The axillary nerve and posterior circumflex humeral artery course posteriorly through the quadrilateral space (Fig 1), an anatomic area bounded by the humerus, teres minor, teres major, and triceps muscles. These neurovascular structures are susceptible to injury or compression, which, if present, may cause shoulder pain, paresthesia, and localized tenderness to palpation, a clinical entity termed quadrilateral space syndrome.
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