Abductor pollicis brevis muscle

What is Abductor pollicis brevis muscle?

The abductor pollicis brevis muscle is a small, triangular muscle located in the hand. It is one of the intrinsic muscles of the hand, meaning that it originates and inserts within the hand itself.

As its name suggests, the primary function of the abductor pollicis brevis muscle is to abduct the thumb, meaning it moves the thumb away from the palm of the hand. It also helps in opposition & extension of the thumb.

This muscle is innervated by the median nerve, which is a nerve that originates from the brachial plexus and runs down the arm and into the hand. The abductor pollicis brevis muscle is an important muscle for fine motor control of the hand, and its proper function is crucial for performing many daily activities, such as grasping and manipulating objects.

There are four muscles in the thenar’s muscles group; abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, and opponens pollicis. The thenar eminence is the elevation they create on the palm’s radial (lateral) aspect.

Under the skin is the most lateral and superficial of the thenar muscles, the abductor pollicis brevis. It connects the thumb’s proximal phalanx to the scaphoid and trapezium carpal bones via the flexor retinaculum.

The abduction of the thumb at the carpometacarpal joint is the primary function of the abductor pollicis brevis.

Origin of Abductor pollicis brevis muscle

It originates from the front of the transverse carpal ligament and extends into the tubercles of the scaphoid and trapezium, with the abductor pollicis longus tendon occasionally contributing.

Insertion

A short tendon connects the muscle to the base of the thumb’s proximal phalanx on the radial side.

Relations

The fusiform abductor pollicis brevis muscle is directly above the opponens pollicis and flexor pollicis brevis muscles at the surface of the thenar eminence. The thenar branch of the median nerve travels through a gap created by these three muscles. The abductor pollicis brevis’s superficial aspect is traversed by the superficial palmar branch of the radial artery.

Innervation

The median nerve’s recurrent (thenar) branch innervates the abductor pollicis brevis (root values C8 and T1).

Blood supply

The abductor pollicis brevis is vascularized by the superficial palmar branch that derives from the radial artery.

Function of Abductor pollicis brevis muscle

The abduction of the thumb at the carpometacarpal and metacarpophalangeal joints is the primary function of the abductor pollicis brevis muscle. The abductor pollicis longus muscle and this action work together. In addition, the abductor pollicis brevis makes it easier to move the thumb toward the fingertips in the opposition to the carpometacarpal joint and to flex the metacarpophalangeal joint. All of the previously mentioned elements of this muscle are of incredible importance for the appropriate working of the hand, like getting a handle on round objects or completing errands that request accuracy (for example composing and sewing).

Clinical relevance

• Carpal tunnel syndrome
• Median and ulnar nerve lesions
• Syringomyelia
• Motor neuron disease
• Peripheral neuropathy

Assessment

By providing resistance to abduction upward and away from the palm’s plane, the function can be evaluated.

Abductor pollicis brevis muscle stretching

With adduction and flexion of the thumb at the carpometacarpal joint and radial deviation of the hand at the wrist joint, the abductor pollicis longus is stretched.

Abductor pollicis brevis muscle strengthening exercise

With your palm facing you, wrap a rubber band around your thumb and grab one end with your free hand.
Holding the band taut, pull it across your palm.
Against the band’s resistance, move your thumb away from your palm.
Go into the subsequent repetition by controlling your thumb back until it is resting against the side of your hand.
By pulling harder on the rubber band, you can make your abductor pollicis brevis work harder.
Perform 15 repetitions for each thumb.

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