The tibial nerve is the largest branch of the sciatic nerve and the largest nerve for the ankle block. It provides sensory innervation to the heel and to the sole of the foot. The tibial nerve divides into the medial calcaneal, medial plantar, and lateral plantar branches near the ankle.¹ In some subjects the takeoff of the medial calcaneal branch from the tibial nerve can be imaged above the ankle joint.

The order of anatomic structures from anterior to posterior at the medial malleolus is as follows: Tom, Dick, AVN, Harry (tibialis posterior tendon, flexor digitorum longus tendon, posterior tibial artery and veins, tibial nerve, flexor hallucis longus tendon). Therefore, the tibial nerve lies on the heel side of the posterior tibial artery. The posterior tibial artery is often accompanied by two flanking veins. This neurovascular bundle, consisting of one artery and two veins, can have a Mickey Mouse ears appearance if light touch with the transducer is applied (similar to the appearance of the brachial artery and veins near the elbow).

Edema or infection often makes routine ankle block ineffective or contraindicated.² However, tibial nerve imaging can be difficult in some surgical patients with peripheral vascular disease because vascular landmarks for the nerve are not present. Tibial nerve block in the leg avoids the footdrop that occurs with more proximal popliteal block of the sciatic nerve. This can be an advantage for ambulatory surgery patients.