- Indications: surgery of the foot and toes
- Two deep nerves: posterior tibial, deep peroneal
- Three superficial nerves: superficial peroneal, sural, saphenous
- Local anesthetic: 5-6 mL per nerve
Needle insertion for saphenous nerve block of the ankle.
An ankle block is essentially a block of four terminal branches of the sciatic nerve (deep and superficial peroneal, tibial, and sural) and one cutaneous branch of the femoral nerve (saphenous). Ankle block is simple to perform, essentially devoid of systemic complications, and highly effective for a wide variety of procedures on the foot and toes. For this reason, this technique should be in the arma mentarium of every anesthesiologist. At our institution, an ankle block is most commonly used in podiatric surgery and foot and toe debridement or amputation.
It is useful to think of the ankle block as a block of two deep nerves (posterior tibial and deep peroneal) and three superficial nerves (saphenous, sural, and superficial peroneal). This concept is important for success of the block because the two deep nerves are anesthetized by injecting local anesthetic under the fascia, whereas the three superficial nerves are anesthetized by a simple subcutaneous injection of local anesthetic.
The common peroneal nerve separates from the tibial nerve and descends alongside the tendon of the biceps femoris muscle and around the neck of the fibula. Just below the head of the fibula, the common peroneal nerve divides into its terminal branches: the deep peroneal and superficial peroneal nerves. The peroneus longus muscle covers both nerves.
The deep peroneal nerve runs downward below the layers of the peroneus longus, extensor digitorum longus, and extensor hallucis longus muscles to the front of the leg (Figure 22-2). At the ankle level, the nerve lies anterior to the tibia and the interosseous membrane and close to the anterior tibial artery. It is usually sandwiched between the tendons of the anterior tibial and extensor digitorum longus muscles. At this point, it divides into two terminal branches for the foot: the medial and the lateral. The medial branch passes over the dorsum of the foot, along the medial side of the dorsalis pedis artery, to the first interosseous space, where it supplies the web space between the first and second toe. The lateral branch of the deep peroneal nerve is directed anterolaterally, penetrates and innervates the extensor digitorum brevis muscle, and terminates as the second, third, and fourth dorsal interosseous nerves. These branches provide innervation to the tarsometatarsal, metatarsophalangeal, and interphalangeal joints of the lesser toes.
Anatomy of the ankle. artery dorsal pedis, deep peroneal nerve.
The superficial peroneal nerve (also called the musculocutaneous nerve of the leg) provides muscular branches to the peroneus longus ...