Subscapular Spaces are (1) quadrangular and (2) triangular intermuscular spaces in the scapular region, that are clearly viewed from behind after reflecting the posterior part of the deltoid. The knowledge of subscapular spaces is necessary during surgery in the shoulder region.

Quadrangular Space

Boundaries

Quadrangular subscapular spaces are bound by 4 sides which are as follows:

Superior:

Inferior: Teres major.

Medial: Long head of the triceps.

Lateral: Surgical neck of the humerus.

Structures Going Through This Space

1. Axillary nerve.

2. Posterior circumflex humeral artery and vein.

Upper Triangular Space

Boundaries

Upper Triangular Subscapular spaces are bound by 3 sides that are as follows:

  • Superior: Teres minor.
  • Lateral: Long head of triceps.
  • Inferior: Teres major.

Structure going through this space

Circumflex scapular artery (this artery interrupts the origin of teres minor to reach the infraspinous fossa).

Lower Triangular Space

Boundaries

  • Medial: Long head of triceps.
  • Lateral: Shaft of humerus.
  • Superior: Teres major.

Structures Going Through Lower Triangular  spaces