Lateral triangular space

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The lateral triangular space, also called the triangular interval or lower triangular space  or triceps hiatus, is a space connecting the axilla to the posterior compartment of the arm. It should not be confused with the similarly named medial (upper) triangular space.

Gross anatomy

It is a downwards pointing triangle with a base superiorly and apex inferiorly.

Boundaries
  • medially: lateral border of the long head of triceps brachii muscle
  • superiorly: inferior border of the teres major muscle
  • lateral: medial border of the upper humerus
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