QS
Quadrangular Space
Quadrangular space transmits the axillary nerve and posterior circumflex humeral artery below teres minor.
RegionUpper Limb
System-
The quadrangular space is an anatomical interval located in the posterior shoulder region. It serves as a passageway for important neurovascular structures traveling from the axilla to the posterior arm, most notably the axillary nerve and the posterior circumflex humeral artery.
Boundaries
Border | Structure |
---|---|
Superior | Teres minor muscle |
Inferior | Teres major muscle |
Medial | Long head of triceps brachii |
Lateral | Surgical neck of the humerus |
Contents
- Axillary nerve (branch of the posterior cord of the brachial plexus)
- Posterior circumflex humeral artery (branch of the axillary artery)
Relations
- Located posterior to the glenohumeral joint and deep to the deltoid muscle
- Lateral to the triangular space and superior to the triangular interval
Function / Significance
- Serves as a conduit for axillary nerve and vascular structures to reach the deltoid and surrounding posterior shoulder
- Important surgical and clinical landmark in posterior shoulder approaches
Clinical Significance
- Quadrangular Space Syndrome: Compression of the axillary nerve or posterior circumflex humeral artery within the space, causing:
- Paresthesia over the deltoid region
- Deltoid and teres minor weakness
- Posterior shoulder pain aggravated by abduction and external rotation
- Shoulder Dislocation or Humeral Fracture: May injure axillary nerve as it passes through this space
Comparative Anatomy
The quadrangular space is a human-specific anatomic configuration that allows for enhanced mobility and neurovascular routing in the upper limb, supporting complex shoulder movement and upper extremity function.
Published on May 12, 2025
Last updated on May 12, 2025
Last updated on May 12, 2025