Syndrome of the Tendinous Arch of the Adductor Pollicis Muscle

The transverse head of the adductor pollicis muscle originates from the anterior margin of the third metacarpal bone. The oblique head and the deep head of the flexor pollicis brevis muscle share a common origin — the volar ligaments covering the trapezoid and the capitate bones. Connecting the heads of the two adductor pollicis muscles, the tendinous arch forms the roof of a tunnel, the floor of which is the third metacarpal bone. The terminal branch of the deep branch of the ulnar nerve dives through this tunnel to innervate the adductor pollicis.