Acromioclavicular (A-C) Joint Reconstruction

Alan M Reznik, MD, MBA
© 2008 AMR

A fall directly on the shoulder can cause the joint to “separate.” “Separation” of the shoulder (as opposed to shoulder dislocations) is the common term used for a sprain of the AC Joint. They range from minor or grade 1 separations that can be treated with rest, ice and an anti-inflammatory to complete displacements with the bone buttonholed through the trapezius muscle, irreducible, and tenting the skin, grade 4, 5 and 6.

Shoulder separations occur frequently in sports particularly football. The main cause of A-C joint dislocation is a fall on the point of the shoulder, a tackle or a fall onto an outstretched hand. Fall from a height, and other high energy injuries, are also major causes of AC joint separations. They also can occur skiing, slipping on ice, at work (a fall off a ladder or unprotected height), and in motor vehicle accidents.

Shoulder separations are a different injury than shoulder dislocations and they involve the small joint that connects the collar bone to the small bone above the ball and socket of the shoulder the acromion (see Figures 1 and 2). The joint can be felt as a prominent bump or ridge on the top of your shoulder. The joint is held together by strong ligaments called the coracoclavicular ligaments and the AC joint capsule.  In higher energy injuries, the AC joint can dislocate just like ball and socket of shoulder. In the more serve types all of the ligaments holding the collar bone in place are torn.

Diagnosis is made by history and examination. The ligament loss allows muscles attached to the clavicle to pull it away from the shoulder.  The injury causes pain and difficulty moving the arm, and depending upon the severity, may produce a very prominent bump on the top of the shoulder. An x ray will confirm the separation.

Figure 2 A-C Joint Separation: Note that the collar bone is significantly higher than the acromion, making this a more severe separation. In this case, the bone tip is tenting the skin.

In simple dislocations there is only a sprain and the clavicle does not move too much out of place.  Treatment may consist of rest, immobilization with a sling, ice and use of an anti-inflammatory medication.  Certain exercises done under the supervision of a physical therapist may also be useful. 

If the ligaments holding it in position are completely ruptured, then the clavicle moves upwards and backwards (see above figure 2).  Patients may complain of popping, catching or pain with overhead activities.  The deformity may be very visible and disconcerting. The deformity itself is not the true indication for surgical repair. There are several clear indications for repair. They include:

1. Significant tenting or the skin: in these cases the muscle may be trapped below the bone and the bone edge is directly under the skin or the bone may be “button holed’ or stuck in the muscle casing pain with motion.
2. There are nerve symptoms, shooting pains or numbness, in the hand or arm with any motion.
3. There is significant loss of use of the dominant arm or in many cases the non-dominant arm.

If there is a significant deformity and or symptoms with activities of daily living, surgery may be required to bring the clavicle back into its normal position. The goal is to restore stability and function to the shoulder. Surgery is not indicated for small separations, minimal deformity or for only cosmetic reasons. 

Healed Incision for the repair	Full elevation at eight weeks post op.

X-ray showing reduced AC Joint and bone tunnels.

The vast majority of the time the surgery is very successful. Remember, there is always a small risk of complications including, but not limited to, infection or failure of the repair. Having AC joint ligament reconstruction surgery in cases with minor or weak indications is not worth even the limited risks of surgery and discouraged. In some of those minor cases, a less risky approach, like an arthroscopic Mumford procedure -- resection of the prominent tip of the distal collar bone -- or even no surgery at all may, be a better choice.

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