Surgical Experiences of the Tarsal Tunnel Syndrome

Surgical Experiences of the Tarsal Tunnel Syndrome
Jae Taek Hong, M.D.,1 Sang Won Lee, M.D.,1 Byung Chul Son, M.D.,1
Jae Hoon Sung, M.D.,1 In Soo Kim, M.D.,1 Moon Chan Kim, M.D.2
Department of Neurosurgery,1 St. Vincent Hospital, The Catholic University of Korea, Suwon, Korea
Department of Neurosurgery,2 Kangnam St. Marys’ Hospital, The Catholic University of Korea, Seoul, Korea
Objective : Tarsal tunnel syndrome is a rare compressive neuropathy. In Korea, the reported cases of the tarsal tunnel syndrome are mainly related to diagnosis, so there are only a few reports about the surgical result. We report the significance of the decompressive surgery for the tarsal tunnel syndrome. Methods : Seven patients with tarsal tunnel syndrome were treated surgically. The patients were aged 31-70 years (mean 53.1 years), and all of them complained of pain or dysesthesia of the sole of the foot. The posterior tibial nerve and its branches were decompressed through the flexor retinaculum and under the abductor hallucis muscle fascia. Results : Surgical decompression was beneficial in most patients with tarsal tunnel syndrome in their feet. Neither wound infection nor recurrence of symptoms was found during the follow up period (mean 12.9 months). Conclusion : Surgical decompression is the good option for the treatment of the tarsal tunnel syndrome, especially in the cases of short symptom duration or mass lesion.
KEY WORDS : FootTarsal tunnel syndromeDecompressive surgery.
C linical A
rticle
Introduction
Tarsal tunnel syndrome (TTS) is a rare entrapment neuropathy of the posterior tibial nerve or its branches at the vicinity of
the ankle joint caused by diverse etiologies. The main symptoms of TTS are podalgia, abnormal sensation, and the change in motor functions, etc2,22,25).
The etiology, symptoms and treatments of TTS are reported to be similar to the entrapment neuropathy of the median nerve, so called carpal tunnel syndrome (CTS) and thus referred to as CTS of the ankle joint, sometimes9,19). The characteristics of TTS are its low absolute frequency, the difficulty of early diagnosis due to its vague symptoms in many cases, and the poor outcome of surgery due to the delayed decision of surgery22).
As its therapeutic modes, most investigators believe that only the surgical decompression is effective1,14,21). The efficient therapeutic mode is controversial, however, as a few investigators have reported the high success rate of the conservative treatment28). We identified prognostic factors related to the outcome of treatments by the analysis of TTS patients treated by surgery in
the last 6 years. Here, we report the results together with a brief review of reports in the literature.
Materials and Methods
The study population was 7 patients diagnosed as TTS and treated by the decompression of tarsal tunnel and neurolysis
at our hospital from 1998 to 2003. The diagnosis was made based on history taking, thorough neurological examination, electromyo- gram (EMG), and radiographic tests such as sonogram, magnetic resonance image (MRI). The diagnosis was confirmed finally by surgical findings and histological tests.
Sex, age, the site, the etiology, the duration of symptoms, the presence or absence of pain, abnormal sensation, Tinel sign, the presence or absence of muscle atrophy, and the follow up period compared patients in individual cases. The presurgical and the postsurgical results were compared by Takakura’s rating scale that calculate the point based on the pain in the foot, causalgia, Tinel sign, the presence of absence of abnormal sensation, muscle atrophy and muscle weakness. In Takakura's rating scale, 10 points is excellent, 8-9 points is good, 6-7 points is average, and less than 5 points is poor27).
Indication for surgery was the pain or abnormal sensation in the posterior tibial nerve and the branches spreading radial to its traveling direction, the pain in the plantar with Tinel signs, and the positivity in EMG. Sonogram or MRI was performed to confirm
ReceivedMay 27, 2004 AcceptedAugust 16, 2004 Address for reprintsSang Won Lee, M.D., Department of
Neurosurgery, St. Vincent Hospital, The Catholic University of Korea, 93-6 Chi-dong, Paldal-gu, Suwon 442-723, Korea Tel031) 249-7190, Fax031) 245-5208 E-mail : [email protected]
J Korean Neurosurg Soc 36 : 443-447, 2004K I S E P
Tarsal Tunnel Syndrome
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the space occupying lesions such as the tumor mass, synovitis, bony spur of the calcaneus, and other bone lesions in the vicinity of the tarsal tunnel. Surgical procedure was the decompression of the posterior tibial nerve as well as the medial and lateral plantar nerve. In patients with the space occupying lesions that were confirmed during the presurgical test, the lesions were removed. Prior to surgery, air tourniquet was applied to the thigh for the hemostasis of the surgical area. The nerve function was confirmed by measuring the nerve action potential(NAP) during surgery. In the surgery, applying the end of the medial malleolus as the reference point, the flexor retinaculum was exposed by the curved medial excision. The decompression was performed by excising a portion of the fascia of the abductor hallucis muscle to identify the distal part of the medial and lateral plantar nerve.
Results
The age range of the patients was from 31 years to 70 years. The mean age was 53.1 years. The sex ratio was 3 males
and 4 females. The ratio of the right and left was 4:3, which was not significantly different. The symptom duration was from 3 months to 36 months. The mean duration was 15.1 months and the mean follow-up period was 12.9 months (2~30months). The frequent clinical symptoms were abnormal sensation and pain in the plantar area. Most symptoms were aggravated by walking and decreased by resting. The pain radiating to the medial calf was observed in some cases. In clinical examination, upon performing the percussion on the posterior margin of the medial malleolus and the running area of the posterior tibial nerve, the positivity of Tinel signs, the spread of abnormal sensation to the distal area, was detected in all patients. In 2 cases with intensified Tinel sign in the running area of the medial planar nerve (case 1 and case 2), space-occupying lesions (ganglion and bony spur) were identified by radiographic tests. The outcome of surgery was analyzed by Takakura's rating scale. The recovery pattern, from the presurgical 3.3 (1-6) to the postsurgical 7.4 (3-10), was detected. In most
cases, the pain in the plantar area was attenuated at early times. Tinel sign, abnormal sensation in the planar area, and muscle atrophy were recovered slowly. The overall postsurgical score was 2 excellent, 3 good, 1 fair, and 1 poor (Table 1).
The ganglions removed from the case 1 and 6 were originated from the connective tissue of the perineurium. During its removal, special attentions have been paid while incising subcutaneous tissues to avoid iatrogenic injury. The surgery was performed readily as the size, location and the adhesion to the nerve was assessed prior to surgery by magnetic resonance image. During the surgery, the compression of the tibial nerve and its branches by the ganglion was detected (Fig. 1, 2). The outcome of surgery was good : excellent in 1 case and good in 1 case.
In the adhesion cases caused by fibrous proliferation in the vicinity of the nerve (Fig. 3), the external neurolysis of each nerve and the decompression of the flexor retinaculum were performed. The outcome of surgery was excellent in 1 case, good in 2 cases, and average in 1 case. The overall surgical outcome of the idiopathic fibrous thickening cases was poorer than the cases with space occupying lesions. In the case with the nerve injury by trauma and subsequent bony spur formation after trauma (case 2), the outcome was relatively poor (Fig. 4).
The outcome according to age was better in younger patients group (less than 60 years) except in the case of trauma. In the analysis according to the duration of symptoms, the outcome was relatively good in cases less than 4 months. It is noteworthy that in a patient diagnosed with diabetic neuropathy in preoperative EMG (case 3), the outcome of treatments was good.
Discussion
TTSis a recently defined disease, although the sequela of the injury of the posterior tibia nerve has been reported
previously. In 1960, Kopell and Thompson18) described TTS for the first time. Keck and Lam16) described the definition of TTS in 1962. TTS is an entrapment neuropathy that the flexor
retinaculum compresses the post- erior tibial nerve and its branch posterior to the medial malleolus. Although the precise frequency of this disease entity is not known yet, it is reported to be rarer than CTS or cubital tunnel syndrome2).
Anatomically, the flexor retina- culum is the structure forming the roof of the tarsal tunnel that is referred to as the lacinate ligament in some reports24). The tibia forms
Table 1. Summary of the clinical findings in the seven patients
Case Age
Side Pain Tinel Sensory Muscle Sx duration F/U duration Takakura score
Etiology /Sex sign disturb atrophy (Months) (Months) preop postop
1 55/M Rt O O O X 04 02 3 10 Ganglion cyst
2 31/M Lt O O O O 12 30 1 13 Trauma,
Osteophyte
3 70/F Lt(B) X O O X 16 07 5 09 Idiopathic, DM
4 36/F Lt X O X X 03 06 6 10 Idiopathic
5 66/F Rt(B) O O O X 36 18 1 06 Idiopathic
6 57/M Lt O O O X 11 20 3 08 Ganglion cyst
7 57/F Rt(B) O O O X 24 07 4 08 Idiopathic
Disturb : Disturbance, Sx : Symptom, F/U : Follow Up, preop : Preoperative score, postop : Postoperative score, Rt : Right, Lt : Left, (B) : Both tarsal tunnel syndrome with unilateral decompression surgery
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the anterior bou- ndary the tarsal tunnel and the Talus and the Calcaneus forms the lateral boun- dary of the tarsal tunnel. The fle- xor retinaculum covers the tarsal tunnel and attac- hed to the fascia of the tibialis po- sterior muscle, the flexor digito- rum longus mu- scle and flexor hallucis longus muscle. The fle- xor retinaculum is a radial struc- ture with various shapes and thic-
kness, and its range is diverse. In some cases, it reaches above the medial malleolus by 10 cm and attached to the distal susten- taculum tali20).
The posterior tibial nerve is a branch of the sciatic nerve that runs along the posterior lower limbs, between the gastrocnemius muscles, the medial side of the tibia, and divided to the medial, lateral plantar nerve and medial calcaneal nerves in the vicinity of the tarsal tunnel14). In most cases, posterior tibial nerve bifurcates into the medial and lateral plantar nerves after passing the distal flexor retinaculum. As the medial calcaneal nerve has been reported passing through the flexor retinaculum at 34%, it is the structure that attentions should be paid during the surgery
for TTS5,6,10). There are two most stenotic areas in the tarsal tunnel. The one is the flexor retinaculum, and the other is under the abductor hallucis fascia. Flexor retinaculum is the area where the medial and lateral plantar nerve changes their direction and move down to the sole of the foot. Compartmental- izaion of the tarsal tunnel under the flexor retinaculum is created by several deep fibrous septa that extend from the undersurface of
the flexor retinaculum between the tendons and neurovascular bundle. This causes the posterior tibial nerve to be relatively immobile and vulnerable to traction forces or space occupying lesions6,10). Under the abductor hallucis muscle, there are separate anatomic tunnel for medial and lateral plantar nerve11). The fascia of abductor hallucis muscle forms the roof for both of these tunnels. The division between the medial and lateral plantar tunnels is a fibrous septum that originates from the fibro- osseous canal of the flexor hallucis longus tendon or directly from the calcaneus. The nerve entrapment occurs readily in these areas and thus causes TTS11). Thus, operative treatment should take into account the compression of the posterior tibial nerve by the flexor retinaculum and also the plantar nerves under the abductor hallucis.
TTS occurs primarily in adults. Its various etiologies, classified as internal and external factors, have been reported. The external factors are dislocated bony spur of the talus, the calcaneus, or the tibia, accessory flexor digitorum longus, the varus deformity
Fig. 1. A : Ultrasound examination of the ankle revealing a hypoanechoic mass (arrow) with well-defined borders. The mass size is 2.5x1.3cm. B : Coronal T1-weighted image demonstrates the abductor hallucis muscle (white arrow) in its entirety. A cystic mass (black arrow) is located under the muscle. C : Operative appearance of a ganglion causing tarsal tunnel syndrome. Bluish colored cystic mass (white arrow) is located along the medial plantar nerve (white star burst). Posterior tibial nerve (black arrow) branches off medial and lateral plantar nerve (check mark).
A B C
Fig. 2. Photomicrograph showing fibrous con- nective tissue without lining cells (arrows) that is characteristic of ganglion cyst (H&E, X200).
Fig. 3. Histologic finding of the idiopathic tarsal tunnel syndrome (Case 4). Thickening of the fibrous structure and hyaline degeneration is identified (H&E, X200).
Fig. 4. A : Preoperative axillary view of the left foot showing that the bony spur (arrow) is located on the medial side of the calcaneus. B : Postoperative X-ray showing removal of the bony mass (arrow) on the medial side of the calcaneus.
A B
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of the posterior plantar area, the tendosynovitis of the adjacent tendon, ganglion cyst, or deterioration of the adjacent soft tissues and bones. Internal factors are varices, fibrosis of the adjacent nerves, neurofibroma, etc. However, some cases without precise etiology havebeen reported12). In our patients, the most frequent cause was the idiopathic fibrotic thickening of the flexor retinaculum and abductor fascia along the nerve that was detected in 4 cases. Ganglion was 2 cases and the overgrowth of bony spur was 1 case. It has been reported that, in contrast to CTS, bilateral TTS is rare9). However, we experienced 3 cases of bilateral TTS (43%). We performed the decompression only on the side with severe symptoms.
The characteristic clinical symptoms of TTS are the pain and abnormal sensation in the plantar area, muscle atrophy, etc. Such clinical symptoms are not sufficient for the diagnosis as they were observed in various other diseases. Recently, in patients with symptoms suspicious of TTS and exhibiting Tinel signs on the plantar area, the diagnosis is confirmed by EMG and other electrophysiological tests26). It has been reported, however, that although the specificity of EMG is superior, its sensitivity is low. In EMG, the false negative of TTS has been reported to be at least 9.5 %. Thus, recently, the importance of the conduction test of the sensory nerve such as the decrease of the potential of the sensory induction, the amplitude and the latency of the motor nerve is emphasized3,17). As supplemental radiographic tests, plain radiography, sonogram, computerized tomography (CT), and MRI have been applied. Among them, MRI has been reported to be able to confirm the abnormal structure of the bones and soft tissues of the ankle joint. T1- weighted image is very useful to assess the anatomical configur- ation. T2-weighted image is very useful to obtain the contrast image of tumors in soft tissues, the fluid retention, and the inflammatory condition. By performing MRI prior to surgery, the extent of the mass lesions can be identified precisely as well as the adhesion of the nerve and other causes can be assessed beforehand. This allows avoiding iatrogenic neuro-vascular damage during surgery and identifying adequacy of decompression. By applying MRI after surgery, the presence of the remaining space occupying lesion and the requirement of resurgery can be determined7,23). As we can see in patients with the neuropathy limited to the medial plantar nerve such as our case 1 and 2, if clinical symptoms were local, it may be space-occupying lesions. In such cases, radiographic tests prior to surgery allow to identify the lesion site, the precise range of lesions, and its condition. This permitted us to make the surgery plan readily and to shorten the surgery time.
Other diseases to be considered are lumbosacral radiculopathy, peripheral neurititis, diabetic neuropathy, peripheral vascular
diseases, interdigital neuroma, plantar fasciitis, bony spur of the calcaneus, etc. Such diseases can be distinguished by thorough history taking, clinical examination, and various supplemental tests. Particularly, prior to treatments, TTS should be distinguished from lumbosacral radiculopathy, which can be achieved by the tests for the tenderness on the posterior tibial nerve, Tinel sign, and electromyogram. The distinction may be difficult, however, if the invasion occurred only in the ventral branch of the first sacral root8,13).
The treatments for TTS are classified to conservative treatment and surgical treatment. Patients with mild symptoms may be treated by the brace of the ankle joint, administration of anti- inflammatory agents, or comfortable shoes. In patients unresponsive to conservative treatments, especially in patients with space occupying lesions, a surgical treatment is required13). It has been reported that the outcome of surgical treatment is good in over 90 % patients16,25). The outcome of surgery for TTS due to tumors or cysts has been reported to be better than trauma or idiopathic25,27). In addition, the outcome of early diagnosis and treatment has been reported to be superior. Thus, it has been suggested that in patients with the pain or abnormal sensation in the planar, more aggressive tests and treatments for TTS may be required25). As the age of TTS patients is high, the accopanying diabetic neuropathy was frequently observed. However, the decompression has been reported to be effective in diabetic patients with the pain in the ankle joint accompanying Tinel sign, more aggressive treatments have been recommended in patients who diagnosed early29). Recently, as endoscopic surgery has been suggested as a surgical means for CTS, there have been a few report related to the endoscopic techniques for TTS4,15). However, it is not clear that the two conditions are completely analogous and is also unclear whether simple release of the flexor retinaculum without the release of the abductor fascia is adequate for all or most patient18). Many author's experience has shown that release of the abductor fascia is also an important part of the surgical procedure of the TTS and endoscopic surgery is unable to decompress the fascia of the abductor hallucis sufficiently. Thus, for its popular application, additional researches are required.
Conclusion
TTSis a relatively rare disease entity and should be suspected when a patient reports a burning sensation at the anterior
sole of the foot. If lesions were diagnosed early and the cause was confirmed as mass lesions by supplement tests especially in the young age, the outcome of surgery is anticipated to be good. Thus, in patients with the pain or abnormal sensation in the
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plantar area, it may be necessary to consider TTS and confirm by various tests for early diagnosis and aggressive surgical treatment.
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