Muscle
Extensor pollicis longus
Extensor of the thumb's terminal joint
High-yield
The tendon passes through wrist compartment 3 and forms the ulnar border of the anatomical snuffbox. Its course around Lister's tubercle creates an important clinical landmark.
Overview
Its tendon changes direction around the dorsal radial tubercle, also called Lister's tubercle, before crossing toward the thumb. It reaches the distal phalanx and straightens the IP joint.
Reference facts
- Origin
- Posterior middle ulna with the adjacent interosseous membrane
- Insertion
- Dorsal base of the distal phalanx of the thumb
- Action
- Extends the thumb IP and MCP joints and helps extend and adduct the thumb
- Innervation
- Posterior interosseous nerve, commonly C7-C8
- Blood supply
- Interosseous arterial branches; dorsal carpal and radial branches also supply portions of the tendon
Clinical correlation
A distal radius fracture can be followed weeks later by tendon rupture. Loss of active thumb IP extension after such an injury warrants assessment; it does not occur after every fracture.
Frequently asked questions
What does the extensor pollicis longus do?
The extensor pollicis longus extends the thumb IP and MCP joints and helps extend and adduct the thumb.
What nerve innervates the extensor pollicis longus?
Posterior interosseous nerve, commonly C7-C8.
Where does the extensor pollicis longus attach?
Origin: Posterior middle ulna with the adjacent interosseous membrane. Insertion: Dorsal base of the distal phalanx of the thumb.
What is the blood supply of the extensor pollicis longus?
Interosseous arterial branches; dorsal carpal and radial branches also supply portions of the tendon.