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Article

Hand and Wrist Sonography

Middleton, William D. M.D.*; Teefey, Sharlene A. M.D.; Boyer, Martin I. M.D.

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Abstract

Objectives: After reading this article and completing the posttest, the learner should be able to:

  • Describe the sonographic appearance of normal structures in the hand and wrist.
  • Describe the sonographic appearance of ganglion cysts and list their common locations.
  • List the sonographic findings in tenosynovitis and in tendon ruptures.
  • Describe the sonographic appearance and list the common locations of giant cell tumors in the hand and wrist.

Sonography is an excellent modality for investigating many structures of the hand and wrist. It is best used when the problem is well localized and when the clinical question is relatively specific. Patients with diffuse hand and wrist symptoms and poorly defined clinical questions are generally best evaluated with magnetic resonance imaging. This article reviews the sonographic appearance of normal structures in the hand and wrist and describes several well-established situations in which ultrasound can provide reliable and useful information.

SONOGRAPHIC ANATOMY

The tendons of the hand and wrist appear similar to tendons elsewhere in the body. The multiple fibers in tendons produce multiple, closely packed, linear reflections within the tendon substance. 1,2 This has been referred to as the fibrillar echotexture of tendons and it is seen on longitudinal views when the long-axis of the tendon is perpendicular to the direction of the sound pulse (Fig. 1A). In this orientation, the fibers act as specular reflectors, producing high-level echoes that impart a hyperechoic appearance to the tendon (Fig. 1A). When longitudinal views are obtained at other orientations, the fibers act as scatterers of sound, producing low-level echoes that result in a hypoechoic appearance to the tendon (Fig. 1A). 2 This phenomena of variable echogenicity depending on the relative orientation of the structure being imaged and the direction of sound is referred to as anisotropy. When scanning in the transverse plane, the anisotropic effect is evident when the transducer is rocked back and forth. For this reason, frequent reorientation of the probe is often necessary when scanning in the transverse plane (Fig. 1B).

FIG. 1.
FIG. 1.:
Normal tendon. A. Dual longitudinal views of the flexor pollicis longus tendon in the thenar eminence. When viewed so that the long-axis of the tendon is perpendicular to the direction of sound (left side), the tendon demonstrates its normal hyperechoic fibrillar architecture (arrows). When viewed at a nonperpendicular angle (right side), the tendon becomes hypoechoic and the internal fibers are difficult to see. B. Same tendon viewed in a transverse plane again demonstrates the difference in the appearance of the tendon (arrows) when viewed at different angles.
Figure 1
Figure 1:
Continued

Tendon anisotropy is often seen in the hand when imaging the flexor tendons over the fingers. Because pulley mechanisms secure the tendon immediately adjacent to the bones, the tendons parallel the surface of the bone as they travel over the phalanges and the interphalangeal joints. This results in an undulating course such that on longitudinal scans, there are segments that are perpendicular to the direction of sound and segments that are not (Fig. 2). Therefore, some segments will appear hyperechoic and some will appear hypoechoic. This variability must be recognized as an effect of anisotropy to avoid confusion with tendon tears.

FIG. 2.
FIG. 2.:
Tendon anisotropy. Longitudinal view of the volar aspect of the third digit over the proximal phalanx shows the varying echogenicity of the flexor tendon (T) secondary to the effect of anisotropy. The hypoechoic segment of the tendon should not be confused as an abnormality. Also, notice the smooth, bright reflection from the surface of the proximal phalanx (arrows).

A unique aspect of tendon anatomy in the hand is the association of the deep and superficial flexors of the fingers. The flexor digitorum profundus is the deep tendon that inserts on the base of the distal phalanx and provides flexion of the distal interphalangeal joint. The flexor digitorum superficialis, which provides flexion of the proximal interphalangeal joint, is located immediately anterior to the profundus. Differentiating these tendons is easiest in the transverse plane and more difficult in the longitudinal plane (Fig. 3). At the level of the proximal phalanx, the superficial tendon splits and the two halves wrap around the profundus, ultimately inserting on the base of the middle phalanx. 3,4 This split is visible sonographically when high-resolution probes are used (Fig. 4).

FIG. 3.
FIG. 3.:
Normal flexor tendons. A. Transverse view of the flexor tendons of the finger demonstrate the flexor digitorum profundus (p) and the flexor digitorum superficialis (s). These tendons are immediately adjacent to each other and can sometimes be difficult to distinguish. B. Longitudinal view shows the flexor tendons (T) overlying the metacarpal phalangeal joint. The superficial and deep tendon are difficult to distinguish on longitudinal views.
Figure 3
Figure 3:
Continued
FIG. 4.
FIG. 4.:
Flexor digitorum superficialis split. Dual transverse views of the flexor tendons. The view on the left shows the intact proximal superficial tendon (arrows) and the view on the right shows the separation of the distal superficial tendon (arrows) as it starts to wrap around the deep tendon. The deep tendon (D) does not split.

The major nerves of the hand and wrist are also visible. They are composed of multiple internal neuronal fascicles that appear hypoechoic on high-resolution scans. On transverse views, internal nerve fascicles are roughly round and are surrounded by the hyperechoic epineurium, a loose connective tissue composed of collagen and adipose (Fig. 5). 5 Although nerves share some of the characteristics of tendons, they are less prone to anisotropy and are less echogenic than tendons.

FIG. 5.
FIG. 5.:
Normal median nerve. Transverse view of the median nerve (cursors) shows the multiple internal hypoechoic nerve fascicles surrounded by the hyperechoic epineurium.

A variety of other structures are visible with high-resolution sonography. The intrinsic muscles of the hand are seen routinely. Muscles are composed of many fascicles that are separated by fibrous tissue called the perimysium. The entire muscle group is surrounded by the epimysium. Muscle fascicles are hypoechoic and this produces an overall appearance of decreased echogenicity to muscles (Fig. 6). The perimysium creates interfaces between the fascicles that on longitudinal views, appear as linear echogenic reflections and on transverse views, appear as diffuse speckles within a hypoechoic background. 6

FIG. 6.
FIG. 6.:
Normal muscle. Transverse view of the hand demonstrates the hypoechoic appearance of the interosseous muscles (I) and the lumbrical muscles (L). The hyperechoic flexor tendons (T) are seen adjacent to the lumbrical muscles, and the shadowing hyperechoic metacarpals (M) are seen in the deeper aspect of the hand.

The external cortical surface of superficial bones can be visualized well with sonography as a smooth bright reflection (Fig. 2). Therefore, abnormalities that alter the bony surface can be detected sonographically. Although sonography is generally not used as a primary technique for imaging the bones, occult bone lesions are occasionally detected during the evaluation of the overlying soft tissues.

Articular cartilage is a homogeneous structure with few internal reflectors. Thus, it produces few internal echoes. It appears as a thin, smooth, anechoic layer overlying the cortical bone (Fig. 7). In the hand, articular cartilage is often seen well at the metacarpal-phalangeal joints and the interphalangeal joints. 7 Despite its lack of internal echoes, it should not be mistaken for joint fluid. Ligaments have properties similar to tendons but are much more difficult to visualize in the hand and wrist. 7 The retinacula that secure tendons in place are visible on both the dorsal and volar aspect of the wrist (Fig. 8). Digital arteries are now routinely visible with high-frequency color and power Doppler (Fig. 9).

FIG. 7.
FIG. 7.:
Normal cartilage. Longitudinal view of the metacarpal head demonstrates the anechoic layer of articular cartilage (cursors) overlying the metacarpal head. This cartilage measured 0.5 mm in thickness.
FIG. 8.
FIG. 8.:
Normal retinacula. Transverse view of the dorsal aspect of the wrist demonstrates the retinacula (cursors) overlying the extensor digitorum tendons (T). The retinacula appears hyperechoic in the region where its fibers are oriented perpendicular to the sound and appears hypoechoic in other regions.
FIG. 9.
FIG. 9.:
Normal digital arteries. Transverse power Doppler image of the third finger overlying the middle phalanx demonstrates blood flow in the paired digital arteries (arrows) seen on either side of the flexor tendons (T).

TECHNICAL ASPECTS

At our institution, patients undergoing hand and wrist sonography are seated and the radiologist faces the patient to scan. The wrist is placed in a neutral position on an adjustable stand and a small rolled towel is placed beneath the wrist to allow easier movement during the study. We have found that a mound of gel, rather than a stand-off pad, often facilitates proper transducer orientation. One particular advantage ultrasound offers is the ability to perform a dynamic study of the hand and wrist. Given the intimate relationship of many of the pathologic processes of the hand and wrist to the tendons, active or passive flexion and extension of the wrist or fingers during the sonographic examination will not only help to orient the radiologist to the anatomic structures being scanned but also localize the pathologic process to a particular structure. Another capability of sonography is the ease with which the contralateral extremity can be scanned to obtain instant comparison. This can be quite valuable when abnormalities are subtle or confusing.

Because the structures of the hand and wrist are all so superficial and many are quite small, adequate sonographic evaluation is more dependent on high-resolution techniques than almost anyplace else in the body. Because penetration requirements are limited, high-frequency transducers can be used. For most structures in the hand and wrist, frequencies in the range of 10 to 15 MHz are most appropriate. These types of probes are now available on most high-end ultrasound equipment. Because resolution in the near field is best with linear array probes, they should be used almost exclusively for hand and wrist sonography.

A number of new techniques are now available to improve image quality. One-and-one-half-dimensional array transducers allow for focusing in the elevational plane and can reduce the thickness of the sonographic slice, thus producing improved spatial resolution (Fig. 10). Tissue harmonic imaging analyzes the harmonic signals created by the fundamental sound pulse and reduces image noise. 8 Real-time compounding steers the sound in multiple directions and produces images with reduced noise as well (Fig. 11). Extended field of view capabilities are now becoming widespread and reduce the limitation of the narrow field of view intrinsic to real-time sonography (Fig. 12). This allows for improved display of large lesions and improved visualization of anatomic relationships. 9

FIG. 10.
FIG. 10.:
Image improvement with 1.5-dimensional array. A. Longitudinal view of the radial artery obtained with a conventional 9.0-MHz transducer demonstrates multiple internal echoes throughout the lumen of the radial artery (cursors) caused by slice thickness artifact. B. Similar view obtained with a 9.0-MHz, 1.5-dimensional array demonstrates a normal-appearing anechoic lumen. This difference is caused by the narrow slice thickness that is possible with 1.5-dimensional arrays.
Figure 10
Figure 10:
Continued
FIG. 11.
FIG. 11.:
Image improvement with real-time compounding. A. Transverse view of the median nerve (arrows) with conventional imaging. B. Transverse view of the median nerve (arrows) with real-time compounding. With real-time compounding, sound is steered at multiple different angles, resulting in improved reflection from tissue interfaces and better visualization of the internal fascicular architecture of the median nerve.
Figure 11
Figure 11:
Continued
FIG. 12.
FIG. 12.:
Extended field of view imaging. A. Conventional linear array scan of the proximal interphalangeal joint (PIP) and overlying flexor tendons (T). B. Extended field of view scan of the metacarpal-phalangeal joint (MCP) and the proximal interphalangeal joint (PIP). Note how the flexor tendons (T) are seen over a much greater length on the extended field of view scan.
Figure 12
Figure 12:
Continued

TENDON DISEASE

Tenosynovitis

Tenosynovitis refers to inflammation of the tendon sheath and can be caused by multiple etiologies. Rheumatoid arthritis is a common cause of inflammatory tenosynovitis. The hand and/or wrist may be involved in more than half of patients with rheumatoid arthritis. 10 Patients usually present with painless swelling of the third, fourth, fifth, and sixth extensor compartments or of the flexor tendons. Gouty tenosynovitis of the hand is a common cause of crystalline tenosynovitis, but it is not typically seen in patients whose disease has been well managed. 10 Calcific tenosynovitis is another cause of crystalline tenosynovitis with an unclear etiology. Amyloidosis frequently affects the hand, producing plaque-like deposits along the flexor tendons within the carpal tunnel or digits, potentially leading to median nerve compression, trigger finger, or flexion contracture. 10 Acute suppurative tenosynovitis is often caused by a penetrating injury but may be hematogenous in origin. 11 It frequently occurs in immunologically compromised patients or patients with diabetes. The infectious process usually begins in the distal flexor tendon sheath but may extend proximally. The most common infecting organism is Staphylococcus aureus. 11 Chronic tenosynovitis caused by mycobacteria or fungus also occurs. 12

Although controversial, tenosynovitis may be caused by repetitive work-related injury. 13 Rheumatoid arthritis, diabetes mellitus, calcium pyrophosphate deposition disease, gout, hypothyroidism, tuberculosis, fungal infections, and collagen vascular disease predispose to work-related tenosynovitis. 13 It may occur in any of the six extensor compartments. In the flexor compartment, the flexor carpi ulnaris or radialis or digital flexor tendons are most commonly involved. 13,14

De Quervain disease and trigger digit are two of the more common types of idiopathic tenosynovitis. De Quervain disease involves the first extensor compartment (abductor pollicis longus and extensor pollicis brevis tendon sheaths) at the level of and proximal to the radial styloid process. 15 It is more common in women than in men (6:1) and usually occurs between the ages of 30 and 50 years. 10 Patients have pain along the radial side of the wrist that increases with movement of the thumb and tenderness and swelling approximately 1 to 2 cm proximal to the radial styloid. 10 Trigger finger is also an idiopathic tenosynovitis. Pathologic changes include fibrocartilaginous metaplasia at the level of the A1 pulley (metacarpophalangeal joint) and flexor tendon surface. 10 It occurs more commonly in women than in men (2–6:1) and has a peak incidence between the ages 40 and 60 years. 10 The thumb is most commonly affected, followed in descending order by the ring, long, little, and index fingers. 10 Most patients have pain and triggering and/or locking of the digit. 10

Tenosynovitis can be diagnosed sonographically when there is fluid distending the tendon sheath and/or thickening of the tendon sheath (Figs. 13A,B). 16 The fluid is usually anechoic, although complicated tenosynovitis (infectious or hemorrhagic) may have fluid with low-level echoes. Tendon sheath thickening may be diffuse and smooth or eccentric and nodular. With active inflammation, there is usually a detectable hypervascularity on color and power Doppler (Fig. 13C). 16 The findings in trigger finger include tendon thickening, a hypoechoic nodule on the flexor tendon surface proximal to the A1 pulley, synovial sheath thickening and fluid, and small peritendinous cysts. 17 In most cases, it is possible to determine the cause of the tenosynovitis based on the ultrasound findings, clinical history, and associated laboratory findings. When necessary, ultrasound-guided aspiration and biopsy can also be performed to establish the diagnosis. Complications to look for include tendon involvement and rupture, cellulitis, compressive neuropathies, abscess formation, and osteomyelitis.

FIG. 13.
FIG. 13.:
Tenosynovitis. A. Transverse view of the extensor tendons demonstrates fluid (F) distending the extensor tendon sheath. B. Longitudinal view of an extensor tendon (T) in a different patient demonstrating fluid (F) distending the tendon sheath and thickening of the tendon sheath (arrows). C. Transverse color Doppler view of the extensor tendons demonstrates hypervascularity of the synovial tissue associated with these tendons.
Figure 13
Figure 13:
Continued
Figure 13
Figure 13:
Continued

Tendon Rupture

Tendon rupture may be spontaneous in the setting of rheumatoid arthritis or chronic tenosynovitis, but it may also be caused by trauma. In the flexor tendons, traumatic avulsion occurs when there is sudden forced extension of the finger during maximum contraction of the flexor digitorum profundus muscle. 4 This commonly occurs in young male athletes and most often affects the ring finger. It produces an inability to flex the distal interphalangeal joint. The eventual clinical outcome is improved by early diagnosis and surgical repair.

Tendon rupture is seen on ultrasound as inability to identify normal tendon in its expected location (Fig. 14A). 16 A small amount of fluid may be seen at the site of the tear and in the sheath in the acute setting, but significant hematomas are unusual. Sonography is extremely useful in identifying the location of the proximal fragment, which can help to minimize the size of the initial surgical incision. In the flexor tendons, the proximal tendon fragment usually retracts either into the palm or to the level of the A3 pulley (proximal interphalangeal joint), or to the level of the A4 pulley (mid phalanx). The easiest way to find the proximal tendon is to start in a transverse plane at the distal aspect of the finger and scan proximally until a mass is encountered (Fig. 14B). That mass will represent the tip of the proximal tendon. The blunt tip of the proximal tendon can then be seen on longitudinal views (Fig. 14C). It is not uncommon to see shadowing around the end of the retracted tendon (Fig. 14D). This is presumably caused by curling of the distal fibers and subsequent sound refraction. It does not indicate calcification or avulsed bony fragments unless there is an associated hyperechoic focus at the leading edge of the shadow.

FIG. 14.
FIG. 14.:
Tendon rupture. A. Dual longitudinal views of the left (LT) and right (RT) distal interphalangeal joints (large arrows) of the ring finger. The normal flexor digitorum profundus tendon (small arrows) is seen crossing the joint and inserting on the distal phalanx on the right side. No tendon is seen on the left side. B. Transverse view of the flexor tendons of the right (RT) and left (LT) ring finger at the level of the metacarpals in the same patient shown in A. Note the normal appearance on the right and the hypoechoic enlarged deep flexor tendon on the left. This represents the retracted blunt tip of a torn tendon. C. Longitudinal view of the flexor digitorum profundus tendon (T) in a different patient showing the retracted blunt tip (arrows) of a torn tendon. D. Longitudinal view of the flexor pollicis longus tendon (T) in a different patient demonstrates refractive shadowing arising from the retracted tendon fragment (arrows).
Figure 14
Figure 14:
Continued
Figure 14
Figure 14:
Continued
Figure 14
Figure 14:
Continued

GANGLION CYSTS

Ganglion cysts are the most common cause for palpable masses in the hand and wrist. They are most common in young women, although they can occur at any age and in both sexes. 18 Approximately 10% of patients will have a history of trauma. 19,20 Ganglion cysts typically contain a thick mucinous fluid and are relatively tense. They present with either localized pain (small ganglions) or a palpable mass (large ganglions).

Although they can occur in a multitude of locations, there are four typical locations. Approximately 60% to 70% occur on the dorsal wrist (Fig. 15). Dorsal ganglion cysts usually originate from the radial carpal joint capsule at the site of the scapholunate ligament and penetrate the ligament via a thin neck to enter the scapholunate space. 18 They may dissect proximally or distally.

FIG. 15.
FIG. 15.:
Dorsal wrist ganglion. A. Transverse view of the dorsal aspect of the wrist at the level of the scapholunate joint demonstrates a slightly septated cyst (C) overlying the scaphoid (S) and lunate (L) bones. B. Extended field of view scan of the dorsal wrist demonstrates the same cyst (C) and its relationship to the distal radius (R) and proximal capitate (CAP).
Figure 15
Figure 15:
Continued

Approximately 20% of ganglia arise on the volar side of the wrist. Volar ganglia frequently extend around the flexor carpi radialis tendon (Fig. 16) and/or the radial artery (Fig. 17). 18 They typically arise from one of the radiocarpal joints along the radial aspect of the wrist. 21

FIG. 16.
FIG. 16.:
Volar wrist ganglion associated with the flexor carpi radialis tendon. A. Transverse view of the flexor carpi radialis tendon (T) demonstrates a cyst (C) located superficially that is intimately related to the tendon. B. Longitudinal view of the flexor carpi radialis tendon (FCR) in a different patient demonstrates a cyst (C) overlying the tendon.
Figure 16
Figure 16:
Continued
FIG. 17.
FIG. 17.:
Volar wrist ganglion associated with the radial artery. A. Longitudinal power Doppler view of the radial artery demonstrates a cyst (C) adjacent to and deviating the radial artery. B. Transverse power Doppler view of the volar wrist in a different patient demonstrates the radial artery (RA) and the flexor carpi radialis tendon (FCR). A lobulated ganglion cyst (GC) is seen infiltrating between these structures.
Figure 17
Figure 17:
Continued

The third most common location for a ganglion cyst is along one of the flexor tendon sheaths (Fig. 18). These account for approximately 10% of ganglia and typically occur near the metacarpal phalangeal joints. 18 Finally, ganglion cysts can arise from the interphalangeal joints, usually caused by underlying degenerative arthritis. These cysts have also been called mucous cysts.

FIG. 18.
FIG. 18.:
Ganglion cyst associated with the flexor digitorum superficialis/profundus tendon sheath. A. Longitudinal view of the flexor tendons (T) overlying the metacarpal-phalangeal joint demonstrates a small cyst (C) overlying the flexor tendons. B. Transverse view at the same level demonstrates the tendons (T) and the overlying cyst (C).
Figure 18
Figure 18:
Continued

The appearance of ganglia on ultrasound is predictable. Like other fluid-containing structures, ganglia are typically anechoic with well-defined walls. 19 Through-transmission is usually detectable unless the cyst is small. Because of slice thickness artifact, small ganglia may also have low-level internal echoes. In some cases, a tortuous neck may be seen leading toward the joint of origin (Fig. 19). With large ganglia, there are often folds or septations, particularly near the neck. Ganglion cysts that have ruptured may be difficult to distinguish from a solid mass. Usually, the presence of at least some fluid and the typical locations will suggest the diagnosis (Fig. 20). The sensitivity of ultrasound in the detection of ganglia is comparable to that of magnetic resonance imaging. Both detect approximately 90% of ganglia in the wrist. False-negatives are primarily caused by small ganglia. 19

FIG. 19.
FIG. 19.:
Ganglion cyst neck. Longitudinal view of the dorsal wrist demonstrates a tortuous neck (arrows) extending from a ganglion cyst (C) toward the deep joint space.
FIG. 20.
FIG. 20.:
Ruptured ganglion cysts. A. Transverse view of the dorsal wrist overlying the scaphoid (S) and lunate (L) bones. Soft-tissue thickening (large arrows) is seen overlying these bones. Small cystic elements (small arrows) are seen in the deep aspect of the mass. This combination of findings and this location should suggest the diagnosis of a ruptured ganglion cyst. B. Longitudinal view of the flexor tendons (T) of the finger of a different patient demonstrates an area of soft tissue thickening (arrows) overlying the tendon. No definite cystic elements are seen. This appearance is nonspecific, but the possibility of a ruptured ganglion cyst should be considered. This was subsequently confirmed surgically.
Figure 20
Figure 20:
Continued

In addition to diagnosis, ultrasound can be used to guide aspiration and the injection of steroids into ganglia. In the vast majority of cases, this produces symptomatic relief in the short-term, and in most, relief continues for many months. If necessary, a repeat injection can be performed if the symptoms reoccur. 22

SOFT TISSUE MASSES

Giant Cell Tumor

After ganglion cysts, giant cell tumors (GCT) represent the most common cause of a mass in the hand. 23 They are a benign disorder of proliferative synovium arising from the tendon sheaths. It is not clear if they are reactive or neoplastic. Histologically, GCT of the tendon sheaths are identical to pigmented villonodular synovitis. Giant cell tumors are most common in 30 to 50-year-olds and are seen more often in women than in men. They occur typically along the volar surface of the first three fingers and are usually isolated lesions. 24 They grow slowly and are relatively painless. 23,24 The treatment of choice is surgical resection. Approximately 20% will recur after surgery.

Sonographically, GCT are solid, homogeneous, hypoechoic masses located adjacent to tendons (Fig. 21). 25 Large GCT may partially surround the tendon (Fig. 22). However, because they arise from the sheath and not the tendon, they do not move with the tendon when the finger is flexed and extended. 26 Approximately 10% will produce a pressure erosion on the adjacent bone (Fig. 23). High-frequency color Doppler will generally show detectable internal blood flow, and in some cases, the mass will appear quite vascular (Fig. 24).

FIG. 21.
FIG. 21.:
Giant cell tumor of the tendon sheath. A. Longitudinal view of the flexor tendon (T) of the thumb demonstrates a homogeneous hypoechoic solid mass (cursors) overlying the tendon. B. Longitudinal view of the distal interphalangeal joint of the ring finger of a different patient demonstrates the deep flexor tendon (T) and a homogeneous hypoechoic solid mass (cursors) overlying the tendon. Both of these patients have findings typical of giant cell tumors. Subsequent surgery confirmed the diagnosis in both patients.
Figure 21
Figure 21:
Continued
FIG. 22.
FIG. 22.:
Giant cell tumors. A. Transverse view of the flexor tendon (T) of the thumb demonstrates a hypoechoic homogeneous soft tissue mass (m) surrounding the superficial, lateral, and deep aspects of the tendon. B. Transverse view of the flexor tendons (T) of the fifth finger in a different patient demonstrates a soft tissue mass (m) surrounding the medial, lateral, and deep aspect of the tendon. In both of these cases, large giant cell tumors have partially encased the tendons.
Figure 22
Figure 22:
Continued
FIG. 23.
FIG. 23.:
Giant cell tumor with bony erosion. Longitudinal view of the metacarpal demonstrates erosion of the cortical surface (arrows) by a soft tissue mass (m).
FIG. 24.
FIG. 24.:
Giant cell tumor vascularity. Longitudinal view of the proximal thumb demonstrates a hypoechoic soft tissue mass (m) adjacent to the flexor tendon (T). Color Doppler demonstrates hypervascularity of this typical GCT.

Hemangioma

Hemangiomas account for approximately 5% to 10% of benign hand tumors. Typically, soft tissue hemangiomas contain nonvascular tissue including fat, smooth muscle, and fibrous tissue. They are most common in patients between 20 and 40-years-old and are seen with equal frequency in men and women. 27 Sonographically, hemangiomas appear as solid masses and range from hypoechoic to hyperechoic (Fig. 25). 28 They may be poorly defined and are often difficult to evaluate with ultrasound. They are typically compressible. Phleboliths may be detectable as small, hyperechoic, shadowing reflectors. Detectable vascularity is variable, but hemangiomas may be hypervascular at color Doppler sonography (Fig. 25).

FIG. 25.
FIG. 25.:
Hemangioma. A. Transverse gray-scale view of the hand overlying the third and fourth metacarpals. A hypoechoic soft tissue mass (cursors) is seen in the tissues superficial to the metacarpals. B. Color Doppler view of the same area demonstrates intense hypervascularity of this mass. The clinical findings and the sonographic appearance are both consistent with a hemangioma. This patient has been followed-up clinically with no change for more than 1 year.
Figure 25
Figure 25:
Continued

Glomus Tumor

Glomus tumors arise from the neuromyoarterial bodies generally in the palm and the fingers and account for less than 5% of hand tumors. They are most frequent in the fingertip in a subungual location. 25 Patients complain of spasmodic pain, temperature sensitivity, and tenderness. 29 Because the tumors are seldom more than a few millimeters in size, a mass is frequently not palpable. There may, however, be a blue discoloration to the affected nailbed. 29

Sonographically, glomus tumors are solid but quite hypoechoic and may demonstrate some posterior acoustic enhancement. 28 Although they are well marginated, in the subungual region, they may be flattened and more difficult to detect. An associated pressure erosion in the underlying bone may be visible. With high-frequency Doppler, hypervascularity can be detected. 28

Neural Tumors

Nerve tumors are relatively rare in the hand but are among the most common benign tumors of the upper extremity. Nomenclature is confusing, with schwannomas often being referred to as neurilemomas. Most schwannomas arise from the larger and deeper peripheral nerves. They are usually painless masses that appear between the ages 30 and 60 years. 23 In the upper extremity, they often occur along the flexor surface of the forearm and hand. 30 They arise from Schwann cells at the periphery of nerves and are eccentric to the nerve. 23 Neurofibromas, however, arise from the central nerve fascicles. 30 Neurofibromas tend to involve the smaller cutaneous nerves. They occur in a younger group of patients but otherwise share most of the clinical features of schwannomas. Neuromas are a proliferative response to nerve injury and are not considered to be true nerve tumors. 30

In general, nerve tumors are homogeneous and hypoechoic (Figs. 26A,B). 28 Although they are solid, they often attenuate sound less than surrounding structures so they may demonstrate posterior enhancement (Figs. 26A,B). 28 Color and power Doppler typically show hypervascularity (Fig. 26C). They can be diagnosed definitively only when their continuity with the nerve can be documented (Fig. 26B). This is possible with the larger nerves but generally not possible with the smaller branch nerves. However, in patients with nerve-centered symptoms, detection of a hypoechoic solid mass in the expected course of the nerve is generally sufficient to strongly suggest the diagnosis.

FIG. 26.
FIG. 26.:
Nerve tumors. A. Longitudinal view of the wrist demonstrates a solid, hypoechoic, oval lesion in the superficial tissues with slight increased through-transmission. This is a neurofibroma in a patient with neurofibromatosis. Because it arises from a small superficial nerve, its neural origin is not evident sonographically. B. Longitudinal view of the ulnar nerve (N) in a different patient demonstrates a soft tissue mass (m) arising directly from the nerve. In this case, the neural origin of the lesion is evident. As in the patient shown in A, increased through-transmission is evident. The underlying flexor tendons to the fourth finger are also seen. C. Power Doppler view of the same patient as shown in B demonstrates the hypervascularity typical of neural tumors.
Figure 26
Figure 26:
Continued
Figure 26
Figure 26:
Continued

Malignant Tumors

Malignant soft tissue tumors of the hand and wrist are relatively rare. Given the abundant synovial tissue in the many joints and tendon sheaths of the hand and wrist, it is not surprising that the most common is synovial cell sarcoma. Other rare tumors include malignant fibrous histiocytoma, fibrosarcoma, liposarcoma, neurosarcoma, and angiosarcoma.

FOREIGN BODIES

Foreign bodies are a common problem after penetrating injuries of the hand and wrist. If not detected and removed, they can be a source of persistent pain, soft tissue infection, and abscess. In most cases, successful surgical removal depends on accurate localization via imaging. Many foreign bodies such as metal can be detected and localized radiographically. However, some foreign bodies such as glass, wood, and vegetable matter are radiolucent and are not detectable with radiographs.

Ultrasound is an excellent means of detecting radiolucent foreign bodies in the hand and wrist. It is also helpful in precisely localizing radiopaque bodies that were initially detected with radiographs. In the hand, the sensitivity of ultrasound ranges from approximately 75% to 100%, depending on the size and location of the foreign body. 31 False-positive results are uncommon and thus the specificity approaches 100%. Once found, ultrasound can then be used to guide the removal of foreign bodies.

The sonographic appearance of foreign bodies is relatively constant regardless of the composition. All appear as hyperechoic structures (Fig. 27), although the brightness of the reflection may vary with the size and type of the foreign body as well as its orientation with respect to the ultrasound beam (Fig. 28). 32 Acoustic shadowing is present when the foreign body is big enough (Fig. 27). Glass and metal may produce a comet-tail or ring-down artifact. Inflammatory tissue may surround the foreign body and produce a hypoechoic halo (Fig. 28). Abscess formation will appear as a complex fluid collection. In many cases, color Doppler will show an inflammatory hyperemia surrounding the foreign body (Fig. 29).

FIG. 27.
FIG. 27.:
Foreign body. Longitudinal view of the metacarpal-phalangeal joint of the third digit demonstrates two highly echogenic, minimally shadowing, glass foreign bodies overlying the flexor tendons to the finger. This is a typical appearance for foreign bodies.
FIG. 28.
FIG. 28.:
Variable echogenicity of a foreign body. A. Transverse view of the proximal fifth finger demonstrates a minimally echogenic splinter (cursors) surrounded by hypoechoic inflammatory tissue. B. Similar view with the transducer reoriented so that the splinter is perpendicular to the sound displays the splinter as a more highly echogenic structure that is easier to detect and recognize sonographically.
Figure 28
Figure 28:
Continued
FIG. 29.
FIG. 29.:
Foreign body with inflammatory hyperemia. A. Transverse view of the palm demonstrates a vertically oriented foreign body (arrows) caused by a splinter. B. Similar power Doppler view demonstrates intense hypervascularity associated with the inflammatory response adjacent to the foreign body.
Figure 29
Figure 29:
Continued

CARPAL TUNNEL SYNDROME

Carpal tunnel syndrome (CTS) is the most common compressive peripheral neuropathy of the upper extremity. It is being diagnosed with increasing frequency in patients with occupations that require repetitive motion or produce mechanical stress on the median nerve, such as typists, transcriptionists, musicians, jackhammer operators, carpenters, and others. 33,34 Pregnancy, rheumatoid arthritis, chronic renal failure, diabetes mellitus, amyloidosis, and tenosynovitis are other risk factors unrelated to occupation. 34

Patients typically have pain and paraesthesias in the distribution of the median nerve, often worse at night and reproducible with certain repetitive activities. 33,34 Electromyography is considered the gold standard for the diagnosis of CTS; however, it is invasive, painful, operator-dependent, and may be normal in the presence of nerve compression. 33,34

Sonography can also be used to study the median nerve. 34 The cross-sectional area of the median nerve can be calculated using the equation for an ellipse. Lee et al. showed that the mean cross-sectional area of the normal median nerve was 9.3 mm 2 in women and 8.3 mm 2 in men. 34 Patients with CTS have an enlarged median nerve. 34 When electromyography findings were correlated with median nerve cross-sectional area, Lee et al. noted that a cross-sectional measurement of 15 mm 2 or greater corresponded with a moderately to severely abnormal electromyography that indicated the need for carpal tunnel release. 34 A cross-sectional area less than 15 mm 2 corresponded to a normal to mildly abnormal electromyography that indicated conservative management. Although results such as this are encouraging, sonographic evaluation of patients with suspected CTS has not gained widespread acceptance. Further studies examining clinical outcome, costs, and patient satisfaction will be necessary before the role of sonography and other imaging tests in the evaluation of CTS is defined.

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Keywords:

Hand; Abnormalities; Injuries; Wrist; Ultrasound

© 2001 Lippincott Williams & Wilkins, Inc.