Deep Peroneal Nerve Block

Anatomy and Physiology

The deep peroneal nerve innervates muscles of the anterior leg compartment and the dorsum of the foot. It is also responsible for the sensation of the first interdigital cleft of the foot, or the space between the first and second digits. The nerve is derived from the common peroneal (fibular) nerve, which as part of the sciatic nerve originates from the dorsal branches of L4, L5, S1, and S2. [3] In the popliteal fossa, the sciatic nerve divides into the common peroneal nerve and the tibial nerve. The common peroneal nerve then divides into the superficial and deep peroneal nerves. In the lower leg, the deep peroneal nerve descends, along with the anterior tibial artery, just anterior to the interosseous membrane. The nerve provides motor innervation to the muscles of the anterior compartment. It tracks along the lateral aspect of the anterior tibial artery and crosses the anterior aspect of the ankle between the extensor hallucis longus and extensor digitorum longus muscles. Approximately 1.3 cm above the ankle joint, the nerve divides into its 2 terminal branches, the lateral and medial branches. The lateral branch passes deep to the extensor digitorum brevis and extensor hallucis brevis muscles and provides their motor innervations. It also provides sensory innervation to the ankle and sinus tarsi. The medial branch courses medially along the dorsum of the foot lateral to the dorsalis pedis artery. The extensor hallucis brevis tendon crosses over the nerve, and the nerve terminates in the first interdigital cleft of the foot where it provides sensory innervation.[4][5][6][7][8]

Indications

Indications for a deep peroneal nerve block include:

• Regional anesthesia for the ankle or foot during surgery
• Analgesia for burns to the foot
• Laceration repair of the first interdigital cleft[9]
• Anterior tarsal tunnel syndrome

Contraindications

Contraindications to a deep peroneal nerve block include:

• Local anesthetic allergy/anaphylaxis
• Patients receiving high levels of local anesthetic are at risk for local anesthetic systemic toxicity (LAST)
• Overlying cellulitis or abscess at the injection site
• Patient refusal
• Patients at risk for compartment syndrome at the site of injection [10]
• Caution is advised in patients who are anticoagulated but can still be performed due to foot and ankle being compressible sites

Equipment

Equipment for the procedure includes:

• Isopropyl alcohol, Chlorhexidine gluconate, or povidone-iodine
• Local anesthetic: The type and quantity vary depending on the intended duration of the block. Five milliliters of lidocaine 2% for a short-medium duration block (1 to 2 hours), 5 mL of bupivacaine 0.5%, or ropivacaine 0.5% (2 to 4 hour block)
• Ultrasound machine with high frequency (greater than 8 MHz) linear probe
• Sterile gel and ultrasound probe cover
• Short bevel block needle, typically 25-27 gauge
• 10 or 20 mL syringe[11][12]

Personnel

A practitioner (podiatrist or orthopedic surgeon) trained in ultrasound-guided regional anesthesia techniques and support staff to administer rescue medications in the event of an adverse reaction.

Preparation

Obtain informed consent from the patient including risks, benefits, and alternative therapies to the procedure. Conduct a pre-procedure "time out" to verify patient identity with name, date, and MRN, confirm allergies, and confirm the site at which you will be administering the nerve block. Position the patient so that the dorsal surface of their foot and anterior leg is easily accessible. This is best achieved by having the patient lay down in bed with their knees bent and the plantar surfaces of their feet firmly against the bed. Prior to initiating the block, perform a detailed neurovascular exam of the extremity to be blocked and document any preexisting abnormalities. Aseptic technique is used with the application of chlorhexidine gluconate 2% or povidone-iodine solution to the skin of the injection site. Apply a sterile ultrasound probe cover and sterile gel to the high-frequency linear probe. Draw up the anesthetic solution in a sterile syringe and have appropriate monitors attached to the patient (e.g. pulse oximeter, blood pressure cuff, and ECG leads).   

Technique or Treatment

The nerve block is performed in the following steps:

1. Place the ultrasound probe on the ventral fold of the ankle in a transverse orientation of the leg about 1 to 2 cm proximal to the level of the medial and lateral malleoli
2. Identify the anterior tibial artery and track along both distally and proximally to ensure this is the correct vessel
3. The deep peroneal nerve will be the white honeycomb-like structure lying lateral next to the anterior tibial artery
4. Insert your needle in-plane and parallel to the probe surface
5. Advance your needle until it is just superficial to the deep peroneal nerve, making sure you always visualize your needle tip as you advance
6. Aspirate the syringe to ensure you are not in a vessel
7. Inject 1 to 2 mL of local anesthetic while visualizing the spread of the fluid around the nerve
8. Repeat steps 1 to 7 with slight adjustments to the needle to coat the entire nerve until you achieve a satisfactory level of anesthesia[7][5][12]

Complications

Complications include:

• Bleeding
• Infection
• Local anesthetic systemic toxicity (LAST syndrome)
• Allergic reaction to the local anesthetic 
• Vascular puncture
• Intramuscular hematoma
• Intravascular injection
• Nerve damage[13]

Clinical Significance

Blocking the deep peroneal nerve will provide anesthesia to the interdigital cleft between the first and second toes of the foot. While it does not provide a large amount of sensory innervation, it is still important for patients who are undergoing foot or ankle procedures, such as a bunionectomy. The increased prevalence of ultrasound has also allowed easy visualization of the nerve and increased the success rate of onset to ankle block. While blocking the deep peroneal nerve and the other nerves of the ankle during surgery, it has been shown this nerve block can improve outcomes in the patient's pain postoperatively. This nerve block can also be performed successfully using the extensor hallucis brevis musculotendinous junction as an anatomical landmark.[1][14][15]

Enhancing Healthcare Team Outcomes

A majority of the time the deep peroneal nerve block is used when performing ankle or foot surgery. As with any surgery, the process is a well-coordinated effort of an interprofessional healthcare team, in this case specifically the surgeon, anesthesiologist, and nursing staff. For these surgeries, either the surgeon or anesthesiologist places the block and nursing is available with medication for an adverse reaction. In a large randomized trial, they found with well-organized care between specialties that there was a low risk of neurologic or nerve block site complications for post-operative complications.[16] (Level 1) It is also important to work closely with pharmacy and nursing during these situations to monitor for local anesthetic systemic toxicity or LAST syndrome. With pharmacy and nursing, they have access and could administer intralipid 20% (1.5 mL/kg bolus, 0.25mg/kg per hour drip) in the case of cardiac arrest due to LAST. These procedures require cohesive team approaches and all members of the interprofessional team are integral to a successful procedure. [Level 5]