Abductor digiti minimi abducts the little finger at the metacarpophalangeal joint.
The abductor digiti minimi (ADM) is a superficial intrinsic muscle located on the ulnar side of the hand. It is one of the three hypothenar muscles and is primarily responsible for abduction of the little finger away from the midline of the hand. This muscle contributes to grip strength and hand balance, especially during object manipulation.
The abductor digiti minimi is positioned along the medial border of the palm. It lies superficial and lateral to the flexor digiti minimi brevis and opponens digiti minimi and forms the most prominent part of the hypothenar eminence.
ADM is a fusiform muscle that originates from the pisiform and inserts onto the proximal phalanx of the fifth digit.
The abductor digiti minimi has several functions:
Innervated by the deep branch of the ulnar nerve (C8–T1).
The ADM lies medial to the flexor digiti minimi brevis and superficial to the opponens digiti minimi. It is the most superficial and medial of the hypothenar muscles. The ulnar nerve and artery pass deep to it within Guyon’s canal before entering the palm.
The muscle forms the medial bulge of the hypothenar eminence and is easily palpable on the ulnar side of the palm during resisted abduction of the little finger.
The ADM develops from the ulnar portion of the hand’s mesenchymal muscle mass. It reflects the specialization of the fifth digit in humans for grip and fine adjustment.
In many quadrupeds, the ADM is less developed due to limited use of the fifth digit. In humans, its evolution supports enhanced hypothenar function, enabling greater dexterity, grip adjustment, and lateral hand stabilization.