Abductor Pollicis Brevis Muscle

Abductor Pollicis Brevis Muscle Anatomy

The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle and therefore contributes to the bulk of the palm’s thenar eminence.

Origin

It originates from the flexor retinaculum of the hand, the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium.

The muscle fibers start from these points and join to produce a single muscle belly that extends lateral (distally and radially) in the direction of the thumb. The muscle terminates in a flat tendon close to the insertion, where it attaches to the radial aspect of the thumb’s proximal phalanx base. The tendon’s lateral slips connect to the extensor pollicis longus tendon’s expansion.

Insertion

It inserts as a thin, flat tendon into the lateral side of the base of the first phalanx of the thumb and the capsule of the metacarpophalangeal joint.

Nerve supply

It is innervated by the recurrent branch of the median nerve.

Blood Supply

It is supplied by the superficial palmar branch of the radial artery

Action

• Abduction of the thumb is defined as the movement of the thumb anteriorly, in a direction perpendicular to the palm.
• The abductor pollicis brevis does this by acting across both the carpo-metacarpal joint and the metacarpo-phalangeal joint.
• It also assists in the opposition and extension of the thumb.

Structure

Just beneath the skin is a narrow, flat muscle called the abductor pollicis brevis. Since it is a thenar muscle, it makes up the majority of the thenar eminence of the palm.

It begins at the tubercle of the scaphoid bone, the flexor retinaculum of the hand, and occasionally the tubercle of the trapezium.

It is inserted into the capsule of the metacarpophalangeal joint and the lateral side of the base of the thumb’s first phalanx by a thin, flat tendon that runs lateral and downward.

Relations

Immediately above the opponens pollicis and flexor pollicis brevis muscles, on the surface of the thenar eminence, lies the fusiform abductor pollicis brevis muscle. The thenar branch of the median nerve travels via a gap formed by these three muscles. The superficial aspect of the abductor pollicis brevis is crossed by the superficial palmar branch of the radial artery.

Examination

By offering resistance to abduction both up and away from the palm’s plane, the function can be evaluated.

Abductor Pollicis Brevis Muscle Exercise

Strengthening Exercise

• Hook a rubber band around your thumb with your palm facing you, and grab one end with your free hand.
• Pull the band across your palm and hold it so it’s taut.
• Open your thumb away from your palm against the resistance of the band.
• Control your thumb back until it’s resting against the side of your hand and then go into the next repetition.
• You can increase how hard your abductor pollicis brevis has to work by pulling harder on the rubber band.
• Complete 15 reps for each thumb.

Stretching exercise

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

Clinical Importance

De Quervain disease: Tenosynovitis of the sheath or tunnel that surrounds two tendons that control the movement of the thumb. These two muscles are the Extensor Pollisis Brevis, Abductor Pollisis Longus, and Brevis Muscle.

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