Sesamoid Bone, Posterior View

Description

Presented in a posterior (dorsal) view of the male hand skeleton, the carpal bones form the proximal row at the wrist with the metacarpals extending distally to the proximal, middle, and distal phalanges. At the level of the metacarpophalangeal and interphalangeal joints, articular margins are visible as discrete joint intervals. A small sesamoid is positioned within a tendon near a digital joint, lying palmar to the axis of motion even though the hand is viewed dorsally. Small bone. Big mechanics. Sesamoid bones in the hand are most often associated with the thumb metacarpophalangeal joint, embedded in the tendinous apparatus of the flexor pollicis brevis and adductor pollicis and functioning to increase the moment arm across the joint while protecting the tendon from compressive load. This relationship becomes clinically concrete when evaluating painful thumb MCP motion after hyperabduction injury, where ulnar collateral ligament rupture (gamekeeper’s or skier’s thumb) and sesamoid displacement can be part of the same trauma pattern, and where a sesamoid can also be mistaken for a small fracture fragment on radiographs. Use this posteriorly oriented hand osteology plate to teach carpal-to-phalangeal alignment in gross anatomy and hand surgery courses, to label joint levels and landmarks in a textbook figure, or to support radiology and orthopaedic content discussing normal variants versus avulsion fractures around the thumb MCP. Anatomical accuracy verified by SciePro's Medical Advisory Board.