Topic Overview

Rotator Cuff (SITS Muscles)

Components

• Supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

Attachments

• Surround head of humerus and blend with shoulder joint capsule.

Functions

• Stabilize humeral head in glenoid cavity.

• Provide dynamic support during movements.

• Individual actions:

  • Supraspinatus → initiates abduction (0–15°).

  • Infraspinatus + Teres minor → lateral rotation.

  • Subscapularis → medial rotation, adduction.

Clinical Anatomy

• Rotator cuff tear (most commonly supraspinatus tendon) → painful abduction.

• Painful arc syndrome → pain in 60–120° abduction.

• Weakness of rotation depending on tendon involved.

• Clinical tests:

  • Empty can test (supraspinatus).

  • External rotation test (infraspinatus/teres minor).

  • Lift-off test (subscapularis).

Intermuscular Spaces of the Scapular Region

1. Quadrangular Space

• Boundaries:

  • Above → teres minor.

  • Below → teres major.

  • Medial → long head of triceps.

  • Lateral → surgical neck of humerus.

• Contents:

  • Axillary nerve.

  • Posterior circumflex humeral artery & vein.

• Clinical:

  • Axillary nerve injury here → deltoid paralysis, regimental badge anesthesia.

2. Upper Triangular Space

• Boundaries:

  • Above → teres minor.

  • Below → teres major.

  • Lateral → long head of triceps.

• Contents:

  • Circumflex scapular artery.

• Clinical:

  • Important part of scapular anastomosis.

3. Lower Triangular Space (Triangular Interval)

• Boundaries:

  • Above → teres major.

  • Medial → long head of triceps.

  • Lateral → lateral head of triceps/humerus.

• Contents:

  • Radial nerve.

  • Profunda brachii artery.

• Clinical:

  • Radial nerve vulnerable here → wrist drop if injured.

Dissection of Scapular Region (Rotator Cuff + Spaces)

Step 1: Exposure

• Incise skin over scapula and shoulder.

• Reflect skin and superficial fascia to expose deltoid.

Step 2: Reflect Deltoid

• Cut deltoid near its origin and reflect laterally.

• This exposes underlying rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis).

Step 3: Identification of Muscles

• Above spine → supraspinatus.

• Below spine → infraspinatus.

• Lateral border → teres minor (superior), teres major (inferior).

• Anterior scapula → subscapularis.

Step 4: Expose Intermuscular Spaces

• Trace long head of triceps between teres minor and teres major → forms medial boundary of quadrangular and triangular spaces.

• Identify contents:

  • Axillary nerve and posterior circumflex humeral vessels in quadrangular space.

  • Circumflex scapular artery in upper triangular space.

  • Radial nerve and profunda brachii artery in lower triangular space.

Step 5: Clinical Demonstration

• Palpate for posterior shoulder injuries involving axillary nerve.

• Demonstrate overhead abduction → showing rotator cuff stabilization.