The sternum, also known as the breastbone, is located in the mid portion of the anterior chest wall and can be divided into three distinct parts; the manubrium, body and xiphoid process. In children, these elements are joined by cartilage which then ossifies to bone during adulthood.
The manubrium is the most superior portion of the sternum, with a trapezoid shape. The superior aspect of the manubrium is concave, producing a visible depression underneath the skin known as the jugular notch. On either side of this notch is a large fossa lined with cartilage, which articulates with the medial ends of the clavicles and forms the sternoclavicular joints. Additionally, on the lateral edges of the manubrium are a facet for articulation with the costal cartilage of the 1st rib, and a demifacet for articulation with part of the costal cartilage of the 2nd rib. The manubrium also articulates with the body to form the sternal angle, which can be felt as a transverse ridge of bone on the anterior aspect of the sternum.
The body of the sternum is the largest portion and is flat and elongated. It articulates with the manubrium superiorly (manubriosternal joint) and the xiphoid process inferiorly (xiphisternal joint). It is marked by numerous articular facets (cartilage lined depressions in the bone) on the lateral edges, which articulate with the costal cartilages of ribs 3-6. There are also smaller facets for articulation with parts of the second and seventh ribs - known as demifacets.
The xiphoid process is the most inferior and smallest part of the sternum. It is variable in shape and size and is located at the level of the T10 vertebrae. The process is largely cartilaginous in structure and completely ossifies late in life - around the age of 40. In some individuals, the xiphoid process articulates with part of the costal cartilage of the seventh rib.
Fractures of the sternum are associated with severe blunt trauma to the chest, such as in a vehicular accident, and are relatively uncommon. The sternum typically fractures into several pieces which is known as a comminuted fracture. The most common site of fracture is the manubriosternal joint - where the manubrium meets the body of the sternum. Despite the degree of damage to the sternum, the fragments are usually not displaced due to the attachment of the pectoralis muscles.
Sternal fractures have a high mortality rate (25-45%) usually due to associated heart and lung injuries which occur simultaneously with the primary trauma. It is therefore crucial to check patients with sternal fractures for visceral injury and investigate them with X-ray, CT and/or ultrasound.
The sternum is a flat bone found in the center of the thoracic cage, and is composed of three parts: the manubrium, the body, and the xiphoid process. The lateral edges of the body are marked by numerous articular facets (cartilage-lined depressions in the bone). These articular facets articulate with the costal cartilages of ribs 3-6 and smaller facets for articulation with parts of the second and seventh ribs, known as demifacets.
The xiphoid process is the most inferior and smallest part of the sternum and is variable in shape and size, with its tip located at the level of the T10 vertebrae. This part of the sternum is largely cartilaginous in structure, and usually completely ossifies late in life (around the age of 40). In some individuals, the xiphoid process articulates with part of the costal cartilage of the seventh rib.
Sternal fractures are associated with severe blunt trauma to the chest, such as in a vehicular accident and are relatively uncommon. Typically, the sternum will break into several pieces; this type of fracture is classified as a comminuted fracture. The most common site of fracture is the manubriosternal joint - where the manubrium meets the body of the sternum. Despite the degree of damage to the sternum, the fragments are not usually displaced due to the attachment of the pectoralis muscles.
Sternal fractures have a high mortality rate (25-45%), which is not due to the fracture itself but usually as a result of heart and lung injuries, which are likely to occur simultaneously with the primary trauma. Because of this, it is crucial to check patients with sternal fractures for visceral injury. X-rays, CT scans, and ultrasounds are common investigations. Visceral injury associated with sternum fractures can occur in the form of:
Clinical examination, laboratory tests, imaging, and electrocardiogram are the necessary investigations to assess sternum fractures.
It is essential to understand the anatomy, articulations, and clinical relevance of sternum fractures in order to properly evaluate and treat affected patients. The high mortality rate associated with these fractures makes it all the more important to be familiar with the clinical and radiological findings so that appropriate treatment can be offered in a timely and effective manner.
