The body of the sternum, also called the mesosternum, is the elongated central portion of the sternum. It lies between the manubrium superiorly and the xiphoid process inferiorly, connected by the sternal angle (angle of Louis) at the manubriosternal joint. The body is flat, elongated, and slightly convex anteriorly and concave posteriorly, contributing to the anterior wall of the thoracic cage. Laterally, it articulates with the costal cartilages of the second through seventh ribs, forming a major structural component for rib attachment. It provides protection for the heart, great vessels, and anterior mediastinal structures, as well as an anchoring surface for multiple thoracic and abdominal muscles.

Synonyms

• Mesosternum

• Corpus sterni

• Middle sternum

Function

• Forms part of the anterior thoracic cage, providing structural support

• Serves as a protective shield for the heart, lungs, and mediastinum

• Provides articulations for ribs (2nd–7th costal cartilages)

• Acts as an attachment site for pectoralis major, sternocleidomastoid, rectus abdominis, and intercostal muscles

• Plays a role in respiratory mechanics by stabilizing the thoracic wall

Arterial Supply

• Perforating branches of the internal thoracic arteries

• Anterior intercostal branches of the internal thoracic artery

• Contributions from the anterior intercostal arteries

Venous Drainage

• Drains into the internal thoracic veins

• Secondary drainage into the anterior intercostal veins

Nerve Supply

• Sensory innervation via anterior cutaneous branches of intercostal nerves (T2–T6)

• Periosteum and sternocostal joints receive innervation from intercostal nerves

MRI Appearance

T1-weighted images:

• Cortical bone of the sternum appears low signal intensity (hypointense)

• Bone marrow within the sternum appears intermediate to high signal depending on fat content

• Useful for identifying marrow lesions, fractures, or infiltrative disease

T2-weighted images:

• Cortical bone remains hypointense

• Bone marrow demonstrates intermediate to high signal, accentuating edema or tumor infiltration

• Pathological conditions such as osteomyelitis or metastases appear as hyperintense regions

STIR (Short Tau Inversion Recovery):

• Suppresses fat, making marrow edema, fractures, and tumors appear bright hyperintense

• Normal cortical bone remains dark (low signal)

T1 Post-Contrast (Gadolinium-enhanced):

• Pathological conditions such as infection, metastasis, or primary bone tumors show heterogeneous or intense enhancement

CT Appearance

Non-contrast CT:

• Body of sternum appears as a hyperdense cortical bone plate with central trabecular bone

• Clearly shows sternal articulations with costal cartilages

• Excellent for detecting fractures, cortical irregularities, or sclerosis

Contrast-enhanced CT (CECT):

• Enhances adjacent soft tissues, useful for detecting retro-sternal masses, infections, or tumor invasion

• Sternal marrow changes can be evaluated in the context of systemic disease