Acromioclavicular Joint Separation

The acromionclavicular (AC) joint is a diathrodial joint with a fibrocartilaginous disk.  The disk has a great variation in size and shape and eventually undergoes rapid degeneration until it is essentially non-functional by the fourth decade of life. The acromioclavicular joint is stabilized by the acromioclavicular and coracoclavicular ligaments.  The acromioclavicular ligaments stabilize the joint in the anteroposterior direction. The coracoclavicular ligament is made up of the trapezoid and conoid ligaments. The coracoclavicular ligament is the prime suspensory ligament of the upper extremity. The deltoid and trapezius muscles are also important in supplying dynamic stability to the AC joint.

Injuries to the acromioclavicular joint generally occur from falls onto the shoulder and are more common in males age 20-30 years old. These injuries occur more frequently in football players, rugby players and hockey players. Injury causes pain over the AC joint and may lead to a deformity of the shoulder with the end of the clavicle being promient.

AC separations are classified and treated based on which ligaments are injured and the amount of elevation of the clavicle.

Type I AC Separation Type I: The AC and CC ligaments are strained but remain intact. The AC joint remains stable. Their may be tenderness and swelling isolated to the AC joint, but no palpable deformity of the AC joint and there is minimal pain when moving the arm. Type I AC separations are treated with a sling, ice and pain medications as needed. Patients may resume activities when they are painfree. Symptoms usually subside in 7-10 days.
Type II AC Separation Type II: The AC ligaments are disrupted, but the coracoclavicular ligaments remain intact. Patients have pain and swelling around the AC joint. The end of the clavicle may be elevated and arm motion causes pain. Type II injuries are treated with a sling for 7-10 days or until symptoms subside. Patients may begin an early gradual rehab program. Patients should avoid heavy lifting and contact sports for 8-12 wks.
Type III AC Separation Type III: The acromioclavicular and coracoclavicular ligaments are disrupted. Patients have pain in the AC joint and shoulder. The clavicle is generally visibly elevated and patients have pain with any shoulder ROM. The treatment of type III injuries remains controversial.  Non-operative management is generally recommended.  Surgery may be considered for young, athletic individuals, heavy laborers, and those who do overhead work with type III injuries. Surgical treatment involves reconstruction the injured AC and CC ligaments. The is done with a tendon graft. The risks of surgery include but are not limited to: Infection, Recurrent AC instability, Shoulder Pain, Shoulder stiffness, Clavicle fracture, Coracoid process fracture, Hardware failure, Incisional scar (cosmesis), CRPS, Numbness surrounding the incision, Risk of anesthesia including heart attack, stroke and death, DVT/PE. Althought complications can occur most patients are satisfied with their surgical outcomes.
Type IV AC Separation Type IV: Type IV injuries are rare. In these injuries the clavicle is posteriorly displaced into or through the trapezius muscles. The acromioclavicular and coracoclavicular ligaments are disrupted and the deltoid and trapezius muscle insertions are disrupted. These injuries are usually very painful, and cause significant pain with any movement of the shoulder. Type IV injuries are treated surgically. Surgical treatment involves reconstruction the injured AC and CC ligaments. The is done with a tendon graft. The risks of surgery include but are not limited to: Infection, Recurrent AC instability, Shoulder Pain, Shoulder stiffness, Clavicle fracture, Coracoid process fracture, Hardware failure, Incisional scar (cosmesis), CRPS, Numbness surrounding the incision, Risk of anesthesia including heart attack, stroke and death, DVT/PE. Althought complications can occur most patients are satisfied with their surgical outcomes.
Type V AC Separation Type V: The acromioclavicular and coracoclavicular ligaments are disrupted and the deltoid and trapezius muscle insertions are disrupted. IN type V injuries the end of the clavicle is greatly elevated. These injuries are usually very painful, and cause significant pain with any movement of the shoulder. Type V injuries are treated surgically. Surgical treatment involves reconstruction the injured AC and CC ligaments. The is done with a tendon graft. The risks of surgery include but are not limited to: Infection, Recurrent AC instability, Shoulder Pain, Shoulder stiffness, Clavicle fracture, Coracoid process fracture, Hardware failure, Incisional scar (cosmesis), CRPS, Numbness surrounding the incision, Risk of anesthesia including heart attack, stroke and death, DVT/PE. Althought complications can occur most patients are satisfied with their surgical outcomes.
Type VI AC Separation Type VI: The acromioclavicular and coracoclavicular ligaments are disrupted with inferior dislocation of the end of the clavicle under the coracoid process. These injuries are usually very painful, and cause significant pain with any movement of the shoulder. Type V injuries are treated surgically. Surgical treatment involves reconstruction the injured AC and CC ligaments. The is done with a tendon graft. The risks of surgery include but are not limited to: Infection, Recurrent AC instability, Shoulder Pain, Shoulder stiffness, Clavicle fracture, Coracoid process fracture, Hardware failure, Incisional scar (cosmesis), CRPS, Numbness surrounding the incision, Risk of anesthesia including heart attack, stroke and death, DVT/PE. Althought complications can occur most patients are satisfied with their surgical outcomes.

Further information about AC separations can be found at the following sites:

Every person and their particular circumstances are different so the treatment for your shoulder may be different than those discussed above. Please read this information carefully. Write down any questions that you have about your injury and its treatment and discuss them with your orthopaedic surgeon.

Synonyms: 
Acromioclavicular dislocation, acromioclavicular separation, AC dislocation

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