This is a brief tutorial just to look at some of the important structures which lie at the level of the sternal angle.
The sternal angle is this angle formed between the manubrium of the sternum and the body of the sternum. It's important because we know that this level marks the level of the intervertebral discs which lies between thoracic vertebra T4 and T5. It's an important structure because it marks the location of other structures in the body. We'll take a look at some of the structures which lie at this angle.
This sternal angle is also called the Angle of Louis. The mnemonic I use for remembering the structures at the Angle of Louis is RATPLANT. The first structure is the second rib, so the R of RATPLANT. Well, it's really the costal cartilage, but it just helps with the mnemonic. You’ve got the second costal cartilage of the second rib articulating with the manubrium and the body of the sternum.
And then next, you've got the A of RATPLANT. That refers to the arch of the aorta. I've just isolated those structures here. You can see the beginning and the end of the arch of the aorta lie roughly at this level.
The next structure is the trachea. The trachea bifurcates at around this level. You can see the splitting into the two bronchi at this level.
And then next, we've got the pulmonary trunk bifurcation. Just isolating it there, you can see the pulmonary trunk bifurcates into its right and left branches.
And then the L refers to two things. First, we've got the left recurrent laryngeal looping under the arch of the aorta. You can see that here. I've just isolated those structures. You've got the vagus nerve coming down and the left recurrent laryngeal looping under the arch of the aorta.
The other L structure is the ligamentum arteriosum. Just going back into this mode here, you can see the little ligamentum arteriosum connecting the arch of the aorta to the pulmonary trunk.
And then the A refers to the azygos system draining into the superior vena cava. If we just rotate the model around, you can see the sternal angle here and you've got the azygos vein draining into the SVC at roughly this T4, T5 sternal angle level.
The N is just to make this mnemonic work a bit better. It refers to nerves, so you've got the cardiac plexus which lies around the sternal angle level.
Finally the last letter, T refers to the thoracic duct emptying into the left subclavian vein. I've just switched into this transparent mode and we can see the thoracic duct here in green. It drains into the left subclavian vein.
You’ve got the subclavian vein coming off the axillary vein and it drains into the brachiocephalic vein, the left brachiocephalic vein. Where the subclavian vein meets the internal jugular vein, you've got the brachiocephalic vein.
And just before this junction, you've got the emptying of the thoracic duct into the left subclavian. This occurs a big higher than the Angle of Louis, but it's useful to remember this landmark.
That’s RATPLANT to help you remember these structures that lie at the level of the sternal angle. I hope that's been helpful.