Abductor Pollicis Brevis, Anterior View

Description

Dominating the radial side of the palmar (anterior) hand, the abductor pollicis brevis forms the most superficial bulk of the thenar eminence, lying lateral to the flexor pollicis brevis and superficial to the opponens pollicis. Its fleshy belly arises from the flexor retinaculum and adjacent carpal region (typically the scaphoid tubercle and trapezium), then courses distally and slightly laterally toward the base of the proximal phalanx of the thumb. Medially, the palmar aponeurosis and the long flexor tendons of the digits sit deeper in the central palm, while the first metacarpal and phalanges provide the bony framework against which the thenar muscles contour. Thumb abduction is only part of the story. Clinically, the abductor pollicis brevis is a workhorse for assessing median nerve integrity because it is supplied by the recurrent branch, which can be compromised in carpal tunnel syndrome, lacerations at the thenar crease, or iatrogenic injury during open release. Thenar atrophy and loss of palmar abduction are often easiest to appreciate at this muscle. Electromyography and nerve conduction studies frequently target the abductor pollicis brevis because its motor response is accessible and reproducible, and its weakness helps distinguish median neuropathy from ulnar-sided intrinsic hand dysfunction. Hand anatomy instructors use this anterior view to teach surface anatomy of the thenar eminence and the layered organization of thenar musculature relative to the flexor retinaculum and first ray. It also fits cleanly into hand surgery and rehabilitation materials when explaining median nerve lesions, carpal tunnel decompression approaches, or tendon transfer planning to restore thumb palmar abduction. Anatomical accuracy verified by SciePro's Medical Advisory Board.