Quadrangular space

The quadrangular space is an anatomical region of the shoulder that is clinically significant due to the structures that pass through it. It is one of the three spaces in the posterior shoulder region, the others being the triangular space and the triangular interval.

Anatomy

The quadrangular space is bounded by the following structures:

• Superiorly: the teres minor muscle.
• Inferiorly: the teres major muscle.
• Medially: the long head of the triceps brachii muscle.
• Laterally: the surgical neck of the humerus.

Contents

The quadrangular space contains two important structures:

• The axillary nerve, which innervates the deltoid and teres minor muscles.
• The posterior circumflex humeral artery, which supplies blood to the deltoid muscle and shoulder joint.

Clinical Significance

The quadrangular space is clinically significant because it can be the site of a condition known as "quadrangular space syndrome." This syndrome occurs when the axillary nerve and/or the posterior circumflex humeral artery are compressed within the space, leading to symptoms such as shoulder pain and weakness in the deltoid muscle.

Quadrangular Space Syndrome

Quadrangular space syndrome is characterized by:

• Pain in the shoulder, especially during overhead activities.
• Weakness or atrophy of the deltoid muscle.
• Possible paresthesia (tingling or numbness) in the shoulder region.

Diagnosis is typically made through clinical examination and imaging studies such as MRI. Treatment may involve physical therapy, anti-inflammatory medications, or surgical decompression in severe cases.

Also see

• Triangular space
• Triangular interval
• Axillary nerve
• Posterior circumflex humeral artery
• Shoulder anatomy