Flexor Digiti Minimi Brevis

The Flexor Digiti Minimi Brevis (Flexor brevis minimi digiti, Flexor digiti quinti brevis) lies under the metatarsal bone on the little toe, and resembles one of the Interossei.

It arises from the base of the fifth metatarsal bone, and from the sheath of the Fibularis longus; its tendon is inserted into the lateral side of the base of the first phalanx of the fifth toe. Occasionally a few of the deeper fibers are inserted into the lateral part of the distal half of the fifth metatarsal bone; these are described by some as a distinct muscle, the opponens digiti quinti.

Flexor 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.

Origin: Base of the fifth metatarsal
Insertion: Proximal phalanx of the fifth metatarsal
Action: The primary action is to flex the fifth digit
Blood Supply: Lateral Plantar artery
Innervation: Lateral plantar nerve

Origin and Insertion of Flexor Digiti Minimi Brevis

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.

Nerve Supply of Flexor Digiti Minimi Brevis

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.

Blood supply

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 a lateral plantar artery

Functions

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.

References

[bg_collapse view=”button-orange” color=”#4a4949″ expand_text=”Show More” collapse_text=”Show Less” ]

[/bg_collapse]