A 28-year-old man sustains an anterior dislocation of the shoulder during a fall. After reduction he cannot abduct the arm and has numbness over the lateral aspect of the shoulder just below the acromion. The injured nerve passes through which anatomical space, and which muscle it supplies accounts for the sensory loss pattern?

• A Triangular space; teres major
• B Costoclavicular space; subclavius
• C Triangular interval; long head of triceps
• D Quadrangular space; deltoid ✓

Explanation

The axillary nerve is the most commonly injured nerve in anterior shoulder dislocation. It runs through the quadrangular space bounded by subscapularis above, teres major below, the long head of triceps medially and the surgical neck of the humerus laterally, where it is vulnerable to stretch against the dislocating head. It supplies the deltoid and teres minor, and its superior lateral cutaneous branch gives the regimental badge sensory loss over the lateral shoulder.

Reference: Gray's Anatomy for Students, 4th ed.

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Written and medically reviewed by the StethoPrep medical team.