Os triangulare

Dr Henry Knipe et al.

The os triangulare (or os intermedium antebrachii or os triquetrum secundarium) is an accessory ossicle located between the ulna styloid, lunate and triquetrum 1-2.

They may be unilatreal or bilateral and the main differential diagnosis is non-union of a ulna styloid process fracture 1, 3

Differential diagnosis

  • lunula: lies at the tip of the ulna styloid
  • persistent ulna styloid ossicle
  • ulna styloid fracture
Upper limb anatomy
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Article Information

rID: 25056
Section: Anatomy
Synonyms or Alternate Spellings:
  • Os triquetrum secundarium
  • Os triangulare
  • Os intermedium antebrachii

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Cases and Figures

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    Os triangulare
    Figure 1: os triangulare (annotated image)
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    Case 1
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    Case 2
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    Case 3
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