My intention with this post, and similar ones going forwards, is to provide a glimpse of what the Osteopathic lens will allow people to see. At the moment I am going to speak about a connection that I noticed by chance while studying for my online anatomy and physiology exam. I was flipping through my Principles of Anatomy and Physiology when I saw a diagram of the muscles of the thorax.
I happened to notice the coracoid process and the soft tissue attached to it. Funny enough, I saw the tendon for the short head of the biceps, the coracobrachialis, and the tendon for the pectoralis minor. I then imagined what those two tendons would look like if the arm were overhead and I started to think that the short head of the biceps, the coracobrachialis, and the pectoralis minor are functionally the same when the arm is overhead as the direction of the fibers of all three muscles align in that position. They share a common attachment point (as already mentioned) as well as common nerve roots (C5-C7).
This seems like a strange connection in standard anatomy but it is a big deal to an Osteopath. The outstretched arm can be used to have an affect on ribs 2-5 (individual variations of ribs 2-4 or 3-5 are possible) through the connection of the biceps to the pectoralis minor through the coracoid process.
To go a little outside of Osteopathy, I asked myself what might the purpose of this connection be? Why would a mechanical connection between these three muscles matter when an arm is outstretched? The best answer I have right now is that, functionally, humans need to have an efficient way to bridge the gap between objects overhead and bringing them closer to the mid-line. What might that mean? Reaching for fruits in a tree and bringing them down to our mouths, holding on to an object above us and bringing ourselves up to that object as in a chinup or other climbing activities. It is also very interesting to note that the nerve root for all three muscles exists in the exact same place – the musculocutaneous nerve for the biceps/coracobrachialis and the lateral pectoral nerve for the pectoralis minor both come from the C5-C7 nerve roots.
A lot of this may be inconsequential to the majority of the population to consider. For a Classical Osteopath, these are the considerations that make or break an effective treatment.
For the Osteopathic students reading this, look at the diagram a little closer and note how ribs as low as the ninth can be accessed through the serratus anterior. Also, look at the other accompanying diagram to notice how important it is to have proper soft tissue balance of pectoralis minor due to the large amount of nervous tissue and blood vessels that pass deep to it.