Oblique Head of the Adductor Pollicis, Anterior View

Description

Arising from the capitate and the bases of the second and third metacarpals, the oblique head of the adductor pollicis occupies the deep palm and sweeps distally and laterally toward the ulnar side of the thumb. Its fibers converge on a tendon that inserts on the medial (ulnar) base of the proximal phalanx of the pollex and the ulnar sesamoid within the metacarpophalangeal joint capsule, lying deep to the flexor pollicis brevis and close to the tendon of flexor pollicis longus. An anterior perspective also places the transverse head (from the shaft of the third metacarpal) in the same plane, with the first dorsal interosseous positioned more dorsolaterally and the long flexor tendons to the digits tracking distally beneath the palmar aponeurosis. Deep thenar anatomy is crowded. This view matters when teaching thumb pinch mechanics and when localizing ulnar nerve deficits. The deep branch of the ulnar nerve innervates adductor pollicis, so weakness or denervation produces loss of key pinch and a positive Froment sign, often accompanied by visible wasting in the first web space. Surgeons working in the thenar space and around the deep palmar arch also use the adductor plane as a landmark, since the muscle forms part of the floor for neurovascular structures traveling toward the thumb and index finger. Use it in gross anatomy and hand anatomy modules to differentiate intrinsic thenar muscles and to trace tendon-to-bone insertions at the thumb metacarpophalangeal joint. The illustration also suits neurology and hand therapy materials discussing ulnar neuropathy at Guyon canal, electromyography target selection for adductor pollicis, and postoperative rehabilitation focused on restoring key pinch strength. Anatomical accuracy verified by SciePro's Medical Advisory Board.