Triangular Space

The triangular space is a small anatomical interval in the posterior shoulder region. Unlike the adjacent quadrangular space, it transmits only a vascular structure — the scapular circumflex artery. It serves as a key surgical and anatomical landmark in posterior shoulder dissections.

Boundaries

Contents

• Scapular circumflex artery (branch of the subscapular artery, from the axillary artery)

Relations

• Medial to the quadrangular space
• Superior to the triangular interval
• Posterior to the scapulothoracic region, lying deep to the deltoid

Function / Significance

• Allows the scapular circumflex artery to pass from the axilla into the scapular region
• Forms part of the collateral circulation around the scapula

Clinical Significance

• Scapular Collateral Circulation: In cases of axillary artery occlusion, the scapular circumflex artery provides an alternative route for blood to reach the distal limb
• Surgical Landmark: Important in posterior surgical approaches and flap dissections (e.g., latissimus dorsi flap)
• Not commonly involved in compressive syndromes like the quadrangular or triangular interval

Comparative Anatomy

The triangular space and its contained vessel are part of the human-specific vascular design that supports highly mobile scapulohumeral function. The scapular anastomosis plays a role in maintaining perfusion despite positional changes or vascular compromise.