Upper limb

Extensor Pollicis Longus

Musculus extensor pollicis longus

Origin

Posterior surface of the ulna (middle third) and the interosseous membrane

Insertion

Base of the distal phalanx of the thumb

Function

Extends the interphalangeal and metacarpophalangeal joint of the thumb and adducts the thumb

Innervation

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

Movement & chain

Bends around the dorsal tubercle of the radius (Lister's tubercle) like a pulley, changing the pulling direction toward the thumb.

Palpation

Forms the posterior (ulnar) border of the anatomical snuffbox, clearly visible when lifting the thumb off the plane of the hand.

Clinical

Can rupture spontaneously after a wrist fracture (for example a distal radius fracture) due to friction over Lister's tubercle.

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