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Topic

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Sternum

The sternum is a flat, elongated bone located in the midline of the anterior thoracic wall. It forms the anterior portion of the thoracic cage and articulates with the clavicles and the costal cartilages of the first seven ribs, contributing to the stability and protection of the thoracic cavity. The sternum is composed of three parts:

  • Manubrium: the superior broad portion that articulates with the clavicles and the first rib cartilages

  • Body (gladiolus): the central and longest portion, articulating with the costal cartilages of ribs 2–7

  • Xiphoid process: the small, inferior portion, which may be cartilaginous in youth and ossifies in adulthood

The sternum serves as a major protective shield for vital mediastinal organs, including the heart and great vessels, and acts as a crucial landmark for CPR, central venous access, and surgical procedures such as sternotomy.

Synonyms

  • Breastbone

  • Thoracic midline bone

  • Sternal plate

Function

  • Protects heart, lungs, and great vessels in the anterior mediastinum

  • Provides attachment for ribs and costal cartilages to form the thoracic cage

  • Serves as an origin and insertion point for chest wall muscles (pectoralis major, sternocleidomastoid, sternohyoid, sternothyroid)

  • Maintains structural stability of the thoracic skeleton

  • Acts as a surgical landmark in cardiac and thoracic surgery

Arterial Supply

  • Internal thoracic (mammary) arteries (primary source)

  • Perforating branches of the anterior intercostal arteries

  • Contributions from superior epigastric arteries

Venous Drainage

  • Drains via internal thoracic veins

  • Communicates with anterior intercostal veins

  • Venous drainage ultimately returns to the brachiocephalic veins

Nerve Supply

  • Periosteum and overlying soft tissues supplied by anterior cutaneous branches of the intercostal nerves

  • Deep innervation of bone via vasomotor and sensory fibers traveling with nutrient vessels

MRI Appearance

T1-weighted images:

  • Cortical bone appears low signal (black)

  • Bone marrow within sternum shows high signal in adults due to fatty marrow; lower signal in children due to red marrow

  • Pathology such as fractures, infiltration, or metastasis appears as areas of altered signal intensity

T2-weighted images:

  • Cortical bone remains low signal

  • Bone marrow shows variable intermediate signal, depending on red vs. fatty marrow composition

  • Lesions (tumors, infection, marrow edema) appear hyperintense relative to normal marrow

STIR (Short Tau Inversion Recovery):

  • Normal cortical bone remains low signal

  • Marrow edema, infection, or tumor infiltration appears bright hyperintense, making it very sensitive for fractures and metastases

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal sternum shows minimal or no enhancement

  • Pathological areas (infection, tumor, inflammatory lesions) show heterogeneous or focal enhancement

CT Appearance

Non-contrast CT:

  • Cortical bone is hyperdense (bright white), trabecular marrow appears lower density

  • Provides excellent detail of sternal fractures, lytic or sclerotic lesions, and congenital anomalies (e.g., sternal cleft)

Contrast-enhanced CT (CECT):

  • Enhances adjacent soft tissues and vascular structures, but sternum itself shows no direct enhancement

  • Useful for assessing tumor invasion, infection, or mediastinal extension of lesions

  • Ideal for trauma evaluation and preoperative planning for sternotomy

MRI images

Body of sternum MRI coronal image -img-00000-00000

CT image

Body of sternum CT coronal image -img-00000-00000