Adductor Pollicis

Fan-shaped muscle, deep in palm, contacts metacarpals and interossei. Two heads.

Origin, Insertion and Nerve Supply

Feature	Detail
Oblique head	Capitate + bases of 2nd & 3rd metacarpals
Transverse head	Anterior shaft of 3rd metacarpal (distal two-thirds)
Insertion	Medial side, base of proximal phalanx of thumb (sesamoid often present)
Nerve supply	Deep branch of ulnar nerve (C8, T1)

Deep palmar arch + deep branch of ulnar nerve pass between oblique and transverse heads to reach the palm

Tests adductor pollicis (ulnar nerve, deep branch)
Patient grips flat object between thumb and index finger
Weak adductor pollicis → compensates by flexing IP joint of thumb (flexor pollicis longus, median nerve)
IP flexion of thumb = positive Froment’s sign → ulnar nerve palsy

Adductor pollicis is a fan-shaped muscle lying deep in the palm, in contact with the metacarpals and interossei. It has two heads of origin.

Feature	Detail
Oblique head	Capitate bone and bases of the 2nd and 3rd metacarpal bones
Transverse head	Anterior surface of the shaft of the 3rd metacarpal bone (distal two-thirds)
Insertion	Medial side of the base of the proximal phalanx of the thumb (a sesamoid bone is often present at this insertion)
Nerve supply	Deep branch of the ulnar nerve (C8, T1)

Adduction of the thumb — brings the thumb back towards the palm/index finger, providing power for the pincer (key) grip.

The deep palmar arch and the deep branch of the ulnar nerve pass forward between the two heads (oblique and transverse) of adductor pollicis to reach their destinations in the palm.

Tests the integrity of adductor pollicis (ulnar nerve, deep branch).
The patient grips a flat object (e.g., a sheet of paper) firmly between the thumb and index finger of each hand while the examiner tries to pull it away.
If adductor pollicis is weak (ulnar nerve palsy), the patient compensates by flexing the interphalangeal joint of the thumb using flexor pollicis longus (median nerve) to maintain grip — this substitution, producing thumb IP flexion, is a positive Froment’s sign, indicating ulnar nerve palsy.

Diagram content will be added later.