Shoulder Separation is a Common Injury

So, what exactly is an AC separated shoulder?

Shoulder Separation also referred to as AC (acromioclavicular) dislocation or AC separation is a very common injury typically as a result of a direct force on the top of the acromion (shoulder blade) or fall on an outstretched hand. To better understand this injury, we have to take a step back and review the anatomy of the shoulder girdle.

Shoulder Girdle

The shoulder girdle (clavicle and scapula) is only truly connected to the rest of the body at the joint formed between the clavicle and sternum (breastbone).  The shoulder therefore is suspended and supported by many muscles that originate or insert on the bones making up the shoulder.  The shoulder is really suspended from the clavicle (collarbone), being held in place by the ligaments between the coracoid (shoulder blade) and clavicle, along with the AC joint capsule, as well as the multiple muscles surrounding the shoulder.

Click here to watch a video about a Separated Shoulder.

AC Joint Capsule

So if just the AC joint capsule is injured but the ligaments are preserved, this is considered a mild separated shoulder and does not result in a big bump or prominence of the clavicle. As the severity of the separated shoulder injury increases and more damage is done-the ligaments suspending the shoulder blade are torn-the shoulder now drops down, leaving the clavicle elevated, resulting in a bump. With even more injury, the clavicle can also be displaced or moved higher up, further back, or even pushed down as well.

Type III Shoulder Separation

The mild levels of injury are typically treated like any other sprain (think mild ankle sprain, for instance) and usually do not require any sort of surgical treatment to regain normal use. The really severe levels of injury are typically treated with shoulder surgery. The most controversial type of injury is the Type III Shoulder Separation, where the ligaments and AC capsule are disrupted. This is the same injury suffered by NFL quarterback Sam Bradford during his last year of collegiate play at Oklahoma. In some patients with a lot of muscle tone or bulk, the muscles are sometimes able to compensate for the injury by holding the shoulder girdle reduced while the injuries heal. Unfortunately, for many patients with this injury, the amount of shoulder drop that occurs cannot be fully compensated and they experience significant pain and dysfunction.

Weaver-Dunn Surgery

Literally hundreds of surgical procedures have been described to repair and/or reconstruct high-grade shoulder separations. The vast majority of these procedures are based on a modification of a surgery called the . This surgery and all the subsequent modifications involve transferring another ligament [the CA (coracoacromial) ligament] to take the place of the torn CC ligaments (coraco-clavicular). Unfortunately, these procedures have been limited by highly variable success rates. The CA (coracoacromial) ligament is also increasingly recognized as important for shoulder function. Although the incidence of a separated shoulder is relatively high, the number of surgeons performing more than 5 shoulder separation surgeries annually is very small-meaning that most orthopedic surgeons perform these procedures only rarely. Especially for technically advanced procedures, it is very difficult for the surgeon only performing the procedure rarely to develop any sort of reliable expertise. Add to this the vast array of procedures available and it is not uncommon to see surgeons trying a different type of reconstruction procedure for each separated shoulder subsequent case.

Also see AC dislocation and AC reconstruction

Author
Vivek Agrawal, MD

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