Ultrasound-guided posterior tibial nerve block at the ankle is utilized as a diagnostic and therapeutic maneuver in the evaluation and treatment of foot and ankle pain thought to be mediated via the posterior tibial nerve. Ultrasoundguided posterior tibial nerve block at the ankle can also be used for surgical anesthesia for distal lower extremity surgery when combined with saphenous and common peroneal nerve block or lumbar plexus block. Ultrasoundguided posterior tibial nerve block at the ankle with local anesthetic may be used to palliate acute pain emergencies, including postoperative pain, pain secondary to traumatic injuries of the lower extremity including ankle and foot fractures, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective.

Ultrasound-guided posterior tibial nerve block at the ankle can also be used as a diagnostic tool when performing differential neural blockade on an anatomic basis in the evaluation of ankle and foot pain as well as in a prognostic manner to determine the degree of neurologic impairment the patient will suffer when destruction of the tibial nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the posterior tibial nerve at the ankle. Posterior tibial nerve block at the ankle with local anesthetic and steroid is occasionally used in the treatment of persistent ankle and foot pain when the pain is thought to be secondary to inflammation or when entrapment of the posterior tibial nerve at the ankle is suspected. Posterior tibial nerve block at the ankle with local anesthetic and steroid is also indicated in the palliation of pain and motor dysfunction associated with diabetic neuropathy.

Electrodiagnostic testing should be considered in all patients who suffer from posterior tibial nerve dysfunction to provide both neuroanatomic and neurophysiologic information regarding nerve function. Magnetic resonance imaging and ultrasound imaging of the popliteal fossa as well as anywhere along the course of the tibial nerve are also useful in determining the cause of posterior tibial nerve compromise (Fig. 157.1).

The tibial nerve is one of the two major continuations of the sciatic nerve, the other being the common peroneal nerve (Fig. 157.2). The tibial nerve provides sensory innervation to the posterior portion of the calf, the heel, and the medial plantar surface (Fig. 157.3). The posterior tibial nerve splits from the sciatic nerve at the superior margin of the popliteal fossa and descends in a slightly medial course through the popliteal fossa. The tibial nerve at the knee lies just beneath the popliteal fascia and is readily accessible for neural blockade. The tibial nerve continues its downward course, running between the two heads of the gastrocnemius muscle, passing deep to the soleus muscle. The nerve courses medially between the Achilles tendon and the medial malleolus, where it divides into the medial and lateral plantar nerves, providing sensory innervation to the heel and medial plantar surface (Fig. 157.4). The posterior tibial nerve is occasionally subject to compression at this point and is known as posterior tarsal tunnel syndrome (Figs. 157.5 and 157.6).