for tendons, but rather a coarser pattern resembling a honeycomb. Nerves are also less anisotropic than tendons. Thus, in transverse view, when the tendons are very dark due to anisotropy, the nerve will be brighter than the tendons, but when the tendons are made maximally bright, the nerve will be slightly darker than the tendons. This technique can be useful to help identify the nerve. In longitudinal view, the tissues typically become anisotropic in the distal part of the carpal tunnel due to the wrist naturally assuming an extended position when it is supinated. By placing a rolled-up towel under the metacarpals, the wrist can be positioned closer to neutral, thus allowing better visualization of the distal carpal tunnel.

Finger Joints

Dorsal views of the metacarpal-phalangeal (MCP) joints require floating the transducer on a layer of gel to optimize the image. There is a natural dip in the contour of the bone between the articular portion of the metacarpal and the metacarpal neck, most prominently in the second MCP (Fig. 3.7). This dip can mimic an erosion, especially as this is a region that tends to get erosions. However, the bony groove will not have any irregularities in transverse views, thus differentiating normal anatomy from an erosion. Transverse views will also show synovium which has been pushed away from the midline by the extensor tendon. This highlights the importance of orthogonal views to confirm sonographic pathology.

Fig. 3.7

Dorsal and lateral metacarpal–phalangeal joint . (a) shows a dorsal longitudinal view of a metacarpal-phalangeal joint (MCP). The transverse section through the orange line is shown in (b). The arrow points to the thin synovial reflection, normally seen proximal to the joint cleft. (c, d) are both lateral longitudinal views through the MCP, with c being more dorsal and 1d being more volar. The lateral collateral ligament is best seen in (c). (e–g) show transducer scanning position required to obtain the ultrasound images. (Me) metacarpal, (Ph) phalange, (e) extensor tendon, (col) collateral ligament

Ulnar views of the fifth MCP joint and the radial views of the second MCP joint are critical for assessment of bone erosions and synovitis at the capsular attachment. In fact, ultrasound sensitivity for MCP joint erosions approaches that of MRI in the second and fifth MCP joints but is significantly less in the third and fourth MCP joints due to the lack of access for medial and lateral views. As one scans from a lateral to a dorsolateral view, the metacarpal part of the joint transitions from a curved to a flat, “ski slope”-shaped contour.

Volar views of the MCP joint need to extend proximally enough to visualize the full extent of the synovial capsule which stretches back beyond the palmar plate (Fig. 3.8). This reflection is normally a flat hypoechoic line which swells like a balloon when inflamed and with effusion. The flexor tendon lies superficial to the palmar plate over the metacarpal and is directly over the phalanx in the distal part of the joint. The A1 pulley is superficial to the flexor tendon at the level of the MCP joint and is normally very thin and hard to visualize, especially in longitudinal view. Thickening of the A1 pulley can contribute to mechanical “trigger finger.”

Fig. 3.8

Volar MCP and PIP joints . (a) shows the volar longitudinal view of the MCP joint with the orange line on the section where the transverse in (b) was taken. The arrow shows the small synovial reflection proximal to the MCP joint cleft and to the palmar plate (pp). Note that the palmar plate is between the flexor tendon and the metacarpal bone on the metacarpal side of the MCP joint. (c) shows the volar longitudinal view through the proximal interphalangeal joint, with the orange line indicating the level at which (d), the PIP volar transverse view, was taken. The arrow again points to the synovial reflection. Photographs (e–h) show transducer scanning position required to obtain images (a–d). (Me) metacarpal, (Ph) phalanx, (pp) palmar plate, (F) flexor tendon, (mPh) middle phalanx

The dorsal view of the proximal interphalangeal (PIP) joint shows the extensor hood, which can be inflamed and distended in cases of synovitis, but joint effusion is more likely to be visualized on the volar aspect of the joint where the capsule reflects proximally over the phalangeal bone surface (Fig. 3.8). Dorsal views of the distal interphalangeal (DIP) joint also allow visualization of the nail bed where lesions of psoriatic arthritis (PsA) might be found, while the volar views allow visualization of the flexor tendon insertion.

Pathology

Synovitis

Synovial tissue is intra-articular, typically hypoechoic, and poorly compressible. Power Doppler signal may be present depending on the degree of hyperemia. In the finger joints, the synovium reflects proximally from the joint cleft. In the dorsal wrist, the synovial tissue reflects distally for the radiocarpal and intercarpal joints, but the radioulnar synovium reflects proximally (Fig. 3.9). In the volar wrist, the radiocarpal synovium also reflects proximally. In evaluating Doppler signal, ensure that you do not mistake normal vascular flow for synovitis by first identifying the synovium in gray scale and then looking specifically in that tissue for Doppler signal. The capsular attachment points are also worth evaluating for Doppler signal especially as these are the spots where erosions are most likely to occur in erosive arthritis.

Fig. 3.9

Synovial hypertrophy, effusion, and power Doppler synovitis. (a) demonstrates a dorsal longitudinal view of an MCP joint with synovial hypertrophy outlined, extending far proximal to the joint cleft. This image also shows synovial hyperemia (grade 2—more than one vessel but less than half of the volume of the synovium) and synovial effusion (asterisk). (b) demonstrates a dorsal longitudinal view of the wrist with synovial hypertrophy outlined, extending distal to the joint cleft of the radiocarpal joint and to that of the intercarpal joint. (c) demonstrates a dorsal longitudinal view, while (d) demonstrates orthogonal (dorsal transverse) view of the same wrist. Note that there is synovial hypertrophy and grade 3 (radiocarpal) and grade 2 (midcarpal) power Doppler signal/synovitis. There is a small radiocarpal effusion (asterisk). (R) radius, (L) lunate, (C) capitate, (e) extensor tendons (fourth compartment)

The ultrasound assessment for wrist synovitis is comparable to MRI [5]. Semiquantitative assessment of power Doppler signal can be established based on previously established criteria: grade 0 no signal, grade 1 single dot of Doppler, grade 2 less than half of the synovial tissue is filled with Doppler, grade 3 more than half of the synovial tissue is filled with Doppler [6].

Erosions

Erosions are defined as intra-articular breaks in the cortical margin which can be seen in perpendicular planes. Sometimes, it is impossible to tell whether the image represents an erosion or an osteophyte in a single plane of view; however, on the orthogonal view, an erosion will still look like a “pot hole” in the cortex, while an osteophyte will be a hyperechoic lesion superficial to the surface of the cortex (Figs. 3.10 and 3.11). Ultrasound has been found to be more sensitive for erosive changes in the finger joints than radiographs [7]. The sides of the MCP and PIP joints are particularly important to evaluate for erosions. In the wrist, the lunate bone presents a challenge to the sonographer as there is normally a feeding vessel that enters the lunate. The spot where the vessel enters the lunate can appear as an erosion (Fig. 3.12) and sometimes as an erosion with Doppler signal! To complicate this issue further, real lunate erosions tend to occur in this same location. True pathologic erosions are generally larger, have more irregular cortical borders, and frequently cause reverberation artifacts deep to the surface of the erosion. Erosions that are larger than 2.5 mm are more specific to inflammatory erosive forms of arthritis like RA (specificity of 68%) [3]. Erosions smaller than 2 mm can be seen in osteoarthritis, and erosions of <1 mm can be seen in people without arthritis. The location of the erosion can also suggest its cause: erosions at the ulnar styloid, second MCP, and fifth MCP are more specific to RA (87% when greater than 2.5 mm). Sensitivity of ultrasound of MCP erosions is 42% compared to multidetector CT, with specificity of 91%. By comparison, MRI sensitivity is 68%, and specificity is 96% [8]. However, due to the availability of the lateral acoustic window in the second MCP, ultrasound sensitivity for erosion in these joint increases to 92%, compared to only 25% in the fourth MCP [8].

Fig. 3.10

Erosion vs. osteophyte . (a, b) demonstrate longitudinal and transverse views of a cortical erosion (dashed measurement lines) on the dorsal side of a metacarpal (Me), with a normal-appearing phalanx (Ph). In contrast, (c, d) show orthogonal views through an osteophyte (arrows) on the dorsal surface of an MCP joint. The erosion is a “pothole” in the cortical surface, while the osteophyte is a jagged protuberance from the bone surface which results in a cortical defect that is sometimes called “step-off” lesion

Fig. 3.11

Metacarpal radial side erosions . (a) demonstrates numerous small erosions (arrows) on the radial longitudinal view of the metacarpal (Me), just deep to the collateral ligament (col) and proximal to the phalanx (Ph). Doppler signal suggests that further damage is occurring. (b) demonstrates the transverse radial view of the metacarpal, confirming that the breaks in the cortical margin can be seen in perpendicular plains

Fig. 3.12

Lunate vascular channel vs. quiescent erosion vs. active erosion . (a) is a transverse view through the first carpal row, and (b) is the longitudinal view through the midline of the wrist. The arrows point to the vascular channel in the lunate. (c) demonstrates quiescent erosion (i.e., doesn’t contain power Doppler signal) (dashed measurement lines) in the dorsal aspect of the metacarpal head in advanced rheumatoid arthritis; please note that there is active power Doppler synovitis in the cleft of metacarpal joint, and the joint shows subluxation. (d) demonstrates active erosion (i.e., one that contains power Doppler signal indicative of active rheumatoid pannus) on the radial side of the second metacarpal in rheumatoid arthritis. (L) lunate, (S) scaphoid, (R) radius, (C) capitate, (4th) fourth compartment tendons, (Me) metacarpal, (Ph) phalanx

In addition to the location of erosion, other ultrasound findings may help differentiate RA from similarly erosive forms of arthritis such as psoriatic arthritis. The distance between the ventral side of the nail and the dorsal aspect of the distal phalanx may be increased in PsA compared to patients with RA [9]. Furthermore, Gutierrez M et al. have found that paratenon Doppler signal over the extensor tendons at the level of the MCP joints is found in 50/82 fingers studies in 20 patients with PsA, compared to only 4/83 fingers studies in 18 patients with RA [10] (Fig. 3.13).

Fig. 3.13

Extensor tendinitis . (a) shows a dorsal longitudinal view of the interphalangeal joint. The asterisk indicates synovial proliferation, while the arrows indicate swelling around the extensor tendon (e). The Doppler view in (b) shows hyperemia in the synovium but more so in the paratenon region around the extensor tendon. This is also shown in transverse in (c)

Tendon and Ligament Pathology

Tenosynovitis can be the initial presentation of RA. In 90 consecutive patients with RA, half had tenosynovitis in at least one wrist tendon [11]. Tenosynovial effusions will appear as anechoic halos around tendons in transverse view. Very hypoechoic muscle fibers can be mistaken for a tenosynovial effusion as they transition into tendon fibers. These two are most easily differentiated by scanning proximally toward larger and more obvious parts of the muscle belly. Tenosynovial effusion can also be confused with thickened retinaculum on the dorsal wrist (especially first and fourth compartments) and with thickened pulleys on the volar MCP joints. Careful imaging will show that the retinaculum is outside of the tendon sheath and is hypoechoic rather than anechoic as long as no anisotropic artifact is present. Furthermore, both retinaculum and pulley lesions are very focal, while tenosynovial effusions tend to spread down tendon sheath (Fig. 3.14). On the dorsal side of the fingers, the extensor tendon lacks a tenosynovium; thus, a tendinitis and/or paratenonitis is possible but not a true tenosynovitis.

Fig. 3.14

Flexor tendon pathologies . (a) demonstrates a normal flexor tendon (f), with a normal A1 pulley (arrow). (b) shows the loss of normal fibrillar fibers of the flexor tendon (^) just distal to the A1 pulley (arrow) in a patient with a trigger finger. There is a subtle indentation of the A1 pulley on the flexor tendon. (c) shows a finger with flexor tenosynovitis (asterisk). Notice that the tenosynovium is swollen all along the flexor tendon, rather than focally, and is compressed at the level of the A1 pulley (arrow). (d) shows a mild case of Dupuytren’s contracture, with the thick arrow pointing to the thickened and disorganized fascia, while the thin arrow points to the A1 pulley. The thickened fascia causes some artifactual hypoechoic signal from the tendon deep to it

In stenosing tenosynovitis , the A1 pulley is thickened causing pinching of the flexor tendon as it tries to squeeze through the narrowed tunnel between the A1 pulley and the volar plate. The tendon thus becomes thickened distal to the A1 pulley, and with a dynamic exam, one can see the tendon fibers stop moving as the thickened tendon reaches the A1 pulley. In Dupuytren’s contracture, the primary abnormality is thickened and disorganized fascia fibers superficial to the flexor tendon, which exerts a downward force on the tendon resulting in finger contracture.

The pathophysiology of DeQuervain’s disease is similar to that of the trigger finger; due to microtrauma, the retinaculum at the distal radius becomes thickened and hypoechoic (Fig. 3.15). Thus, when providing an injection for treating this condition, the needle should be passed as quickly as possible through the sensitive retinaculum, and aspiration should not be attempted. In addition, some patients develop a true tenosynovitis which can be diagnosed by using power Doppler. Tenosynovitis of this compartment can occur due to microtrauma but also can be seen in scleroderma, crystal-induced, and inflammatory arthritis.

Fig. 3.15

DeQuervain’s tenosynovitis . (a) shows a longitudinal view of the first extensor compartment: the extensor pollicis brevis (epb) tendon, with the thickened retinaculum (arrow) above, and the radial styloid below (R). (b) shows the first compartment in transverse. The retinaculum is thickened primarily around the extensor pollicis brevis (epb), and there is a septum between the epb and the abductor pollicis longus (apl). In such a case, ultrasound can help direct the injection to the most affected retinaculum. (c) demonstrates longitudinal while (d) demonstrated transverse view of the distal first extensor compartment with tenosynovial thickening (arrows), apl tendon thickening, and intrasubstance splitting indicative of chronic tendinosis. Active tenosynovitis and tendinitis distal to the extensor retinaculum are suggested by the presence of power Doppler signal within tenosynovium and the tendon proper, respectively. (R) radial styloid, (Sc) scaphoid, (Tr) trapezium

Medially, the extensor carpi ulnaris tendon sheath can be inflamed in RA and other inflammatory conditions (Fig. 3.16). There can also be associated erosions of the distal ulna which would be suggestive of RA. Distal to the ulna is the TFCC. Ultrasound has not been found to be a sensitive technique for evaluation of TFCC tears as these tears typically are in the deep part of the TFCC which is hidden from the ultrasound waves. However, calcification of the TFCC due to CPPD is better visualized by ultrasound than by radiography [4, 12]. The hyperechoic stippling that occurs in the ligaments and meniscal homologue due to CPPD is as dense as bone. Turning the gray-scale gain down until all the soft tissues become anechoic will highlight the bone and CPPD deposits (Fig. 3.16). Chondrocalcinosis deposits can also be seen in the scapholunate ligament. This ligament can be ruptured due to mechanical trauma and also due to severe inflammation from crystalline or erosive arthritis. Ligamentous tear presents as absence of the typical hyperechoic fibrils between the scaphoid and lunate, increased distance between the bones statically [13], or widening of the distance between the bones dynamically as the patient squeezes a ball in the palm of their hand (Fig. 3.17). The normal scapholunate interval has been reported to be 2.9–4.5 mm [14].

Fig. 3.16

Ulnar pathology . (a) demonstrates tenosynovitis of the extensor carpi ulnaris tendon (ecu) superficial to the ulna (U) sulcus and trapezium (Tr), with the arrow pointing to distended tenosynovium. (b) is the corollary transverse view of ECU tenosynovitis. (c) shows a longitudinal view of ECU tendinitis with hypogenic tendon fibers and Doppler signal along the tendon and along erosions (^) in the distal ulna. (d) shows the transverse view of the same region of erosion and clarifies that the ECU tendon is subluxed out of the ulnar sulcus. (e, f) exemplify hyperechoic changes of the triangular fibrocartilage complex (asterisk) typical for calcium pyrophosphate deposition disease in longitudinal and transverse views

Fig. 3.17

Scapholunate ligament pathology . (a) demonstrates an intact scapholunate ligament (arrow) between the scaphoid (S) and lunate (L) and below the extensor tendons of the 4th, 3rd, and 2nd compartments. (b) depicts a torn scapholunate ligament (arrowhead) in a relaxed wrist—the hyperechoic ligament fibers are missing, and the distance between the scaphoid and lunate is slightly increased. (c) depicts the same wrist while squeezing a ball, resulting in widening of the distance between the scaphoid and lunate due to the torn ligament. (d) demonstrates calcification of the scapholunate ligament (arrow). Lunate osteophytes can also be readily appreciated

Ultrasound can aid in detection of subclinical tenosynovitis in scleroderma patients (27% with the use of ultrasound vs. 6% on clinical examination) [15]. The same study compared hand involvement between scleroderma and rheumatoid arthritis and showed that the frequency of ultrasound detected tenosynovitis was comparable between both conditions (27% of scleroderma vs. 25% of rheumatoid cases). While “inflammatory tenosynovitis” was seen in both scleroderma and rheumatoid patients, the so-called mixed and fibrosing tenosynovitis (described as hyperechoic tendon sheath thickening) were the unique sonographic patterns seen only in scleroderma patients. In addition, sclerosing tenosynovitis was typically localized to extensor tendons. It is not known, however, how these different sonographic patterns relate to different disease activities or different stages of the tendon and tenosynovial involvement in scleroderma patients (Fig. 3.18).

Fig. 3.18

Extensor tenosynovitis in scleroderma . (a) demonstrates dorsal transverse view, while (b) demonstrates dorsal longitudinal view of the distal wrist. Note the thickening and the fibrotic appearance of the tenosynovium of the fourth extensor compartment tendons. (R) radius, (L) lunate, (C) capitate, (S) scaphoid, (4th e)  fourth extensor compartment tendons

Nodules

Ligamentous tears can lead to ganglion cyst formation; cysts on the dorsal wrist are typically superficial to the scapholunate ligament (70%), while 13% are volar, arising from the flexor tendon sheath, and another 12% are volar but not from the flexor tendons [7]. These cysts tend to have well-defined margins, anechoic internal appearance, and produce acoustic enhancement (Fig. 3.19). Despite being fluid-filled, they are frequently non-compressible due to a tight surrounding capsule. In addition, large ganglia may contain some hyperechoic speckles within the anechoic gel-like material due to suspended air bubbles. These air bubbles are a clue to the hyperviscosity of the cyst contents, as air bubbles will not be found in regular synovial fluid. Most ganglia are multiloculated, while only 12% have surrounding Doppler signal [16]. Clinically, ganglion cysts may mimic giant cell tumors. By ultrasound, giant cell tumors are located near flexor tendons; are hypoechoic and homogeneous, as opposed to anechoic cysts; and almost all have either peripheral or central vascularity [17].

Fig. 3.19

Ganglion cyst . (a) shows a longitudinal view of a ganglion cyst (arrow) distal to the radius (R), superficial to the lunate (L) and capitate (C), and below the extensor tendons. The ganglion has very defined borders and an anechoic center. (b) shows the same cyst in transverse, between the scaphoid (S) and capitate (C). (c) demonstrates a ganglion cyst associated with a flexor tendon (f) over the metacarpophalangeal joint in longitudinal view. Notice that the flexor tendon is more hyperechoic deep to the cyst than to either side of the cyst due to “acoustic enhancement” artifact. The transverse view in (d) shows the characteristic multiloculated ganglion structure

Gouty nodules in the wrist are quite different in appearance from ganglia, with heterogeneous internal echogenicity, no acoustic enhancement, and occasionally cast shadows on the underlying tissues when the tophi are calcified [18, 19]. Gouty nodules are associated with other ultrasound findings typical for gout such as the double-contour sign, where monosodium urate crystals precipitate on the surface of hyaline cartilage and reflect ultrasound waves (Fig. 3.20). This produces a thick, irregular line parallel to the contour of the bone (double contour) that is visible independent of the angle with which the sound waves strike the monosodium urate lined surface [18]. Rheumatoid nodules can also be seen in the hands. In contrast to gouty nodules, these are most commonly homogeneous with a hypoechoic center [19]. Another distinguishing feature is that RA nodules are usually single, while tophaceous nodules tend to deposit in clusters [20].

Fig. 3.20

Gouty nodules (tophi) and double-contour sign . (a) demonstrates dorsal longitudinal view of a metacarpophalangeal joint and (b) demonstrates an orthogonal view of the same joint through metacarpal head. Several clustered tophi (asterisks) and double-contour sign (arrows) can be readily identified. Double-contour sign is reproduced in both orthogonal views and has irregular and “bulky” appearance which distinguishes it from interface sign sometimes seen in joints with small effusion. (Me) metacarpal, (Ph) phalanx

Nerve Impingement

Ultrasonography is helpful in the evaluation of nerve impingement in the wrist, particularly median nerve impingement (Fig. 3.21). Numerous studies have shown that nerve impingement results in nerve swelling proximal to the impingement point and that the degree of nerve swelling correlates with the degree of nerve dysfunction as assessed by EMG/NCV studies [21]. Maximal median nerve cross-sectional area measurement has emerged as the most validated ultrasound criteria for diagnosing median nerve impingement [22]. Median nerve size less than 8 mm² has a negative likelihood ratio for carpal tunnel syndrome of 0.13, while a size of equal to or greater than 12 mm² has a positive likelihood ratio of 19.9 [23]. For median nerve sizes between these limits, comparison to the asymptomatic side or comparison to the size of the same nerve 12 cm proximal to the carpal tunnel is useful: a distal to proximal ratio of greater than 1.4 has been shown to be both sensitive and specific for median nerve impingement [24]. In cases where the median nerve is bifid, the two portions of the median nerve can be measured separately, and then their surface areas are combined [25, 26]. In addition to establishing median nerve impingement, ultrasound can help detect causes for the impingement such as synovial or tenosynovial swelling or mass lesions (from crystal deposition, ganglion cysts, etc.). Furthermore, ultrasound can help detect anatomic abnormalities such as flexor digitorum muscle that extends further distally than normal into the carpal tunnel. Similarly, for questions of ulnar nerve impingement in Guyon’s canal, the maximal nerve caliber can be compared to ulnar nerve caliber more proximally in the forearm.

Fig. 3.21

Carpal tunnel pathology . (a) demonstrates, in longitudinal section, effusion and synovium (asterisk) from the joints between the radius (R), lunate (L), and capitate (C) exerting upward pressure on the flexor tendons (f) and the median nerve (M). This results in constriction of the nerve and swelling proximal to the retinaculum. (b) confirms the findings in transverse view of the carpal tunnel, with the pisiform (P) in view medially. (c, d) show tenosynovial hypertrophy and effusion (arrows) of the flexor (f) tendons surrounding the median nerve (M) and potentially causing nerve impingement. The scaphoid tuberosity (S) makes the lateral border of the carpal tunnel. (e, f) depict hyperechoic material (outlined) in the radiocarpal joint due to CPPD deposition disease causing constriction of the median nerve. (g) demonstrates transverse view of the carpal tunnel showing bifid median nerve (M1, M2), which is considered a normal variant but can be associated with median nerve dysfunction and predisposition to carpal tunnel syndrome. (h) demonstrates transverse view of the carpal tunnel showing bifid median nerve with patent median artery (arrow)

Conclusion

Ultrasound examination of the hand and wrist can be extremely useful in the evaluation of patients with tendon, joint, or nerve pathology. Evaluation and management of common rheumatologic conditions involving the hand and wrist, such as inflammatory arthritis and crystal-induced arthritis, as well as mechanical conditions such as DeQuervain’s tendinitis or carpal tunnel syndrome, can be enhanced by the use of musculoskeletal ultrasound.

Review Questions

• 1. On a dorsal transverse image of a wrist, the radioulnar joint synovium can best be identified in which of the following locations?

  • (a) Deep to the extensor digiti minimi tendon

  • (b) Radial to Lister’s tubercle

  • (c) Distal to the radius

  • (d) Distal to the lunate

• 2. On ultrasound imaging, DeQuervain’s tendinitis is most commonly manifested by which of the following?

  • (a) Anechoic, compressible material surrounding the first extensor compartment at the distal radius

  • (b) Hypoechoic, non-compressible material surrounding the first extensor compartment at the distal radius

  • (c) Loss of fibrillar architecture of the extensor pollicis longus tendon

  • (d) Disruption of the cortical margin at the distal radius seen in orthogonal planes

• 3. Ulnar imaging of the wrist reveals a 2.5-mm cortical disruption of the ulna cortical surface and anechoic material surrounding the extensor carpi ulnaris tendon as well as Doppler signal surrounding the extensor carpi ulnaris. These findings most suggest which of the following?

  • (a) Osteoarthritis

  • (b) Gout

  • (c) Rheumatoid arthritis

  • (d) Psoriatic arthritis

• 4. Which of the following can help distinguish the median nerve from the surrounding tendons?

  • (a) The nerve is more anisotropic.

  • (b) The nerve has a finer echotexture.

  • (c) The nerve slides more with finger flexion.

  • (d) The nerve is surrounded by a bright epineurium.

• 5. This longitudinal view of the dorsal wrist clearly demonstrates which of the following?

  • (a) Extensor tenosynovitis

  • (b) Radiocarpal synovitis

  • (c) Intercarpal synovitis

  • (d) Dorsal ganglion cyst

• 6. These orthogonal views of the volar metacarpal-phalangeal joint demonstrate which of the following?

  • (a) Synovial effusion

  • (b) Tenosynovial effusion

  • (c) Gouty nodule

  • (d) Ruptured palmar plate

• 7. This longitudinal view of the volar wrist demonstrates which of the following?

  • (a) Muscle belly surrounding a flexor tendon, impinging the median nerve

  • (b) Tenosynovial effusion impinging the median nerve

  • (c) Median nerve with neuroma

  • (d) Gouty tophus impinging on median nerve

• 8. This transverse power Doppler scan of the volar wrist demonstrates which of the following?

  • (a) Wrist effusion

  • (b) Neuroma of the median nerve

  • (c) Flexor tenosynovitis

  • (d) Thickening of the flexor retinaculum

• 9. Which of the following most accurately describe sonographic findings in this dorsal longitudinal power Doppler image of the wrist?

  • (a) Lunate erosion, radiocarpal power Doppler synovitis, and blood flow in the dorsal carpal arch

  • (b) Radiocarpal synovial hypertrophy, lunate erosion, and radiocarpal power Doppler synovitis

  • (c) Dorsal fat pad hyperemia and cortical vascular channel of the lunate

  • (d) Cortical vascular channel of the lunate and blood flow in the dorsal carpal arch

• 10. Which of the following findings are seen on this ulnar longitudinal view of the wrist?

  • (a) Tenosynovial thickening of ECU tendon, calcification of triangular fibrocartilage, and ulnar styloid erosion

  • (b) Tenosynovial thickening of ECU tendon, calcification of triangular fibrocartilage, and ulnar styloid osteophytes

  • (c) Calcification of triangular fibrocartilage and triquetrum erosion

  • (d) Calcification of triangular fibrocartilage and triquetrum osteophytes

Answers

• 1. (a) Deep to the extensor digiti minimi tendon

• 2. (b) Hypoechoic, non-compressible material surrounding the first extensor compartment at the distal radius

• 3. (c) Rheumatoid arthritis

• 4. (d) The nerve is surrounded by a bright epineurium.

• 5. (a) Extensor tenosynovitis

• 6. (a) Synovial effusion

• 7. (b) Tenosynovial effusion impinging the median nerve

• 8. (c) Flexor tenosynovitis

• 9. (d) Cortical vascular channel of the lunate and blood flow in the dorsal carpal arch

• 10. (d) Calcification of triangular fibrocartilage and triquetrum osteophytes