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Abductor Pollicis Brevis

originHand 6a

  • tuberosity of the scaphoid and the ridge of trapezium;
  • another slip originates from the transverse carpal ligament;


  • Lateral surface of the base of the proximal phalanx of thumb;


  • abdcution and medial rotation of the metacarpal of the thumb;


nerve supply


  • although opposition is result of coordinate function of all long and short muscles that act on the thumb, APB is most important single muscle that takes part in this complex movement;
  • it rotates internally and abducts the thumb away from index metacarpal, internally rotates andabducts the proximal phalanx of thumb on its metacarpal, and assists EPL in extending IP joint of the thumb;
  • in the cases of carpal tunnel syndrome, it is APB which atrophies, and if this atrophy is severe the thumb cannot be pronated