The anatomy of the quadrilateral space with reference to quadrilateral space syndrome.

Quadrilateral space syndrome is a rare condition in which the contents of the quadrilateral space, the axillary nerve and the posterior circumflex humeral artery, are compressed, leading to vague symptoms of shoulder pain, tenderness over the quadrilateral space on palpation, and teres minor and deltoid denervation. Fibrous bands within the quadrilateral space are often cited in the literature as a cause of compression in quadrilateral space syndrome; however, Cahill and Palmer did not see these bands in cadaveric dissection. These are postulated to cause compression of the quadrilateral space contents in abduction and external rotation of the shoulder. To clarify the anatomic features that may predispose the development of quadrilateral space syndrome, 16 cadaveric shoulders were studied. Dissection revealed that fibrous bands are a common finding in the quadrilateral space, being present in 14 of 16 shoulders. The most common site for a fibrous band was between the teres major and the long head of the triceps. Where the bands were present, both internal and external rotation of the shoulder caused a reduction in the cross-sectional area of the quadrilateral space.