The APL is one of the two tendons in the first extensor compartment (with EPB) whose tenosynovitis produces de Quervain disease. It passes through the first compartment at the radial styloid where the tendons change direction, creating friction against the tight retinaculum during repetitive thumb and wrist movements. Multiple tendon slips of the APL are present in 90 percent of people.
| Origin | Posterior radius, ulna, and interosseous membrane (middle thirds) |
|---|---|
| Insertion | Radial side of the base of the first metacarpal |
| Nerve Supply | Posterior interosseous nerve (C7, C8) |
| Blood Supply | Posterior interosseous artery |
| Actions | Abduction of the thumb at the CMC joint; Extension of the thumb CMC joint; Radial deviation of the wrist |
|---|
APL abducts the thumb by pulling the first metacarpal base radially and volarly, positioning the thumb for pinch and grip. Its radial deviation component of wrist motion is important in dart-throwing movements.
De Quervain tenosynovitis involving the APL and EPB first extensor compartment tendons produces radial styloid tenderness and positive Finkelstein test (pain with ulnar deviation and thumb in palm). Multiple APL slips in a subdivided first compartment may require individual release of each compartment subdivision for adequate decompression.
The APL and EPB tendons form the volar border of the anatomical snuffbox, palpable between the radial styloid and the first metacarpal base during thumb abduction and extension.
First extensor compartment stenosing tenosynovitis of APL and EPB producing radial wrist pain with positive Finkelstein test, managed with injection and surgical compartment release.
