The causes of sternal protrusion in patients are as follows: 1, congenital developmental abnormalities: the sternal angle is congenitally larger, so the sternum will appear to protrude, especially among the more emaciated patients, if the sternal angle has a mild hyperplasia, it can show up as a very obvious protrusion on the body surface. 2, sternal injury: to consider is caused by previous injury to the sternum, such as the previous occurrence of sternal fracture, fracture malalignment 3, fibrocartilage hyperplasia, deformity: to consider the sternum lateral fibrocartilage hyperplasia and deformity, also prone to sternal protrusion.