The superficial peroneal nerve (superficial fibular nerve) is a mixed nerve that carries sensory information from the anterolateral aspect of the leg and the greater part of the dorsum of the foot (except for the first web space). Entrapment of the superficial peroneal nerve is not uncommon and can present with pain in the sensory distribution of the nerve with or without paresthesia. Block of the superficial peroneal nerve provides relief of symptoms of the entrapment and also provides anesthesia for surgical procedures involving the dorsum of the foot. It is better to perform the block under ultrasound guidance to avoid collateral damage of the neurovascular structures and get a more effective block.[1][2]
The superficial peroneal nerve arises as 1 of the 2 terminal branches of the common peroneal nerve at the level of the neck of the fibula in 81%. It originates between the fibular neck and the knee joint in about 9%. In the remaining 10%, it originates above the knee joint line.[3] The nerve runs over the upper part of fibula deep to the peroneus longus muscle; then it passes through peroneus longus to run between it and the peroneus brevis muscles. It descends between the peroneus brevis and the extensor digitorum longus muscles being more superficial. The nerve pierces the deep (crural) fascia becoming superficial through the peroneal tunnel at the junction of upper two-thirds and lower one-third (approximately 12 cm above the ankle). The nerve gives motor innervation to the peroneus longus and brevis muscles and sensory branches that carry sensory information from the anterolateral aspect of the leg and the greater part of the dorsum of the foot (except for the first web space).[4]
Superficial Peroneal Nerve Pain
Entrapment
Trauma
Complex Regional Pain Syndrome of the Ankle and Foot[6]
Anesthesia for Surgical Procedures
Well-trained physicians in landmark-based and ultrasound-guided nerve blocks can perform the procedure (including anesthesiologists and physiatrists).
Landmark-Guided Technique
High-Level Block
Inject 6 to 10 ml of the injectant to ensure satisfactory block at the site of the maximal tenderness which is 10 to 15 cm proximal to the lateral malleolus at the anterolateral aspect of the leg.
Low-Level Block
Inject 6 ml of the injectant to ensure satisfactory block just anterior to the lateral malleolus.
In both techniques, operators introduce the needle from inferior to superior targeting the long axis of the nerve or from lateral to the medial targeting the short axis of the nerve.
Ultrasound-Guided Technique
The operator introduces the needle from the lateral to the medial using "in-plane approach" to inject 3 to 5 ml of the injectate targeting the short axis of the nerve.
Ultrasound-Guided Catheter Technique
The operator places the linear transducer posterolaterally about 12 cm distal to the knee to visualize the nerve. Low amplitude peripheral nerve stimulation (0.5 mA [0.1 ms] stimulus) applied to reproduce the patient’s pain and insert the catheter under the ultrasound guidance through the "in-plane approach" to target the short axis of the nerve. The operator injects a bolus of 15 mL of the injectate (containing 0.25% bupivacaine with epinephrine 1:200,000 and clonidine 25 mcg) via the catheter.
Benefits of Ultrasound Guidance
Superficial peroneal nerve carries sensations from the anterolateral aspect of the leg and the greater part of the dorsum of the foot (except for the first web space). Entrapment of the superficial peroneal nerve is not uncommon. Because of its long course, the entrapment can occur between the fibula and peroneus longus, within peroneus longus, between peroneus brevis and extensor digitorum longus muscles, at the fascial tunnel where it emerges through the deep fascia to become superficial, the lower third of the fibula and in front of the lateral malleolus. Patients having entrapment of the nerve suffer from pain, tingling, and paresthesia along anterolateral aspect of the leg and most of the dorsum of the foot. The differential diagnosis includes L5 radiculopathy, lumbosacral plexopathy, Sciatic mononeuropathy, common peroneal neuropathy, arterial insufficiency, and anterior compartment syndrome. Blocking of the nerve eases the symptoms of the entrapment and allows for painless surgical procedures for pathologies over the dorsum of the foot in the area supplied by the superficial peroneal nerve. The ultrasound-guided block provides better results and lower complications than the landmark-guided block.[10][11][12]
Physicians performing superficial peroneal nerve block should master the ultrasound scanning of the superficial peroneal nerve in people with a classic origin and anatomic course and those with anatomic variations of the origin and the course. Also, They should master excellent clear needle tip visualization under ultrasound guidance to avoid nerve injury or intra-neural injection. Assisting staff as nurses should be ready to deal with complications and use medications to manage systemic complications of the used local anesthetics. (Level V)
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