Extensor digitorum [digitalis] brevis muscle

The extensor digitorum or digitalis brevis muscle is a muscle of the pelvic limb located on the dorsal side of the metatarsus.

Conformation: It is composed of a fleshy fasciculated blade that divides distally into several branches, giving tendons to each phalanx except the fifth. In equids and ruminants, it is formed by a single indivisible blade.

Origin: Dorsal-distal part of the calcaneus and ligamentous tissues of the tarsus.

Insertion: On the proximal end of the proximal phalanx, on the tendons of the corresponding extensor digitorum longus muscle, or on the tendons of the interosseous muscles, depending on the species.

Relations: It covers the dorsal surface of the metatarsus and the dorsal artery of the foot. It is itself covered by the tendinous structures of the extensor digitorum longus muscle and by the dorsal fascia of the foot.

Action: It is accessory to the extensor digitorum longus muscle, and therefore participates in the extension of the fingers and the flexion of the tarsus.

Vascularization: Branches of the dorsal artery of the foot.

Innervation: Deep fibular nerve.

Description: The extensor digitorum or digitalis brevis muscle is a muscle of the pelvic limb located on the dorsal face of the metatarsal. It is a muscle of the foot that originates on the dorsodistal part of the calcaneus and the surrounding ligamentous tissues of the tarsus. It then forms a broad fleshy blade that may be simple or divided into fascicles depending on the species, covering the dorsal surface of the metatarsal. These fascicles give rise distally to branches and then tendons that attach to the proximal end of the proximal phalanges of each toe, except for the fifth, or they may join the tendons of the extensor digitorum longus or interosseous muscles. It is covered by the tendinous structures of the extensor digitorum longus muscle and by the dorsal fascia of the hindfoot. The dorsal artery of the foot, which passes under this muscle, gives it branches for its vascularization. The deep fibular nerve innervates it as well as the extensor digitorum longus, which it assists in the extension of the fingers and flexion of the tarsus.

Variations:

• In equines, it consists of a single flattened triangle-shaped blade located between the tendon of the extensor digitalis longus muscle and the tendon of the extensor digitalis lateralis muscle at their junction, on which it attaches.