Shoulder Injuries in the Performing Arts: Dislocations

With the video and witness reports circulating about Mark Ballas's injury during DWTS rehearsal, this is a good time to review the differences between the most common acute shoulder injuries.  This is the first in a series on shoulder injuries in the performing arts.

This series of articles will address fairly damaging acute shoulder injuries.  Unless otherwise noted, these injuries are substantial enough that they should not be self-treated until after you've seen a medical professional who has instructed you to do so.  These traumatic shoulder injuries should be treated as emergencies, since there is a high risk of significant complications if they are improperly or incompletely cared for (these complications can include nerve damage, internal bleeding, and nonunion fractures).  Some of the injuries discussed in this series can be caused by falls or collisions, but these articles will focus on other mechanisms of injury.

Terminology

When it comes to shoulder injuries, there is often some confusion surrounding terminology.  Some of this is due to the use of the word "shoulder" as a bit of a catch-all term to describe the entire interconnected system spanning from the center of the body to the upper arm (in front and back).  Remember the kids' song that goes "the hip bone's connected to the...thigh bone....")?  Turns out, it's (mostly) true - everything's connected.

The true shoulder joint is the glenohumeral joint - the ball and socket joint between the upper arm bone and the trunk. The scapula, also called the shoulder blade, is part of the glenohumeral joint, forms a joint with the collarbone, and is connected to the spine through muscles in the upper back.  Muscles in the chest, neck, and upper and lower back direct the positioning and movement of the true shoulder joint.  Therefore, thinking of the shoulder joint in isolation from the rest of the regions of the body that affect it is not only difficult, but it makes no sense.  This is why medical professionals use the term "shoulder girdle" to describe the entire system surrounding the shoulder joint, including the collar bone, shoulder blade, humerus (upper arm bone), spine, and all of the muscles associated with the shoulder.

So, while "dislocated shoulder" and "separated shoulder" sound like they are very similar injuries to the same body part - and are often confused or used interchangeably - they actually are very distinct injuries to entirely different structures within the shoulder girdle.  The treatment and long-term effects of the following injuries are very different, so early - and correct - identification of an acute injury to the shoulder is essential to a complete recovery.  This article discusses shoulder dislocations.  Check back later for a breakdown of shoulder separations and other shoulder girdle injuries.

Shoulder Dislocation

What you feel

At the time of the injury, you feel a pop or a thunk in your shoulder joint.  Your body's natural reaction is to crumple over and grab your elbow.  Your instincts will be to use your body and other hand to provide a make-shift sling to support the weight of your arm, limiting motion and decreasing pain at the shoulder joint.  Typically, when you dislocate your shoulder, you will drop anything you're holding (which can be dangerous, depending on the weight and location of the object - or if what you're holding is another person).  You may have numbness or tingling throughout your arm (or you may not notice it because of the pain).  With your other hand, you will be able to feel the ball end of the upper arm bone about an inch or two below the normal location of the shoulder joint.  Depending on your physique and what you're wearing over your shoulders, you may be able to see this as well.  The entire shoulder girdle and arm area will hurt immediately after the injury, but the pain will center around the glenohumeral joint.

What happens to your body

The diagnosis of a shoulder dislocation refers to an injury to the glenohumeral joint. When the glenohumeral joint dislocates, the ball-and-socket joint of the shoulder comes apart.  The ball part of the joint (the upper arm bone) pulls or rotates (or both) too far away from what the joint can withstand and it pops out of the socket made by the glenoid cavity on the shoulder blade.  The upper arm bone rubs over (and can damage or partially remove) the cartilage ring lining the shoulder's socket (the labrum).  All of the arm's nerves and blood vessels run through the armpit, placing them in a prime location to become damaged when the shoulder dislocates and the head of the humerus (the ball of the joint) shifts down due to gravity.  This is why you may feel numbness and tingling throughout the shoulder.

Joint dislocations - throughout the body, not just in the shoulder - cause cartilage damage to the joint surfaces of the bones, and they stretch out or tear the ligaments and other connective tissue surrounding the joint.  Both of these "side effects" can lead to long-term problems.  The cartilage damage can lead to early joint degeneration, fragmented cartilage or bone blocking movement within the joint, osteochondral defects (pieces of the joint-covering cartilage wear away or break off and the exposed bone underneath causes pain), and early arthritis.  Ligament and joint capsule damage can lead to an unstable joint, making it more likely for the joint to become injured during activities that previously would not have caused an injury.  A shoulder dislocation leads to more dislocations on that shoulder.  In fact, many people with multiple shoulder dislocations develop multi-directional instability, wherein the shoulder joint is so "loose" that it will regularly dislocate during normal daily tasks like showering or getting dressed.

How it can happen in the performing arts

Shoulder dislocations most commonly occur with the arm externally rotated and elevated to the side (abducted) above the height of the shoulder.  The easiest way to think of this is to picture a baseball pitcher about to throw a ball.  This position can happen when you're lifting something overhead with your hand outside the plane of your shoulder and a little bit behind you (instead of directly above your shoulder).

In the performing arts, this bad positioning happens most frequently during lifting motions: dance lifts, moving props or scenery, lifting a tuba or drum over your head.  Shoulder dislocations can also occur with a swift yank on the arm (slipping while grabbing on to something stationary, choreography to get off the floor quickly with the help of a partner - that's why you need to pull, too!) or by doing floorwork that places the shoulder in the position described above (especially when the floorwork requires you to push against the floor with your arm while in this position).

The key to dealing with non-contact shoulder dislocations is to try to avoid them in the first place.  The best way to do this is to use correct form, avoiding fatigue and overtraining, avoiding using your arm in an abducted and externally rotated position (mentioned above) especially while lifting, and regularly performing a shoulder strengthening program.

Be sure to check back for the next article in the shoulder injury series.