Calcaneal Nerve

At the medial ankle, the tibial nerve, a continuation of the medial trunk of the sciatic nerve, passes deep to the flexor retinaculum in the space between the medial malleolus and the medial wall of the calcaneus (Fig. 16.10a). The retinaculum consists of a thin fascia and forms the roof of the tarsal tunnel (Fig. 16.10). In addition to the nerve, the tarsal tunnel encloses the tibialis posterior, flexor digitorum longus and flexor hallucis longus tendons, the posterior tibial artery and two veins (Fig. 16.10a,b). Posteroinferior to the medial malleolus, the tibial nerve divides into the medial and lateral plantar nerves and the calcaneal nerve, which is responsible for the sensitive supply of the heel (Fig. 16.11). The plantar nerves supply the intrinsic foot muscles, except for the extensor digitorum brevis, which is innervated by the deep peroneal nerve. The posterior tibial artery accompanies the nerve deep to the flexor retinaculum and, inferior to the medial malleolus, it divides into medial and lateral plantar arteries (Fig. 16.11). 

Tarsal tunnel syndrome refers to the entrapment of the main trunk of the tihial nerve and/or of its divisional branches (medial plantar nerve, lateral plantar nerve, calcaneal nerve) at the medial aspect of the ankle. This syndrome has an insidious clinical onset with numbness or pain in the foot and ankle and paresthesias in the sole of the foot, often with the heel being spared. However, clinical and electromyographic diagnosis of tarsal tunnel syndrome is often not straightforward, especially when a soft-tissue swelling on the medial ankle is absent. Depending on the site of compression, tarsal tunnel syndrome produces different clinical syndromes that can be classified as proximal or distal. The proximal syndrome consists of entrapment of the main trunk of the tibial nerve in the... 

Fig.16.11. Normal tibial nerve at the tarsal tunneL Gross dissection of the tarsal tunnel gives a closer look to the tibial nerve (arrows) and its divisional branches, the medial (1) and lateral (2) plantar nerves, and the calcaneal branches (arrowheads), a, posterior tibial artery. The insert on the left of the figure indicates the site of the anatomic specimen illustrated...

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