Acromioclavicular Separation
Acromioclavicular Anatomy video Animated description of the anatomy of the acromioclavicular and coracoacromial ligaments.
Acromioclavicular Separation video Animated description of the different types of shoulder separation. Acromioclavicular Separation Surgery video 3D animation demonstrating an operation commonly used to treat acromioclavicular separation. Evaluating Acromioclavicular Injuries video 3D animation describing the evaluation of a separated shoulder. Acromioclavicular Injuries picture album Several pictures illustrating the anatomy, diagnosis, and treatment of AC separations. AC Separation Classification animated gif Animated gifs demonstrating Types I-VI acromioclavicular separations.
A separated shoulder is a sprain of the acromioclavicular joint.  This is where the scapula, the shoulder blade, meets the clavicle, the collar bone.  The bony process where the clavicle meets the scapula is called the acromion.  Ligaments hold the acromion to the clavicle and stabilize the joint.  A blow to the point of the shoulder can stretch and tear the ligaments that stabilize the AC joint.  A stretched or torn ligament is known as a sprain.  The sprain can be mild or severe depending on how badly the clavicle was separated from the acromion. Treatment depends on the severity.  Most shoulder separations are treated without surgery.  The arm is placed into a sling to put the shoulder at rest and allow the ligaments at the AC joint to heal.  Sometimes the end of the clavicle remains prominent, leaving a permanent but small deformity. More severe AC separations are treated surgically.  An incision is made over the AC joint and the clavicle is pushed back into position.  Sutures or a plate and screws are used to hold the clavicle in place. A separated shoulder is not the same as a dislocated shoulder.  A shoulder dislocation is when the humeral head (the ball in the shoulder joint) dislocates from the glenoid (the socket). The acromioclavicular joint, or AC joint, is where the scapula, or shoulder blade, meets the clavicle, or collar bone.  It is located at the point of the shoulder.  The bony process extending from the scapula where it meets the clavicle is known as the acromion.  Another bony process, located below the clavicle, is called the coracoid.  Both of these processes provide places for ligaments to attach.  Ligaments are strong, fibrous bands that attach bones together.  The ligaments involved in the acromioclavicular joint help to hold the acromion and the end of the clavicle in place.  They are named for the bone landmarks that they attach to.  The acromioclavicular ligament attaches the acromion to the clavicle.  It can be further divided into two separate ligaments, the superior acromioclavicular ligament on top, and the inferior acromioclavicular ligament on the bottom.  The coracoacromial ligament attaches the coracoid to the acromion.  The coracoclavicular ligaments attach the coracoid to the clavicle.  They are known as the trapezoid ligament, in the front, and the conoid ligament, in the back.  The ends of the acromion and clavicle are capped with smooth, hyaline cartilage.  The joint is surrounded by a capsule and filled with synovial fluid.  An intraarticular disc, sometimes called the meniscus of the AC joint, extends from the joint capsule between the acromion and clavicle.  The acromioclavicular joint allows for a gliding motion during shoulder movement.   Diagnosis and Treatment of Acromioclavicular Separation History:  Acromioclavicular injuries result from a blow to the point of the shoulder.  This is especially common among young, active people who sustain sports injuries such as a fall onto the shoulder.  The injury results in immediate pain.  While the entire shoulder may hurt, pain eventually localizes to the acromioclavicular joint.  Some people seek care after noticing a deformity. Physical examination:  The shoulder is tender at the acromioclavicular joint.  There is frequently a deformity at the AC joint caused by the prominent end of the clavicle where it has separated from the acromion.  Allowing the arm to hang freely puts tension on the damaged ligaments and causes pain.  The person often holds the arm against the body for support because taking tension off the AC joint is more comfortable.  Shoulder adduction (reaching across the body to the other shoulder) is especially painful. Imaging:  If an AC separation is suspected, x-rays of the shoulder should be obtained.  In type I injuries, the x-rays may appear normal.  In type II and more severe injuries, the end of the clavicle is displaced in relation to the acromion.  The position of the clavicle and the amount of separation are used to grade the severity of the injury.  Sometimes a stress view is helpful.  The x-ray is taken while the injured person holds a weight to accentuate the separation.  Stress views may be helpful to evaluate type III injuries if surgery is being considered or if an AC separation is suspected but not visible on the initial x-rays.  But they are not obtained routinely because they put extra tension across the injured joint and cause unnecessary discomfort. Type I:  Type I AC injuries occur when the acromioclavicular ligament is stretched and partially torn, but not completely disrupted.  The acromioclavicular joint remains stable.  The arm is placed in a sling to put the shoulder at rest.  Ice is applied to the AC joint as needed.  Over the next 1-2 weeks shoulder range-of-motion can be advanced as tolerated and sports can be resumed. Type II:  Type II AC injuries occur when the acromioclavicular ligament is completely torn.  This allows more movement at the AC joint and the elevation of the clavicle is more evident on x-rays.  The arm is placed in a sling or shoulder immobilizer for 2-4 weeks.  Range-of-motion exercises can begin at that time, but strenuous shoulder activity is avoided for 6-12 weeks. Type III:  Type III AC injuries occur when the acromioclavicular ligament and coracoclavicular ligaments are completely torn.  This results in more instability.  The clavicle is 100% displaced from the acromion.  Treatment is usually nonoperative, but surgery may be considered for athletes, heavy lifters, and those who would prefer a scar over the AC joint as opposed to a deformity. Type IV:  Type IV AC injuries occur when the ligaments that stabilize the acromioclavicular joint are completely torn and the clavicle is pushed backwards into the trapezius muscle.  This injury requires surgical repair. Type V:  Type V AC injuries occur when the ligaments that stabilize the acromioclavicular joint are completely torn and the deltoid and trapezius muscles are torn away from the clavicle.  The scapula droops downward, preventing the shoulder from healing.  This injury requires surgical repair. Type VI:  Type VI AC injuries occur when the ligaments and muscles that stabilize the acromioclavicular joint are torn and the clavicle is dislocated and lodged underneath the coracoid.  This injury requires surgical repair. Acromioclavicular Separation Surgery While type I and II acromioclavicular separations are treated non-operatively, some type III injuries are treated with surgery.  Type IV, V, and VI shoulder separations are also treated surgically.  The surgical procedure is known as open reduction - internal fixation.  The patient is placed under anesthesia.  An incision is made near the acromioclavicular joint at the top of the shoulder.  The deltoid and trapezius muscles are dissected out of the way.  The end of the clavicle often needs to be excised because of damage to the joint and the articular cartilage.  The clavicle is then reduced, or pushed back into place.  Several methods have been developed to hold the clavicle in place.  Most of these methods involve using grafts, sutures, anchors, or hardware to fix the clavicle to the coracoid.  Small tunnels are made through the clavicle and the coracoid.  The graft or suture is passed through the tunnels and fixed in place.  The incision is closed and the arm is placed in a sling. Rehabilitation following acromioclavicular joint repair surgery takes about 4 to 5 months and is usually done with the help of a physical therapist.  Many orthopedic surgeons have strict protocols that should be followed to prevent failure of the repair and to improve outcomes.  No matter how well the surgery went, the outcome will not be good without proper postoperative rehabilitation. For the first six weeks following surgery, emphasis is placed on protecting the newly repaired joint.  The shoulder is placed into a sling and care is taken to avoid letting the arm hang without support.  This places too much stress on the repaired joint.  Gentle range-of-motion exercises are begun during this phase as directed by the surgeon. After six weeks, the joint has healed long enough to be more stable.  More aggressive stretching begins.  Early, light strengthening exercises can begin too slow down muscle atrophy as directed by the surgeon.  After 10-12 weeks, range-of-motion should approach normal.  By now the AC joint is sturdy enough to begin more aggressive strengthening exercises.