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.
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.
So if just the AC joint capsule is injured but the ligaments are preserved, this is considered a mild shoulder separation and does not result in a big bump or prominence of the clavicle. As the severity of the 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.
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 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.
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 Weaver-Dunn surgery. 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 shoulder separation 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.
Several major nerves and vessels also travel close to this area of the shoulder girdle and these can be involved in the mechanism of injury and must be greatly respected during any surgical approach. Other potential complications include:
- Loss of reduction of the clavicle (does not stay in proper position)
- Clavicle or coracoid fracture
- Painful scar
- Deltoid/Trapezius muscle detachment
Many patients with this injury also have other injuries (rotator cuff tear, labrum tear, unstable shoulder, etc.) requiring treatment at the same time, so a reliable arthroscopic approach offers many advantages for both the patient and surgeon. Our technique offers the following advantages:
- An arthroscopic technique potentially offers reduced morbidity, improved cosmesis, and the ability to address concurrent shoulder pathology.
- A single 4.5mm tunnel in the clavicle and coracoid instead of larger or multiple tunnels help reduce the risk of subsequent fracture.
- The continuous suture loops placed through the coracoid and clavicle provide uniform compression of the graft at the coracoid and clavicle. Rather than relieve load from the graft, they create a tension band construct to maintain graft tension and position.
- Placing the graft at the superior cortex of the coracoid more accurately reproduces the anatomic location of the native CC ligaments and avoids the possibility of anterior clavicle translation with passage of the graft around the clavicle.
- The risk of neurovascular injury to structures medial to the coracoid is reduced as no dissection medial to the coracoid is required.
- The placement of a single drill hole in the clavicle at 35mm medially allows the two limbs of the graft to reproduce the anatomic course and function of the Trapezoid and Conoid ligaments.
- The #7 Adjustable Loop Toggle Loc Device has an average peak load of 1664.1N, 374.1lbs with 0mm cyclic loading slippage under testing resulting in the highly desirable likelihood of failure of the graft rather than at the points of fixation.
The combination of high initial strength of fixation with gradual incorporation of the graft to recreate the native ligaments offers both early return to function and long term durability.
Suffering a major shoulder injury like a high grade shoulder separation is painful enough; don’t make it worse by not doing your homework and finding the best solutions available to allow you to return to your regular routine as soon as possible. In summary, we present a strong and reliable arthroscopic technique for anatomic reconstruction as an option for significantly symptomatic high grade acute and chronic shoulder separations as well as previously failed surgeries for shoulder separations.