What is the clinical significance of the sternal angle (Angle of Louis) in respiratory anatomy?

• A. It marks the level of the tracheal bifurcation
• B. It marks the level of the tracheal bifurcation and the articulation of the second rib with the sternum
• C. It marks the location of the first rib
• D. It indicates the level of the diaphragmatic hiatus

Answer: (B)

The sternal angle is a reliable surface landmark because it marks where the manubrium and body of the sternum meet, and at that level the second rib articulates with the sternum. This makes it the easiest place to count ribs and estimate thoracic levels. Importantly, behind this point the trachea divides into the right and left main bronchi, and the carina sits at approximately the same level. So this angle serves as a clue to both the bifurcation of the trachea and the second-rib articulation, which is precisely why the statement about these two features is the best description. The other options point to ribs or openings at different levels (first rib, diaphragmatic hiatus) and don’t capture the key relationship to the airway bifurcation.