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M01.03.002 Quadrangular Space Anatomy
The quadrangular space is an anatomical region located in the posterior axilla, functioning as a passage for neurovascular structures between the axilla and the posterior compartment of the arm.
In this guide, we will discuss:
- Anatomical Boundaries
- Contents
- Clinical Relevance: Quadrangular Space Syndrome
1. Anatomical Boundaries
The quadrangular space is a rectangular-shaped area defined by four distinct borders:
| Boundary | Anatomical Structure |
|---|---|
| Superior | Inferior margin of the teres minor |
| Lateral | Surgical neck of the humerus |
| Medial | Long head of the triceps brachii |
| Inferior | Superior aspect of the teres major |
Key Point
This anatomical layout forms a passageway critical for vascular and neural structures traveling to and from the arm.
2. Contents of the Quadrangular Space
| Structure | Function/Role |
|---|---|
| Axillary Nerve | Innervates the deltoid and teres minor muscles; provides sensation to the skin over the deltoid region. |
| Posterior Circumflex Humeral Artery & Vein | Supplies and drains blood from the posterior upper arm. |
The quadrangular space serves as a critical conduit for these structures, ensuring communication between the axilla and the posterior upper arm.
3. Quadrangular Space Syndrome
Definition:
Quadrangular space syndrome occurs when the axillary nerve and posterior circumflex humeral artery are compressed as they pass through the quadrangular space.
Causes:
- Hypertrophy of the muscular borders of the quadrangular space
- Formation of fibrotic bands between the muscles
Clinical Features:
| Symptom | Description |
|---|---|
| Pain | Localized pain in the shoulder region, often exacerbated by abduction or external rotation. |
| Paresthesia | Tingling or numbness in the axillary nerve distribution (deltoid area). |
| Reduced Shoulder Movement | Difficulty in performing abduction and external rotation. |
Dissection Images
- Fig. 1: Posterior view of the shoulder region showing the quadrangular space.
- Fig. 2: Neurovascular structures of the quadrangular space, including the axillary nerve and posterior circumflex humeral artery.
Points to Remember
- Borders: Inferior margin of teres minor (superior), surgical neck of humerus (lateral), long head of triceps brachii (medial), and superior aspect of teres major (inferior).
- Contents: Axillary nerve and posterior circumflex humeral artery (and vein).
- Clinical Significance: Compression in quadrangular space syndrome leads to pain, paresthesia, and impaired shoulder movement.
- Anatomical Context: Lies posteriorly, facilitating passage between the axilla and posterior compartment of the arm.
Bibliography
- Textbook of Anatomy: Upper Limb and Thorax.
- Gray’s Anatomy for Students, 4th Edition.