Flexor retinaculum

Figure 9.2 Posterior tibial tendon released from flexor retinaculum with extensive rupture, scarring, and loss of paratenon.

Striking fusiform enlargement of the median nerve at the distal forearm through the palm, characterized hy an increased hulk of hyperechoic adipose tissue in the epineurium that surrounds and is interposed between normal-appearing fascicles (Fig. 4.5a-d) (Murphey et al. 1999 Chen et al. 1996). At the carpal tunnel level, the affected median nerve may become symptomatic earlier than other nerves due to its encroachment by the flexor retinaculum. In these instances, detection of nerve fascicles that appear focally swollen within the adipose mass indicates compression and the need for carpal tunnel release (Fig. 4.5e-g). Debulking of the mass may compromise the intraneural vasculature causing catastrophic motor and sensory deficits or an intense healing response that may further jeopardize function (Marom and Helms 1999). 

Fig. 10.56a,b. Carpal tunnel syndrome in amyloid arthropathy, a Longitudinal 12-5 MHz US image through the carpal tunnel with b diagram correlation shows the bulk of amyloid substance (asterisks) contained in the deep portion of the tunnel that compresses the flexor tendons (ft) and the median nerve (MN) against the flexor retinaculum (arrowheads). The patient had chronic renal failure and underwent long-term hemodialysis... 

Nakamichi K, Tachibana S (1992) Transverse sliding of the median nerve beneath the flexor retinaculum. J Hand Surg [Br] 17 213-216... 

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. 16.30 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... 

From the hook of the hamate bone and flexor retinaculum. 

Superficial Head Ridge of the trapezium and the flexor retinaculum Deep Head Ulnar side of first metacarpal. 

In the hypothenar eminence, this muscle is contained within the fascia, and it is attached to the flexor retinaculum and the border (medial) of the palmar Aponeurosis. 

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