deep forearm extensors

• Extensor Indicis:

  O: Posterior aspect of lower ulna

  Adjacent interosseus membrane

  R: Distally

  I: Blends with the extensor hood of the proximal phalanx of the index finger

  A: Assists extensor digitorum on index finger

  Aids wrist extension

  NS: Posterior interosseous branch of radial nerve (C5,6,7,8,T1)
• Abductor Pollicis Longus:

  O: Posterior aspect of ulna inferior to anconeus

  Interosseus membrane

  Middle 1/3 of radius

  R: Distally

  I: Lateral side of base of 1st MC

  Additional slip to trapezium

  A: Abduction of 1st CMC joint

  NS: Posterior interosseous branch of radial nerve (C5,6,7,8,T1)
• Extensor Pollicis Longus:

  O: Posterior ulna and adjacent interosseous membrane proximal to extensor Indicis

  R: Distally

  I: Small triangular expansion into dorsal surface distal phalanx of thumb

  A: Extension of all joints of the thumb

  Assists in extension and radial deviation of wrist

  NS: Posterior interosseous branch of radial nerve (C5,6,7,8,T1)
• Extensor Pollicis Brevis:

  O: Posterior aspect of middle 1/3 of radius

  Adjacent interosseous membrane

  R: Distally

  I: Dorsal aspect base of proximal phalanx of thumb

  A: Extension of 1st MCP and CMC joints

  NS: Posterior interosseous branch of radial nerve (C5,6,7,8,T1)