Extensor pollicis longus muscle

Extensor pollicis longus (EPL) is a muscle of the deep compartment in the posterior compartment of the forearm. It passes through the 3^rd extensor compartment of the wrist, then continues mediallylaterally towards the thumb around Lister's tubercle. The tendon of EPL defines the ulnar border of the Anatomical snuff box.

Summary

• origin:posterior surface of the middle 1/3 of the ulna and interosseous membrane
• insertion: posterior surface of the base of the distal phalanx of thumb
• innervation: posterior interosseous nerve (C7 and C8), a continuation of the deep branch of the radial nerve (C7, C8)
• arterial supply: anterior and posterior interosseous arteries
• action: extends the thumb at the carpometacarpal and interphalangeal joints, and partially adducts 1^st metacarpal

Related pathology

• distal intersection syndrome
• EPL tenosynovitis, common after activities such as drum playing