Anatomy of Adductor Pollicis

Courtesy: Prof Nabile Ebraheim, University of Toledo, Ohio, USA

Adductor pollicis muscle

It is a small muscle of the hand and that is a very important muscle.

Anatomy of the muscle

Origin
2 heads :
1. Transverse head- arises from the radial surface of the body of 3rd metacarpal
2. Oblique head- arises from the second and third metacarpals. Also arises from capitate bone and adjacent carpals.

Insertion:

• 2 heads converge into a tendon and inserts along with the fibers of flexor pollicis brevis into the medial side(ulnar aspect at the base of proximal phalanx)of the thumb.
• There is a sesamoid bone passing in the tendon.
• The tendon inserts into the ulnar sesamoid bone of the thumb.
• It also inserts into the dorsal apparatus.

Function

• The predominant action of the adductor pollicis is adduction of the thumb metacarpal.
• It draws the first metacarpal laterally to oppose the thumb towards the center of the palm and rotate it medially.
• The adductor pollicis also works on the interphalangeal joint(ip)causing extension of that joint.
• It also works on the metacarpophalangeal joint (mcp) causing flexion of that joint.
• Action of the adductor pollicis muscle is complicated:
  1. First metacarpal adduction
  2. MCP flexion
  3. IP extension

INNERVATION

• Deep branch of ulnar nerve(C8,T1)