The sternum is located in the center of the chest and is a bone that is flat and sword-shaped. Structures located behind the sternum are called retrosternal, and structures located to the side are called parasternal. The bone consists of the handle (manubrium sterni), body (corpus sterni), and sword process (processus xiphoideus), respectively.
What is the sternum?
The sternum (Latin: breastbone) is a long, flat bone at the front of the chest. This forms from the ribs, sternum, and cartilaginous extensions. The sternum is 17cm long on average, usually shorter in women than in men. The term sternum comes from swords used in ancient times that had a similar shape to the sternum.
Anatomy and structure
At the end of the handle near the head, there is an indentation (incisura jugularis) that is very palpable and marks the so-called jugular fossa. To the left and right of the notch are the articular surfaces that connect the clavicles in the sternoclavicular joint (sternoclavicular joint). The sternoclavicular joint is located at the anterior end of the sternum and can be palpated through the skin. The second rib attaches between the body of the sternum and the handle, and ribs 3 to 7 attach to the notches of the sternum body. The xiphoid process marks the lower end of the sternum. It can have different shapes: Either it is compactly or bi-radially formed or bent backward or forward. In the child, all three parts of the sternum are not yet fused together; they only ossify in the course of life. Between the sternum body and sternum handle there is a palpable elevation called angulus sterni (sternal angle). The sternum contains red bone marrow, so it is possible to perform a bone marrow puncture over the sternum. However, a sternal puncture is rare today because the pericardium or the heart chambers could be punctured. For this reason, iliac crest puncture, which is associated with fewer risks, is preferred today.
Functions and tasks
Together with the 12 thoracic vertebrae and the 12 ribs, the sternum forms the rib cage. The sternum stabilizes the rib cage and protects the heart and lungs, respectively. However, the ribs do not fuse rigidly with the sternum, but they are movable through the rib-sternal joints, which enables breathing. The first seven pairs of ribs are directly connected to the sternum by cartilaginous processes, the following three pairs of ribs are connected via the costal arch, and the last two pairs have no connection to the sternum. Heart transplants or bypass operations normally take place at the open heart. The sternum is then cut longitudinally during the operation so that the chest is open and the surgeon can reach the heart in this way. A distinction is made here between a total sternotomy, in which the entire sternum is cut, and a partial sternotomy, in which the surgeon cuts only the lower or upper part of the sternum.
Diseases and complaints
A possible disease in the sternal area is sternal swelling, which can occur mostly due to microfractures of the bones due to overuse or after surgical procedures involving a thoracic opening. Swelling is then visible externally in the chest and rib area, and patients also suffer from severe pain when inhaling or exhaling. The pulse is accelerated and there is an increased feeling of heat. The physician detects sternal swelling with the help of a pressure test, and it is treated with painkillers and pain therapy. In very severe cases, the corresponding drugs are also injected directly into the spinal cord, but heat and cold therapies or acupuncture also help very well. Rather rare are fractures of the sternum, which can be caused, for example, by a blow or in a car accident. A fracture is caused either by the impact on the steering wheel or by the seat belt itself. In this context, edema in the lungs or pulmonary contusions also occur. If there is a fracture of the sternum, this is therefore always an indication of other injuries. Pain in the area of the sternum can also be projections from other organs.For example, angina pectoris, a heart attack or diseases of the esophagus cause pain behind the sternum. But the pain of a stomach ulcer can also spread to the sternum. Another cause is so-called costochondritis, in which the cartilage between the ribs and sternum is inflamed. Costochondritis is rather rare and usually occurs in the course of systemic diseases (for example, Reiter’s disease). Some babies have a congenital hole in the sternum, usually located on the right side. Pathological changes of the sternum also include the so-called funnel chest. In this case, the cartilage connections between the ribs and sternum change and the front part of the chest sinks in. Another deformity is the keel or chicken breast. In this case, the sternum is protruding like a keel, which is psychologically stressful, especially for those affected. The cause is thought to be a strong growth of the cartilage, which triggers a protrusion of the sternum. If the sternum is twisted in the longitudinal axis, this is called a Harrenstein deformity. In this case, the ribs protrude above the sternum on one side, but are lowered on the other side.
