Flexor digiti minimi brevis of the footFlexor digiti mini brevis is a small muscle found in the sole of the foot. As the plantar muscles of the foot can be classified into three groups (medial to lateral) or four layers (from superficial to deep), this muscle can be described as;
- One of the lateral plantar muscles, together with the abductor digiti minimi and opponens digiti minimi.
- A part of the muscles of the third layer, along with the flexor hallucis brevis and adductor hallucis.
Flexor digiti mini brevis is one of the muscles responsible for flexing the toes. Other muscles in this category include flexor digitorum longus, flexor accessorius (quadratus plantae), flexor digitorum brevis, flexor hallucis brevis, dorsal and plantar interossei and lumbricals.
Now you may be wondering how is it that there is a flexor digiti minimi brevis muscle in the foot. This phenomenon originates from the homology between the certain muscles of the hand and foot, defined by their common pattern of attachments and functions.
This article will discuss the anatomy and function of flexor digiti minimi brevis muscle in the foot.
|Origin||Base of metatarsal bone 5, long plantar ligament|
|Insertion||Base of proximal phalanx of digit 5|
|Action||Metatarsophalangeal joint 5: Toe flexion|
|Innervation||Lateral plantar nerve (S2 – S3)|
|Blood supply||Arcuate, lateral tarsal and lateral plantar arteries|
Origin and insertion
Flexor digiti minimi brevis arises from two sites:
- Medial aspect of the plantar surface of base of 5th metatarsal bone
- Tendon sheath of fibularis longus muscle
The muscle courses over the plantar surface of 5th metatarsal before tapering into its tendon. The tendon, which blends with the tendon of abductor digiti minimi, inserts to the lateral surface of the base of proximal phalanx of 5th toe.
Flexor digiti minimi brevis lies inferior to the fifth metatarsal bone and is invested by the plantar aponeurosis. It is medial to abductor digiti minimi and lateral to third plantar interosseous muscle. Lateral branch of lateral plantar nerve is medial and superficial to flexor digiti minimi.
Like all the lateral foot muscles, flexor digiti minimi brevis is innervated by the lateral plantar nerve (S2-S3), which is a branch of the tibial nerve.
Check out the videos below to review the different ways of classifying the muscles of the foot.
There are three main vessels that supply flexor digiti minimi brevis.
- Anterior tibial artery, via its two branches; arcuate and lateral tarsal arteries
- Posterior tibial artery, via lateral plantar artery
Flexor digiti minimi brevis causes flexion across the 5th metatarsophalangeal joint. By doing this, the muscle provides structural support to maintain the lateral longitudinal arch of the foot, which is important for weight-bearing during periods of long-standing.