Extensor digitorum brevis

The extensor digitorum brevis is a small muscle located on the dorsum of the foot. It originates from the superolateral surface of the calcaneus and the surrounding interosseous talocalcaneal ligament, and inserts via tendons into the dorsal aspects of the second, third, and fourth toes. Its function is to assist in extension of the toes at the metatarsophalangeal and interphalangeal joints. The muscle is innervated by the deep peroneal (fibular) nerve and receives its main vascular supply from the lateral tarsal artery.

Origin: Calcaneus

Insertion: Toes

Nerve: Deep peroneal nerve

Action: Extends digits 2, 3, and 4

Antagonist: Flexor digitorum longus, Flexor digitorum brevis

Description: The Extensor digitorum brevisis a broad, thin muscle, which arises from the forepart of the upper and lateral surfaces of the calcaneus, in front of the groove for the Peronaeus brevis; from the lateral talocalcanean ligament; and from the common limb of the cruciate crural ligament. It passes obliquely across the dorsum of the foot, and ends in four tendons. The most medial, which is the largest, is inserted into the dorsal surface of the base of the first phalanx of the great toe, crossing the dorsalis pedis artery; it is frequently described as a separate muscle—the Extensor hallucis brevis. The other three are inserted into the lateral sides of the tendons of the Extensor digitorum longus of the second, third, and fourth toes.

Variations.—Accessory slips of origin from the talus and navicular, or from the external cunei-form and third metatarsal bones to the second slip of the muscle, and one from the cuboid to the third slip have been observed. The tendons vary in number and position; they may be reduced to two, or one of them may be doubled, or an additional slip may pass to the little toe. A supernumerary slip ending on one of the metatarsophalangeal articulations, or joining a dorsal interosseous muscle is not uncommon. Deep slips between this muscle and the Dorsal interossei occur.

Nerves.—It is supplied by the deep peroneal nerve.

Actions.—The Extensor digitorum brevis extends the phalanges of the four toes into which it is inserted, but in the great toe acts only on the first phalanx. The obliquity of its direction counteracts the oblique movement given to the toes by the long Extensor, so that when both muscles act, the toes are evenly extended.