The Front Mu point of the Pericardium, Ren 17, is an important and frequently used point for many acupuncturists. It is located aligned with 4th intercostal space directly on the body of the sternum. Most texts including, A Manual for Acupuncture, lists no warning around the safety of needling this point. When teaching students I always discuss the possible danger of a sternal foramen.
Sternal foramen, small holes in the bone, occur in a portion of the population. A hole in the body of the sternum leaves the heart vulnerable and thereby makes needling Ren 17 potentially dangerous. I think it is important for acupuncturist and students to be aware this anatomical variation exists.
5% of the Population
There have been a variety of studies seeking to determine how frequent foramen appear in the population. Studies have been conducted on cadavers and using radiographic imaging. Conclusions vary from 4.3% to 6.7% of the population — roughly 5% of the population. One study reports that the majority of the foramen found are located near the 4th rib space (the sternochondral articulation).
The foramen can vary in size. They can range from tiny 2mm spaces all the way to 22mm. Overall the mean size is generally reported to be between 4.5mm to 7mm. These are rather small spaces but much larger than acupuncture needles. There are published photographs of foramen and radiographic images as well. These images depict foramen on the larger end of the spectrum. Nevertheless it is helpful to see how obvious these spaces are in the body structure.
To Needle Safely
There are two steps we can take when needling Ren 17 to ensure safety for our clients.
- Palpate. As acupuncturists, our hands are one of our greatest tools. Before inserting a needle, we ought to take the time to examine and palpate the sternal body. Any dips or softs spots in the body of the sternum will alert us to the possibility of a foramen. The very smallest spaces may not be palpable, but certainly the more dangerous medium to large spaces will be noticeable. In the event of any unusual findings, I recommend choosing another point.
- Needle Angle. Ren 17 is taught to be needled in a transverse or oblique manner. Given the potential harm of needling through a foramen, one should never needle perpendicularly. I recommend needling at a depth of 0.2-0.3 cun deep and as obliquely as possible. A shallow insertion will prevent the needle from coming near the bone. The more oblique the angle, the greater protection there is to prevent sliding into a small foramen that was not detected upon palpation.
The combination of palpating and strong oblique insertions are simple precautions to take for our clients.
I am not looking to be alarmist about Ren 17. It is safely needled by thousands of acupuncturists every day. There are reports in medical literature looking at the frequency of these foramen and urging our field to take them seriously. The greater awareness we have of sternal foramen the greater confidence we can have about needling safely for our clients.