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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.
Anatomy of Abductor 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.
The abductor hallucis muscle is located in the medial border of the foot and contributes to form the prominence that is observed on the region. It is inserted behind on the tuberosity of the calcaneus, the flexor retinaculum, and the plantar aponeurosis.[1] Its muscle body, relatively thick behind, flattens as it goes forward. It ends in a common tendon with the medial head of the flexor hallucis brevis that inserts on the medial surface of the base of the first proximal phalanx and its related sesamoid bone. Its medial surface is superficial and covered with the muscle’s fascia and the skin.[rx]
Abductor Hallucis
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Origin: Calcaneal tuberosity
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Insertion: Base of the great toe and the proximal phalanx.
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Action: Abduct the great toe
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Blood Supply: Medial plantar artery
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Innervation: Medial plantar nerve
Origin and Insertion of Abductor Hallucis
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.
Nerve Supply
- Abductor hallucis is supplied by the medial plantar nerve. The nerves that supply it enter the muscle from its upper border.
- 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.
Blood Supply
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
Function
- 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.
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