Ankle Block

Andrew Lyons

Fred G. Mihm

DEFINITION

Ankle block is a highly effective peripheral nerve block that results in anesthesia of the entire foot. This block has been shown to reduce both postoperative pain and opioid consumption following foot surgery.¹^,²
Though a number of injections are required, a low total volume of local anesthetic injectate is required to successfully perform an ankle block.
The ankle block can be useful due to its relatively low-risk profile, technical ease, and efficacy.
Typical plastic surgery procedures that utilize this block include tendon repair and distal foot or toe amputation.

ANATOMY

An ankle block is the selective blockade of both the saphenous nerve and the four terminal branches—deep and superficial peroneal, tibial, and sural nerves—of the sciatic nerve.
Ankle block is considered to be an easy block to perform because the terminal nerves of interest are generally superficial and are reliably located next to readily identifiable surface landmarks.

POSITIONING AND PREPARATION

Ankle block is most commonly performed with the patient in the supine position.
Elevation of the foot by bolstering the calf with a pillow will facilitate access to the ankle (FIG 1).
It is helpful to have an assistant available to gently place the leg in either internal or external rotation.

MATERIALS

Topical disinfectant (chlorhexidine, betadine, or equivalent)
Sterile gloves
Ultrasound with a small, high-frequency linear probe
20-mL sterile syringe
22-gauge short-bevel block needle
Non-epinephrine containing local anesthetic

GENERAL CONSIDERATIONS

The goal of the ankle block is to deliver local anesthetic adjacent to the five nerves that innervate the foot.
Needle insertion can be either in-plane or out-of-plane for each of the terminal nerve blocks that comprise an ankle block.
3 to 5 mL of local anesthetic per nerve is required for a successful block.
The tibial nerve should be addressed before blocking the other nerves because of its relatively larger size and resultant resistance to the effects of local anesthetics.
The use of ultrasound guidance augments the clinical efficacy of an ankle block, especially for the tibial and deep peroneal nerves, which are relatively deep.³^,⁴^,⁵^,⁶
A small high-frequency linear ultrasound transducer is recommended.

FIG 1 • Proper positioning of the foot is essential when performing an ankle block. The patient is placed supine and a pillow is used to facilitate access to the ankle.

TECHNIQUES

▪ Tibial Nerve