Ankle Block: Analgesic distribution

Ankle blocks can be performed for some operations involving the foot and toes. Blocks can be performed on three superficial nerves (superficial peroneal, sural, and saphenous) and two deep nerves (deep peroneal and posterior tibial). The decision to block individual nerves is determined by the location of the surgery and analgesic distribution of these nerves.

The superficial peroneal nerve emerges from the anterolateral compartment of the lower leg, 5-10 cm above the lateral malleolus. At this location, it divides into medial and lateral dorsal cutaneous nerves that provide sensory innervation to the dorsum of the foot.

At the ankle, the deep peroneal nerve usually lies between the tendons of the anterior tibial and extensor digitorum longus muscles. It then divides into a medial branch, which provides sensory innervation to the web space between the first and second toes, and a lateral branch, which innervates the extensor digitorum brevis muscle and branches to provide innervation to the tarsometatarsal, metatarsophalangeal, and interphalangeal joints of the lesser toes.

The sural nerve is formed from the medial sural nerve (branch of the tibial nerve) and the lateral sural nerve (branch of the common peroneal nerve); it provides sensory innervation to the lateral aspect of the foot and fifth toe. It also provides innervation to the lateral malleolus, Achilles tendon, and ankle joint.

The saphenous nerve (branch of the femoral nerve) provides sensory innervation to the medial aspect of the ankle and foot.

The posterior tibial nerve lies beneath the superficial and deep fasciae of the leg at the level of the medial malleolus; it divides into lateral and medial plantar nerves just inferior to the malleolus. The posterior tibial nerve provides sensory innervation to the plantar aspect of the foot. It also supplies cutaneous, articular, and vascular branches to the medial malleolus, ankle joint, and Achilles tendon.