Quadrilateral space syndrome caused by a humeral osteochondroma: a case report and review of literature.

Quadrilateral space syndrome (QSS) is a rare condition in which the posterior humeral circumflex artery and the axillary nerve are entrapped within the quadrilateral space. The main causes of the entrapment are abnormal fibrous bands and hypertrophy of the muscular boundaries. Many other space-occupying causes such as a glenoidal labral cyst or fracture hematoma have been reported in the literature. However, we could not find a report on classical QSS caused by an osteochondroma. The aim of this case report is to attract attention to an unusual etiology of shoulder pain, and to emphasize the importance of physical examination and x-ray imaging before performing more complex attempts for differential diagnosing.