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1 posts from January 2010

January 26, 2010

The Vulnerable Shoulder

 One of the most fascinating aspects of the shoulder is looking at it from a perspective of comparative anatomy.  The shoulder joint has evolved an amazing amount when looking at prehistoric man to its current form.  Possibly, next to the thumb, this is the joint that has changed the most over time.  As mammals went from walking on their hands to upright, the body was able to sacrifice some of the bony connection at the shoulder and make it more of essentially a soft tissue connection.

 With this change from a more classic ball and joint to a more free-floating ball and joint, we were able to add the amazing amount of range of motion of 270 degrees.  The fact that we can keep our arms away from our body with the current shoulder structure allows us to work above our heads.  

There are some specific areas of vulnerability in the shoulder, and the most common problem people have, far and away, is that the supraspinatus tendon.  This is the – this is where most shoulder pathologies start.  There are a few reasons why this area gets damaged.  The first of which is location between two hard objects.  Essentially, the ball of the humerus and this supraspinatus muscle and tendon runs on top of the ball and inserts along the distal aspect of the arm bone on top of the ball, if you will.  Above the supraspinatus tendon is another hard area, the acromioclavicular structure.

Obviously, this can lead to a sandwiching effect, a pinch.  In fact, another name for the shoulder or rotator cuff problems is impingement syndrome.  In addition to having a tendency to be pinched, this area is also hypovascular.  It’s at the end of the line of the arteries, and therefore has – is uniquely vulnerable towards a lack of blood flow.  These two factors, in my opinion, are what lead to the vast majority of shoulder pain.  We can’t revascularize or change the blood supply of the shoulder, so we really need to prevent it from getting pinched.

This is critical to prevent the process that leads to rotator cuff tendonitis, impingement syndrome, rotator cuff tears. 

Thank you