Ankle Block (Landmark Technique) - Procedures

Ankle block covers the five nerves around the ankle joint. Three nerves are located anteriorly and supply the dorsal aspect of the foot. Two nerves are located posteriorly and supply the volar aspect. A complete nerve block of the foot requires blocking three subcutaneous nerves and two deeper nerves. Overlap of the sensory distribution frequently necessitates blocking multiple nerves for adequate anesthesia. 

1. Deep peroneal - Deep - Supplies Anteriorly 
2. Posterior tibial - Deep - Supplies Posteriorly 
3. Saphenous - Superficial - Supplies Anteriorly 
4. Superficial peroneal - Superficial - Supplies Anteriorly 
5. Sural nerves - Superficial - Supplies Posteriorly 

Depending on the desired area of anesthesia, one or more of the five nerves are blocked. Nerve block of the sural and posterior tibial nerves together anesthetizes the bottom of the foot and is the most useful combination.

Indications

Procedures on the foot (lac repair, I&D, FB removal, wound irrigation). The rationale for using Ankle block over infiltration anesthesia on the sole is that skin of the sole is thicker and more tightly bound to the underlying fascia making skin puncturing quite difficult and painful. Large amounts of anesthetic on sole may lead to painful distention of the tissue and circulatory compromise of the microvasculature.

Relevant Anatomy and Sensory supply of 5 nerves around Ankle Joint

Image from Roberts & Hedges - Clinical Procedures in Emergency Medicine

Site of Injections (2 deep injections and 3 bands)

1. Posterior Tibial Nerve - Posterosuperior to the posterior tibial artery between medial malleulus and Achilles. At a depth of 1 cm, inject 3 to 5mls of anesthetic.

2. Deep Peroneal Nerve - Palpate the EHL and anterior tibial tendons (Ask the patient to dorsiflex the foot and big toe) and inject 3-5mls LA 1 cm superior to the medial malleolus under the EHL tendon until it strikes the tibia. 

3. Superficial Peroneal - Inject 4 to 10 mL of anesthetic subcutaneously in a band between the EHL tendon and the lateral malleolus. 

4. Saphenous - Inject 3-5ml of LA subcutaneously in a band between the medial malleolus and the anterior tibial tendon. 

5. Sural Nerve - Block at the lateral aspect of the ankle between Achilles and the lateral malleolus. Inject 3 to 5 mls of anesthetic subcutaneously in a band like fashion at about 1 cm above the lateral malleolus. 

All five nerves can be blocked by placing subcutaneous band blocks around 75% of the ankle circumference and two deep injections: one next to the palpable posterior tibial artery (Post Tibial Nerve) and the other under the extensor tendon of the big toe (Deep Peroneal Nerve).

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic