“…There are many unproved or partially proved hypotheses regarding the etiology of ISP including transection of major bronchi, ligament distraction or strain as the result of surgical retraction, shoulder joint strain from intraoperative mal-positioning, myofascial involvement, irritation of the pleura by chest drains, and referred pain from irritation of the pericardium, mediastinum, or diaphragmatic surface [3, 5, 11, 17, 20, 21]. …”