Corpus: Extensor digitorum muscle

Origin

The extensor digitorum muscle originates from the lateral epicondyle of the humerus, lateral to the extensor carpi ulnaris muscle. Additionally, it has origin points on the septa that separate it from adjacent muscles, as well as on the antebrachial fascia.

Insertion

The muscle runs approximately centrally on the dorsal side of the forearm towards distal and eventually divides into four tendons that extend to the wrist. These tendons proceed under the extensor retinaculum in the fourth tendon compartment distally and diverge on the back of the hand to extend to fingers II-V. There, they merge with the dorsal aponeurosis of the respective finger, attaching to their middle and distal phalanges.

Variant

In some instances, an independent muscle belly for the tendon to the second finger can be observed. Additionally, the tendon to the fifth finger may be absent. Double tendons for individual fingers have also been documented.

The innervation of the extensor digitorum muscle is provided by the deep branch of the radial nerve, with fibers from segments C6 and C7.

The extensor digitorum muscle facilitates the extension of fingers II-V (in the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints), dorsiflexion at the wrist, and ulnar abduction.

During the neurological examination, the extensor digitorum reflex is tested.