The sternal angle of Louis is an important anatomical landmark where several structures come together. At this level, the manubrium and body of the sternum articulate to form the manubriosternal joint. The trachea bifurcates into the right and left main bronchi, and the pulmonary trunk divides into the right and left pulmonary arteries. Several important blood vessels and nerves also lie at this level, including the azygos vein, deep cardiac plexus, and ligamentum arteriosum.

1. ANATOMICAL AND CLINICAL
EVENTS AT OR NEAR THE
STERNAL ANGLE OF LOUIS
OLUWOLE AKINOLA

2. Sternal angle of Louis as a useful anatomical
and clinical landmark

3. At the level of the sternal angle,
• Manubrium sterni articulates
with the body of the sternum
• to form manubriosternal joint
• a secondary cartilaginous joint or
symphysis
• Second costal cartilage
articulates with the sternum
• T4 and T5 vertebrae articulate
with each other
• an intervertebral disc intervening
between them

4. • Superior and
inferior
mediastina are
continuous
• at the imaginary
transverse sternal
plane

5. • Trachea bifurcates into right
and left main bronchi
• Pulmonary trunk divides into
right and left pulmonary
arteries
• Tracheobronchial nodes
surround tracheal bifurcation
• Azygos vein joins SVC from
behind
• Deep cardiac plexus of nerves
lies anterior to the bifurcation
of the trachea
• Ligamentum arteriosum
connects the aortic arch to the
left pulmonary artery

6. • Ascending aorta is continuous
with the aortic arch anteriorly,
• while the aortic arch is
continuous with the descending
thoracic aorta posteriorly

7. • Thoracic duct
crosses from the
right to the left of
midline
• as it ascends on the
vertebral column

8. •Auscultation for the
pulmonary and aortic
valves
• At the 2nd intercostal
space
• Close to sternal margin
• Pulmonary valve
auscultated near the
left sternal margin
• and aortic valve
auscultated near the
right sternal margin