Describe the Common Fibular Nerve
The common fibular nerve is formed as sciatic nerve bifurcates at the apex of popliteal fossa: follows medial border of biceps femoris and its tendon; passes over posterior aspect of head of fibula and then winds around neck of fibula deep to fibularis longus, where it divides into deep and superficial fibular nerves.
Supplies skin on lateral part of posterior aspect of leg via the lateral sural cutaneous nerve; also supplies knee joint via its articular branch
What does the Superficial Fibular Nerve supply?
fibularis longus and brevis and skin on distal third of anterior surface of leg and most of the dorsum of foot
What does the Deep Fibular Nerve supply?
anterior muscles of leg, dorsum of foot and skin of first interdigital cleft; sends articular branches to joints it crosses
Describe the Anterior Tibial Artery
The smaller terminal branch of the popliteal branch, the anterior tibial artery, supplies structures in the anterior compartment.
It begins at the inferior border of the popliteus muscle and immediately passes anterolaterally through a gap in the interosseous membrane to descend on the anterior surface of this membrane between the TA and EDL.
At the ankle joint, midway between the malleoli, the anterior tibial artery becomes the dorsalis pedis artery.
Where do you palpate for the posterior tibial artery?
posterior to medial malleolus
Describe the Dorsalis Pedis Artery and where you would palpate for it
The dorsalis pedis artery is a continuation of the anterior tibial artery distal to inferior extensor retinaculum.
Descends anteromedially to first interosseous and divides into plantar and arcuate arteries.
Palpable on dorsum of foot (medial border; extensor hallucis longus, lateral border; extensor digitorum longus)
To palpate, ask person to extend big toe (bring toe towards them) and palpate lateral to tendon.
Describe the blood supply to the lateral compartment of the leg
The lateral compartment does not have an artery coursing through it. Instead, perforating branches and accompanying veins supply blood to drain blood from the compartment.
Proximally perforating branches of the anterior tibial artery penetrate the anterior intermuscular septum
Inferiorly, perforating branches of the fibular artery penetrate the posterior intermuscular septum along with their accompanying veins
Discuss injury of the common fibular nerve
Because of its superficial position, the common fibular is the nerve most often injured in the lower limb mainly because it winds subcutaneously around the fibular neck, leaving it vulnerable to direct trauma.
This nerve may also be severed during fracture of the fibular neck of severely stretched when the knee joint is injured or dislocated.
Severance of the common fibular nerve results in flaccid paralysis of all muscles in the anterior and lateral compartments of the leg (dorsiflecors of ankle and everters of foot)
Individuals with a common fibular nerve injury may also experience a variable loss of sensation on the anterolateral aspect of the leg and the dorsum of the foot.
Why does Foot Drop occur?
The loss of dorsiflexion of the ankle causes foot-drop which is further exacerbated by unopposed inversion of the foot. This has the effect of making the limb “too long” – the toes do not clear the ground during the swing phase of walking.
What is a Steppage Gait and why is it commonly employed in cases of flaccid paralysis?
Because the dropped foot makes it difficult to make the heel strike the ground first as in a normal gait, a steppage gait is commonly employed in the case of flaccid paralysis.
The steppage “high-stepping” gait is where extra flexion is employed at the hip and knee to raise the foot as high as necessary to keep the toes from hitting the ground.
Sometimes an extra “kick” is added as the free limb swings forward in an attempt to flip the forefoot upward just before setting the foot down.
What other action apart from dorsiflexion and eversion is lost in flaccid paralysis foot drop?
The braking action normally produced by eccentric contraction of the dorsiflexors is also lost in flaccid paralysis foot-drop.
Therefore the foot is not lowered to the ground in a controlled manner after heel strike; instead the foot slaps the ground suddenly, producing a distinctive “clop” and greatly increasing the shock both received by the forefoot and transmitted up the tibia to the knee.
Discuss Deep Fibular Nerve Entrapment
Excessive use of muscles supplied by the deep fibular nerve e.g. during skiing, running and dancing may result in muscle injury and oedema in the anterior compartment. This entrapment may cause compression of the deep fibular nerve and pain in the anterior compartment .
Compression of the nerve by tight-fitting ski boots for example may occur where the nerve passes deep to the inferior extensor retinaculum and the extensor hallucis brevis. Pain occurs in the dorsum of the foot and usually radiates to the web space between the 1st and 2nd toes.
Discuss Superficial Nerve Entrapment
Chronic ankle sprains may produce recurrent stretching of the superficial fibular nerve, which may cause pain along the lateral side of the leg and dorsum of the ankle and foot. Numbness and paresthesia may be present and increase with activity.