Muscle Name: abductor pollicis brevis
AKA:
Abbreviation: APB
Spinal Nerve Roots:
C8
T1
Brachial Plexus Trunks:
lower trunk
Brachial Plexus Cords:
medial cord
Named Nerves:
median nerve
Proximal Attachment: Transverse carpal ligament, the scaphoid and trapezium
Distal Attachment: Radial base of proximal phalanx of thumb and the thumb extensors
Action: Abduction of the thumb by acting across the carpometacarpal joint and the metacarpophalangeal joint. It also assists in opposition and extension of the thumb.
Needle Insertion: With the hand supinated, the needle is inserted into the patients lateral thenar eminence, at the middle of the metacarpal bone.
Activation for EMG: With the hand supinated, have the patient abduct the thumb.
Pitfalls:
- If the needle is inserted too laterally the opponens pollicis will be sampled.
- If the needle is inserted too medially the flexor pollicis brevis (median and ulnar innervation) will be sampled
- This is considered to be more painful than most intrinsic hand muscles.
Notes:
