Tendon Sheaths of the Extensor Pollicis Brevis as, Posterior View

Description

Running along the dorsoradial distal forearm, the extensor pollicis brevis tendon is shown within its synovial tendon sheath (vagina tendinis), deep to the extensor retinaculum and adjacent to the tendon of abductor pollicis longus in the first dorsal compartment. From a posterior (dorsal) perspective, the sheath tracks distally toward the base of the proximal phalanx of the thumb, lying lateral to the tendons of extensor digitorum and extensor indicis and superficial to the carpal bones. Faint bony contours of the radius, carpus, metacarpals, and phalanges orient the course of the tendon as it crosses the dorsum of the wrist. Clean landmarks. Clinical relevance centers on stenosing tenosynovitis of the first dorsal compartment, where thickening of the extensor retinaculum and synovial sheath restricts glide of extensor pollicis brevis, often together with abductor pollicis longus, producing the pain pattern classically provoked by the Finkelstein maneuver. This posterior relationship also matters during ultrasound-guided injection and surgical release, because septation within the compartment can isolate the EPB sheath and leave symptoms if only the APL side is decompressed. Dorsal thumb tendons get confused easily in teaching; placing EPB relative to the retinaculum and neighboring extensor tendons helps prevent that. Use this artwork in hand anatomy and upper-limb musculoskeletal courses to teach extensor compartments, synovial sheath function, and the surface anatomy of the radial styloid region. It also fits operative atlases and patient-facing materials covering De Quervain release, tendon sheath injections, and rehabilitation after first-compartment tenosynovitis. Anatomical accuracy verified by SciePro's Medical Advisory Board.