Tarsal Tunnel Syndrome

Tarsal tunnel syndrome refers to pain and paresthesia in the plantar aspect of the foot and toes due to nerve entrapment or compression at the level of the posterior tibial nerve or its branches as they pass through the tarsal tunnel.

The flexor retinaculum forms the roof of the tarsal tunnel. Anteriorly, the flexor retinaculum inserts on the anteromedial surface of the medial malleolus and posteriorly, it inserts into the medial tuberosity of the calcaneus. Inferiorly the flexor retinaculum splits to envelop the abductor hallucis muscle.

The floor of the tarsal tunnel is formed by the medial surface of the talus, the sustentaculum tali, and the medial wall of the calcaneus.

The structures of the tarsal tunnel, from anterior to posterior, include the well-known Tom, Dick, and Harry: the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial neurovascular bundle, and the flexor hallucis longus tendon.

Nerve compression can be intrinsic or extrinsic. Intrinsic causes include accessory muscles, ganglion cysts, neurogenic tumors, varicose veins, lipomas, synovial hypertrophy, and scar tissue. Extrinsic causes include foot deformities, hypertrophic and accessory muscles, os trigonum, and excessive pronation in some sports.

References

• Erickson SJ, Quinn SF, Kneeland JB, Smith JW, Johnson JE, Carrera GF, Shereff MJ, Hyde JS, Jesmanowicz A. MR imaging of the tarsal tunnel and related spaces: normal and abnormal findings with anatomic correlation. AJR Am J Roentgenol. 1990 Aug;155(2):323-8.
• Rosenberg ZS, Beltran J, Bencardino JT. From the RSNA Refresher Courses. Radiological Society of North America. MR imaging of the ankle and foot. Radiographics. 2000 Oct;20 Spec No:S153-79.