Saphenous nerve blockade is used to diagnose and treat pain disorders of the saphenous nerve distribution in the foot.
After informed consent is obtained, the patient is placed in a prone position with the foot elevated on 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 1-in. (2.5-cm), 25-gauge needle is inserted immediately above and anteriorly to the medial malleolus and advanced to the anterior border of the tibia. After negative aspiration, 3 to 5 mL of local anesthetic is injected over the course of the needle to block the saphenous nerve (see Fig. 67-19).
FIGURE 67-19. Nerve blocks at the ankle. Approach for nerve injection and neural blockade at the ankle.
The saphenous nerve is the terminal branch of the femoral nerve. It becomes cutaneous at the lateral aspect of the knee joint and follows the great saphenous vein to the medial malleolus. It supplies cutaneous innervation to the medial aspect of the lower leg anterior to the medial malleolus and the medial aspect of the foot, and may extend as far forward as the metatarsophalangeal joint.
Hematoma and intravascular injection are possible due to the close proximity of the great saphenous vessels. If an arterial puncture occurs, prolonged direct pressure is usually adequate to prevent the development of a hematoma.