Extensor Expansion of the Hand

Description

Eeep structures of the extensor expansion of the digits of the hand

(A) and (B): Diagrammatic representation of the extensor expansion of the four ulnar fingers. The dorsal view (B) shows the ligaments cut and laid out on both sides of the finger. The oblique retinacular ligament (ORL) is blue; the transverse retinacular ligament (TRL) is red and the connection to the C1 pulley (C1LRL) is green. (C): Ulnovolar view of a ring finger with instruments under the ORL, TRL and C1.

Other Names

• Extensor Expansion of the Hand
• Extensor Tendon Complex of the Hand
• Extensor Apparatus

Introduction

• Specialized connective tissue structure that supports extensor tendon insertion onto the phalanges
• Acts to balance the large number of muscles acting on the fingers

Structure

• Triangular shape, begins at the level of the metacarpophalangeal joint
• Formed from the extensor digitorum (fingers) tendons, extensor pollicis longus tendon (thumb)
• Extensor hood
  • Tendons flatten out as they approach the metacarpophalangeal joint
  • Fan out and wrap around the distal metacarpal, proximal phalanx
  • Sagittal band is well defined at this point
• Courses along the dorsal surface of the proximal phalanx
• Divides into three parts
  • Central slip: inserts onto the base of the middle phalanx
  • Lateral bands (x2): insert onto the base of the distal phalanx

Tendon Attachments

• Fingers
  • Extensor indicis: lies medially to the tendon of the extensor digitorum, inserts onto the extensor hood centrally
  • Extensor digiti minimi: lies medially to the tendon of the extensor digitorum, inserts onto the extensor hood centrally
  • Palmar interossei, Dorsal interossei: inserts onto the lateral bands of the extensor expansion
  • Lumbricals: inserts onto the radial aspect of the extensor expansion (distal to the interossei insertion)
• Thumb
  • Adductor pollicis
  • Abductor pollicis brevis
  • Extensor pollicis brevis

Oblique Retinacular Ligament

• Origin: proximal phalanx, flexor tendon sheath
• Insert: lateral bands of the extensor apparatus
• Links the movement of the PIPJ with the DIPJ

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Clinical Significance

• Boutonniere Deformity
• Central Slip Injury
• Mallet Finger

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See Also

• Hand and Wrist Anatomy (Main)
• Finger Pain (Main)
• Hand Pain (Main)

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