The sternum (or breastbone) is a level bone situated at the anterior aspect of the thorax. The lies in the midline that the chest and has a ‘T’ shape.
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As part of the bony thoracic wall, the sternum help protect the internal thoracic viscera – such as the heart, lungs and also oesophagus.
In this article, we shall look at the osteology the the sternum – its ingredient parts, articulations, and clinical correlations.
Fig 1 – Anatomical position of the sternum in the body thorax.
Parts that the Sternum
The sternum have the right to be separated into 3 parts; the manubrium, body and xiphoid process. In children, these elements are joined by cartilage. The cartilage ossifies come bone during adulthood.
The manubrium is the most superior portion of the sternum. The is trapezoid in shape.
The superior aspect of the manubrium is concave, producing a depression well-known as the jugular notch – this is visible underneath the skin. Either side of the jugular notch, there is a large fossa lined with cartilage. This fossae articulate through the medial ends of the clavicles, forming the sternoclavicular joints.
On the lateral edge of the manubrium, there is a facet (cartilage inside wall depression in the bone), for articulation v the costal cartilage the the first rib, and a demifacet (half-facet) for articulation with component of the costal cartilage of the 2nd rib.
Inferiorly, the manubrium articulates with the body of the sternum, developing the sternal angle. This deserve to be felt together a transverse ridge that bone top top the anterior element of the sternum. The sternal angle is commonly used together an help to count ribs, together it marks the level the the second costal cartilage.
The body is flat and elongated – the largest part of the sternum. It articulates v the manubrium superiorly (manubriosternal joint) and also the xiphoid procedure inferiorly (xiphisternal joint).
The lateral edges of the body are significant by plenty of articular facets (cartilage inside wall depressions in the bone). This articular facets articulate with the costal cartilages of ribs 3-6. There are smaller sized facets for articulation with components of the 2nd and saturday ribs – recognized as demifacets.
The xiphoid process is the most inferior and smallest component of the sternum. It is variable in shape and also size, through its tip located at the level that the T10 vertebrae. The xiphoid procedure is mainly cartilaginous in structure, and fully ossifies so late in life – roughly the age of 40.
In part individuals, the xiphoid process articulates with component of the costal cartilage of the saturday rib.
Fig 2 – The articulations and parts of the sternum.
Clinical Relevance: Fractures that the Sternum
Sternal fractures are associated with serious blunt trauma to the chest, such as in a automobile accident. They are reasonably uncommon.
Typically, the sternum will certainly break into several piece – this kind of fracture is classified as a comminuted fracture. The most common site the fracture is the manubriosternal joint – wherein the manubrium meets the body of the sternum. Despite the level of damage to the sternum, the fragments are not commonly displaced as result of the attachments of the pectoralis muscles.
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Sternal fractures have a high mortality price (25-45%). This is not as result of the fracture itself, however usually together a result of heart and lung injuries, i m sorry are most likely to take place simultaneously v the primary trauma. Since of this, that is vital to examine patients v sternal fractures because that visceral injury. X-ray, CT and also ultrasound are common investigations.