Tarsal tunnel syndrome

1-It is a fibro-osseus tunnel extending from the medial malleolus to the tarsal navicular bone.

-Bony floor is composed of talus, sustentaculum tali and calcaneum.

-Fibrous roof is composed of flexor retinaculum.

-It is present on the medial aspect of foot, so it includes muscles present in the medial compartment of the ankle previously mentioned in addition to arteries, nerves and veins, all these structures are covered with flexor retinaculum.

-There are two muscles related to tarsal tunnel which are abductor hallocis (ABH) which present superficial to flexor retinaculum while the other one is deep to contents of tarsal tunnel and adherent to surface of calcaneum which is quadratus planti(not important). 

 

2-Causes of compression include:

-From muscles---Ganglion or sarcoma.

-From muscle sheath---Tenosynovitis.

-From veins---Varicose veins(T1=black, T2=white due to slow flow of blood).

-From nerves---Neuroma.

-From fat---Lipoma.

-Fibrosis.

-Tarsal coalition: due coalition of talus bone and calcaneum.

Tarsal tunnel syndrome secondary to ganglion cyst. Axial T2-weighted MR image reveals a ganglion cyst (*) interposed between the flexor digitorum longus (d) and flexor hallucis longus (h) tendons and abutting the adjacent neurovascular bundle (arrow).

MR imaging of tarsal tunnel syndrome. a,b Axial T1WI (a) and spin-echo T2WI (b) demonstrate a lipoma (arrowheads) in the upper tarsal tunnel, compressing the posterior tibial nerve (arrows). c,d Axial T1WI (c) and spin-echo T2WI (d) demonstrate a ganglion (arrowheads) in the lower tarsal tunnel, possibly compressing the lateral plantar nerve (short arrow). The medial plantar nerve is not well visualized. The medial calcaneal nerve (long arrow) is well depicted. Both patients had a tingling sensation in the foot. AH abductor hallucis muscle