Extensor Pollicis Brevis Muscle

Extensor pollicis brevis ( EPB) Muscle Anatomy

Extensor pollicis brevis (EPB) is one of the muscles of the deep layer of the posterior compartment of the forearm. Along with extensor pollicis longus, it is responsible for extension of the thumb. Along with abductor pollicis longus it passes through the 1st extensor compartment of the wrist. It is one of the extrinsic muscles of the hand.

Origin :

It originates from the posterior surface of distal third of radius and interosseous membrane.

Insertion :

It inserts on the posterior aspect of base of proximal phalanx of thumb.

Nerve supply :

The Posterior interosseous nerve supplies the muscle.

Blood supply :

The Posterior interosseous artery and anterior interosseous artery supplies the muscle.

Action :

It act as the thumb extensor at carpometacarpal and metacarpophalangeal joint.

Clinical Relevance :

The tendons of the EPB and the Abductor Pollicis Longus (APL) are enclosed in a common sheath at the dorsum of the wrist. Due to forceful or repetitive movements of the thumb and wrist, the friction increases between both tendons, resulting in the inflammation in their shared tendon. This condition, known as De Quervain’s Tenosynovitis.

Strengthening exercise :

Isometric Thumb Extension Exercise :

• Sit upright in a chair with your forearm and palm flat on the table and the tip of your thumb fully bent.
• Place a finger from your opposite hand on the back of your thumb between the knuckle and end joint of your thumb.
• Try to lift your thumb back from the table, using your opposite hand to resist the movement.
• Try to hold this position without moving, making sure that you keep the tip of your thumb bent.

Stretching exercise:

The extensor pollicis brevis is stretched with flexion of the thumb at the carpometacarpal and metacarpophalangeal joints and radial deviation of the hand at the wrist joint.

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