Origin and Course
The superficial fibular nerve arises from the bifurcation of the common fibular nerve (n. fibularis communis). This division occurs within the superior musculo-fibular canal, approximately 6–7 cm distal to the apex of the fibular head.
Subsequent course of the nerve:
- Emerges from the gap between the heads of the fibularis longus muscle.
- Descends within the lateral compartment of the leg, running between the lateral group muscles along the anterior intermuscular septum (septum intermusculare anterius cruris).
- In the lower third of the leg, the nerve pierces the deep fascia of the leg (fascia cruris).
- Continues distally onto the foot, lying superficially in the loose subcutaneous tissue deep to the superficial veins.
Motor Innervation
The nerve contains motor fibers (spinal segments L4–S1 / L5–S1) that innervate the lateral compartment muscles of the leg. These muscles are responsible for eversion and plantarflexion/dorsiflexion assistance of the foot:
- Fibularis longus muscle (m. peroneus longus) — originates from the head and upper lateral surface of the fibula and the crural fascia. Its tendon passes posterior to the lateral malleolus into the sole. The muscle everts and plantarflexes the foot, depresses the medial border, and supports the transverse arch. Supplied by the fibulo-peroneal and anterior tibial arteries.
- Fibularis brevis muscle (m. peroneus brevis) — originates from the lower 2/3 of the lateral surface of the fibula and inserts onto the base of the 5th metatarsal bone. Performs eversion of the foot and raises its lateral border. Supplied by the fibular and anterior tibial arteries.
Sensory Innervation and Branches
After becoming subcutaneous, the superficial fibular nerve provides cutaneous sensation to the anterolateral aspect of the leg and the major part of the foot dorsum.
On the dorsum of the foot, it gives off the following cutaneous branches:
- Medial dorsal cutaneous nerve (n. cutaneus dorsalis medialis) — supplies the medial half of the foot and the great toe (hallux).
- Intermediate dorsal cutaneous nerve (n. cutaneus dorsalis intermedius) — supplies the adjacent skin of the 2nd–3rd and 3rd–4th digits.
The terminal branches of the nerve are the dorsal digital nerves of the foot (nn. digitales dorsales pedis), which supply the dorsal skin of the toes.
Note: The nerve does not innervate the first web space, nor the lateral and medial margins of the foot.
Clinical Significance
In fibular nerve mononeuropathy (unrelated to direct trauma or traction), characteristic sensory deficits develop: loss of sensation over the anterolateral leg and the dorsum of the foot.
To confirm the diagnosis and detect axonal or demyelinating abnormalities, nerve conduction studies (NCS) and electromyography (EMG) testing motor and sensory fibers are recommended. The diagnostic criterion for a superficial branch lesion is a decreased or absent sensory nerve action potential (SNAP) when testing the superficial fibular nerve compared to the unaffected contralateral side.