17 Tarsal Tunnel Release Abstract Tarsal tunnel release is a surgical decompression by dividing the flexor retinaculum to relieve the symptoms of a tarsal tunnel syndrome. The tarsal tunnel syndrome is a compression neuropathy of the tibial nerve or its branches. The etiology is still not completely understood, which could explain the variable outcomes of release in the literature. Keywords: tarsal tunnel syndrome, neuropathy tibial nerve, release flexor retinaculum • Tarsal tunnel syndrome was described in 1960 by Kopell and Thompson,1 and it was named by Keck2 and Lam3 in 1962. • Synonym: posterior tibial neuralgia. The tarsal tunnel is a fibro-osseous space at the posteromedial side of the ankle. Its anatomical boundaries are the flexor retinaculum, the posteroinferior side of the medial malleolus, the medial wall of the talus, and calcaneus. The following structures pass through the tarsal tunnel: tibialis posterior tendon, flexor digitorum longus tendon, tibialis posterior artery, tibialis posterior vein, tibial nerve, and the flexor hallucis longus tendon (also known as “Tom, Dick, And Very Nervous Harry”) (Fig. 17.1). The tibial nerve divides into the nerve to the calcaneus, medial plantar nerve, and the lateral plantar nerve within the tarsal tunnel. The first branch of the tibial nerve in the tarsal tunnel is the nerve to the calcaneus, which goes from the tarsal tunnel through the flexor retinaculum to the surface. More distal in the tarsal, the tibial nerve splits into the medial and lateral plantar nerve, with the lateral nerve giving off a branch to the adductor digiti quinti muscle just as it exits the tunnel and passes under the abductor hallucis muscle. • If the patient has complaints of compression neuropathy of the tibial nerve and conservative therapy fails; or • If there is a benign (bone) tumor, such as lipoma, ganglia, or exostosis. • The clinical presentation of tarsal tunnel syndrome is pain behind the medial malleolus, which radiates to the plantar side of the foot. The medial side of the ankle or toes can also be involved. • The pain can be described as burning, tingling, or dysesthesia/paresthesia. • Worsening of the symptoms can be provoked by prolonged walking, standing still, or lying in bed. • The diagnosis is not always easy to make due to other lower limb conditions such as polyneuropathy with diabetes or radiculopathy of L5–S1. If patients have unexplained paresthesias in the foot, toes, or medial side of the calf, physicians must keep this disorder in mind.4 • Causes of tarsal tunnel syndrome can be divided into three groups: • Begins with examination of the foot and ankle; look for deformation of the foot such as pes planovalgus or a varus position of the hind foot. • Let the patient show where he or she experiences the pain. With palpation, the physician can check for soft-tissue tumors. • Tinel’s sign can be positive; but if it is negative, this does not exclude tarsal tunnel syndrome. • Provocation maneuvers, such as the dorsiflexion-eversion test, can be useful. • In chronic complaints, also intrinsic muscle weakness or contractures can be found.5 • After clinical examination, an X-ray of the ankle is made for eventual deformities of the bone. If this shows nothing, compression due to soft tissue must be evaluated due to ultrasound or magnetic resonance imaging (MRI). • Irritation in the tarsal tunnel can be seen on the MRI without direct soft-tissue compression, which can indicate tarsal tunnel syndrome. However, MRI findings must correlate with clinical findings. Pathophysiological findings can also be found in asymptomatic patients.6 • Another diagnostic tool described in the tarsal tunnel is an electromyogram (EMG). An EMG does not exclude tarsal tunnel syndrome if this is normal. Also, an abnormal EMG does not show any correlation with the final outcome of surgical decompression. • Nonsteroidal anti-inflammatory drugs. • Corticosteroid injection. • Physiotherapy. • Walking cast/sleeping splint. • Peripheral artery disease with insufficient blood flow to the ankle/foot. • Idiopathic cause of tarsal tunnel syndrome has inferior outcomes compared to cases where the cause of compression is found.7 • Release of the tibial nerve or its branches by splitting the flexor retinaculum and if needed excision of the benign (bone) tumor. Goal is to decompress the tibial nerve. • Good exposure of structures. • Direct identification and freeing of the tibial nerve and its branches. • Ability to evaluate for and remove any space-occupying lesions/masses within the tarsal canal. • Make an adequately long incision to allow full visualization and release of the tunnel and the tibial nerve. • Perform an extraneural release only. Intraneural neurolysis should be avoided to prevent excess scar tissue formation within the nerve. • Ensure full hemostasis has been obtained before incision closure. Bleeding around the nerve can result in excess scar tissue and recurrent compression. Apply a tourniquet around the upper leg for good view during the operation. The patient should lie on his or her back with the operated leg in external rotation (Fig. 17.2). This can be aided by placing a hip bump under the contralateral hip. The foot is in 70-degree plantar flexion. Depending on the wishes of the patient and anesthesiologist, patient can get a distal nerve block in the popliteal fossa. The longitudinal incision is made on the medial side of the ankle at the height of the medial malleolus, in the soft spot between the tibia and Achilles tendon. The incision must almost form a straight line until the navicular tuberosity (Fig. 17.3). Coagulate any superficial veins which obstructs further incision. Use small dissecting scissors for splitting the subcutaneous fatty tissue and the fascia until the muscle tissue is visible (proximally the flexor digitorum longus and distally the abductor hallucis). An alternate incision is more longitudinal placed midway between the posteromedial border of the tibia and the anteromedial border of the Achilles tendon, starting about 6 cm proximal to the medial malleolus. This lies directly over the path of the tibial nerve. Distal to the malleolus, the incision is curved slightly anteriorly along the path of the nerve to cross the medial heel over the proximal aspect of the abductor hallucis muscle belly under which the first branch of the lateral plantar nerve (Baxter’s nerve) runs and is often entrapped.
17.1 Introduction
17.1.1 History
17.1.2 Anatomy
17.2 Indications
17.2.1 Pathology
Idiopathic.
Intrinsic (pressure within the tarsal tunnel), such as osteophytes, hypertrophic retinaculum, ganglia, lipoma, neuroma, or enlarged veins.
Extrinsic (pressure out of the tarsal tunnel), such as direct trauma, constrictive foot wear, hind foot varus or valgus, postsurgical scarring, diabetes, or generalized lower limb edema.5
17.2.2 Clinical Evaluation
17.2.3 Radiographic Evaluation
17.2.4 Nonoperative Options
17.2.5 Contraindications
17.3 Goals of Surgical Procedure
17.4 Advantages of Surgical Procedure
17.5 Key Principles
17.6 Preoperative Preparation and Patient Positioning
17.7 Operative Technique
17.7.1 Incision
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