Upper limb
Tendon sheath of first extensor compartment (APL and EPB)
Vagina tendinum musculorum abductoris longi et extensoris brevis pollicis
- Origin
- Osteofibrous tunnel located on the lateral aspect of the radial styloid beneath the extensor retinaculum
- Insertion
- Invests the tendons of abductor pollicis longus (APL) and extensor pollicis brevis (EPB) extending to the thumb base
- Function
- Facilitates low-friction gliding of the thumb abductor and extensor tendons across the radial styloid process
- Innervation
- Superficial branch of the radial nerve (sensory and nociceptive endings)
- Movement & chain
- Stressed during repetitive thumb abduction, extension, and combined wrist ulnar deviation
- Palpation
- Palpable over the radial styloid; tenderness, localized swelling, and thickening present in inflammatory states
- Clinical
- De Quervain tenosynovitis (stenosing tenovaginitis of the 1st dorsal compartment); diagnosed via a positive Finkelstein / Eichhoff test
- Segmental innervation
- C6–C7 spinal segments
- In clinical practice
- Common in postpartum mothers and repetitive keyboard users; managed with thumb spica splints, ergonomic modification, ultrasound-guided corticosteroid injection, and surgical release of the first dorsal compartment
- Region in the model
- Upper limb