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Extensor Digitorum Brevis Fourth Slip

musculus extensor digitorum brevis (fasciculus quartus)

The fourth slip of extensor digitorum brevis is the most lateral EDB slip to a lesser toe, inserting into the fourth toe. It is the smallest of the lesser toe EDB slips and lies on the lateral dorsal foot. There is no EDB slip to the fifth toe — the fifth toe is served solely by the extensor digitorum longus and extensor digiti minimi.

Nerve: Deep peroneal nerve (L5, S1) Blood Supply: Arcuate artery, lateral tarsal artery Region: Foot & Ankle

Anatomical Data

Origin, Insertion & Supply

Origin	Dorsal surface of the calcaneus, lateral portion of EDB origin, adjacent to extensor digitorum brevis main belly
Insertion	Dorsal surface of the proximal phalanx of the fourth toe and lateral EDL tendon to the fourth toe
Nerve Supply	Deep peroneal nerve (L5, S1)
Blood Supply	Arcuate artery, lateral tarsal artery

Biomechanics

Function & Actions

Actions	Extends the fourth MTP joint; Assists dorsiflexion of the fourth toe

Clinical Relevance

Clinical Notes

The absence of an EDB slip to the fifth toe means that fifth toe extension weakness selectively indicates extensor digitorum longus injury rather than EDB or deep peroneal nerve foot-level injury. The fourth EDB slip borders the classic approach for the fourth web space Morton's neuroma. Individual EDB slip atrophy creates a cascading pattern of dorsal foot wasting visible in advanced peripheral neuropathy.

Palpation

Palpated on the lateral dorsum of the foot over the fourth metatarsal during resisted fourth toe extension.

Pathology

Common Injuries & Conditions

Fourth Web Space Compression

EDB fourth slip involvement in fourth intermetatarsal space pathology contributing to limited fourth toe extension and dorsal forefoot pain with resisted extension.