Oblique Head of the Abductor Pollicis, Anterior View

Description

Running obliquely across the deep thenar compartment, the oblique head of the adductor pollicis is highlighted in red on the anterior (palmar) aspect of a male hand. Its broad proximal attachment spreads from the capitate and adjacent carpal region onto the bases of the second and third metacarpals, then converges distally toward the ulnar side of the thumb. Superficial to it lie the palmar aponeurosis and the flexor tendons with their synovial sheaths, while the first dorsal interosseous sits more laterally and dorsally between the first and second metacarpals. Deep in the palm, the muscle approaches the ulnar sesamoid and the medial base of the proximal phalanx of the thumb, blending with the extensor expansion. Small structure, big consequences. That distal insertion matters in thumb pinch mechanics because the adductor pollicis provides the power component of key pinch, counterbalancing the abductor pollicis brevis and opponens pollicis to stabilize the first metacarpophalangeal joint during precision grip. The deep branch of the ulnar nerve typically supplies this muscle, so ulnar neuropathy at Guyon canal or a deep palmar branch injury produces weak thumb adduction and a positive Froment sign, a finding that helps separate ulnar from median nerve dysfunction in thenar weakness. In operative anatomy, the adductor aponeurosis and its relationship to the ulnar collateral ligament complex are relevant during repair of skier’s thumb and when exposing the ulnar side of the MCP joint. Hand anatomy instructors can pair this anterior view with cross-sectional or dorsal plates to teach layered thenar dissection, metacarpal relationships, and the course of the deep palmar arch near the adductor pollicis. It also fits well in orthopedic, plastic surgery, and hand therapy materials discussing pinch strength testing, ulnar nerve lesions, and post-injury rehabilitation of the thumb MCP. Anatomical accuracy verified by SciePro's Medical Advisory Board.