Flexor Hallucis Brevis

Medial Plantar Nerve, Tibial Nerve, Sciatic Nerve, Ventral Division Sacral Plexus, SI, S2. 

The two muscle bellies originate from a tendinous expansion of the tibialis posterior muscle insertion and from the cuneiform and the cuboid. 

The two tendons end at each side of the base of the proximal phalanx of the big toe, the medial one in a common tendon with that of the abductor, and the lateral one in a common tendon with that of the adductor hallucis brevis. 

For medial head only Proximal and medial to the tendon of the flexor hallucis longus. 

If the electrode is inserted too laterally it will be in the adductor hallucis if inserted too medially it will be in the abductor hallucis. 

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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). 

Several tendons of extrinsic muscles of the foot, such as the tibialis posterior, the flexor hallucis longus and the flexor digitorum longus, the peroneus brevis and longus, travel in close proximity to the plantar aspect of the tarsal bones. The explanation of the course of these tendons in the foot continues the description in Chapter 16. After crossing the medial malleolus, the tibialis posterior assumes a straight course to fan out and insert into the tuberosity of... 

Fig. 17.14. Plantar fascia. Transverse 12-5 MHz US image obtained in the region of midfoot demonstrates the plantar fascia (arrows) as a sharply defined flattened anisotropic band 1-2 mm thick, located superficial to the flexor digitorum brevis muscle (fdb), the quadratus plantae muscle (qp) and the flexor hallucis longus tendon (fht). The photograph at the upper left of the figure indicates probe positioning...

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