Extensor hallucis brevis !
The extensor hallucis brevis is a small muscle on top of the foot that helps lift the big toe at its base joint.
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What it is
The part of the short extensor muscle on top of the foot that goes to the big toe.
What it does
Helps lift the big toe.
Key facts
- Origin
- Superolateral calcaneus (medial part of the extensor digitorum brevis mass)
- Insertion
- Dorsal base of proximal phalanx of big toe
- Action
- Extends big toe at MTP joint
- Nerve
- Deep fibular nerve (L5–S1) (some texts: S1–S2)
- Blood supply
- Dorsalis pedis artery
Relations
- Medial
- Extensor hallucis longus tendon
- Lateral
- The rest of extensor digitorum brevis
- Deep
- Dorsalis pedis artery and deep fibular nerve, crossed by its tendon, and the first dorsal interosseous
- Superficial
- Dorsal venous arch, branches of the superficial fibular nerve and the skin
How to find it
With the big toe lifted at its base, a thin tendon lies lateral to the extensor hallucis longus tendon over the first metatarsal; its small belly lies with the rest of the short extensor on the lateral dorsum.
Examination
- Big-toe extension testing separates the two extensors: only the long extensor lifts the tip (interphalangeal joint), so after a complete long extensor cut the tip cannot lift while extension at the base remains
On imaging
Usually not assessed apart from the extensor digitorum brevis, whose medial slip it forms on ultrasound or MRI. Its tendon, heading for the big toe, crosses over the dorsalis pedis artery and is a handy landmark when finding the artery with Doppler ultrasound. Atrophy together with the other short dorsal extensors on MRI suggests a deep fibular nerve lesion.
Clinical notes
- Extension of the MTP joint kept by this muscle can hide a complete extensor hallucis longus laceration unless the interphalangeal joint is tested
- The dorsalis pedis artery, deep to its tendon, is at risk in dorsal incisions over the first intermetatarsal space
- Its tendon can be rerouted as a tenodesis to pull the big toe back into line in hallux varus, a complication of bunion surgery
Test yourself
Think of the answer, then tap the question to see it.
Where does the extensor hallucis brevis insert, and which joint does it extend?
On the dorsal base of the big toe's proximal phalanx; it extends only the MTP joint.
Which artery does the extensor hallucis brevis tendon cross near the first intermetatarsal space?
The dorsalis pedis artery, which lies deep to it and is at risk in dorsal incisions there.
What nerve supplies the extensor hallucis brevis?
The deep fibular nerve, like the rest of the dorsal foot muscle mass.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- extensor brevis hallucis TA2 2670
- Official Spanish (DeCS)
- Músculo extensor corto del dedo gordo
- English (TA2)
- Extensor hallucis brevis
- Also called
- extensor hallucis brevis muscle
Related
- Extensor hallucis longus
- Extensor digitorum brevis
- Deep fibular nerve
- Top-of-foot arteries
- Calcaneus
- Cuboid
- Intermediate cuneiform
- Lateral cuneiform
Sources: Terminologia Anatomica (TA2); Anatomy, Bony Pelvis and Lower Limb, Foot Muscles.
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Representative model, for educational purposes only.
