Tendon Sheaths Beneath the Skin of the Hand, Palmar View

Description

Beneath the palmar skin, the fibrous digital tendon sheaths form tight osteofibrous tunnels that run from the metacarpophalangeal joints to the distal phalanges, enclosing the flexor digitorum superficialis and flexor digitorum profundus tendons as they course distally toward their insertions. Proximally, the synovial flexor sheaths expand into the radial and ulnar bursae at the level of the carpal tunnel, where the flexor pollicis longus sheath and the common flexor sheath lie deep to the flexor retinaculum. Digital neurovascular bundles track along the radial and ulnar sides of each digit, positioned lateral to the tendon sheath walls and then curving volarly toward the pulp. Flexor sheath anatomy matters because pathology often targets the sheath before the tendon. Stenosing tenosynovitis (trigger finger) classically arises at the A1 pulley over the metacarpal head, where thickening of the fibrous sheath and synovium impedes tendon glide and produces catching or locking in flexion. Infection follows the same compartments: pyogenic flexor tenosynovitis spreads within the synovial sheath, and continuity between the ulnar bursa and the little finger sheath explains rapid proximal extension into the palm, while the radial bursa can carry infection from the thumb toward the wrist. Palmar sheath relationships also support teaching of pulley biomechanics and surgical planning, from A1 pulley release to incision placement that respects the digital arteries and nerves during tendon repair or sheath drainage. Use this artwork in hand anatomy modules, operative hand surgery atlases, emergency medicine references on Kanavel signs, and patient education on trigger finger and flexor tendon sheath infections. Anatomical accuracy verified by SciePro's Medical Advisory Board.