The long abductor muscle of the thumb is the most lateral of the deep posterior muscles of the forearm. It originates on the dorsal face of the ulna, distal to the crest of the supinator muscle, on the interosseous membrane and on the dorsal face of the radium.
With his insertion tendon he crosses the 1st dorsal carpal ligament duct and inserts himself at the base of the first metacarpal bone. Part of the tendon continues towards the trapezius, while a further part merges in many cases with the tendon of the extensor short muscle of the thumb.
Its main function is abduction of the thumb but it also intervenes in the abduction and palmar flexion of the hand.
It is innervated by the deep branch of the radial nerve (C7-C8), is sprinkled by the posterior interosseous artery.
ORIGIN Dorsal face of the ulna; interosseous membrane; dorsal face of the radium |
INSERTION Base of the first metacarpal bone |
ACTION Thumb abduction, abduction and palmar flexion of the hand |
INNERVATION Radial nerve, deep branch (C7-C8) |
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