Anatomy of #Extensor Pollicis Brevis

Courtesy: Prof Nabil Ebraaheim, University of Toledo, Ohio, USA

Origin

• Posterior surface of the radius

• Interosseous membrane of the forearm

Insertion

• Base of the proximal phalanx of the thumb

Nerve Supply

• Posterior interosseous nerve

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Function

• Extension of the thumb at the metacarpophalangeal joint

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Anatomical Relationships

• Forms the lateral border of the anatomical snuffbox

• Lies in the first dorsal extensor compartment of the wrist

• Shares this compartment with the abductor pollicis longus tendon

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Clinical Importance

De Quervain’s Tenosynovitis

• Involves inflammation of:

  • Extensor pollicis brevis

  • Abductor pollicis longus

• Common epidemiological features:

  • More frequently seen in women

  • Often associated with the postpartum period

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Anatomical Variation

• The extensor pollicis brevis tendon may lie in a separate subcompartment

• Failure to recognize this variation during surgery can lead to:

  • Incomplete decompression

  • Persistent symptoms after release of the first dorsal compartment

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Clinical Features

• Pain over the radial aspect of the wrist, often present even at rest

• Localized tenderness over the first dorsal extensor compartment

• Pain aggravated by thumb movements and wrist deviation

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Clinical Test

Finkelstein Test

• The patient makes a fist with the thumb tucked inside the fingers

• The wrist is deviated toward the ulnar side

• The test is considered positive if:

  • Sharp pain is elicited over the radial side of the wrist

  • Indicates inflammation of the tendons within the first dorsal compartment

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Key Points for Clinical Practice

• Always consider anatomical variations of the extensor pollicis brevis tendon

• Incomplete surgical release is a common cause of treatment failure

• Accurate clinical examination and anatomical understanding are essential for optimal outcomes