Extensor pollicis brevis muscle

Origin and insertion

The muscle is located on the posterior surface of the forearm and has the following attachment points:

• Origin: posterior surface of the radius and interosseous membrane (membrana interossea). The muscle belly is located lateral and distal to the abductor pollicis longus muscle (m. abductor pollicis longus).
• Tendon course: runs toward the hand and passes through the first osteofibrous compartment beneath the extensor retinaculum (retinaculum musculorum extensorum) together with the tendon of m. abductor pollicis longus. Along their path, these two tendons run superficially, crossing the tendons of the extensor carpi radialis longus and brevis. At the same time, they lie proximal to the tendon of the extensor pollicis longus (m. extensor pollicis longus).
• Insertion: dorsal surface of the base of the proximal phalanx of the thumb.

What is its function?

Contraction of the extensor pollicis brevis produces the following movements:

• Extends the proximal phalanx of the thumb.
• Abducts the thumb.
• Participates in radial (lateral) abduction of the entire hand.

Blood supply and innervation

• Innervation: radial nerve (n. radialis), specifically its branch — the posterior interosseous nerve (n. interosseus posterior). Motor fibers originate from spinal segments C7–C8.
• Blood supply: posterior interosseous artery (a. interossea posterior) and radial artery (a. radialis).

Topography and clinical significance

• «Anatomical snuffbox»: the tendon of m. extensor pollicis brevis (along with m. abductor pollicis longus) forms the lateral, or radial, boundary of this triangular depression on the wrist. The medial boundary is formed by the tendon of the extensor pollicis longus. The floor of the snuffbox is formed by the scaphoid (os scaphoideum) and trapezium bones. In the subcutaneous tissue of this region run the cephalic vein (v. cephalica) and the superficial branch of the radial nerve, while beneath the deep fascia lies the radial artery, the pulse of which can be palpated here.
• De Quervain syndrome: tenosynovitis of the first compartment, through which the tendons of m. extensor pollicis brevis and m. abductor pollicis longus pass. The condition manifests as pain in the region of the radial styloid process. Pain is tested using Finkelstein's test.

Do not confuse with: extensor hallucis brevis

In anatomical nomenclature, there is a muscle with a similar name in the lower limb — extensor hallucis brevis (m. extensor hallucis brevis). It originates from the dorsal surface of the anterior part of the calcaneus and inserts into the base of the proximal phalanx (or sesamoid bone) of the big toe. Its function is extension of the big toe, and it is innervated by the deep fibular nerve (n. peroneus profundus, segments L4–S1).

Class and exam questions

What else to study on this topic

• Abductor pollicis longus muscle (m. abductor pollicis longus)
• Extensor pollicis longus muscle (m. extensor pollicis longus)
• Anatomical snuffbox and its contents
• De Quervain syndrome

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.