Learning Objective:
At the end of this section, students should be able to describe the borders and contents of the triangular interval and explain its clinical significance in relation to radial nerve compression.
The triangular interval is an anatomical space located immediately below the axilla. It serves as a conduit for structures passing between the anterior and posterior compartments of the upper arm and between the posterior compartment and the axilla.
Borders of the Triangular Interval
The triangular interval is oriented with a superior base and an inferior apex. Three distinct borders define it:
| Border | Structure |
|---|---|
| Superior | Inferior border of the teres major |
| Lateral | The shaft of the humerus and the lateral head of triceps brachii |
| Medial | Lateral border of the long head of triceps brachii |
Key Point: The triangular interval provides a pathway for the radial nerve and profunda brachii artery.
Contents of the Triangular Interval
The triangular interval allows communication between the axilla and the posterior compartment of the arm. The structures passing through it are:
| Structure | Function |
|---|---|
| Radial nerve | Innervates the posterior compartment of the arm |
| Profunda brachii artery | Supplies blood to the posterior compartment of the arm |
| Accompanying venae comitantes | Assist in venous return |
Clinical Relevance
Points to Remember
- Orientation: The triangular interval has a base superiorly and an apex inferiorly.
- Key Contents: Radial nerve and profunda brachii artery.
- Clinical Concern: Compression of the radial nerve can lead to pain, paraesthesia, and motor deficits.
