What if I told you that there’s an important structure holding your spine together that you’ve never heard of? In fact, your doctor has also likely never heard of this structure nor does he likely know what it does. The structure is the TDF and the thoracodorsal fascia function is to hold your lower spine together and acts as the bridge that ties your arms into your lower body. The TDF is also the strong fascial covering of the back muscles that allows them to have max power. You may have seen those tight sports undergarments that are very rigid and pro-port to give athletes more strength. These companies borrowed the concept from the body’s own fascia, which are tight and semi-rigid coverings of muscles that provide more “oomph” to the muscles. If you look at the picture above to the left, you’ll see the TDF is colored red on this top down cross section of the low back. Note how it ties into the central back ligaments and acts to pull them tight and squeeze the multifidus muscle underneath. The importance of these spine ligaments in providing low back stability was discussed in a prior post. The latissimus dorsi muscles (“lats”) allow you to do a chin up by pulling your arms down and anchoring in your low back, pulling the TDF tight when you do. Why would this be important? When you go to lift something, your spine needs to act like the steel infrastructure of a skyscraper. The lats pull on the TDF, which in turn tightens the ligaments to protect the back by making it rigid. What if the lats are weak or the TDF or ligaments or loose? You lift without being able to protect your spine.
Now look at the picture to the right above. I’ve again highlighted the TDF and it’s connections in red. Note that the opposite lat pulls on the TDF and that this in turn pulls on the SI joint ligaments, making them tight. In fact, imagine that line of force going all the way down to the floor, anchoring you to the ground. So what happens if the SI joint ligaments are loose in this equation? You end up again with a part of the spine (the SI joint) that can’t protect yourself when you lift.
Finally, look at the picture in the middle above. This is what happens when you take a step or lift your leg. The TDF from the opposite side along with the butt muscles on the same side hold you up! So having a tight and functioning TDF is necessary for the simple things as well.
The upshot? If the TDF is so important, why don’t we hear more about it? Well, regrettably our focus for physician compensation has been on surgical procedures, where the TDF is just another tissue to be moved around. There simply isn’t much money to be made by focusing on what the TDF does and whether it’s working properly. Having said that, how can you help your TDF and back muscles? Simple lat pull downs are a start, especially if you place your mental focus on what’s happening with your low back while you do them. So the next time you pick something up and your back goes out, think about the TDF and consider getting yours looked at by a musculoskeletal specialist who knows what it is and what it does.