Extensor Pollicis Longus Tendon Sheath, Posterior View

Description

Running along the dorsal wrist, the extensor pollicis longus tendon sits within its synovial sheath as it approaches the distal radius and then redirects obliquely around Lister’s tubercle (dorsal tubercle of the radius). From this posterior perspective, the tendon’s course crosses from a more ulnar position in the distal forearm toward the radial side of the hand, then continues distally toward the thumb. The distal radius and ulna frame the radiocarpal region proximally, with the carpal row (including scaphoid and lunate on the radial side and triquetrum on the ulnar side) and the bases of the metacarpals forming the bony platform beneath the sheath. Lister’s tubercle is the landmark. That change in direction at Lister’s tubercle matters because it creates a mechanical pulley where friction, swelling, or attrition can concentrate, and it explains why extensor pollicis longus rupture is a known delayed complication after nondisplaced distal radius fractures and after dorsal wrist fixation. The third dorsal compartment anatomy also guides safe portals and screw trajectories in dorsal approaches to the distal radius, where prominence can abrade the tendon within its sheath. Understanding the tendon’s dorsal crossing pattern helps distinguish extensor pollicis longus pathology from first dorsal compartment disease (de Quervain tenosynovitis), which lies more radial and involves APL and EPB. Educators can place this view into hand and upper limb gross anatomy labs to teach the extensor retinaculum compartments and to anchor Lister’s tubercle as a surface landmark for injection, arthroscopy orientation, and physical exam of thumb extension. Publishers and clinicians will find it well suited for operative technique manuals, radiology correlations with dorsal wrist ultrasound, and patient education on post fracture tendon complications. Anatomical accuracy verified by SciePro's Medical Advisory Board.