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Extensor Pollicis Brevis Tendon

tendo musculi extensoris pollicis brevis

The EPB tendon shares the first extensor compartment with the APL and is involved in de Quervain tenosynovitis alongside APL. A separate subcompartment for EPB within the first compartment is present in up to 34 percent of people and is associated with higher rates of de Quervain syndrome, as the separate septum prevents adequate decompression during surgery unless both subcompartments are released.

Region: Hand & Wrist

Biomechanics

Function & Actions

MCP extension of the thumb; forms the anterior (volar) border of the anatomical snuffbox with APL

Clinical Relevance

Clinical Notes

De Quervain tenosynovitis involves the first extensor compartment containing APL and EPB, producing pain at the radial styloid reproduced by the Finkelstein test (thumb flexion into the palm with ulnar wrist deviation). Failure of corticosteroid injection to relieve symptoms may indicate a separate EPB subcompartment that requires targeted release. Surgical release must open both the APL and any EPB subcompartment to prevent recurrence.

Pathology

Common Injuries & Conditions

De Quervain Tenosynovitis

First compartment APL and EPB tenosynovitis producing radial wrist pain positive on Finkelstein test, managed with injection and surgical decompression for refractory cases.