Turkish Nellrosurgery 10: 131 - 134, 2000 irak: Tarsal Iwiiid syiidro1Hc

Tarsal Tunnel Syndrome:With Atypical

Report ofEtiology

Two Cases

Tarsal

Atipik

Tnel Sendromu:Iki Olgu Sunumu

BAYRAM iRAK, MEHMET BAHADIR GVEN, NIHAT TOSUN

Yznc Yil University School of Medicine, Departments of Neurosurgery (MBG, Be) and Orthopedics andTraumatology (ND, Van, Trkiye

Received : 10.11.1998 ~ Accepted : 1.06.1999

Abstract: Tarsal tunnel syndrome involves compressionof the posterior tibial nerve due to trauma, repetitivemicrotrauma, ankle fracture, tumors of the tunnel contents,and systemic diseases including ankylosing spondylitis,uremia, and rheumatoid arthritis. The symptoms are focalpain, and paresthesia over the distribution of the posteriortibial nerve and its branches. The diagnosis is based onphysical examination findings and electrophysiologicalevaluation. Surgery is the only curative treatment. Herewe deseribe two cases of tarsal tunnel syndrome, both ofwhich arose due to unusual causes. One patient developedproblems associated with deep venous thrombosis of theleg that occurred secondary to a spinal operation, and thesecond case was associated with rheumatoid arthritis. The

patients were operated on under local anesthesia, andoutcome was good in both cases.

Key word s: Deep venous thrombosis, rheumatoid arthritis,tarsal tunnel syndrome

INTRODUCTION

Tarsal tunnel syndrome (TTS)is an uncommon,and likely underdiagnosed, clinical condition (4,13).Diagnosis and appropriate treatment require a clearunderstanding of the anatamy of the tunnel and itscontents. The tarsal tunnel, located at the ankle, is

zet: Tarsal tnel sendromu posterior tibial sinirin degisiksebeplerle sikismasi ile ortaya ikan bir durumdur. Bazisistemik hastaliklar, travmai tekrarlayan mikrotravma,ayak bileginde olusan kiriklar, tnel ieriklerindenbirisinin tmral olusumu gibi sebeplerle ortaya ikabilir.Agri ve sinirin dagilim blgesinde paresteziler vehipereztezilerle karakterizedir. Tanida fizik muayene veelektrofizyolojik alismalar nemlidir. Bu yazida birisispinal cerrahi yapilmis bir hastada gelisen derin yentrombozu sonrasi digeri ise romatoid artritli bir hastadaolmak zere atipik etiyolojili iki tarsal tnel sendromuyakasi tartisildi.

Anahtar kelimeler: Derin yen trombozu, Romatoid artrit,tarsal tnel sendromu

the anatamical counterpart of the carpal tunnel inthe wrist, the site where carpal tunnel syndrome(CTS) develops. The tarsal tunnel is located posteriorand inferior to the medial malleolus of the tibia. The

lancinate ligament, alsa known as the flexorretinaculum, forms the roof of the tunnel. Thisligament is thinner than its counterpart at the wrist,

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Turkish Neurosiirgery 10: 131 - 134, 2000

the transverse carpal ligament. The lancinateligament extends from the medial maIIeolus to themedial tubercle of the cakaneus. The bony floor ofthe tunnel is formed by the medial aspect of thecakaneus and the posterior aspect of the medialmaIIeolus. The contents of the tunnel, listed frommost anterior to most posterior, are the tendons ofthe posterior tibialis, flexor digitorum longus, andflexor halIucis longus muscles, the posterior tibialvessels, and the posterior tibial nerve (5,11,14). Avariety of conditions are known to ca usesymptomatic entrapment of the tibial nerve in thetarsal tunnel (2,3,12). In this report, we present twounusual cases of TTS.

CASE 1

A 45-year-old male patient was admitted to theNeurosurgery Clinic at Yuzuncu Yil UniversityMedical Center with the complaint of back and thighpa in on the right side. Neurologic examinationrevealed a positive straight-Ieg raising test andweakness on dorsifIexion of the foot. Magneticresonance imaging confirmed the diagnosis of rightposterolateral L4-L5 disc hemiation. A microlumbardiscectomy procedure was performed with thepatient in the prone position. The early postoperativeperiod was uneventful. The patienfs pain resolvedand his strength on foot dorsifIexion retumed tonormaL. However, on postoperative day 5 hedeveloped deep venous thrombosis (DVT) in his rightleg. This was treated with low-molecular weightheparin. On the tenth day of the heparin treatment,the patient no longer had complaints related to theDVT, but he suddenly developed pain andparesthesia on the medial aspect of his right foot.The clinical findings and results of anelectrophysiological examination were consistentwith the diagnosis of TTS. Surgery was advised.Local infiltration anesthesia was carried out, a skinincision was made over medial maIIeolus, and theflexor retinaculum was released in standard fashion,as for CTS. There was no improvement in thepatient's condition in the early postoperative period;however, at arecheck 2 months after the TTS surgeryhe was asymptomatic and his neurologicexamination wasnormal.

CASE 2

A 50-year-old male patient, who had been

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irak: Tarsal l/lIlue! syiiaroiiie

diagnosed with rheumatoid arthritis 4 years prior topresentation, was assessed for the complaint ofweakness in both feet and both hands. He had been

prescribed vario us nonsteroidal antiinfIammatorydrugs for his arthritic condition and was usingSalazopyrin at the time of admission. The patient hadcomplained of burning pain in the feet, particularlyat night, and weakness of the hands and feet eversince he was diagnosed with rheumatoid arthritis. Aneurological examination revealed atrophy in thehypothenar region of both hands, and on theanteromedial aspect of the soles of feet. PositiveTinel's signs indicated CTS in the right hand andTTS in the left foot, and neurophysiologicalexaminations confirmed these diagnoses. Thepatient underwent surgery for both conditions.In the ankle operation, the tarsal tunnel wasopened and the flexor retinaculum was cut. Thepatienfs pain in the left foot resolved completely inthe early postoperative period, and 3 months afterthe procedure he was free of TTS symptoms in theleft foot.

DISCUSSION

Tibial iterve

The posterior tibial nerve, which is a terminalbranch of the sciatic nerve, enters the tarsal tunneljust behind the posterior tibial vessels. The nervedivides into three terminal branches either within the

tunnel or at its distal end, forming the cakaneal,medial plantar, and lateral plantar nerves. Thecakaneal nerve, which is purely sensory in nature,may course superficial to the lancinate ligament. Themedial and lateral plantar nerves, which supply theintrinsic muscles of the foot and provide sensoryinnervation to the sole, pass through separateopenings at the origin of the abductor halIucismuscles. Each of these openings is formed by fibroustissue, which puts the nerve branches at risk ofbeingcompressed individualIy. With regard to sensorydistribution, the medial plantar nerve correspondsto the median nerve, and the lateral plantar nerve tothe ulnar nerve (5,11,13).

Clinical preselltation and diagllosisTTS may develop after trauma to the osseous

or soft tissue structures of the ankle (1), or due totenosynovitis of any etiology, to systemic conditionssuch as chronic uremia or rheumatoid arthritis (12),to venous stasis after prolonged standing or ankle

Turkis/i Neiirosurgery 10: 131 - 134, 2000

fractures (1,2,6),or to muscle action or muscle growth(5,11). The syndrome is particularly common inrunners and mountain climbers, whose activitiesdemand repetitiye dorsiflexion of the ankle joint (1).The most common complaint is burning pain orparesthesia on the plantar aspect of the foot and toes.Often the paresthesia is confined to the medial orlateral aspect of the sole, the region that correspondsto the distribution of the medial and lateral plantarnerves. Activity aggravates the symptoms, and thepa in tends to be worse at night. There mayaiso beatrophy and weakness of the intrinsic muscles of thefoot.

Concerning diagnosis, Tinel's sign can beelicited by palpating the area proximal to the tarsaltunnel (13,14,15). Electroneuromyography (ENMG)can also help with diagnosis, but if a patient hasaiready undergone tarsal tunnel release surgery,clinical historyand physical examination are moreimportant for determining the extent and site of tibialnerve irritation. The typical ENMG study in a caseof TTS reveals the following: normal conductionvelocity in the posterior tibial nerve prolonged distalmotor lateney to the abductor hallucis, representingmedial plantar nerve problems; prolonged distalmotor lateney to the abductor digiti quinti pedis,representing lateral plantar nerve problems;and decreased amplitude of evoked musclepotentials in the abductor hallucis or theabductor digiti quinti pedis (9,14). Computerizedtomography and magnetic resonance imaging mayalso be used to identHy compression of the tunnelstructures, and can be used to follow up patients withnonsurgical causes of TTS, such as tenosynovitis(8,10,11).

Treatment

TTS generally responds better to surgicaltreatment than conservative management. Theindications for surgery are incapacitating focal painassociated with paresthesia and hyperesthesia, withall problems being refractory to nonsurgical therapy.The operation can be done under general, spinal, orlocal anesthesia, according to surgeon or patientpreference and the patient's general health status. Acurvilinear incision is made 1.5 cm distal andposterior to the medial malleolus. Dissection revealsthe flexor retinaculum, which is divided to exposethe posterior tibial nerve. The deep fibrous septationsin the tunnel must be severed to release the structures

irak: Tarsal tuiiiiel syiiilro1llf

from any constriction. it is important to follow themedial and lateral plantar nerves to the point wherethey go deep into the tissue near the origin of theabductor hallucis longus. Any fibrous bands atthese locations must also be severed (4,14). Re