Flexor hallucis brevis muscle

Structure

Flexor hallucis brevis muscle arises, by a pointed tendinous process, from the medial part of the under surface of the cuboid bone, from the contiguous portion of the third cuneiform, and from the prolongation of the tendon of the tibialis posterior muscle which is attached to that bone. It divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first phalanx of the great toe, a sesamoid bone being present in each tendon at its insertion. The medial portion is blended with the abductor hallucis muscle previous to its insertion; the lateral portion (sometimes described as the first plantar interosseus) with the adductor hallucis muscle. The tendon of the flexor hallucis longus muscle lies in a groove between the two. Its tendon usually contains two sesamoid bones at the point under the first metatarsophalangeal joint.

Innervation

The medial and lateral head of the flexor hallucis brevis is innervated by the medial plantar nerve. Both heads are represented by spinal segments S1, S2.

Variation

Origin subject to considerable variation; it often receives fibers from the calcaneus or long plantar ligament. Attachment to the cuboid bone sometimes wanting. Slip to first phalanx of the second toe.