Common Fibular Nerve Flashcards
What are the nerve roots of the common fibular nerve?
L4-S3
What are the motor functions of the common fibular nerve?
Innervates the short head of the biceps femoris directly
Supplies, via branches, the muscles in the lateral and anterior compartments of the leg
What are the sensory functions of the common fibular nerve?
Innervates the skin over the upper lateral and lower posterolateral leg
Supplies (via branches) cutaneous innervation to the skin of the anterolateral leg, and the dorsum of the foot
Where does the common fibular nerve begin?
At the apex of the popliteal fossa, where the sciatic nerve bifurcates into the tibial and common fibular nerves
What is the anatomical course of the common fibular nerve?
It follows the medial border of the biceps femoris, running in a lateral and inferior direction, over the lateral head of the gastrocnemius.
What happens as the common fibular nerve passes over the lateral head of the gastocnemius?
It gives rise to two cutaneous branches, which contribute to the innervation of the skin of the leg
How does the common fibular nerve enter the lateral compartment of the leg?
The nerve wraps around the neck of the fibula, passing between the attachments of the fibularis longus muscle
Where does the common fibular nerve terminate?
When it passes between the attachments of the fibularis longus muscle
How does the common fibular nerve terminate?
By dividing into the superficial fibular and deep fibular nerves
What muscle does the common fibular nerve innervate?
The short head of the biceps femoris
What is the biceps femoris muscle part of?
The hamstring muscles
What do the hamstring muscles do?
Flex at the knee
What muscles does the superficial fibular nerve innervate?
The muscles of the lateral compartment of the leg- fibularis longus and brevis
What do the muscles of the lateral compartment of the leg do?
Act to evert the foot
What muscles does the deep fibular nerve innervate?
The muscles of the anterior compartment of the leg- the tibialis anterior, extensor digitorum longus and extensor hallucius longus
Some intrinsic muscles of the foot
What do the muscles of the anterior compartment of the leg do?
Act to dorsiflex the foot, and extend the digits
What happens if the common fibular nerve is damaged?
The patient may lose the ability to dorsiflex and evert the foot and extend the digits
What cutaneous branches arise directly from the common fibular nerve?
Sural communicating nerve
Lateral sural cutaneous nerve
Where to the cutaneous branches of the common fibular nerve arise?
Just as it moves over the lateral head of the gastrocnemius
What does the sural communicating nerve combine with?
A branch of the tibial nerve to form the sural nerve
What does the sural nerve do?
Innervates the skin over the posterolateral leg
What does the lateral sural cutaneous nerve?
Innervates the skin over the upper lateral leg
What is the sensory function of the superficial fibular nerve?
Innervates the skin of the anterolateral leg, and dorsum of the foot (except the skin between the first and second toes)
What is the sensory function of the deep fibular nerve?
Innervates the skin between the first and second toes
How is the common fibular nerve most commonly damaged?
By a fracture of the fibula, or use of a tight plaster cast
What can any fractures of the fibular cause?
Nerve palsy
Why can any fractures of the fibular cause nerve palsy?
Because the anatomical course of the common fibular nerve causes it to wrap round the neck of the fibula
What will happen in patients with common fibular nerve damage?
They will lose the ability to dorsiflex the foot at the ankle joint, and hence the foot will appear plantarflexed- known as footdrop
May present with a characteristic gait, as a result of the footdrop
Loss of sensation over the dorsum of the foot, and the lateral side of the leg
Why is innervation preserved on the medial side of the leg in common fibular damage?
By the saphenous nerve, a branch of the femoral
Why is innervation preserved on the heel and sole in common fibular nerve damage?
Supplied by the tibial nerve, a branch of the sciatic
