Extensor Pollicis Brevis Tendon Sheath, Posterior View

Description

Running along the dorsoradial wrist, the extensor pollicis brevis tendon passes within its synovial tendon sheath of the first extensor compartment, superficial to the distal radius and radial styloid and coursing distally toward the base of the proximal phalanx of the thumb. Adjacent dorsally and slightly ulnar lies the extensor pollicis longus as it angles toward Lister’s tubercle, while the abductor pollicis longus shares the same compartment with extensor pollicis brevis and sits more radial and proximal. Carpal landmarks beneath the sheath include the scaphoid and trapezium laterally, with the metacarpal bases and thumb rays extending distally. Tight anatomy. That confined osteofibrous tunnel matters because it is the substrate for de Quervain tenosynovitis, where thickening of the extensor retinaculum and synovium restricts tendon excursion and produces pain over the radial styloid during thumb extension and abduction. A posterior (dorsal) perspective clarifies why a septated first dorsal compartment can defeat steroid injection or limited release, and why surgical decompression must respect the nearby superficial branch of the radial nerve and dorsal radial artery. It also frames the mechanics behind a positive Finkelstein or Eichhoff maneuver. Hand surgery teaching files can pair this view with surface anatomy for landmark-based injections into the first extensor compartment and with operative diagrams for first dorsal compartment release. It also fits cleanly into gross anatomy and musculoskeletal ultrasound curricula when explaining how tendon sheath pathology differs from intra-articular synovitis at the radiocarpal joint. Anatomical accuracy verified by SciePro's Medical Advisory Board.