AC Joint Stabilization

The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle. It is a plane synovial joint.

A common injury to the AC joint is dislocation, often called AC separation or shoulder separation. This is not the same as a “shoulder dislocation,” which refers to dislocation of the glenohumeral joint.

Acromioclavicular joint dislocation is particularly common in collision sports such as ice hockey, football, Judo, rugby and aussie rules, and is also a problem for those who participate in swimming, horseback riding, mountain biking, biking, snow skiing and skateboarding. The most common mechanism of injury is a fall on the tip of the shoulder or FOOSH (falls on outstretched hand).

Acromioclavicular joint dislocations are graded from I to VI.

Grading is based upon the degree of separation of the acromion from the clavicle with weight applied to the arm.

  • Grade I is slight displacement of the joint, and a badly stretched or partially torn AC ligament.
  • Grade II is a partial dislocation of the AC joint with a complete disruption tear of the AC joint and a partial disruption of coracoclavicular ligament.  Grades I and II seldom require surgery and heal by themselves, though physical therapy may be required.
  • Grade III is complete disruption of AC and CC ligaments.  The joint will be very tender and swollen on examination. Grade III separations most often do not require surgery and shoulder function should return to normal after 6–12 weeks. However, there will be some physical deformity of the shoulder with a noticeable bump resulting from the dislocation of the clavicle.
  • Grades V-VI are complications on a ‘standard’ dislocation involving a displacement of the clavicle, and will almost always require surgery.

Few issues in orthopaedic surgery are more contentious than the continuing debate concerning operative or conservative treatment for a dislocated acromioclavicular joint. Both schools of thought can put forward excellent results to support their case.

Not all conservatively treated acromioclavicular dislocations do well.   Because the results of conservative treatment are in general so good, it seems only reasonable to treat the majority of patients conservatively. Unfortunately, there are no reliable means of determining which patients will not do well, and hence surgery must always play a part.

Procedures

Arthroscopic AC Joint Reconstruction

Arthroscopically assisted acromioclavicular joint reconstruction avoids the large incisions necessary with open shoulder procedures reconstructions. This acromioclavicular joint reconstruction technique via the subacromial space does not violate the rotator cuff space. During the procedure, your surgeon will place the arthroscope into the subacromial space, and a bursectomy is performed through a lateral subacromial portal.

The coracoacromial ligament is released from the acromion with an electrocautery and an arthroscopic elevator. A nonabsorbable suture is passed through the coracoacromial ligament with a suture passer, and an arthroscopic suture grasper is used to deliver both ends of the suture out through the lateral portal. The coracoid is identified and isolated using a radiofrequency ablator placed through the anterior portal while visualizing through the lateral portal. A semitendinosus allograft is used to reconstruct the coracoclavicular ligament. A nonabsorbable suture is passed through both ends of the allograft. Three strands of nonabsorbable suture are braided together. The tendon and the braided suture are shuttled around the coracoid. The ends of the braided suture and the tendon sutures are grasped by the clamp and pulled out the acromioclavicular joint incision.  The acromioclavicular joint is reduced by pushing down on the distal clavicle with a bone tamp while simultaneously lifting the acromion upward by superiorly loading the humerus at the elbow. Once the acromioclavicular joint is reduced or slightly over-reduced, the braided suture is tied down securely.  The incision is closed in standard fashion, and a sling is applied.

In acute dislocation, the aim is to restore completely normal functioning anatomy. All the ruptured structures are repaired, and the joint is temporarily stabilized either by transarticular pin or a coracoacromial screw.

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