Ankle Block

Published on 16/03/2015 by admin

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Last modified 22/04/2025

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Chapter 6 Ankle Block

Overview

1. The following five nerves are involved in an ankle block: posterior tibial, superficial peroneal, deep peroneal, saphenous, and sural.
2. The posterior tibial and deep peroneal nerves are deep to the fascia, whereas the remainder of the nerves are superficial.

Indications for use

1. Foot fracture reduction
2. Soft tissue injuries about the foot

Precautions

1. Avoid intravascular and intraneural injections.
2. Do not use an ankle block for fractures of the ankle.

Pearls

1. The posterior tibial and deep peroneal nerve blocks should be performed first, because these nerves are deep to the fascia. Attempting to block the superficial nerves first will result in subcutaneous injection of anesthetic that may distort local anatomy.
2. The superficial nerves require only a subcutaneous injection of anesthetic.

Equipment

1. Antiseptic: Chlorhexidine prep stick or alcohol-soaked gauze
2. Syringe: Three 10-mL syringes
3. Needle:

a. Large-bore, blunt-tipped, drawing-up needle
b. 1½-inch, 25-gauge needle

4. Anesthetic:

a. Lidocaine: 15 mL of 2%
b. Bupivacaine: 15 mL of 0.5%

5. Sterile gloves
6. 4 × 4 inch gauze

Basic technique

1. Patient positioning:

a. The patient is supine.
b. The leg should be positioned either on a footrest or off the edge of the bed.
c. The posterior aspect of the ankle must be accessible.

2. Landmarks:

a. Posterior tibial nerve:

(1) Medial malleolus
(2) Posterior tibial artery (the nerve is posterior to this)

b. Deep peroneal nerve:

(1) Medial and lateral malleoli (the line connecting the two malleoli is the intermalleolar line)
(2) Extensor hallucis longus (EHL) tendon
(3) Extensor digitorum longus (EDL) tendon
(4) Anterior tibial artery (dorsalis pedis) (the nerve is immediately lateral to the artery)

c. Superficial peroneal nerve: Lateral malleolus
d. Saphenous nerve: Medial malleolus
e. Sural nerve:

(1) Lateral malleolus
(2) Lateral border of Achilles tendon
(3) Calcaneus

3. Steps:

a. Block the posterior tibial nerve.
b. Block the deep peroneal nerve.
c. Block the superficial peroneal nerve.
d. Block the saphenous nerve.
e. Block the sural nerve.

Detailed technique

Prepare the anesthetic. Three syringes should be prepared.

Posterior Tibial Nerve

1. Position the patient.
2. Palpate landmarks:

a. Palpate the medial malleolus and posterior tibial artery.
b. Mark the medial malleolus and posterior tibial artery, if desired.
c. Mark the injection site immediately posterior to the tibial artery at the level of the medial malleolus.

3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject anesthetic (Figure 6-1):

a. Enter at a 90-degree angle to the skin.
b. Maintain patient contact to note any paresthesias.
c. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
d. Advance the needle until contact is made with the bone.
e. Withdraw the needle 1 to 2 mm.
f. Inject 3 to 5 mL of anesthetic. Be vigilant for any warning signs of intravascular injection.
g. Use a fan technique to block cutaneous branches or anomalous anatomic branches.

(1) Withdraw the needle to a subcutaneous position.
(2) Redirect anteriorly and advance 0.5 cm.
(3) Inject 2 mL of anesthetic.
(4) Withdraw the needle to a subcutaneous position.
(5) Redirect posteriorly and advance 0.5 cm.
(6) Inject 2 mL of anesthetic.

6. Place a sterile bandage over the injection site.
image

Figure 6-1

Deep Peroneal Nerve

1. Position the patient.
2. Palpate landmarks:

a. Palpate the medial and lateral malleoli. Identify and mark the intermalleolar line.
b. Palpate the EHL tendon by having the patient dorsiflex the hallux.
c. Palpate the EDL tendon by having the patient dorsiflex the lesser toes.
d. Palpate the dorsalis pedis artery.
e. Mark these four structures.
f. Mark the injection site between the EDL and EHL tendons and 2 cm distal to the intermalleolar line. This position is on the lateral border of the dorsalis pedis artery.

3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject anesthetic (Figure 6-2):

a. Enter at a 60-degree angle to the skin.
b. Maintain contact with the patient to ensure that no paresthesias are noted.
c. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
d. Advance the needle until contact is made with the bone.
e. Withdraw the needle 1 to 2 mm.
f. Inject 5 mL of anesthetic. Be vigilant for any warning signs of intravascular injection.
6. Place a sterile bandage over the injection site.
image

Figure 6-2

Superficial Peroneal Nerve/Sural Nerve

1. Position the patient.
2. Palpate landmarks (Figure 6-3):

a. Feel the lateral malleolus.
b. Mark the injection site the breadth of two fingers distal to the tip of the lateral malleolus.
3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject the anesthetic in a ring-type block (Figure 6-4).

a. Enter at a 45-degree angle to the skin.
b. Insert the needle, aiming it in a lateral direction.
c. Maintain contact with the patient to determine if paresthesias are noted.
d. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
e. Advance the needle subcutaneously.
f. Inject 5 mL of anesthetic from the lateral to medial aspect while withdrawing the needle. Be vigilant for any warning signs of intravascular injection.
6. Place a sterile bandage over the injection site.
image

Figure 6-3

image

Figure 6-4

Saphenous Nerve

1. Position the patient.
2. Palpate landmarks:

a. Feel the medial malleolus.
b. Mark the injection site the breadth of two fingers proximal to the tip of the medial malleolus and the breadth of one finger anterior.

3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject the anesthetic in a ring-type block (Figure 6-5).

a. Enter at a 45-degree angle to the skin.
b. Insert the needle, aiming it posteriorly and distally.
c. Maintain contact with the patient to determine if paresthesias are noted.
d. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
e. Advance the needle subcutaneously.
f. Inject 2 to 3 mL of anesthetic from the posterior to anterior aspect while withdrawing the needle. Be vigilant for any warning signs of intravascular injection.
6. Place a sterile bandage over the injection site.
image

Figure 6-5

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