Ultrasonography in Tarsal Tunnel Syndrome - Journal of Ultrasound ...

Article
Ultrasonography in
Tarsal Tunnel Syndrome
Masahiro Nagaoka, MD, Hiromi Matsuzaki, MD
Objective. The purpose of this study was to clarify the diagnostic value of ultrasonography in tarsal
tunnel syndrome. Methods. Seventeen patients (17 feet) with tarsal tunnel syndrome were treated
between 1988 and 2003. Preoperative ultrasonography was performed, and the cause of the syndrome
was confirmed intraoperatively in all cases. Long and short axes of the tarsal tunnel were
scanned to ascertain the presence of any space-occupying lesion. Results. The causes of tarsal tunnel
syndrome, as confirmed by surgery, were ganglia (n = 10), talocalcaneal coalition (n = 1), talocalcaneal
coalition associated with ganglia (n = 3), and varicose veins (n = 3). Among the cases involving ganglia,
hypoechoic or anechoic regions were observed. The mean sizes ± SD of these regions were 19.4
± 8.8 mm in the long axis, 15.2 ± 6.3 mm in the short axis, and 10.4 ± 3.8 mm in depth. Of these, 3
ganglia were not clearly palpable before surgery and were small: 10 × 10 × 7, 13 × 11 × 9, and 9 × 8
× 7 mm. Among the cases involving talocalcaneal coalition, ultrasonography indicated a beak-shaped
bony process on the short axis images. Although these 3 cases were associated with ganglia, this could
not be determined by preoperative palpation. Conclusions. As a diagnostic imaging technique for
tarsal tunnel syndrome, ultrasonography is extremely useful for identifying space-occupying lesions.
Ultrasonography should be performed routinely in patients with suspected tarsal tunnel syndrome.
Key words: entrapment neuropathy; ganglion; talocalcaneal coalition; tarsal tunnel syndrome; ultrasonography.
Abbreviations
MRI, magnetic resonance imaging
Received January 24, 2005, from the Orthopaedic
Department, Surugadai Nihon University Hospital,
Tokyo, Japan. Revision requested February 14,
2005. Revised manuscript accepted for publication
March 14, 2005.
Address correspondence to Masahiro Nagaoka,
MD, Orthopaedic Department, Surugadai Nihon
University Hospital, 1-8-13 Kanda Surugadai,
Chiyoda-ku, Tokyo 101-8309, Japan.
Tarsal tunnel syndrome is a neuropathic entrapment
of the tibial nerve and its branches on the
medial side of the ankle and is characterized by
numbness and pain in the toes and sole of the
foot. Although this syndrome is a common form of
entrapment syndrome of the lower extremity, it is not as
common as carpal tunnel syndrome. Studies have documented
that tarsal tunnel syndrome can be caused by
trauma, foot deformation, varicose veins, ganglia, or talocalcaneal
coalition. 1–4
Tarsal tunnel syndrome is diagnosed by clinical examination
and based on findings such as area of sensory disturbance
and positive Tinel sign over the tarsal tunnel
that are then confirmed by electrodiagnosis. Diagnostic
imaging is also useful for ascertaining the cause of tarsal
tunnel syndrome. Although radiography is essential in
the diagnosis of talocalcaneal coalition, ultrasonography
and magnetic resonance imaging (MRI) can be useful for
diagnosing soft-tissue lesions. 5–8 Our study reports the
utility of ultrasonography for preoperative diagnosis in
© 2005 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 2005; 24:1035–1040 • 0278-4297/05/$3.50

Ultrasonography in Tarsal Tunnel Syndrome
Figure 1. Malleolar-calcaneal axis.
17 patients (17 feet) with tarsal tunnel syndrome
and investigates the diagnostic value of the
technique.
Materials and Methods
Between 1988 and 2003, ultrasonography was
performed preoperatively and then surgery was
performed on 17 patients (11 men and 6 women;
17 feet) with tarsal tunnel syndrome. The mean
age was 42.4 years (range, 12–72 years). Tarsal
tunnel syndrome affected the right foot in 8
patients and the left foot in 9 patients. All patients
showed a positive Tinel sign with percussion of
the tibial nerve over the tarsal tunnel on the
affected side. In all cases, electrophysiologic
examination confirmed abnormality in sensory
nerve conduction velocity between the big toe
and the tarsal tunnel or distal latency of the
abductor hallucis muscle.
Ultrasonographic examinations were performed
with an SSD-1200 scanner (Aloka Co, Ltd,
Tokyo, Japan) equipped with a probe (10-MHz
mechanical sector transducer), and images were
evaluated by an orthopedic surgeon (M.N.) with
several years of experience in musculoskeletal
ultrasonography. Ultrasonographic examinations
were performed within 1 week before
surgery. The probe was positioned parallel
(short axis) and perpendicular (long axis) to the
malleolar calcaneal axis (Figure 1). 9 Preoperative
ultrasonographic findings were compared with
intraoperative findings. If a ganglion was suspected,
the size, location, morphologic characteristics,
and relationship between the posterior
tibial artery and the ganglion were ascertained.
The maximum diameters of each mass were
measured along the long axis and short axis and
from a perspective of depth.
Results
The causes of tarsal tunnel syndrome, as determined
on the basis of intraoperative findings,
were ganglia in 10 cases, talocalcaneal coalition
in 1 case, talocalcaneal coalition associated with
ganglia in 3 cases, and varicose veins in 3 cases.
The findings based on preoperative ultrasonography
were consistent with the intraoperative
findings. There were no false-negative results in
our study.
Ultrasonographic examinations in the 13
cases involving ganglia showed hypoechoic or
anechoic regions. The mean sizes ± SD of these
regions were 19.4 ± 8.8 mm (range, 8–31 mm) in
the long axis, 15.2 ± 6.3 mm (range, 8–25 mm) in
the short axis, and 10.4 ± 3.8 mm (range, 4–16
mm) in depth. The size and morphologic characteristics
of the ganglia as determined intraoperatively
were consistent with data from the
preoperative ultrasonographic examination.
Regarding the relationship between the posterior
tibial artery and the ganglion in these cases,
the artery was positioned under the ganglion in
7 cases, on top of the ganglion in 4 cases, and
adjacent to the ganglion in 2 cases. A mass was
clearly preoperatively palpable in the tarsal tunnel
in 11 of the 17 cases. These cases involved a
ganglion (n = 8) or talocalcaneal coalition associated
with a ganglion (n = 3).
Of the 6 impalpable cases, a diffuse swelling
was seen in 3 patients but was not palpable, and
the 3 ganglia were small: 10 × 10 × 7, 13 × 11 × 9,
and 9 × 8 × 7 mm. The other 3 cases were due to
varicose veins. The varicose veins appeared as
bulbous intermittent hypoechoic shadows in
ultrasonographic examination.
The 4 cases of tarsal tunnel syndrome caused
by talocalcaneal coalition were confirmed by
radiography. Ultrasonography revealed a beakshaped
bony process on short axis images.
Although ganglia accompanied 3 cases, these
were not detected by palpation preoperatively.
1036 J Ultrasound Med 2005; 24:1035–1040

Nagaoka and Matsuzaki
Case Presentation
Case 1
A 64-year-old man had a 2-month history of
numbness in the left foot. Numbness persisted
and was marked in the big toe. The area inferior
to the medial malleolus was diffusely swollen,
and the Tinel sign was positive. Although radiography
showed no abnormality, ultrasonography
revealed a hypoechoic region inferior to the
medial malleolus (Figure 2). Surgery was performed,
and a ganglion was observed under the
flexor retinaculum; the tibial nerve was compressed
under the ganglion (Figure 3). The ganglion
arising from the flexor pollicis longus
muscle tendon sheath was resected with the tendon
sheath. Numbness disappeared 4 months
after surgery.
Case 2
A 16-year-old girl had a 2-month history of
numbness of the right foot. The medial side of
the right foot and big toe exhibited numbness.
A bony prominence was seen inferior to the
medial malleolus of the tibia, and the Tinel sign
was positive. Radiography showed shadowing
indicative of talocalcaneal coalition (Figure 4).
Ultrasonography depicted the coalition as a
beak-shaped lesion shadowing in the long axis
scan. In addition, imaging in the short axis scan
showed an elliptical 8-mm hypoechoic region,
suggesting that the talocalcaneal coalition was
complicated by a ganglion (Figure 5). Surgery
was performed. A ganglion was on the coalition
(Figure 6), and the medial plantar nerve was
over the ganglion and subject to friction during
dorsal flexion of the ankle. The coalition and
ganglion were excised. Numbness disappeared
2 months after surgery.
Although conditions similar to tarsal tunnel syndrome
had been reported previously, Keck
(1962) 10 and Lam (1962) 11 were the first to use
that particular terminology. The tibial nerve
passes through the medial side of the ankle and
branches into the medial plantar nerve, lateral
plantar nerve, and medial calcaneal branch. 9
This area is called the tarsal tunnel and is made
of a neurovascular bundle, a posterior tibial tendon,
a flexor digitorum longus tendon, and a
flexor hallucis longus tendon. These components
are covered by the flexor retinaculum
from the medial malleolus of the tibia to the calcaneus.
Unlike the carpal tunnel, however, components
are separated within the tarsal tunnel
by a septum 3,12 ; therefore, slight changes in this
space can easily result in neuropathy.
The causes of tarsal tunnel syndrome include
idiopathic conditions, traumatic conditions (eg,
calcaneal or ankle fracture), foot deformities
(varus or valgus heel), space-occupying lesions,
and varicose veins. 1,4,13,14 In the Japanese literature,
tarsal tunnel syndrome caused by spaceoccupying
lesions is well documented, with
cases involving ganglia and talocalcaneal coalition
being prominent. 15,16 In 1991, Takakura et
al 17 found that a ganglion or talocalcaneal coalition
was the cause of tarsal tunnel syndrome in
31 of 50 feet. Ultrasonography can be a valuable
means of diagnosing cases such as these.
Talocalcaneal coalition is a congenital fibrous,
cartilaginous, or osseous union that often leads
to tarsal tunnel syndrome. Ultrasonography is
capable of showing the beak-shaped bony
prominence in the tarsal tunnel that indicates
talocalcaneal coalition, without the need
for radiography or computed tomography.
Furthermore, although radiography can identify
this beak-shaped bony prominence, it is not
capable of showing ganglia that often accompany
this condition. 16,18 In 1998, Takakura et al 19
performed preoperative MRI in 5 of 7 patients
with talocalcaneal coalition involving ganglia,
and although the ganglia were detected preoperatively
in 3 cases, they were found only during
Figure 2. Case 1. Long axis sonogram showing an elliptical hypoechoic shadow.
Discussion
J Ultrasound Med 2005; 24:1035–1040 1037

Ultrasonography in Tarsal Tunnel Syndrome
A
B
Figure 3. Case 1. A, After the flexor retinaculum was cut, the medial plantar nerve was found to be compressed by a ganglion. B, The ganglion was
separated from the medial plantar nerve.
surgery in 2 cases. In our 3 cases of talocalcaneal
coalition involving ganglia, the ganglia were
detected preoperatively by ultrasonography in all
cases. Because ganglia are sometimes involved in
the onset of symptoms of tarsal tunnel syndrome,
ultrasonography should be conducted
preoperatively even when the condition has
already been identified by radiography.
Figure 4. Case 2. Radiograph showing talocalcaneal coalition. Asterisk indicates a
portion of the beak.
Several MRI studies on tarsal tunnel syndrome
have been reported 6,20–23 ; however, relatively
few studies involving ultrasonography have
been conducted. Because ultrasonography is
highly capable of showing small lesions, identification
of small masses that cannot be shown
by MRI may be possible. Kerr and Frey 24 noted
that MRI showed no abnormalities in 17 of 19
surgical cases, including 1 case of a ganglion
and 8 cases of varicose veins or varicosities;
however, in 1 of the 2 patients in whom MRI
showed no abnormality, a small ganglion was
seen during surgery. 24 In our study, MRI was
performed in only a small number of patients,
and, subsequently, the results cannot be easily
compared; however, small ganglia that were not
palpable in the tarsal tunnel were shown on
preoperative ultrasonography in 4 cases.
Because dynamic analysis is possible with
ultrasonography, arterial pulsation is easily
assessed. This type of information is useful for
ascertaining positional relationships of the
tarsal tunnel to a space-occupying lesion and
nerves. In addition, during surgery, preoperative
knowledge of the location of any spaceoccupying
lesion is very useful. Moreover, if a
large ganglion is seen, aspiration can be performed
if a nerve is located on the bone side of
the ganglion.
1038 J Ultrasound Med 2005; 24:1035–1040

Nagaoka and Matsuzaki
A
Figure 5. Case 2. A, Short axis sonogram showing the beak-shaped region. Asterisk indicates a portion of the beak. B, Long axis sonogram showing a
small hypoechoic region (arrow) on top of the beak.
B
Varicose veins have been closely examined as
a causative factor in tarsal tunnel syndrome.
10,12,13,23,25,26 Lau and Daniels 14 reviewed
25 articles that studied 186 cases of tarsal tunnel
syndrome in 164 patients and found that
varicosities were the primary cause in 13% of
all operated cases; however, this figure reflects
only operated cases. Our study also deals only
with varicosity as a clear abnormal intraoperative
finding. Future studies will need to analyze
the role of varicose veins in idiopathic cases.
As a diagnostic imaging technique for tarsal
tunnel syndrome, ultrasonography is extremely
useful for diagnosing space-occupying
lesions. When tarsal tunnel syndrome is suspected,
ultrasonography should be performed
routinely.
Figure 6. Case 2. A, The medial plantar nerve (arrow) was positioned above the talocalcaneal coalition. B, A small ganglion (arrow) was found under
the medial plantar nerve.
A
B
J Ultrasound Med 2005; 24:1035–1040 1039

Ultrasonography in Tarsal Tunnel Syndrome
References
1. Cimino WR. Tarsal tunnel syndrome: review of the
literature. Foot Ankle 1990; 11:47–52.
2. DiStefano V, Sack JT, Whittaker R, Nixon JE. Tarsaltunnel
syndrome: review of the literature and two
case reports. Clin Orthop 1972; 88:76–79.
3. Edwards WG, Lincoln CR, Bassett FH III, Goldner JL.
The tarsal tunnel syndrome: diagnosis and treatment.
JAMA 1969; 27:716–720.
4. Radin EL. Tarsal tunnel syndrome. Clin Orthop 1983;
181:167–170.
5. Delfaut EM, Demondion X, Bieganski A, Thiron MC,
Mestdagh H, Cotten A. Imaging of foot and ankle
nerve entrapment syndromes: from well-demonstrated
to unfamiliar sites. Radiographics 2003; 23:
613–623.
6. Machiels F, Shahabpour M, De Maeseneer M,
Schmedding E, Wylock P, Osteaux M. Tarsal tunnel
syndrome: ultrasonographic and MRI features. JBR-
BTR 1999; 82:49–50.
7. Martinoli C, Bianchi S, Gandolfo N, Valle M,
Simonetti S, Derchi LE. US of nerve entrapments in
osteofibrous tunnels of the upper and lower limbs.
Radiographics 2000; 20:199–213.
8. Peer S, Kovacs P, Harpf C, Bodner G. High-resolution
sonography of lower extremity peripheral nerves:
anatomic correlation and spectrum of disease.
J Ultrasound Med 2002; 21:315–322.
9. Dellon AL, Mackinnon SE. Tibial nerve branching in
the tarsal tunnel. Arch Neurol 1984; 41:645–646.
10. Keck C. The tarsal tunnel syndrome. J Bone Joint
Surg Am 1962; 44:180–182.
11. Lam SJS. A tarsal tunnel syndrome. Lancet 1962;
2:1354–1355.
16. Ngaoka M, Satou K. Tarsal tunnel syndrome caused
by ganglia. J Bone Joint Surg Br 1997; 81:607–610.
17. Takakura Y, Kitada C, Sugimoto K, Tanaka Y, Tamai
S. Tarsal tunnel syndrome: causes and results of
operative treatment. J Bone Joint Surg Br 1991;
73:125–128.
18. Yamamoto S, Tominaga Y, Yura S, Tada H. Tarsal tunnel
syndrome with double causes (ganglion, tarsal
coalition) evoked by ski boots: case report. J Sports
Med Phys Fitness 1995; 35:143–145.
19. Takakura Y, Kumai T, Takaoka T, Tamai S. Tarsal tunnel
syndrome caused by coalition associated with a
ganglion. J Bone Joint Surg Br 1998; 80:130–133.
20. Erickson SJ, Quinn SF, Kneeland JB, et al. MR imaging
of the tarsal tunnel and related spaces: normal
and abnormal findings with anatomic correlation.
AJR Am J Roentgenol 1990; 155:323–328.
21. Frey C, Kerr R. Magnetic resonance imaging and the
evaluation of tarsal tunnel syndrome. Foot Ankle
1993; 14:159–164.
22. Lee MF, Chan PT, Chau LF, Yu KS. Tarsal tunnel syndrome
caused by talocalcaneal coalition. Clin
Imaging 2002; 26:140–143.
23. Zeiss J, Fenton P, Ebraheim N, Coombs RJ. Magnetic
resonance imaging for ineffectual tarsal tunnel surgical
treatment. Clin Orthop 1991; 264:264–266.
24. Kerr R, Frey C. MR imaging in tarsal tunnel syndrome.
J Comput Assist Tomogr 1991; 15:280–286.
25. Gould N, Alvarez R. Bilateral tarsal tunnel syndrome
caused by varicosities. Foot Ankle 1983; 3:290–292.
26. Sammarco GJ, Chang L. Outcome of surgical treatment
of tarsal tunnel syndrome. Foot Ankle Int
2003; 24:125–131.
12. Lam SJS. Tarsal tunnel syndrome. J Bone Joint Surg
Br 1967; 49:87–92.
13. Pfeiffer WH, Cracchiolo A III. Clinical results after
tarsal tunnel decompression. J Bone Joint Surg Am
1994; 76:1222–1230.
14. Lau JT, Daniels TR. Tarsal tunnel syndrome: a review
of the literature. Foot Ankle Int 1999; 20:201–209.
15. Kinoshita M, Okuda R, Morikawa J, Abe M. Tarsal
tunnel syndrome associated with an accessory muscle.
Foot Ankle Int 2003; 24:132–136.
1040 J Ultrasound Med 2005; 24:1035–1040