The sternum (breastbone) is a flat, elongated bone in the centre of the chest that forms the anterior (front) part of the rib cage. It consists of three parts: the manubrium (the broad upper section at the level of the first and second ribs), the body (the long middle section, to which ribs 2 through 7 are attached via costal cartilages), and the xiphoid process (the small pointed lower tip). The sternum protects the heart and lungs and provides the bony anchor for the anterior rib cage.
In cardiac surgery, the sternum is divided (sternotomy) to gain access to the heart for open heart operations including coronary artery bypass grafting, valve replacement, and heart transplantation. The sternum is re-wired together with stainless steel wires at the end of the procedure. Healing takes approximately 6 to 8 weeks, during which sternal precautions apply: patients are typically advised to avoid lifting anything heavier than a kettle, and to avoid pushing or pulling with the arms.
In CPR, chest compressions are delivered to the lower half of the sternum, pressing it downwards by 5 to 6 cm to mechanically squeeze the heart and maintain blood flow. This can cause sternal or rib fractures, particularly in older patients, which are an expected and acceptable consequence of effective CPR. A cracked sternum is a treatable injury; inadequate compressions are not.
The xiphoid process is used as an anatomical landmark for positioning hands during CPR and for subxiphoid surgical approaches in certain cardiac procedures.
« Back to Glossary Index