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AC Joint Separation or Shoulder Dislocation

Do You Have an AC Joint Separation or a Shoulder Dislocation?

Shoulder Specialist Dr. J. Michael Bennett talks about the differences between an AC joint separation and shoulder dislocation in this video.  Doctor Bennett is a Board Certified Orthopedic Surgeon.  He is Fellowship Trained as a Sports Medicine Physician with a Certificate of Added Qualification (CAQ) in Sports Medicine.  For an appointment, please call our Sugar Land office at 281-633-8600 or our Houston Galleria office at 713-234-3152.

This video was prepared by Dr. J. Michael Bennett to help patients become more knowledgeable about shoulder injuries.  This video is not a substitute for professional medical advice, diagnosis, or treatment.  You should not act upon any information provided here without first seeking medical advice from a physician.

Here’s Dr. J. Michael Bennett:

Summary of the AC Joint Separation or Shoulder Dislocation Video

Hello, my name is Doctor J. Michael Bennett with the Fondren Orthopedic Group. I am a sports medicine specialist focusing primarily on dealing with pathologies of the shoulder, elbow, and knee.  I’m Fellowship Trained and CAQ (Certificate of Additional Qualification) certified in sports medicine as well as general orthopedic surgery.

The Anatomy of an AC Joint

[Referring to the Shoulder Model] Many times if you injure your shoulder, you may be told you have a shoulder separation, but what is that means depends on what joint is actually involved.  A shoulder dislocation is what we talked about in a previous video, when there is a detachment or a sliding out from the ball and socket mechanism.  A shoulder separation, or what is also known as an acromioclavicular joint separation, or AC joint separation, is when these two bones up top, the acromion, which is this L-shaped bone, and the clavicle are separated. You can feel it in your own shoulder — it comes out of this corner back here and on everyone’s shoulder it’s very prominent, and it comes across like an L shape.  It meets your clavicle bone, which is your collarbone here. These two bones meet each other right above the glenohumeral joint or the shoulder joint.

How an AC Joint Injury Occurs

It’s commonly injured in patients who fall down with their arm at their side and land directly on the shoulder.  This is a very common football injury.  They get an AC joint separation where these two bones end up spraining the ligament between them or dislocating, where the collarbone actually sticks up. When that occurs — this is what it looks like with all the ligaments in place. This is your collarbone coming up and this the L-shaped bone coming right here.  These are the ligaments that stabilize those two bones and you have ligaments here, between the two bones, the acromion and the clavicle, and you have ligaments going down to this coracoid bone here stabilizing this collarbone. So when this pops up or dislocates, what we recommend depends on how displaced that collarbone is from this acromion bone.  

AC Joint Sprain

Often times it’s just minimally displaced and it’s very sore. If that’s the case, you’ll have some swelling there.  Many times it’s treated with conservative measures such as with a sling, ice or rest and letting things calm down before getting back to full activities. That’s more of a sprain of this ligament.

If you have a bigger sprain or a tear of this ligament, you’ll see a little bit of a rise, but not instability, that’s usually seen as a Grade 2 sprain. It’s also treated with conservative measures such as ice and maybe a sling for a few weeks and letting things heal up.

Grade 3 AC Joint Separation

 Now when it starts getting tricky is when you have involvement of all three ligaments here, so you have a tear here, a tear here, and a tear here [pointing to the three ligaments surrounding the joint].  If you have displacement, that’s considered a Grade 3 separation or AC joint separation.   This is where it’s controversial whether or not surgery is indicated or conservative measures should be tried.

There’s two schools of thought. Most of the time I’ll base my recommendation on the patient’s activity level and their expectations.  If it’s a very active person who wants to get back to full contact sports and activities, and they have an unstable shoulder in this area, often times I will give them the option of surgery to reconstruct this area and stabilize the joint.  If it’s a person who doesn’t do too many activities and they’re okay with having a little bump at the AC joint here, many times you can put this in a sling and let it rest and let it heal up.  These ligaments will scar down, but they’ll scar down a different position, and this bone will be raised up a little higher than the other side.  So you will have that sense of asymmetry there in the shoulders, but it will heal and will stabilize.

AC Joint Instability

When you get into Grade 4, 5, and 6, it all depends on where this clavicle bone is in relationship to the acromion. If you it significantly displaced, where it’s obviously popping up, it becomes a big problem in the sense that now you have an unstable AC joint, so the shoulder feels like there’s no support.

It looses a lot of its stability and the muscles around the shoulder start to get fatigued by holding the glenohumeral joint in position — because these ligaments here that attached this acromion to the collarbone, which is which attaches to the sternum is now disrupted. 

When you have a disruption as serious as a Grade 4, 5 or 6, oftentimes we recommend surgery to give the patient that stability. Because this will cause weakness in the shoulder joint, will cause pain, and sometimes it will even cause numbness and tingling down the arm because the nerve plexus, or the neurovascular bundle, comes through here and underneath here. It can become irritated or strained whenever you have any kind of instability between these two structures, but it has to be a pretty severe and significant.  That is called the acromioclavicular joint instability or separation.  

So it’s important when you’re discussing these things with your orthopedic surgeon, that you understand the differences between a shoulder dislocation, an AC joint sprain, an AC joint separation or AC joint instability. 

You need to be very clear on what your options are, and you always have the option of nonoperative management since this is an elective procedure, but you also need to understand what the long-term prognosis is with those options.  If you have any questions or comments, please feel free to visit my website or feel free to call my office at 281-633-8600. Thank you

Call Us for a Shoulder Evaluation

Don’t ignore an unstable shoulder!  Call our Sugar Land office at 281-633-8600 or our Houston office at 713-234-3152 for an appointment today.  You can also click the Book an Appointment button above to make an appointment online.

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Dr. J. Michael Bennett

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