Hand Adductor Pollicis Muscle – Anatomy, Nerve Supply

Hand Adductor Pollicis Muscle indicated an extensive origin of both the transverse and oblique heads. The origins included the second, third, and fourth metacarpal bones and the capitate, trapezoid, and trapezium bones. Soft tissue origins included intermetacarpal ligaments and the anterior fascia of palmar interosseous muscles. An interfascicular dissection of the deep branch of the ulnar nerve within the substance of the adductor pollicis muscle revealed three distinct patterns of terminal branching to the transverse and oblique heads, and to the first dorsal interosseous muscle.

Adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm. It overlies the metacarpal bones and the interosseous muscles.

Structure of Hand Adductor Pollicis Muscle

Oblique head

The oblique head (Latin: adductor obliquus pollicis) arises by several slips from the capitate bone, the bases of the second and third metacarpals, the intercarpal ligaments, and the sheath of the tendon of the flexor carpi radialis. ^[rx]

From this origin the greater number of fibers pass obliquely downward and converge to a tendon, which, uniting with the tendons of the medial portion of the flexor pollicis brevis and the transverse head of the adductor pollicis, is inserted into the ulnar side of the base of the proximal phalanx of the thumb, a sesamoid bone being present in the tendon. ^[rx]

A considerable fasciculus, however, passes more obliquely beneath the tendon of the flexor pollicis longus to join the lateral portion of the flexor pollicis brevis and the abductor pollicis Brevis. ^[rx]

Transverse head

The transverse head (Latin: adductor transversus pollicis) is deeply seated. ^[rx]

It is triangular, arising by a broad base from the lower two-thirds of the palmar surface of the third metacarpal bone; the fibers converge, to be inserted with the medial part of the flexor pollicis brevis and the oblique head into the ulnar side of the base of the proximal phalanx of the thumb. ^[rx]

Origin and Insertion of Hand Adductor Pollicis Muscle

Adductor pollicis arises by two heads which originate from different locations. The transverse head originates from the palmar base of the third metacarpal bone, while the oblique head originates from the capitate bone and palmar bases of second and third metacarpals. From their origin points, the two heads converge into one muscle belly as the fibers run laterally towards the thumb.

The muscle ends in a tendon that contains a sesamoid bone and inserts onto the base of the first proximal phalanx as well as its extensor hood.

Nerve Supply of Hand Adductor Pollicis Muscle

The adductor pollicis is innervated by the deep branch of the ulnar nerve (C8–T1).^[rx]

• Between the oblique and transverse heads is a thin fibrous arcade which the nerve passes as it traverses the palm laterally. The nerve is accompanied by the deep palmar arch. ^[rx]
• Adductor pollicis muscle receives its innervation from the deep branch of ulnar nerve (root value C8, T1).

Function of Hand Adductor Pollicis Muscle

While adduction of the thumb (bringing it back into the plane of the palm of the hand from its previously abducted position) is mainly produced by the adductor pollicis, it can also bring the thumb to the side of the palm and index finger and the flexor pollicis brevis and the opponens pollicis help in thumb adduction.^[rx]

Adductor pollicis is the most powerful of the intrinsic muscles of the hand. Its main function is the adduction of the thumb which is the movement of the thumb towards the index finger from an abducted position. This action is essential for functions that require pinching and gripping. Additionally, the adductor pollicis aids the later stages of opposition of the thumb.

This movement is a combination of actions, namely adduction, medial rotation, flexion and adduction of the thumb so that it can touch each fingertip of the same hand. Thus, the strength of adductor pollicis can be tested by pushing the thumb against the index finger while the examiner attempts to pull them apart.

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