The superficial fibular nerve, also known as the superficial peroneal nerve, is one of the two terminal branches of the common fibular nerve. It originates at the neck of the fibula and travels down the lateral compartment of the leg. This nerve provides innervation to the muscles of the lateral compartment and continues its course superficially to supply the skin of the lower leg and foot.
Location
The superficial fibular nerve runs along the lateral aspect of the lower leg. It first travels between the fibularis longus and fibularis brevis muscles and then pierces the fascia in the lower leg, emerging to become subcutaneous. It continues down to the dorsum of the foot, where it provides cutaneous innervation to most of the dorsal skin of the foot, excluding the web space between the first and second toes.
Structure and Anatomy
The superficial fibular nerve is one of the two terminal branches of the common fibular nerve. It follows a distinct path through the leg, with both motor and sensory components. Below is a detailed description of its anatomy.
Origin
The superficial fibular nerve arises from the common fibular (peroneal) nerve near the neck of the fibula. This is the point where the common fibular nerve bifurcates into the superficial and deep fibular nerves.
Course in the Leg
The superficial fibular nerve descends through the lateral compartment of the leg, running alongside the fibularis longus and fibularis brevis muscles.
Proximal Leg
The nerve begins its course by entering the lateral compartment deep to the fibularis longus muscle, which lies close to the lateral aspect of the fibula. As it continues downward, it runs between the fibularis longus and brevis muscles.
Mid-Leg
In the mid-portion of the leg, the nerve continues between the fibularis longus and brevis, providing motor innervation to these muscles. As it progresses further down the leg, it moves towards the anterior side, piercing the deep fascia of the leg.
Distal Leg
In the distal third of the leg, the superficial fibular nerve becomes subcutaneous as it pierces the deep fascia. At this point, it divides into its terminal sensory branches that continue into the foot. Once it becomes subcutaneous, the nerve runs superficially, beneath the skin, allowing it to provide cutaneous innervation to the lower leg and foot.
Anatomical Relationships
- Proximal Leg: The nerve is deep, located between the fibularis longus and fibula.
- Mid-Leg: It continues deeper, still between the fibularis longus and brevis muscles.
- Distal Leg: The nerve becomes superficial after piercing the fascia and provides sensory innervation to the lower leg.
Branches
The superficial fibular nerve has both motor and sensory branches:
Motor Branches
The motor branches of the superficial fibular nerve innervate the muscles in the lateral compartment of the leg, specifically the fibularis longus and fibularis brevis muscles, which are responsible for eversion of the foot.
Sensory Branches
The superficial fibular nerve’s sensory function is provided by its terminal branches, which arise as the nerve becomes subcutaneous.
- Medial Dorsal Cutaneous Nerve: This branch extends to the medial side of the dorsum of the foot and provides sensory innervation to the skin over the medial and central parts of the dorsum.
- Intermediate Dorsal Cutaneous Nerve: This branch travels towards the lateral side of the dorsum of the foot, supplying the skin of the lateral portion of the foot.
Path into the Foot
Upon reaching the foot, the superficial fibular nerve divides into multiple small cutaneous branches that innervate the skin of the dorsum. These branches provide sensory supply to most of the dorsal surface of the foot, except for the area between the first and second toes, which is supplied by the deep fibular nerve.
Anatomical Landmarks
- Proximal Landmarks: The superficial fibular nerve originates at the fibular neck.
- Mid-Leg Landmarks: It runs between the fibularis longus and brevis muscles.
- Distal Landmarks: It pierces the deep fascia to become superficial, traveling beneath the skin and extending into the dorsum of the foot.
Relations to Other Structures
- Fibularis Muscles: The superficial fibular nerve travels between the fibularis longus and brevis muscles.
- Fascia: It pierces the deep fascia of the leg to become superficial in the lower third of the leg.
- Dorsum of the Foot: The nerve travels superficially across the dorsum of the foot, innervating the overlying skin.
Termination
The superficial fibular nerve terminates in the foot by providing sensory innervation through the medial and intermediate dorsal cutaneous branches, which supply the majority of the skin on the dorsum of the foot, excluding the first web space.
Function
The superficial fibular nerve serves both motor and sensory functions. It plays a crucial role in foot movement, particularly eversion, and provides sensory innervation to the skin of the lower leg and dorsum of the foot.
Motor Functions
The superficial fibular nerve is responsible for innervating the muscles in the lateral compartment of the leg, which control the eversion of the foot. These muscles are crucial in maintaining balance and stability during walking and other activities.
Muscles of the Lateral Compartment of the Leg
- Fibularis Longus (Peroneus Longus): This muscle plays a key role in foot eversion (turning the foot outward) and plantarflexion (pointing the toes downward). It also supports the arch of the foot, contributing to foot stability during walking and running. By everting the foot, it helps prevent ankle sprains.
- Fibularis Brevis (Peroneus Brevis): Similar to the fibularis longus, the fibularis brevis also contributes to foot eversion and plantarflexion. It provides additional stability to the lateral aspect of the foot and helps prevent ankle rolling.
Sensory Functions
The sensory function of the superficial fibular nerve is primarily associated with providing cutaneous (skin) sensation to the distal parts of the leg and the dorsum (top) of the foot.
Sensory Supply to the Lower Leg
Distal Lateral Leg: After piercing the deep fascia, the superficial fibular nerve provides cutaneous innervation to the lower third of the lateral leg. This sensory innervation helps relay information about touch, temperature, and pain from the skin in this region.
Sensory Supply to the Dorsum of the Foot
The superficial fibular nerve provides sensory innervation to the majority of the dorsal surface of the foot through two main branches:
- Medial Dorsal Cutaneous Nerve: This branch supplies sensation to the medial and central parts of the dorsum of the foot. It extends to the skin over the dorsal surface of the first to fourth toes, excluding the web space between the first and second toes.
- Intermediate Dorsal Cutaneous Nerve: This branch provides sensation to the lateral portion of the dorsum of the foot. It innervates the skin over the lateral part of the foot, extending toward the fifth toe.
Exclusion of the First Web Space
The area between the first and second toes is not innervated by the superficial fibular nerve but instead by the deep fibular nerve. This means that the superficial fibular nerve’s sensory supply is limited to the remainder of the dorsal foot.
Clinical Significance
The superficial fibular nerve has important clinical implications, especially related to its role in foot movement and sensation. Dysfunction or injury to this nerve can lead to both motor and sensory impairments, which can affect daily activities such as walking and balance.
Injury and Trauma
The superficial fibular nerve is susceptible to injury due to its superficial location in the lower leg, particularly after it pierces the fascia and becomes subcutaneous. Trauma to the lateral leg, such as fractures or soft tissue injuries, can damage the nerve, leading to sensory loss in the lower leg and dorsum of the foot, as well as weakness in foot eversion.
Chronic Ankle Sprains
Since the superficial fibular nerve innervates muscles responsible for foot eversion (fibularis longus and brevis), injury to the nerve may contribute to instability of the ankle and recurrent ankle sprains. This can occur if the muscles lose strength or coordination, making it harder for the foot to stabilize, particularly on uneven ground.
Nerve Entrapment (Superficial Fibular Nerve Entrapment)
Superficial fibular nerve entrapment occurs when the nerve becomes compressed, often due to excessive pressure, such as from tight footwear, repetitive ankle movements, or swelling. Symptoms include pain, numbness, and tingling along the lateral aspect of the leg and the dorsum of the foot. These symptoms can become aggravated by walking or physical activity.
Surgical Considerations
The superficial fibular nerve is at risk during surgeries involving the lower leg or ankle, such as fracture fixation or tendon repairs. Iatrogenic injury to the nerve can result in motor deficits, such as difficulty with foot eversion, and sensory loss in the affected regions.
