Abductor pollicus longus is one of the deep muscles on the extensor surface of the forearm.
It arises from the middle posterior third of the:
- shaft of the radius
- shaft of the ulna
- intervening interosseous membrane
It inserts into the base of the first metacarpal having traversed the first dorsal extensor compartment of the wrist. It forms the radial border of the anatomical snuffbox at the wrist.
Its action is to abduct and extend the thumb at the carpometacarpal joint.
Abductor pollicis longus is supplied by the posterior interosseous nerve (C7, c8).