Diagnostic ultrasound of the hand and wrist

Diagnostic Ultrasound of the Hand and Wrist John W. Read, FRACR, W. Bruce Conolly, FACS, Marco Lanzetta, MD, Steven Spieiman, Duncan Snodgrass, John S. Korber, FRACR, Sydney, Australia To assess the efficacy, role, and limitations of diagnostic ultrasound in the hand and wrist, the results of 98 examinations performed for a variety of surgical conditions were retrospectively analyzed. Ultrasound was shown to be reliable in evaluating radiolucent foreign body, tendon rupture versus tendon adhesion, tendinitis, peritendinitis, and ganglion cyst (specificity, 1 ; positive predictive value, 1). A correct suggestion of soft tissue mass histology was offered in six of eight operated cases. Tumor size and extent was accurately assessed in all but one case. The observed limitation of ultrasound was a small false negative rate in each category, which related to a variety of factors, including operator dependence, resolution threshold in the submillimeter range, image degradation due to postoperative edema, a narrow field of view, and one instance of indiscrete tumor margination. More work is needed to determine the role (if any) of ultrasound in the evaluation of peripheral nerve, triangular fibrocartilage, dorsal carpal ligament, and bone pathology. (J Hand Surg 1996;21A: 1004-1010.)

Surgical conditions of the hand and wrist that involve the soft tissues may remain a diagnostic challenge when standard x-ray investigation findings are negative. High-resolution ultrasound is a widely available, noninvasive, and nonhazardous imaging test that can offer a solution to this problem. It is also relatively inexpensive when compared with other multiplanar cross-sectional imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI). Furthermore, recent advances in ultrasound technology have significantly improved the display of small superficial structures. We review our initial experience with this modality. From Sports Imaging, and the Hand Unit, Sydney Hospital, and Advanced Medical Imaging, Sydney, Australia. Received for publication June 13, 1994; accepted in revised form ApriI I, 1996. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: John W. Read, FRACR, Sports Imaging, 286 Pacific Hwy, Crows Nest 2065, Australia.

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Materials and Methods The results of 98 ultrasound examinations of the hand and/or wrist requested by a hand surgeon (W.B.C.) between September 1992 and January 1994 were retrospectively reviewed and compared with the final diagnosis as determined by either the subsequent operative findings or, in those patients treated conservatively, the follow-up clinical opinion. All studies were performed with an Acuson 128 ultrasound scanner (Mountain View, CA) using a 7-MHz linear-array transducer and soft polymer block acoustic standoff. In every case, the radiologist had the benefit of access to prior x-ray film results and a provisional clinical diagnosis. Care was taken to ensure that ultrasound artifacts arising from anisotropy, excessive power, and high system gain were avoided. Static images were supplemented by dynamic evaluation of tendon glide, muscle contraction, or joint motion whenever relevant. Color and spectral Doppler methods were used to assess vascularity in selected cases.

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Results

Table 1. Categories of Referral for Ultrasound

Patients referred for ultrasound were divided by clinical presentation into the categories listed in Table 1. The results are summarized in Table 2.

Clinical Presentation

No. Patients

Suspected foreign body Tendon rupture Tendinitis or peritendinitis Ganglion Soft tissue mass Peripheral nerve lesion Bone lesion Nonspecific wrist pain Total

Suspected Foreign Body There were 18 patients referred with suspicion of foreign body (age range, 9-36 years). An ultrasound diagnosis of foreign body (FB) was made whenever a nonanatomic echogenic structure could be established by reference to equivalent "normal" views on the contralateral side. A surrounding hypoechoic halo of inflammatory reaction was often present and served to enhance FB visibility (Fig. 1). Ultrasound correctly detected and accurately localized FB in 9 of 12 operatively proven cases and correctly excluded them in 5 cases. The types of FB detected were wood, glass, thorn, sea urchin spine, and pencil lead. The smallest FB, a fragment of thorn, measured 1 m m in size. There were no instances of false positive diagnosis, but ultrasound findings were falsely negative in three operatively proven cases (the causes for error were size of less than 1 mm, failure to scan a sufficiently wide area in a case of FB migration, and FB location within isoechoic fascia). Ultrasound was noncontributory in one case in which confusion was created by the presence of multiple soft tissue calcifications, and an equivocal report was issued. Plain xray identified only three cases of FB in this series (one sea urchin spine, two fragments of glass).

18 13 12 26 13 5 2 9 98

ultrasound diagnosis of tendon rupture was made if a linear pattern of tendon discontinuity could be demonstrated (Fig. 2), whereas tendon adhesion was characterized by a loss of normal passive tendon glide on real-time scanning. Ultrasound was used to correctly diagnose the presence and site of rupture in six o f seven operatively confirmed cases and to correctly exclude rupture in four cases. The diagnosis of flexor tendon graft rupture, made clinically, was also reached through the use of ultrasound in an additional case that did not subsequently involve surgery. Tendon ruptures successfully detected included the flexor carpi radialis, extensor pollicis longus, flexor digitorum superficialis, flexor digitorum profundus and extensor digitorum co mmunis. There were no instances of false positive diagnosis, but ultrasound findings were falsely negative in one case in which the cause for error was pseudotendon in a 4-year-old girl with a history of flexor digitorum profundus laceration 2 years earlier. In one patient, ultrasound found no evidence of tendon rupture but demonstrated loss of normal passive tendon glide; the oper-

Tendon Rupture There were 13 patients referred with clinical suspicion of tendon rupture (age range, 4-71 years). An

Table 2. Summary of Results Category

Foreign body Tendon rupture Tendinitis Ganglion Soft tissue mass Peripheral nerve lesion Bone lesion Nonspecific wrist pain

Cases

TP

TN

FP

FN

Other

Sens

Spec

Acc

PPV

18 13 12 26 13 5 2 9

9 7 10 24 9 1 1 0

5 4 1 1 0 NA NA NA

0 0 0 0 2 NA NA 0

3 1 1 1 1 NA NA 4

1 1 0 0 1 4 1 5

0.75 0.88 0.91 0.96 0.90 NA NA 0

1.0 1.0 1.0 1.0 NA NA NA NA

0.78 0.85 0.92 0.96 0.69 NA NA NA

1.0 1.0 1.0 1.0 0.82 NA NA NA

NPV

0.63 0.8 0.5 0.5 NA NA NA NA

TP, true positive; TN, true negative; FR false positive; FN, false negative; Other, ultrasound findings equivocal or diagnostic accuracy not verifiable; Sens, sensitivity (TP/TP + FN); Spec, specificity (TN/TN + FP); Acc, accuracy (TN + TP/total); PPV, positive predictive value (TP/TP + FP); NPV, negative predictive value (TN/TN + FN); NA, not applicable.

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Fig. 1. Radiolucent foreign body. Longitudinal ultrasound image shows an 8-ram-long wood splinter (arrow) in the soft tissues anterior to the proximal phalanx of middle finger. Note the surrounding hypoechoic halo of inflammatory reaction.

ative findings in this case were those of tendon adhesion adjacent to an old phalangeal fracture. Ultrasound findings were equivocal in one case in which postoperative edema degraded image quality in a clinical setting of possible tendon rerupture 10 days after surgical repair.

20-57 years). A diagnosis of tendinitis was made by ultrasound whenever diffuse or fusiform tendon swelling could be shown by comparison to the contralaterat side and some degree of localized tenderness was also present on probing with the transducer (Fig. 3). Peritendinitis was diagnosed whenever an abnormal hypoechoic zone of swelling consistent with tenosynovitis, tendon sheath effusion, or inflammatory change in adjacent loose connective tissue could be seen around tendon. Ultrasound was used to correctly diagnose tendinitis or peritendinitis in 10 of 11 cases and to correctly exclude tendinitis in 1 case. There were no instances of false positive diagnosis, but ultrasound findings were falsely negative in one patient with mild flexor carpi radialis tenosynovitis found at operation. Ultrasound contributed useful new information in four cases: substantial resolution of tendon swelling by comparison with old scans in a case of persistent de Quervain's disorder, localization of disease to the first rather than second dorsal compartment in a patient with postulated extensor carpi radialis longus and brevis tendinitis, incidental discovery of an unsuspected small chronic flexor digitorum profundus tendon rupture, and a change of diagnosis in one patient thought to have tendinitis but instead shown to have a suture granuloma.

T e n d i n i t i s or P e r i t e n d i n i t i s

There were 12 patients referred with clinical suspicion of tendinitis or peritendinitis (age range,

Fig. 2. Longitudinal ultrasound image of a ruptured extensor pollicis longus tendon (small, straight arrows) showing a 5-mm-long hypoechoic gap (large, curved arrow) in continuity at the level of Lister's tubercle. The gap was confirmed at surgery. Distal is to the left of image.

Fig. 3. de Quervain's disorder in the right wrist. Transverse and longitudinal images of the first dorsal compartments show relative tendon swelling with associated tenosynovitis on the right side at the level of radial styloid (large arrows indicate abductor pollicis longus tendons; small arrows indicate extensor pollicis brevis tendons).

The Journal of Hand Surgery/Vol. 21A No. 6 November 1996 1007 Ganglion

There were 26 patients referred with suspicion of ganglion (age range, 13-85 years). Of these, no mass was present on physical examination in 5. A diagnosis of ganglion was made by ultrasound whenever a rounded or lobulated mass of markedly hypoechoic appearance with smooth, well-defined walls could be seen immediately adjacent to an appropriate synovial compartment (Fig. 4). A pointed or tapering margin was regarded as the "neck" of the ganglion and taken to indicate the site of ganglion origin from joint. A broad, flat base of association with tendon edge (in the absence of any definable neck) was taken to indicate origin from tendon sheath. Ultrasound was used to correctly diagnose ganglion in 24 of 25 cases (as judged by either surgical exploration or needle aspiration) and to correctly exclude ganglion in 1 case. There were no false-positive diagnoses, but ultrasound findings were regarded as falsely negative in one case in which there was persisting strong clinical suspicion of an occult scapholunate ganglion (this case did not involve surgical exploration). In one case, ultrasound revealed unsuspected concurrent extensor carpi radialis longus tendinitis, and surgery was therefore avoided. A "neck" suggestive of ganglion origin was found in 17 of 25 patients, but open surgical correlation was available in only 5; the findings at operation were in agreement with clinical findings in each instance.

Fig. 4. Dorsal wrist ganglion. Longitudinal ultrasound image shows a large ganglion (asterisk) above the dorsal surface of scaphoid bone. Distal is to the left of image. The lesion margins are rounded, except for the proximal end, which tapers toward the radioscaphoid articulation (arrow) as the suggested point of origin. Low-level echoes indicate contained synovial elements.

Table 3, Soft Tissue Masses Lesion Type

Hemangioma Giant cell tumor of tendon sheath Neurogenic tumor Lipoma Glomus tumor Sarcoid nodule Epidermoid cyst Fibrolipoma Glomangioma Muscle hypertrophy Unknown Total

No. Patients

2 1 2 1 1 1 1 1 1 1 1 13

Soft Tissue Mass

There were 13 patients (Table 3) who presented with soft tissue masses (age range, 16-55 years). A description of the ultrasound features of the various soft tissue masses that can involve the hand and wrist has been provided by Fornage and Rifkin) Of the eight operative cases, ultrasound correctly suggested the final histologic diagnosis in six and accurately described lesion extent in seven. The operated masses correctly diagnosed by ultrasound included one glomus tumor (Fig. 5), one giant cell tumor of tendon sheath, one hemangioma, one lipoma, and two cases of nerve sheath tumor. In one operated case of sarcoid nodule and one operated case of epidermoid cyst, ultrasound did not suggest a specific

Fig. 5. Glomus tumor. Longitudinal ultrasound image of the thumb pulp shows a rounded 3-ram hypoechoic lesion (arrow) contiguous with distal phalanx, later confirmed at operation. Note scalloping of subjacent bone surface.

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diagnosis. Of five nonoperated cases, ultrasound findings were falsely negative in one patient with clinically recurrent fingertip glomangioma (presumably because the lesion was isoechoic with surrounding pulp) and of indeterminate accuracy in one patient for whom the clinical diagnosis was digital ganglion but the sonographic diagnosis was giant cell tumor of tendon sheath. Ultrasound findings were regarded as clinically correct in the remaining three cases (one case of recurrent hemangioma with positive Doppler findings, one case of carpal tunnel fibrolipoma that was confirmed with CT, and one case of hypertrophied lumbrical muscle). In one operated case of extensive lipoma, overall tumor size and extent was better assessed by CT. Peripheral Nerve Lesion

There were five patients referred for ultrasound who presented with neurologic symptoms (age range, 27-72 years). In one case, ultrasound showed a nonpalpable ganglion impinging upon the deep branch of ulnar nerve within Guyon's canal (confirmed at operation). Two patients with a Clinical diagnosis of ulnar neuritis showed fusiform enlargement of the ulnar nerve within Guyon's canal (interpreted as neuroma) but did not undergo surgery. One patient with recurrent paresthesia following carpal tunnel release showed hypoechoic swelling along the line of surgical incision (interpreted as postoperative change), which resolved with conservative management. In another case of ulnar nerve palsy affecting the ring finger, the ultrasound findings were completely negative. No further action was taken, on the basis that a space-occupying lesion had been effectively excluded. Bone Lesion

There were two patients referred for ultrasound with a clinical diagnosis of bone lesion. In one case (with recurrent proximal interphalangeal joint effusion), the position and mobility of an old avulsion fracture fragment at the capsular insertion of the proximal interphalangeal joint was usefully demonstrated. In the other patient (with phalangeal enchondroma), ultrasound was not helpful. Nonspecific Wrist Pain Nine patients with poorly localized and clinically nonspecific wrist pain and with normal findings on plain x-rays (age range, 15-48 years) were referred

for ultrasound. Ultrasound was not useful in determining the cause of pain in any patient. Of these, there were five patients for whom other tests were also noncontributory and no definite final diagnosis was ever made. For three patients, a final diagnosis of triangular fibrocartilage complex (TFCC) tear was made at either arthroscopy or MRI. In one patient, arthroscopy revealed a soft TFCC and the final diagnosis was distal radioulnar joint instability.

Discussion The use of ultrasound has been described in the diagnosis of a wide range of soft tissue conditions involving the hand and wrist, 1-24 but only a minority of these reports have appeared in hand surgery journals. The exact clinical role of ultrasound is still unclear, and the use of ultrasound in everyday surgical practice remains limited. MRI also competes as an excellent soft tissue modality and its findings are perceived as being less operator dependent, easier to understand, and more comprehensive. Nevertheless, ultrasound is faster and better tolerated, provides images of higher spatial resolution, is presently unique in its ability to evaluate soft tissue dynamics in real time, and would be preferred to MRI if shown to have equivalent or greater diagnostic efficacy at lower cost. It should be realized that MRI is an expensive investigation that is n o t free from problems of operator- and equipment-dependent findings. The patient must be cooperative and able to lie very still in somewhat claustrophobic circumstances. In our study, an ultrasound finding of FB, tendon rupture, tendinitis, peritendinitis, or ganglion was diagnostic (specificity, 1; positive predictive value, 1). However, in each of these settings, there was also a small false negative rate. A "normal" ultrasound report was therefore not as reliable, and in this situation there is a need to carefully correlate negative test results with the clinical context. If a strong clinical suspicion persists, further investigation is warranted. A variety of causes for false negative error were encountered, illustrating the limitations of ultrasound: operator skill (eg, FB missed owing to inadequate search), resolution threshold (eg, FB missed owing to submillimeter size), recent operation (eg, wound edema degrading image quality), and inherent difficulty (eg, pseudotendon simulating normal tendon). Nevertheless, the high predictive value of a positive scan result in our study points to a potentially

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useful test. In this setting, the hand surgeon can use an ultrasound diagnosis of abnormality to confidently guide case management decisions. In general terms, ultrasound could be used variously to clarify diagnosis, to monitor disease course or treatment response, to objectively document the presence of disease in work-related cases by comparison with the normal side, or to assist with preoperative planning. Specifically, we suggest the following indications for ultrasound: 1. The diagnosis and localization of FB when conventional x-ray is negative.6,7,17 2. The diagnosis of tendon rupture (and level of rupture) versus tendon adhesion. 2~ 3. The diagnosis of clinically equivocal tendinitis and peritendinitis. 4. The diagnosis of occult ganglion (ultrasound being more accurate and cost-effective than MRI). 21 5. The assessment of ganglion extent and likely site of ganglion origin (whether palpable or occult) in cases considered for open surgery. It should be emphasized that ultrasound remains an operator-dependent modality and that careful scan technique is required to avoid false-positive results. For example, failure to properly compare tendon diameters at equivalent positions could incorrectly suggest tendinitis, owing to an apparent difference in tendon size; or failure tO correctly angle the transducer to avoid artifact arising from anisotropy could produce an incorrect diagnosis of tendon rupture. Soft tissue masses were referred for ultrasound to plan the surgical approach rather than to make a specific diagnosis. The required preoperative information varied from case to case: (1) a determination of lesion number and position (eg, glomus tumor), (2) the mapping of full tumor extent and relation to deep structures, or (3) the exclusion of a firm ganglion (for which there would be no urgency about treatment). Nevertheless, ultrasound was often found to narrow the differential diagnosis or correctly suggest the final pathology (positive predictive value, 0.82), based upon an accurate delineation of lesion morphology and the probable anatomic compartment of origin. Tumor size and extent were also accurately assessed in nearly all cases. The soft tissue masses encountered in our study were exclusively benign; no data on the value of ultrasound for malignant lesions were derived. The observed limitations of ultrasound related to the narrow field of view (transducer width, 38 mm) and the underestimation of tumor extent (owing to indiscrete

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margination) in one patient with an extensive infiltrating lipoma. The exact diagnosis of many soft tissue masses can be achieved only through biopsy. The role of imaging is then chiefly one of preoperative planning or the detection of tumor recurrence. We do not advocate ultrasound for every patient with a soft tissue mass, but we suggest it be considered as one strategy of preoperative work-up when imaging is clinically warranted. The place of ultrasound versus MRI in evaluating soft tissue masses in the hand and wrist will probably depend upon the individual case and the particular requirements of the surgeon. It has been suggested that MRI can sometimes provide a specific diagnosis (eg, lipoma, hemangioma, giant cell tumor of tendon sheath), 22 and we also think that large-area infiltrative processes are better evaluated by MRI. On the other hand, ultrasound may be adequate and more cost-effective if the lesion is small and the objective is simply to provide anatomic delineation. A good example would be glomus tumor, which can present with a long delay between symptom onset and final diagnosis: ultrasound can provide inexpensive diagnosis and accurate localization much earlier. 24 This study shows little benefit in the use of ultrasound for nerve and bone lesions. Patient numbers in both of these categories were unfortunately small, but case management did not change in most situations. Nevertheless, ultrasound can visualize major peripheral nerve trunks and image complex carpal bone surfaces that cannot be readily profiled by plain radiography. These capabilities warrant further investigation. Ultrasound was of no value in the evaluation of poorly localized and clinically nonspecific wrist pain. This finding contributes to our view that diagnostic ultrasound is most effective when targeted to a specific anatomic region and required to answer a specific clinical question. Accordingly, close communication between the hand surgeon and radiologist is a key to the effective use of this test. Notwithstanding our failure to detect three TFCC tears in the group of patients with nonspecific wrist pain, no specific attempt was made during the course of our study to image this abnormality. The major carpal ligaments were also not specifically assessed, despite the fact that these can be seen. Additional roles for ultrasound in the hand and wrist reported by others have included the early diagnosis of acute suppurative tenosynovitis,8 the mapping of rheumatoid pannus in patients being

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considered for synovectomy, la evaluation o f carpal tunnel syndrome, 13 and identification of Stener lesion in cases of injury to the ulnar collateral ligament of thumb. 18,19,23

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