Opponens Digiti Minimi

What is Opponens Digiti Minimi

The opponens digiti minimi (ODM) is a small muscle in the hand, on the ulnar side of the palm. Together with the abductor digiti minimi and the flexor digiti minimi brevis muscles, it forms the hypothenar eminence, the fleshy mound at the base of the 5th digit, just distal to the wrist.

The muscle helps with the movements of the 5th digit or little finger.

Anatomy

Location and Attachments

Origin	Hook of hamate and the adjacent flexor retinaculum
Insertion	Ulnar aspect of the 5th proximal phalanx

Origin

The small triangular intrinsic hand muscle originates from the hook of the hamate bone, on the distal carpal row. Some part of the muscle fibers also arise from the adjacent flexor retinaculum.

Insertion

After originating, the muscle belly courses distally and obliquely towards the ulnar side of the hand. It then inserts along the ulnar border of the 5th proximal phalanx. Its palmar surface on the ulnar side also serves as a minor point of insertion.

Relations With Surrounding Muscles and Structures

The opponens digiti minimi lies deep to the abductor digiti minimi and flexor digiti minimi brevis. The fibers of this small muscle often blends or even fuses with the other two hypothenar muscles.

The muscle is perforated and divided into two bands (lamellae) by the deep branch of the ulnar nerve and the  perforators of the ulnar artery.

Function

Action

Opposition and rotation of the little finger

The muscle acts on the 5th carpometacarpal joint to help flex the little finger, and rotate it laterally. This action deepens the hollow of the palm, and, when combined with lateral rotation and flexion of the interphalangeal joints, it brings the little finger in opposition with the thumb. It is the movement that allows you to bend your little finger to touch your thumb. Opposition of the little finger is important for a strong grip.

Innervation

Nerve

Deep branch of the ulnar nerve (C8 and T1)

Like the other hypothenar muscles, the opponens digiti minimi also receives nerve supply from the deep branch of the ulnar nerve, branching from the brachial plexus with nerve roots C8 and T1.

Blood Supply

Artery

Deep palmar branch of ulnar artery

In addition to the the deep palmar branch of ulnar artery, the muscle also receives blood supply from the deep palmar arch formed by the radial artery.