Flexor Pollicis Longus as, Anterior View

Description

Arising from the anterior surface of the radius and adjacent interosseous membrane, the flexor pollicis longus belly occupies the deep anterior compartment of the forearm, lying lateral to the flexor digitorum profundus and deep to the flexor digitorum superficialis. Distally, its tendon tracks toward the radial side of the wrist, passing deep to the flexor retinaculum within the carpal tunnel before turning into the thumb. The tendon continues along the palmar aspect of the first metacarpal to insert on the base of the distal phalanx of the thumb, anterior to the interphalangeal joint. Bony landmarks of the humerus, radius, ulna, carpal bones, metacarpals, and phalanges frame the muscle’s course. Anterior visualization of flexor pollicis longus matters because it explains why isolated loss of thumb interphalangeal flexion points to anterior interosseous nerve dysfunction. A classic teaching example is the inability to form a tip to tip pinch (the pinch sign) in anterior interosseous nerve palsy, where flexor pollicis longus and the radial part of flexor digitorum profundus are affected without sensory loss. Tendon anatomy at the wrist also anchors discussion of carpal tunnel relationships and the mechanics of stenosing tenosynovitis involving the flexor pollicis longus tendon sheath. Use this asset in gross anatomy and upper limb dissection manuals to support deep anterior forearm compartment teaching, or in hand surgery and orthopaedic texts when illustrating tendon transfer planning, anterior interosseous nerve lesions, or thumb flexion biomechanics. It also fits patient education and rehab materials that need a clear linkage between forearm muscle injury and distal thumb function. Anatomical accuracy verified by SciePro's Medical Advisory Board.