Abductor hallucis muscle
Abductor hallucis is a fusiform muscle located superficially and medially in the foot. Following the classification of plantar foot muscles from superficial to deep, abductor hallucis comprises the first (most superficial) layer of muscles along with the flexor digitorum brevis and abductor digiti minimi. On the other hand, if the foot muscles are studied by groups from medial to lateral, this muscle belongs to the medial plantar muscles of the foot together with the flexor hallucis brevis and adductor hallucis.
The function of this muscle is to abduct and flex the great toe. These actions contribute to the stability of the foot during walking by preserving the central position of the great toe and maintaining the medial longitudinal arch of the foot.
|Origin||Medial process of calcaneal tuberosity, flexor retinaculum, plantar aponeurosis|
|Insertion||Base of proximal phalanx of great toe|
|Action||Metatarsophalangeal joint 1: Toe abduction, toe flexion; Support of longitudinal arch of foot|
|Innervation||Medial plantar nerve (S1-S3)|
|Blood supply||Medial plantar and first plantar metatarsal arteries|
This article will discuss the anatomy and function of the abductor hallucis muscle.
Origin and insertion
Abductor hallucis is a small and slender, but powerful muscle that has three origin points and one insertion. It originates from the medial process of the calcaneal tuberosity, plantar aponeurosis and the superficial layer of flexor retinaculum.
From here, the muscle fibers run anteriorly and medially, forming a tendon at the level of the body of first metatarsal bone. The tendon courses along the medial border of first metatarsophalangeal joint to finally insert to the base of proximal phalanx of great toe.
Abductor hallucis muscle is the most medial muscle of the foot, running medally to flexor hallucis brevis muscle. The plantar surface of the muscle is covered by the plantar aponeurosis, while its dorsal surface is related to the tendon of flexor digitorum longus, medial plantar artery and nerve. The originating fibers of abductor hallucis and calcaneus build a space called porta pedis. This space serves as a tunnel through which lateral and medial plantar nerves and vessels pass.
Abductor hallucis muscle is innervated by the medial plantar nerve (root value S1 - S3), the larger of the two terminal branches of the tibial nerve.
The blood supply for abductor hallucis muscle comes from two arteries;
- Medial plantar artery, a branch of posterior tibial artery
- First plantar metatarsal artery, a branch of lateral plantar artery
As the name of this muscle indicates, its main action is the abduction of the big toe at the first metatarsophalangeal joint. This action preserves the central position of the big toe during walking, and if it’s hindered it may result in deformities of the toes such is hallux valgus.
Together with flexor hallucis longus and flexor hallucis brevis muscles, abductor hallucis aids the flexion of the big toe. The muscle also helps in maintaining the medial longitudinal arch of the foot while walking.
To expand your knowledge check out our learning materials about the muscles of the foot.