Flashcards in Common fibular nerve Deck (18):
Begins at apex of popliteal fossa.
Follows medial border of biceps femoris and then travels in an inferolateral direction over lateral head of gastrocnemius. At this point it gives rise to 2 cutaneous branches.
Nerve wraps around neck of fibula, passing between attachments of fibularis longus. Here it terminates by dividing into superficial fibular and deep fibular nerves.
Common fibular nerve - Short head of biceps femoris
Superficial fibular nerve - lateral leg (fibularis longus and brevis)
Deep fibular nerve - anterior leg (tibialis anterior, extensor digitorum longus, extensor hallucis longus, fibularis tertius) and some intrinsic muscles of the foot (extensor digitorum brevis and extensor hallucis brevis)
Sensory Innervation of sural nerves (2)
Sural commicating nerve - combines with a branch of the tibial nerve to form the sural nerve which innervates the skin over the lower posterolateral leg.
Lateral sural cutaneous nerve - skin over the upper lateral leg
Cause of damage
Fracture of fibula
Tight plaster cast
Consequences of damage
Loss of ability to dorsiflex foot at ankle. This causes deformity called footdrop where foot is permanently plantarflexed
Loss of sensation over dorsum of the foot and lateral leg
Nerve roots of superficial fibular nerve
Anatomical course of superficial fibular nerve
Arises in neck of fibula, descending between fibularis muscles and lateral side of extensor digitorum longus. Here it gives rise to motor branches which supply fibularis longus and brevis.
Continues descent with purely cutaneous function.
When it reaches the lower third of leg it pierces the deep crural fascia and terminates by dividing into medial and intermedial dorsal cutaneous nerves which enter the foot.
Sensory Innervation of superficial fibular nerve
Cutaneous branches - anterolateral leg
Medial and intermedial dorsal cutaneous nerves - dorsum of foot (except webbed space between hallanx and 2nd digit)
Dermatomes L5 and S1
Cause of superficial fibular nerve entrapment (nerve compression)
Ankle sprains or twisting of the ankle - This stretches the nerve
Compression by deep fascia of leg as the superficial fibular nerve exits it (requires surgical decompression of nerve)
Consequence of superficial fibular nerve entrapment
Pain and paresthesia over lower leg and dorsum of foot
How is superficial fibular nerve damaged
Fracture of fibula
Perforating wound to lateral leg
Nerve roots of deep fibular nerve
Anatomical course of deep fibular nerve
Arises in superolateral leg between fibularis longus and neck of fibula
(Follows the course of anterior tibial artery) travels in inferomedial direction passing between the tibialis anterior and extensor digitorum longus
It crosses the ankle joint, passing anterior to distal tibia and deep to extensor retinaculum.
It terminates in dorsum of foot where it divides into lateral and medial branches
Consequence of deep fibular nerve entrapment/compression
Paralysis of anterior leg muscles so patient can't dorsiflex foot (footdrop)
Consequence of footdrop
Difficulty clearing ground during swing phase
Limb looks too long
Foot slaps down on floor when patient walks (can't be lowered in controlled manner)
Develop abnormal gait
Types of abnormal gait with footdrop
Waddling gait - patient leans excessively onto normal limb
Swing out gait - patient abducts abnormal limb
High steppage gait - patient flexes hip and knee excessively on abnormal limb