Sural nerve blockade is used to diagnose and treat pain disorders in the sural nerve distribution.
After informed consent is obtained, the patient is placed in a prone position with the foot supported by a pillow. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A skin wheal is raised lateral to the Achilles tendon at the level of the lateral malleolus. A 1-in. (2.5-cm), 25-gauge needle is inserted to a depth of 1 cm, directed toward the lateral border of the fibula. If a paresthesia is elicited, 2 to 3 mL of a local anesthetic is injected after negative aspiration. If a paresthesia cannot be elicited, after negative aspiration, 3 to 5 mL of local anesthetic is injected subcutaneously in a fan distribution from the lateral border of the Achilles tendon to the lateral border of the fibula to block the sural nerve (see Fig. 67-19).
FIGURE 67-19. Nerve blocks at the ankle. Approach for nerve injection and neural blockade at the ankle.
The sural nerve is a cutaneous nerve that contains fibers from both the tibial and common peroneal nerves. It lies subcutaneous somewhat distally to the middle of the leg and travels with the short saphenous vein behind and below the lateral malleolus. It supplies the posterolateral surface of the leg, the lateral side of the foot, and the lateral aspect of the fifth toe.
Intraneural injection may result in nerve damage. Severe pain on injection suggests the possibility of an intraneural injection, and the needle should be immediately repositioned. Hematoma and intravascular injection are possible, owing to the close proximity of the sural vessels. If an arterial puncture occurs, prolonged direct pressure is usually adequate to prevent the development of a hematoma.