Ultrasound-guided tibial nerve block at the popliteal fossa is utilized as a diagnostic and therapeutic maneuver in the evaluation and treatment of foot and ankle pain thought to be mediated via the tibial nerve. Ultrasound-guided tibial nerve block at the popliteal fossa 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. Ultrasound-guided tibial nerve block at the popliteal fossa 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 tibial nerve block at the popliteal fossa 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 tibial nerve at the level of the popliteal fossa. Tibial nerve block at the knee 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 tibial nerve at the popliteal fossa is suspected. Tibial nerve block at the knee 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 tibial nerve dysfunction to provide both neuroanatomic and neurophysiologic information regarding nerve function. Magnetic resonance imaging (MRI) 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 tibial nerve compromise (Fig. 150.1).

The tibial nerve is one of the two major continuations of the sciatic nerve, the other being the common peroneal nerve (Fig. 150.2). The tibial nerve provides sensory innervation to the posterior portion of the calf, the heel, and the medial plantar surface (Fig. 150.3). The 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 (see Fig. 150.2). The tibial nerve block 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 (Figs. 150.4 and 150.5). 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. The tibial nerve is occasionally subject to compression at this point and is known as posterior tarsal tunnel syndrome.

Ultrasound-guided block of the tibial nerve at the knee can be carried out by placing the patient in the prone position with the arms resting comfortably along the patient’s side (Fig. 150.6). A total of 8 mL of local anesthetic is drawn up in a 12-mL sterile syringe. If the painful condition being treated is thought to have an inflammatory component, 40 to 80 mg of depot steroid is added to the local anesthetic. A linear high-frequency ultrasound transducer is placed in a transverse plane ˜8 cm above the popliteal crease, and an ultrasound survey scan is obtained (Fig. 150.7). The pulsating popliteal artery should be visualized toward the bottom of the image, with the popliteal vein lying just lateral to the artery (Fig. 150.8). Just superficial and slightly lateral to the popliteal vein is the sciatic nerve, which will appear as a bright hyperechoic structure (see Fig. 150.8). Compression of the popliteal vein with pressure on the ultrasound transducer can aid in identification of the sciatic nerve, which lies just superficial to the vein (Fig. 150.9). Color Doppler

can be utilized to help identify the popliteal artery and vein (Fig. 150.10). When the sciatic nerve is identified on ultrasound imaging, the ultrasound transducer is slowly moved inferiorly along the course of the sciatic nerve until the bifurcation of the nerve into the tibial and common peroneal nerves occurs (Fig. 150.11). The tibial nerve is followed in its downward course until it completely separates from the common peroneal nerve (Fig. 150.12). When the tibial nerve is satisfactorily identified, the skin is prepped with anesthetic solution, and a 3½-inch, 22-gauge needle is advanced from the middle of the inferior border of the ultrasound transducer and advanced utilizing an out-of-plane approach with the trajectory being adjusted under real-time ultrasound guidance until the needle tip is resting in proximity to the tibial nerve (Fig. 150.13). When the tip of needle is thought to be in satisfactory position, a small amount of local anesthetic and steroid is injected under real-time ultrasound guidance to confirm that the needle tip is in proximity to the tibial nerve, but not within the nerve itself. There should be minimal resistance to injection. After needle tip placement is confirmed, the remainder of the contents of the syringe are slowly injected. The needle is then removed, and a sterile pressure dressing and ice pack are placed at the injection site.