Flexor Digitorum Longus

Tibial Nerve, Sciatic Nerve, Ventral Division Sacral Plexus, L5, S1, S2. 

From the body of the tibia below the popliteal line. 

Into the base of the distal phalanges of the second, third, fourth and fifth toe. 

Palpate the medial edge of tibia at midshaft and insert electrode just posterior to it. 

Patient to flex the toes, without flexing the ankle. 

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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). 

Fig. 16.26. Normal tibialis posterior tendon. Short-axis 12-5 MHz US image demonstrates the tibialis posterior tendon (tp) that typically exhibits an oval shape and lies in a shallow bony groove (arrowheads) on the posterolateral aspect of the medial malleolus (MM). Compare the size of the tibialis posterior tendon with that of the flexor digitorum longus (fdl). The cross-section of the tibialis posterior is approximately twice than that of the flexor digitorum longus. The photograph at the upper left of...

Fig. 16.30 a,b. Normal tarsal tunnel, a Transverse 12-5 MHz US image obtained posterior to the medial malleolus (MM) demonstrates the tibial nerve (arrow) located close to the posterior tibial artery (a) and veins (v) and posterior to the tibialis posterior (tp) and flexor digitorum longus (fdl) tendons. All these structures lies in the tarsal tunnel and are covered by the flexor retinaculum (arrowheads), b Oblique transverse 12-5 MHz US scan at the medial heel shows the medial and lateral plantar nerves (arrows) as a result of division of the main trunk of the tibial nerve. The photographs at the upper left of the figures indicate probe positioning... 

Fig. 16.59. Transverse 12-5 MHz US image obtained over the medial malleolus in a patient with a proximal tear and retraction of the tibiahs posterior tendon demonstrates the retromalleolar groove occupied by only one tendon, the flexor digitorum longus (fd/j.Note the more anterior position of the flexor digitorum longus tendon relative to the tip of the medial malleolus (MM). See for comparison Figure 16.26...

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... 

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