An unusual cause of the quadrilateral space impingement syndrome by a bone spike

The quadrilateral space impingement syndrome is a clinical syndrome resulting from compression of the axillary nerve and the posterior circumflex humeral artery, with subsequent focal atrophy of the teres minor, with or without involvement of portions of the deltoid muscle. This entity has many etiologies. We are reporting a case of this syndrome caused by a bone spike from a malunited old scapular fracture following a motor vehicle accident. The bone spike impinged on the axillary nerve as it passes through the quadrilateral space, causing focal atrophy of the teres minor muscle. The abnormality was well demonstrated by MD-CT.