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- Anatomy:
    - extensor tunnel I: 
    - origin:
         - small facet of ulnar side of the radius near its middle;
         - on lateral side of dorsal surface on body of the ulna just below the insertion of anconeus & interosseous membrane;
    - tunnel: travels thru the first extensor compartment;
    - insertion:
         - most often this tendon inserts onto the APB muscle or it inserts into the radial side of the base of the 1st metacarpal;
    - action:
         - functions as a wrist flexor and radial deviator;
         - abducts and assists in flexion of the thumb carpmetacarpal;
    - synergists: APB, EPL;
    - nerve: PIN branch of deep radial nerve, C6, C7;

- Other Considerations:
    - annular ligament that restrains abductor pollicis longus & epb over radius is directly over the radial tubercle;
    - this area may be involved in DeQuervain's tenosynovitis;
    - note that almost every APL will have accessory tendons

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Anatomic Study of the Abductor Pollicis Longus: A Source for Grafting Material of the Hand