Hypothenar muscles

Musculi hypothenares

Also known as: hypothenar eminence, abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi, palmaris brevis

Three short muscles that form the hypothenar eminence on the ulnar side of the palm (abductor, flexor and opponens digiti minimi). All are supplied by the deep branch of the ulnar nerve.

Overview

The hypothenar muscles mirror the thenar group on the ulnar side.
- Abductor digiti minimi: from the pisiform (and the FCU tendon) to the medial base of the proximal phalanx of the little finger. Abducts the little finger.
- Flexor digiti minimi brevis: from the hook of the hamate and flexor retinaculum to the base of the proximal phalanx. Flexes the MCP joint.
- Opponens digiti minimi: from the hook of the hamate and flexor retinaculum to the medial border of the 5th metacarpal. Draws the 5th metacarpal forward and rotates it laterally, cupping the palm and helping opposition with the thumb.

The thin subcutaneous palmaris brevis wrinkles the skin over the eminence and protects the ulnar nerve and artery. It is supplied by the superficial branch of the ulnar nerve. The deep branch of the ulnar nerve and the deep branch of the ulnar artery pass between abductor and flexor digiti minimi.

Parts & subdivisions

Abductor digiti minimi

Pisiform → base of the proximal phalanx of digit 5. Abducts the little finger.

Flexor digiti minimi brevis

Hook of the hamate → base of the proximal phalanx of digit 5. Flexes the MCP joint.

Opponens digiti minimi

Hook of the hamate → medial border of the 5th metacarpal. Cups the palm.

Palmaris brevis

Subcutaneous. Wrinkles the hypothenar skin. Superficial branch of the ulnar nerve.

Anatomy

Origin

Pisiform, hook of the hamate and the flexor retinaculum.

Insertion

Base of the proximal phalanx of the little finger and the medial border of the 5th metacarpal.

Action

Abduction, flexion and opposition of the little finger.

Innervation

Deep branch of the ulnar nerve (palmaris brevis: superficial branch).

Nerve roots

C8–T1

Arterial supply

Deep palmar branch of the ulnar artery.

Clinical significance

Guyon's canal syndrome

Compression of the ulnar nerve between the pisiform and the hook of the hamate, e.g. in cyclists ("handlebar palsy"), causes hypothenar and interosseous weakness with variable sensory loss. Dorsal hand sensation is spared because the dorsal cutaneous branch arises proximal to the canal.

Hypothenar hammer syndrome

Repetitive use of the palm as a hammer damages the superficial ulnar artery against the hook of the hamate, causing thrombosis and ischaemia of the ulnar fingers.