Upper limb
Abductor Pollicis Brevis
Musculus abductor pollicis brevis
- Origin
- Flexor retinaculum, tubercle of the scaphoid bone, and the trapezium
- Insertion
- Radial side of the base of the proximal phalanx of the thumb, with extension into the extensor hood
- Function
- Abduction of the thumb (away from the palm, anteriorly); essential part of the opposition movement
- Innervation
- Median nerve (recurrent branch)
- Movement & chain
- Most superficial thenar muscle; together with opponens pollicis initiates the opposition movement by which the thumb tip can reach the fingertips.
- Palpation
- Directly palpable as the most radial muscle belly of the thenar eminence, proximal to the base of the thumb, during active abduction of the thumb perpendicular to the palm.
- Clinical
- Thenar atrophy in carpal tunnel syndrome is usually first visible in this muscle, as it is the only thenar muscle innervated exclusively by the median nerve.
- Segmental innervation
- Median nerve, C8-T1.
- In clinical practice
- This muscle is the standard recording muscle in electroneurographic examination of the median nerve, used among other things in the diagnosis of carpal tunnel syndrome.
- Region in the model
- Upper limb