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Anatomical spaces of the pectoral region

An anatomical space can be loosely classified as any space that is not completely occupied by tissue. There are several anatomical spaces in the pectoral girdle that act as passage ways for neurovascular structures to traverse the upper limb.

Most important are:

  • The suprascapular foramen
  • The quadrangular space
  • The triangular space
  • The triangular interval
Key facts
Suprascapular foramen Superior border: superior transverse scapular ligament
Inferior border: suprascapular notch
Content: suprascapular nerve (below ligament), suprascapular artery (above ligament)
MnemonicAirforce above, Navy below
Quadrangular space Superior border: subscapularis muscle, the capsule of the shoulder joint, teres minor muscle
Inferior border: teres major muscle
Lateral border: surgical neck of the humerus
Medial border: long head of the triceps brachii muscle
Content: axillary nerve, posterior circumflex artery
Triangular space Inferior border: superior border of the teres major muscle
Superior border: inferior border of the teres minor muscle
Lateral border: medial border of the long head of the triceps brachii muscle
Content: circumflex scapular artery
Triangular interval Lateral border: shaft of the humerus
Medial border: lateral border of the long head of the triceps brachii muscle
Content: profunda brachii artery, radial nerve
Clinical relations Trauma, compressions, Quadrilateral Space Syndrome (QSS)

This article will discuss the anatomy and content of the anatomical spaces of the pectoral region.

  1. Suprascapular foramen
  2. Quadrangular space 
  3. (Upper) triangular space
  4. Triangular interval (lower triangular space)
  5. Clinical aspects
  6. Sources
+ Show all

Suprascapular foramen

The suprascapular foramen is situated at the superior lateral border of the scapula. It is bordered superiorly by the superior transverse scapular ligament and inferiorly by the suprascapular notch.

The foramen is the passage way for the suprascapular nerve (travelling under the ligament), originating from the upper trunk of the brachial plexus. The suprascapular artery travels adjacent to the nerve, above the ligament.

Use the following mnemonic to easily remember how the suprascapular artery and nerve are related to each other.

Airforce above, Navy below

  • Artery (suprascapular) runs above the ligament
  • Nerve (suprascapular) runs below the ligament

Quadrangular space 

Located in the axilla, the quadrangular space is bordered superiorly by subscapularis muscle (by teres minor muscle when viewed posteriorly), inferiorly by teres major muscle, laterally by the surgical neck of the humerus and medially by the long head of triceps brachii muscle.

The axillary nerve and the posterior circumflex humoral artery (PCHA) travel posteriorly through the quadrangular space to gain access to the posterior division of the pectoral girdle where they both supply the deltoid.

(Upper) triangular space

The (upper) triangular space acts as a conduit between the anterior axillary compartment and the posterior scapular segment. The superior border of teres major muscle forms the inferior border of the space. The inferior border of teres minor forms the superior border of the space when viewed posteriorly; but when viewed anteriorly, the superior border of the space is formed by the inferior border of subscapularis. Finally, the space is bounded laterally by the medial border of the long head of triceps brachii muscle.

The circumflex scapular artery passes through this space to join the scapular anastomoses.

Circumflex scapular artery (dorsal view)

Triangular interval (lower triangular space)

In a technical sense, the triangular interval lies outside the axilla since it is situated below the inferior border of teres major muscle (the lowest boundary of the axilla). Therefore, this space acts as a pathway between the anterior and posterior divisions of the arm, as well as between the posterior part of the arm and the axilla. It is bordered laterally by the shaft of the humerus and medially by the lateral border of the long head of triceps brachii muscle.

The profunda brachii artery and the radial nerve pass through this space to enter the arm.

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