So far we've gotten pretty deep on the concept of shoulder impingement but it's time to delve a little deeper. Next in the line-up we'll talk about the thoracic spine and ribcage. If you missed the previous parts you can find them here:
If we take a closer look at the shoulder joint and scapula we'll notice that we only have 1 true joint that connects the shoulder to our trunk. The scapula attaches to the clavicle at the acromioclavicular joint and the clavical attaches to our thorax via the sternum at the sternoclavicular joint. These two relatively small joints are the only real joints that connect our arm to our trunk.
- source: conornordengren.com
There is also a connection between the scapulae and the posterior element of our ribcage as seen to the right. Although this is not a true joint we refer to this connection as the scapulothoracic joint. The scapula lies directly on top of our rib cage and slides smoothly across the surface of the ribs during shoulder movement. Because of this, efficient and healthy movement at the scapulothoracic joint has everything to do with the orientation of the ribcage that the scapula slides along. If the position of our ribcage is off, it will change the position of our shoulder blades and as described later, can lend itself to impingement.
Our spine consists of a series of vertebrae stacked on top of each other that extend from the base of our skull down to our sacrum (and a bit lower to our coccyx). The vertebrae that make up our neck are known as cervical vertebrae. The vertebrae in our trunk that attach to our ribs are known as thoracic vertebrae and the vertebrae that make up our lower back are known as lumbar vertebrae. As mentioned previously, the vertebrae in our thoracic spine attach to the ribs. Because of this, the orientation of our ribcage is directly related to the mobility of our thoracic spine.
Food for thought: The thoracic spine's attachment to the ribs creates stability. This can make it difficult to gain mobility in the thoracic spine when we need to.
When we press a barbell overhead we need full mobility of our gleno-humeral joint (shoulder joint), full mobility of the scapulothoracic joint (scapular motion) and full extension range of motion of our thoracic spine in order to get the weight overhead efficiently. If we don't have this mobility we run into issues. (Use this simple test to see if you've got enough mobility)
Now here is where things get interesting. When compared to patients with healthy shoulders, patients with subacromial impingement syndrome have on average less thoracic spine extension mobility (1).
Food for thought: Research from McClure et al. 2006 showed that there was no difference in thoracic spine posture at rest between healthy individuals and those with subacromial impingement. This suggests thoracic spine mobility may be more important that static posture (3).
As we learned previously patients with impingement also present with increased anterior tilting of the scapula (2). As we learned previously, anterior tilting of the shoulder blade decreases room in the subacromial space. This impinges on the tissues that lie within the subacromial space and over time can lead to rotator cuff tears.
Food for thought: More recent research has shown that individuals with subacromial impingement syndrome may have increased posterior tilt when lifting their arms overhead. This may be a compensation pattern to help increase subacromial space and decrease pain and impingement. (3) If this makes no sense don't worry, I found this interesting!
- source: www.dynamicchiropractic.com
Thoracic spine mobility and posterior tilting of the scapula are synonymous. Understanding this concept can be difficult. Think of it this way. As we raise our arms overhead the scapula is supposed to ride flat along the thoracic spine. In healthy overhead motion the scapula will upwardly rotate, elevate and posteriorly tilt. In order to posteriorly tilt properly, the ribcage must create an optimal surface to allow this motion. Adequate thoracic extension creates a more optimal ribcage surface to allow the scapula to do it's job and get our arms overhead safely and efficiently. If we have a large kyphosis and decreased ability to extend at the thoracic spine, the surface of the ribcage will make overhead motion much more difficult.
Now here's a little experiment to help explain the above details. Stand with poor posture with your shoulders and head forward with a big round in your upper back. Keep this posture and try to raise your arms overhead as much as you can. Not too good huh?
Now fix your posture. Pull back your shoulders and tuck your chin. Straighten up your upper back. Now reach overhead again. Better? If we're lacking thoracic spine extension range of motion it's going to make healthy efficient overhead motion impossible.
- source: www.ericcressey.com
On top of that, normal overhead elevation of the shoulder is only 165-170 degrees(4).
165 degrees does not get our arms completely overhead. We'll need full range of motion for all exercises that requires us to press weight overhead (Military Press, Push Press, Push Jerk etc). Our body achieves those last degrees of full 180 degrees of overhead motion with thoracic spine extension. As we learned previously a lack of thoracic spine extension opens ourselves up to shoulder injuries and leads to a pretty weak press. To add insult to injury, a lack of overhead flexibility can cause a compensation somewhere down the chain in order to get our arms completely overhead. Often times we try to achieve extra motion by extending our lumbar spine. (Anyone else smell lower back pain?)
Well, there's the details on the thoracic spine. I think I've strained my brain enough writing about this topic. Give me some time to ice my brain and I'll get back to you next week as we talk about have breathing can effect the shoulder. Until then...
Rotary cups of steel,
Dan Pope
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Resources:
1. Meurer, A., Betz, U., Decking, J., & Rompe, J. (2004). [bws-mobility in patients with an impingement syndrome compared to healthy subjects--an inclinometric study]. Z Orthop Ihre Grenzgeb,144(4), 415-420. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15346302
2. Lukasiewicz AC, McClure P, Michener L, et al. Comparison of 3-dimensional scapular position and orientation between subjects with and without shoulder impingement. J Orthop Sports Phys Ther. 1999;29:574–583.
3. McClure, P., Michener, L., & Karduna, A. (2006). Shoulder function and 3-dimensional scapular kinematics in people with and without shoulder impingement syndrome. Physical Therapy, 86(8), 1075-1090. Retrieved from http://ptjournal.apta.org/content/86/8/1075.full
4. Gulick, D. (2009). Ortho notes. (2nd ed., p. 189). Philadelphia, PA: F.A. Davis Company.
