ultrasound of the ankle and foot - scott memorial...

U l t r a s o u n d of the A n k l e and Foot

Nandkumar M. Rawool and Levon N. Nazarian

Ultrasound is an excellent tool for evaluating common ankle problems, it is more economical than MRI and its real-time nature helps in correlating the study with the symptomatic area. US can be used in ankle to evaluate tendons (including tears, tendinits and tenosynovitis}, joints, plantar fascia, ligaments, soft tissue masses, ganglion cysts, Morton's neuroma, and to look for foreign bodies. Power Doppler can be used to evaluate blood flow in acute inflammatory process and in reflex sympathetic dystrophy. Copyright © 2000 by W.B. Saunders Company

M USCULOSKELETAL ULTRASOUND (US) has opened up new opportunities in the

field of diagnostic ultrasound. US is easily avail- able, economical, and portable. Its ability to be performed in real time helps in clinical correlation of the site of pain and comparison with the contralateral side. Movement of the tendons and joints can be directly visualized with dynamic US scanning. Structures such as tendons are better visualized with US than with MRI. Tendons appear as signal void on MRI but show a characteristic internal architecture on US.

This article reviews techniques and application of US imaging of the ankle and foot.

TECHNICAL ASPECTS

Among the different body areas that can be scanned by musculoskeletal US, we feel ankle US imaging is among the easiest. The tendons run parallel at the most commonly scanned areas and are readily accessible. However, having said this, it should be noted that it will take some practice becoming familiar with the normal appearance of tendons and other structures for one to eventually be able to diagnose pathologic conditions.

As is true in any ultrasound examination, high- resolution equipment is essential. This is especially true in musculoskeletal US, in which pathologies can sometimes be subtle. A high-frequency linear transducer should be used. The frequencies avail- able range from 7 to 13 MHz. Though a 7-MHz frequency linear transducer will usually suffice, a 10- to 13-MHz frequency broadband linear transducer is desirable and will make a significant difference in diagnostic confidence. The transducer should be placed directly on the skin with an acoustic coupling gel; no stand-off pad is neces- sary.

The ultrasound equipment presets that are suit- able for musculoskeletal imaging should be cre- ated. Though new machines or updated software versions on the older machines might have the

preconfigured musculoskeletal presets, it might become essential for one to tune the parameters (such as gray-scale maps, persistence, line density, and so on) for optimal tendon visualization.

NORMAL ANKLE TENDONS

Routine examination of the ankle tendons is begun with the patient in the prone position and the foot hanging off the examination table. We find this approach gives easier access to the posterior, medial, and lateral aspects of the ankle where most of the commonly imaged tendons of the ankle reside.

On US, a normal tendon appears as fine parallel echogenic lines alternating with thinner hypoechoic lines caused by the longitudinally oriented collagen fibrils. (Fig 1A) Though image optimization should be performed as in any other US study, one pitfall common in musculoskeletal (MS) US should be kept in mind: While scanning, it is important to make sure that the US beam is perpendicular to the tendon structure. This will ensure that normal fibers appear echogenic. If the US beam that hits the tendon fibers is not perpendicular, the tendon might appear hypoechoic. This is called anisotropy (Fig 1B). This artifact might lead to the erroneous diagnosis of abnormal tendon. Anisotropy can be corrected with heel-toeing the transducer to align the tendon fibers perpendicular to the beam.

For simplicity, the commonly imaged tendons around the ankle can be divided into groups based on anatomic site:

From the Division of Ultrasound, Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA.

Address reprint requests to Nandkumar M. Rawool, MD, Division of Ultrasound, Department of Radiology, Thomas Jefferson University Hospital, 132 South 10 th St, Philadelphia, PA 19107. E-mail: Nandkumar.Rawool @ maiL tju.edu

Copyright © 2000 by W.B. Saunders Company 0887-2171/00/2103-0007510.00/0 doi: l O.l O53/sult.2000.8561

Seminars in Ultrasound, CT, and MRI, Vo121, No 3 (June), 2000: pp 275-284 275

276 ULTRASOUND OF THE ANKLE AND FOOT

Fig 1. Normal tendon appearance. (A) Normal anterior tibial tendon shows fine parallel echogenic lines alternating with hypoechoic lines. (B) When the US beam hitting the tendon is not perpendicular the tendon appears hypoechoic (arrowheads). This is called anisotropy.

Posterior Tendons

Achilles tendon. The Achilles tendon is the largest tendon in the body and its function is to plantar flex the ankle. The US study is begun with the patient in the prone position. The tendon is first imaged in the longitudinal plane from its origin at the gastrocnemius and soleus muscle to its insertion on the calcaneus (Fig 2A,B). In this view, the Achilles is surrounded by 2 hyperechoic lines. This is the paratenon. ~ The Achilles tendon has no sheath. Dorsiflexion of the ankle helps to stretch the

Achilles tendon and keep it straight during scanning. The retrocalcaneal bursa is visualized at the insertion of the Achilles tendon on the calcaneus (Fig 2B); normally it measures less than 2.5 mm. 2 The Achilles is then examined in the transverse plane, in which it is seen as elliptical in shape (Fig 2C). The size of the normal Achilles tendon de- pends on the gender and habitus of the patient and is approximately 5 to 6 mm in the anterioposterior diameter) Other structures seen from this posterior approach include the pre-Achilles (Kager's) fat pad, the flexor hallucis longus muscle and posterior ankle joint recess.

Medial Tendons

Posterior tibial (PTT), flexor digitorum longus (FDL) and flexor hallucis longus (FHL). The PTT, FDL, and FHL are the primary adductors and inverters of the foot. With the patient still in the prone position, the transducer is placed directly behind the medial malleolus (Fig 3A). The transverse plane is imaged first because it helps get one oriented to the relative size and positions of the PTT and the FDL, which lie side by side (Fig 3B). The posterior tibial tendon measures about 4 to 6 cm in diameter. ~ The FDL tendon is about two thirds the size of PTF and, though not commonly injured, serves as a good size comparison for the PTT. The PTF is the most anterior, followed by the FDL tendon, the neurovascular bundle, and the FHL. The FHL is not part of the routine US study because it is rarely injured, but can be imaged if there is a strong clinical suspicion.

The above tendons are then imaged in the longitudinal plane. The PTT is imaged first. The scan is started at the proximal portion of the PTT above the medial malleolus (Fig 3C), the transducer is then slid distally to follow the PTT around the medial malleolus, up to the insertion at the navicular bone. (the navicular physically can be felt

Fig 2. Achilles tendon. (A) Scanning technique for the Achilles tendon. (B). Normal appearance of the Achilles tendon in longitudinal and (C) transverse axis. (c, cortical echo of the calcaneus).

RAWOOL AND NAZARIAN 277

Fig 3. Medial ankle tendons. Posterior tibial tendon and flexor digitorum Iongus: (A) scanning technique, (B) Normal appearance of PI-~ 'p' and FDL 'f" in transverse at the level of the medial malleolus "M'. (C) Longitudinal scan of PTI" at medial malleolus.

as a prominent bony protrusion distal to the medial malleolus). It should be noted that the PTT fans out at this insertion site; hence it might appear hypoechoic. This anisotropy should not be confused with an abnormality. Then this distal part of the PTT also can be imaged in the transverse plane. Up to 4 mm of fluid has been reported around the distal PTr in normal volunteers. 2

The FDL and the FHL are not commonly abnormal but can be examined scanning posterior to the PTr. The FHL can be followed as it courses under the sustentaculum tali, and all the tendons can usually be followed to their respective insertion sites in the foot.

Lateral Tendons

Peroneus longus (PL) and peroneus brevis (PB). The PL and PB are routinely examined. The primary function of the PL and PB is abduction (eversion) of the foot. The tendons are examined in a manner similar to that of the medial tendons. First, a transverse scan is performed to visualize the tendons; they lie just posterior to the lateral malleolus. Both the tendons are stacked one above the other like pancakes (Fig 4A,B). Transverse and longitudinal scans of the supramalleolar and infra- malleolar portions of the tendons are performed. Normally, some fluid might be seen (up to 3 mm) within the common peroneal sheath. 3

Anterior Tendons

The anterior tibial tendon (ATT), the extensor hallucis longus (EHL) and the extensor digitorum longus (EDL). These tendons can be evaluated. The primary function of these anterior tendons is

Fig 4. Lateral ankle tendons. Peroneal tendons. (A) Trans- verse US of Peroneus Iongus '1" and brevis tendon 'b ' at the level of lateral malleolus 'LM'. (B) Longitudinal US of the peroneai tendons. Note the tendons are stacked one on top of another,


extension or dorsiflexion of the ankle. The ATT, which can be felt as a prominent tendon, is scanned in longitudinal (Fig 1) and transverse view. One may scan other tendons if a strong clinical suspicion exists.

ANKLE TENDON PATHOLOGIES

Achilles Tendon

The Achilles is the most commonly injured ankle tendon. 4 US is useful in the diagnosis of tendinitis and complete and partial tears of the Achilles tendon. The most frequent site of rupture is the zone of relative avascularity located 2 to 6 cm proximal to the calcaneal insertionP Complete tear of the Achilles appears as a focal, complete discontinuity in the normal fibrillar pattern of the tendon. 6 With acute tears, the torn area is often filled with hematoma and appears heterogeneous (Fig 5A,B). Herniation of the Kagar's fat into the defect can sometimes be seen with complete rupture (Fig 5A). With complete tendon tear, the extent of the gap

Fig 6. Achilles partial tear. Longitudinal scan shows presence of a linear anechoic focus (arrow) with the thickened tendon consistent wi th partial tear.

should be measured with foot in dorsi and plantar flexion. Diastasis of the tendon stumps in plantar flexion is used as an indication for surgical repair, whereas complete approximation in plantar flexion is treated conservatively. 7 In chronic rupture, the tendon discontinuity is filled by echogenic granula- tion tissue. 8 A partial Achilles tear might be intrasu- bstance and appear as hypoechoic foci within the tendon (Fig 6). These tears might extend to the tendon surface and be accompanied by paratenonitis, that is fluid and inflammation in the paratenon surrounding the tendon.

In acute tendinitis, the Achilles tendon appears swollen and hypoechoic, either focally or diffusely (Fig 7). 9 There might be associated paratenonitis, presenting as a hypoechoic ring around the tendon. Chronic Achilles tendinitis usually occurs secondary to repetitive trauma and the tendon appears

Fig 5. Achilles tendon complete tear. (A) Longitudinal and (B) transverse scans show absence of normal tendon architecture. Hematoma is present with herniation of the Kager's fat (arrows) into the defect.

Fig 7. Achilles tendon acute tendinitis. Longitudinal scan shows mildly thickened, slightly hypoechoic tendon with fluid in the region of the paratenon (arrowheads).


Fig 8. Achilles tendon chronic tendinitis. Longitudinal scan shows presence of an hypoechoic area (arrows). The tendon is thickened, hut the patient had no symptoms in this ankle.

thickened and heterogeneous. Nodular hypoechoic areas or calcifications also can be seen (Fig 8). 9

US can be valuable in detecting Achilles tendon xanthomas 1° in patients with heterozygous familial hypercholesterolemia. US appearance ranges from a single hypoechoic nodule to diffusely enlarged, heterogeneously hypoechoic tendon.l° US can show the presence of hypoechoic xanthomas before they become clinically apparent, l~ Abnormality of the retrocalcaneal bursa usually can be seen as disten- tion (> 3 mm) and is frequently caused by inflammation or hemorrhagic bursitis. (Fig 9).

Posterior Tibial Tendon (PTT)

Of the 3 medial tendons, PTT is most commonly affected by pathologic processes. Tendinitis/tendinosis and tenosynovitis are the most frequent abnormalities. Clinically, PTT dysfunction is the most common cause of asymmetric flatfoot defor- mity. Other presentations include medial ankle pain, hindfoot valgus, and forefoot abduction. US

has been shown to have sensitivity of 100%, specificity of 88%, and accuracy of 93% in detecting of ankle tendon pathologies, mainly that of the FIT. 12 PTI" tears most commonly occur just distal to the medial malleolus, followed by the insertion on the navicular. 13 Chronic tear from repetitive injury is more common than acute tear.

On US, complete tear is seen as disruption of the tendon fibers, with the gap filled by hematoma. Partial tears of the PTT can be either perpendicular or parallel to the long axis of the tendon (Fig 10). Partial PTT tear appears as a linear hypoechoic area within the substance of the tendon, often correlating with the focal tenderness. Accompanying fluid in the tendon sheath might be seen and, if markedly asymmetric, should be considered abnormal. If PTT tendinitis is accompanied by abnormal fluid in the tendon sheath, the process is properly termed as tenosynovitis, indicating inflammation of the tendon and its surrounding sheath (Fig 11). 14 Tenosy-

Fig 9. Retrocalcaneal bursitis. Longitudinal scan shows an anechoic area consistent with retrocalcaneai bursitis secondary to gout (photo courtesy of J. Antonio Bouffard, MD).

Fig 10. Posterior tibial tendon large acute tear. (A) Longitu- dinal scan shows the tendon is thickened and the tear can be seen traversing the tendon (arrowheads). (B) Transverse scan shows the thickened PTT tendon 'p" wi th heterogeneous appearance. Note the relative size of the flexor digitorum Iongus tendon.


II

Fig 11. Posterior tibial tendon tenosynovitis. Transverse scan of the F i r shows fluid distending the tendon sheath. The tendon itself is slightly heterogeneous but otherwise normal. (TI, tibia)

novitis might result from systemic inflammatory conditions (arthritis, inflammation, gout, and so on) or mechanical factors such as overuse. 15 In tenosynovitis, despite the surrounding fluid, the tendon itself can appear sonographically normal. Thicken- ing of the PTT tendon can be seen, which might be focal or might extend throughout the length of the tendon. PTI" thinning has been seen in rheumatoid arthritis, 16 though there is considerable overlap with control subjects.

Peroneal Tendons (Longus and Brevis)

The common problem seen with the peroneal tendons is subluxation. Subluxation or dislocation of the peroneal tendons is caused by injury to the superior peroneal retinaculum, 17 which is often secondary to a calcaneal fracture or avulsion fracture of the lateral malleolus.18, 19 A congenital fiat or convex fibular groove also can cause dislocation. Inflammation of the peroneal tendon sheath can sometimes be seen (Fig 12).

US provides the advantage of dynamic scanning. US is performed while simultaneously dorsiflexing and everting the ankle. Subluxation is diagnosed if one or both the peroneal tendons are seen lateral and/or anterior to the lateral malleolus.

Peroneal tendon tears are relatively rare. A longitudinal partial tear (called a split) is usually seen and is more common in the peroneus brevis, because of increased stress on this tendon as it is trapped between the PL and the fibula. 2°

Anterior tibial tendon pathology is rare, likely because of the absence of a bony fulcrum and a strong vascular supply to the ATT. 21 A closed spontaneous rupture might occur .22 Sometimes a

tear or inflammation can be caused by trauma. The tendon then appears hypoechoic and is thickened (Fig 13A,B).

OTHER ASPECTS OF ANKLE ULTRASOUND

Plantar Fasciitis

Sometimes a patient presents with the ankle pain, but when asked specifically about the site of pain will point to the plantar aspect of the foot. Plantar fasciitis is reported to be the most frequent cause of inferior heel pain. US is performed with the patient in prone position and the fascia is scanned in the longitudinal axis. The normal fascia has a fibrillar echotexture and measures about 3 to 4 mm in thickness (Fig 14A). In plantar fasciitis, a mean thickness of 5.2 mm has been shown (Fig 14B). 23

Ankle Joint

The anterior joint can be examined with ultrasound in the longitudinal plane. The normal joint capsule is hyperechoic and adjacent to the anterior tibial margin and hypoechoic cartilage of the talar

Fig 12. Peroneus Iongus and brevis tendinosis with tenosynovitis. (A) Longitudinal and (B) transverse scan shows tendinosis with tenosynovitis. Note fluid in the sheath.


Fig 13. Anterior tibial tendon rupture. (A) Longitudinal scan shows the tendon (arrows) is thickened and heterogeneous with loss of normal tendon architecture indicating full-thickness tear. (B) Transverse scan shows the thickened tendon (An'). Note the size relative to the adjacent normal tendons. EHL, extensor hallucis Iongus; EDL, extensor digitorum Iongus.

dome (Fig 15A). 24 A small amount of fluid (up to 3 mm) normally can be seen in the anterior recess. 6

On US, a simple joint effusion can be shown as anechoic fluid (Fig 15B), whereas a complex effusion appears as heterogeneous fluid collection. A complex fluid collection can be caused by infection, inflammatory, or metabolic conditions. Other causes include intra-articular hemorrhage, pigmented villonodular synovitis, or synovial osteo- chondromatosis. US is also useful in showing intra-articular loose bodies. The loose bodies appear as echogenic foci that move within the joint capsule in real time. 25

Ligaments

The anterior talo-fibular ligament is the most commonly injured ankle ligament. 4 Injury can be caused by external rotation force on the tibio-talar syndesmosis. Though diagnosis is usually made clinically or by radiograph showing an avulsion bony fragment, US can be helpful to confirm the diagnosis. Normal ankle ligaments appears echogenic (Fig 16A), but appear thickened and hypoechoic when injured (Fig 16B). A complete tear appears as a hypoechoic gap through the ligament.

Soft Tissue Masses

US is useful in evaluating different soft tissue masses in the ankle. US can differentiate a solid from a cystic mass and help determine its size, shape, and, occasionally, its origin from a specific joint or tendon sheath. On US. a cyst will be anechoic, have a smooth posterior wall, and show increased through transmission. Commonly seen cystic lesions are synovial or ganglion cysts?, 24 Other masses that can be seen by US are lipomas, abscesses, vascular masses (like hemangiomas, arteriovenous malformation [AVM]), and so on. 26

Ganglion Cysts

Ganglion cysts are very common in the ankle and dorsum of the foot, second only to the hand and wrist in frequency. 27 Ganglia might present as asymptomatic masses and might be painful. They

Fig 14. Plantar fascia. Longitudinal scan of the plantar fascia (A) normal (between cursors). C, cortical echo of the distal calcaneus. (B) Markedly thickened and hypoechoic appearance suggestive of plantar fasciitis. (between arrows).

Q

F n


'Fig 17. Ganglion cyst. Palpable and tender lesion on the medial aspect of the ankle shows presence of a cyst with internal echoes (arrowhead) consistent with ganglion.

Fig 15. Anterior ankle joint. (A) Normal tibiotalar joint is hyperechoic with hypoechoic cartilage (arrowheads) of the talsr dome. Cursors show anterior tibial tendon. (B) Small effusion (arrow) is seen.

are periarticular or arise from the tendon sheaths. Most ganglia do not communicate with the joint space. Ganglion cysts are fluid-filled nontumorous structures with a synovium-like lining and a fibrous capsule. On US they appear anechoic (Fig 17), but might contain internal echoes when they are in- flamed or have undergone hemorrhage. When ganglia are large and have been present for a long time, they might cause scalloping of the underlying bone.

Morton's Neuroma

Morton's neuroma is a benign mass of perineural fibrosis affecting the plantar digital nerve. The most common cause involves repetitive trauma or mechanical compression (eg, use of high-heeled shoes).28, 29 Morton's neuroma is most commonly seen in middle-aged patients; more than 80% are

30, 31 women. Patients usually present with pain and paresthesias with walking. The most common loca- tion is the third web space, followed by the second web space, with fewer than 10% seen in the first

Fig 16. Anterior talo-fibular ligament. (A) Normal ligament (cursors). (B) Thickened and hypoechoic ligament (cursors) is seen atthe site of the pain on the contralateral side.

Fig 18. Morton's neuroma. Transverse scan of the foot shows an hypoechoic lesions (arrowheads) in the third web space. 3, third metatarsal, 4, fourth metatarsal.


Fig 19. Foreign body. Longitudinal scan of the plantar aspect of the foot shows a linear echogenic wood splinter (arrowheads). Surrounding inflammation is seen as hypoechoic halo.

and fourth spaces. In 10% of cases they are bilateral, and are multiple in 28% of cases. 28, 31, 32

US can be performed from the dorsal or the plantar aspect of the foot. US scan is performed first in the transverse and then in the longitudinal plane, starting proximal and extending distal to the metatarsal heads, with gentle pressure being ap- plied to the symptomatic metatarsal space. On US, Morton 's neuroma appears as a hypoechoic mass (Fig 18), with an average size of about 5 to 7 mm. 3°, 3], 32 Its relationship to the interdigital nerve can be established with US. US has an accuracy of 95% for detection of Morton 's neuroma. 28

Foreign Bodies

Foreign bodies from penetrating injuries are common in the foot. Foreign bodies include glass, wood, and metal. US is an excellent method for detecting radiolucent foreign bodies. Foreign bodies can be detected by the echoes they produce. Sometimes a distal acoustic shadowing is seen and, in case of metal objects, a comet-tail reverberation artifact can be seen. A hypoechoic halo sometimes can be seen around the foreign body and can aid in localizing the foreign body (Fig 19). US has been shown to have an accuracy of 92%, sensitivity 90%, and specificity 97%. 33 Foreign bodies as small as 1 mm x 0.5 mm have been localized with US .34

Fig 20. Power Doppler US. (A) A ruptured posterior tibia tendon shows increased blood flow compared to (B) contralateral side, where the tendon is normal.

Applications of Power Doppler (PD) US:

PD can be an additional tool in diagnosing musculoskeletal abnormalities. Increased power Doppler flow can be seen in acute inflammatory process (Fig 20 A,B). 35 Increased power Doppler flow has been shown in soft tissues of patients with reflex sympathetic dystrophy. 36

CONCLUSION

US is emerging as a new modali ty for musculoskeletal imaging. US can be performed faster and at lower expense than MRI, and its excellent showing of the tendon structure should make US the first- line modali ty for evaluating ankle tendons. A focal

dynamic examination of the symptomatic area with clinical correlation helps pinpoint the diagnosis. Though US is highly user-dependent, its applications in musculoskeletal US will definitely increase as more experience is gained. We have found that getting the referring physicians involved in the US study has helped increase the awareness of the availabili ty of this new diagnostic modality.

R E F E R E N C E S

1. Martinoli C, Derchi LE, Pastorino C, et al: Analysis of echotexture of tendons with US. Radiology 186:839-843,1993

2. Nazarian LN, Rawool NM, Martin CE, et ah Synovial fluid in the hindfoot and ankle: Detection of amount and distribution with US. Radiology 197:275-278,1995

3. van Holsbeeck MT, Introcaso JH: Musculoskeletal Ultra- sound. St Louis, MO, Mosby-Year Book, 1991, pp 1-327

4. Reinherz RE Zawada S J, Sheldon DP: Recognizing un- usual tendon pathology at the Ankle. J Foot Surg 25:278- 283,1986

5. Scheller AD, Kasser JR, Quigley TB: Tendon injuries about the ankle. Orthop Clin North Am 11 ;801-811,1980

6. Fornage BD: Achilles tendon: US examination. Radiology 159:759-764,1986


7. Thermann H, Hoffman R, Zwipp H, et al: The use of ultrasound in the foot and ankle. Foot Ankle 13:386-390,1992

8. Fornage BD: Achilles tendon: Ultrasound examination. Radiology 159;769-764,1986

9. Fornage BD, Rifkin MD: Ultrasound examination of tendons. Radio Clin North Am 26:87-107,1988

10. Bude RO, Adler RS, Bassett DR, et al: Heterozygous familial hypercholesterolemia: Detection of xanthomas in the Achilles tendon with US. Radiology 188:567-571,1993

11. Bureau N J, Roederer G: Sonography of Achilles tendon xanthomas in patients with heterozygous familial hypercholesterolemia. A JR 171:745-749,1998

12. Waitches GM, Rockett M, Brage M, et al: Ultrasonograph- ic-surgical correlation of ankle tendon tears. J Ultrasound Med 17:249-256,1998

13. Johnston K: Tibialis Posterior Tendon Rupture. Clin Orthop 11:801-811,1983

14. Stephenson CA, Siebert JJ, McAndrew MP, et al: Sono- graphic diagnosis of tenosynovitis of the posterior tibial tendon. J Clin Ultrasound 18:114-116,1990

15. Fessell DP, Vanderschueren GM, Jacobson JA, et al. US of the ankle: Technique, anatomy, and diagnosis of pathologic conditions. Radiographics 18:235-340,1998

16. Coakley EV, Samanta AK, Finlay DB: Ultrasonography of the tibialis posterior tendon in rheumatoid arthritis. Br J Rheumatol 33:273-277,1994

17. Sammarco GJ: Peroneal tendon injuries. Orthop Clin North Am 25:135-145,1994

18. McConkey P, Favero KJ: Subluxation of the peroneal tendons within the peroneal tendon sheath: A case report. Am J Sports Med 15:511-513,1987

19. Church CC: Radiographic diagnosis of acute peroneal tendon dislocation. Am J Roentgen 129:1065-1068,1977

20. Khoury NJ, El-Khoury GY, Saltzman CL, et al: Peroneus longus and brevis tendon tears: MR imaging evaluation. Radiol- ogy 200:833-841,1996

21. Scheller AD, Kasser JR, Quigley TB: Tendon injuries about the ankle. Orthop Clin North Am 11: 801-811,1980

22. Khoury NJ, El-Khoury GY, Saltzman CL, et al: Rupture of the anterior tibial tendon: Diagnosis by MR imaging. A JR 167:351-354,1996

23. Cardinal E, Chhem RK, Beauregard CG, et al: Plantar fasciitis: Sonographic evaluation. Radiology 201:257-259,1991

24. Chhem RK, Beauregard G, Schmutz GR, et al: Ultraso- nography of the ankle and hindfoot. Can Assoc Radiol J 44:337-341,1993

25. Frankel DA, Bargiela A, Bouffard JA, et al: Synovial joints: Evaluation of intra-articular bodies with US. Radiology 206:41-44,1998

26. Vanderschueren G, Fessell DE van Holsbeeck MT: Ankle ultrasound, in Guidelines and Gamuts in Musculoskeletal Ultra- sound. Wiley, 1998

27. Llanger J, Palmer J, Monill JM, et al: MR imaging of benign soft-tissue masses of the foot and ankle. Radiographics 18:1481-1498,1998

28. Sobiesk GA, Wertheimer S J, Schultz R, et al: Sono- graphic evaluation of interdigital neuromas. J Foot Ankle Surg 36: 364-366,1997

29. Zanetti M, Strehle JK, Zollinger H, et al: Morton's neuroma and fluid in the intermetatarsal bursa on MR images of 70 asymptomatic volunteers. Radiology 203:516-520,1997

30. Pollak RA, Bellacosa RA, Dornbluth NC, et al: Sono- graphic analysis of Morton's neuroma. J Foot Surg 31:534- 537,1992

31. Redd RA, Peters VJ, Emery SF, et al: Morton's neuroma: Sonographic evaluation. Radiology 171:415-417,1998

32. Kaminsky S, Griffin L, Milsap J, et al: Is ultrasonography a reliable way to confirm the diagnosis of Morton's neuroma? Orthopedics 20:37-39,1997

33. Jacobson JA, Powell A, Craig JG, et al. Wooden foreign bodies in soft tissue: Detection at US. Radiology 206:45- 48,1998

34. Failla JM, van Holsbeeck MT, Vanderschueren G: Detec- tion of 0.5 mm thick thorn using US: A case report. J Hand Surg 20:456-457,1995

35. Newman JS, Adler RS: Power Doppler sonography: Applications in musculoskeletal imaging. Semin Musculoskel Radiol 2:331-339,1998

36. Nazarian LN, Schweitzer ME, Mandal S, et al. Increased soft-tissue blood flow in patients with reflex sympathetic dystrophy of the lower extremity revealed by power Doppler sonography. A JR 171:1245 - 1250,1998

ultrasound of the ankle and foot - scott memorial...

Documents