Muscular branches of deep fibular nerve

At a glance

English

Muscular branches of deep fibular nerve

Latin (TA2)

Rami musculares nervi fibularis profundi

System

Nerve

Region

Lower limb

Side

Paired, left and right

About the muscular branches of deep fibular nerve

As the deep fibular nerve descends the front of the leg with the anterior tibial artery, it sends a series of muscular branches into the muscles around it. Together these supply every muscle of the anterior compartment of the leg, and after the nerve divides at the ankle its lateral terminal branch adds supply to the short extensors on the dorsum of the foot. In this way the branches control lifting of the foot and extension of the toes.

The first twigs leave high in the leg, where the nerve has just pierced extensor digitorum longus; they enter tibialis anterior and extensor digitorum longus near their upper ends. Tibialis anterior often receives an extra twig from the recurrent genicular branch of the common fibular nerve. Lower down, branches enter extensor hallucis longus, which arises from the middle of the fibula, and fibularis tertius, the small lateral slip of extensor digitorum longus that inserts on the fifth metatarsal. On the foot, the lateral terminal branch passes deep to extensor digitorum brevis and supplies it and its medial part, extensor hallucis brevis.

The muscles these branches serve work together. Tibialis anterior is the main dorsiflexor of the ankle and also inverts the foot. The long extensors of the toes and the great toe dorsiflex the ankle and straighten the toes. Fibularis tertius dorsiflexes and helps evert. The short extensors straighten the medial four toes on the top of the foot. During walking they lift the foot clear of the ground in the swing phase and then lower it gently at heel strike.

If these branches, or the nerve that gives them off, are damaged, the foot drops and slaps down on landing, and the patient compensates with a high-stepping gait. Testing ankle dorsiflexion and great-toe extension against resistance checks the branches at the bedside; great-toe extension also tests the L5 root, which these fibres carry. Compartment syndrome of the anterior leg can compress them within their tight fascial space.

Course and supply

Arises from

The deep fibular nerve along its course in the anterior compartment, and its lateral terminal branch on the foot.

Ends in

End within tibialis anterior, extensor digitorum longus, extensor hallucis longus, fibularis tertius, extensor digitorum brevis and extensor hallucis brevis.

Supplies

Motor to the anterior leg muscles that dorsiflex the ankle and extend the toes, and to the short toe extensors on the dorsum of the foot.