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 an anesthetic that may distort the local anatomy.
- 2.
The superficial nerves require only a subcutaneous injection of an anesthetic.
Equipment
- 1.
Antiseptic: A chlorhexidine prep stick or alcohol-soaked gauze
- 2.
Syringe: Three 10-mL syringes
- 3.
Needles:
- a.
A large-bore, blunt-tipped drawing-up needle
- b.
A 1½-in., 25-gauge needle
- a.
- 4.
Anesthetics:
- a.
Lidocaine: 15 mL of 2%
- b.
Bupivacaine: 15 mL of 0.5%
- a.
- 5.
Sterile gloves
- 6.
4 × 4 in. 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.
- a.
- 2.
Landmarks:
- a.
Posterior tibial nerve:
- (1)
Medial malleolus
- (2)
Posterior tibial artery (the nerve is “posterior” to this)
- (1)
- 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)
- (1)
- c.
Superficial peroneal nerve: Lateral malleolus
- d.
Saphenous nerve: Medial malleolus
- e.
Sural nerve:
- (1)
Lateral malleolus
- (2)
Lateral border of the Achilles tendon
- (3)
Calcaneus
- (1)
- a.
- 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.
- a.
Detailed Technique
Prepare the anesthetic. Three syringes should be prepared.
The Posterior Tibial Nerve
- 1.
Position the patient.
- 2.
Palpate the 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.
- a.
- 3.
Prepare the skin with an antiseptic solution.
- 4.
Numb the skin with ethyl chloride (if desired).
- 5.
Inject the anesthetic ( Fig. 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 the intravascular placement has been avoided.
- d.
Advance the needle until contact is made with the bone.
- e.
Withdraw the needle 1–2 mm.
- f.
Inject 3–5 mL of the 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 the anesthetic.
- (4)
Withdraw the needle to a subcutaneous position.
- (5)
Redirect posteriorly and advance 0.5 cm.
- (6)
Inject 2 mL of the anesthetic.
- (1)
- a.
