Upper limb

Extensor Indicis

Musculus extensor indicis

Origin

Posterior surface of the ulna (distal shaft) and the interosseous membrane

Insertion

Extensor hood (dorsal aponeurosis) of the index finger

Function

Extends the index finger independently of the other fingers

Innervation

Radial nerve (deep branch/posterior interosseous nerve), C7–C8

Movement & chain

Allows pointing while the other fingers remain flexed, because this muscle can be activated independently of extensor digitorum.

Palpation

Difficult to palpate separately; the tendon lies ulnar to the extensor digitorum tendon to the index finger on the dorsum of the hand.

Clinical

Frequently used as a donor for a tendon transfer to restore function after rupture of extensor pollicis longus, for example following a wrist fracture.

Segmental innervation

Part of the C7–C8 myotome via the deep branch of the radial nerve.

In clinical practice

Focus on hand function and edema prevention; ensure IV cannulas and splints maintain functional hand position to prevent joint contractures.

Region in the model

Upper limb