An acromioclavicular joint separation, or AC separation, is a very frequent injury among physically active people. In this injury the clavicle (collar bone) separates from the scapula (shoulder blade). It is commonly caused by a fall directly on the "point" of the shoulder or a direct blow received in a contact sport. Football players and cyclists who fall over the handlebars are often subject to AC separations.
In general, most AC injuries don't require surgery. There are certain situations, however, in which surgery may be necessary. Most patients recover with full function of the shoulder. The period of disability and discomfort ranges from a few days to 12 weeks depending on the severity of the separation. Disruption of the AC joint results in pain and instability in the entire shoulder and arm. The pain is most severe when the patient attempts overhead movements or tries to sleep on the affected side.
What does the inside of the shoulder look like?
The shoulder is the most mobile joint in the human body, with a complex arrangement of structures working together to provide the movement necessary for daily life. Unfortunately, this great mobility comes at the expense of stability. Several bones and a network of soft tissue structures (ligaments, tendons, and muscles), work together to produce shoulder movement. They interact to keep the joint in place while it moves through extreme ranges of motion. Each of these structures makes an important contribution to shoulder movement and stability. Certain work or sports activities can put great demands upon the shoulder, and injury can occur when the limits of movement are exceeded and/or the individual structures are overloaded.Click here to read more about shoulder structure. What is an AC joint separation? An AC joint separation, often called a shoulder separation, is a dislocation of the clavicle from the acromion. This injury is usually caused by a blow to the shoulder, or a fall in which the individual lands directly on the shoulder or an outstretched arm. AC joint separations are most common in contact sports, such as football and hockey.
The severity of an acromioclavicular joint injury depends on which supporting structures are damaged, and the extent of that damage. Tearing of the acromioclavicular ligament alone is not a serious injury, but when the coracoclavicular ligaments are ruptured, the whole shoulder unit is involved, thus complicating the dislocation.
Simple AC injuries are classified in three grades ranging from a mild dislocation to a complete separation:
|rade I - A slight displacement of the joint. The acromioclavicular ligament may be stretched or partially torn. This is the most common type of injury to the AC joint.|
|Grade II - A partial dislocation of the joint in which there may be some displacement that may not be obvious during a physical examination. The acromioclavicular ligament is completely torn, while the coracoclavicular ligaments remain intact.|
|Grade III - A complete separation of the joint. The acromioclavicular ligament, the coracoclavicular ligaments, and the capsule surrounding the joint are torn. Usually, the displacement is obvious on clinical exam. Without any ligament support, the shoulder falls under the weight of the arm and the clavicle is pushed up, causing a bump on the shoulder.|
There are a total of six grades of severity of AC separations. Grades I-III are the most common. Grades IV-VI are very uncommon and are usually the result of a very high-energy injury such as one that might occur in a motor vehicle accident. Grades IV-VI are all treated surgically because of the severe disruption of all the ligamentous support for the arm and shoulder.
What are the signs and symptoms of an AC joint separation?
|Grade I Injury:
|Grade II Injury:
|Grade III Injury:
After evaluating the history of the patient's injury the doctor will examine the shoulder area looking for signs of fracture or dislocation by comparing the overall position of the arm and shoulder to the uninjured side. The AC joint itself is easily examined because it is located right under the skin. The doctor will gently feel the bones and soft tissue around the joint and between the acromion and clavicle. There may be a bump, tenderness or instability, which would suggest a joint separation. Crepitus (noise) as the bones move may indicate a fracture. The doctor also evaluates the patient's range of motion and performs tests to isolate specific areas of pain and weakness.
Further evaluation may include:
The treatment of an AC separation depends on the grade of the injury. The classification helps the physician choose the correct treatment approach. Grades I - III are usually treated non-operatively. The vast majority of patients will have a period of discomfort. Once this discomfort disappears, the shoulder is usually fully functional, although the patient may still have a minor cosmetic defect at the injury site.
Some patients with grade III AC separations may be candidates for early surgical reconstruction. A discussion between the physician and patient should focus on the patient's expectations and possible return to sports. Many surgeons prefer to first treat the AC separation conservatively. If grade III patients develop problems or do not heal properly surgical reconstruction is an option. (Conservative and surgical treatment for grades I - III have essentially the same results after 1 year.)
Most Grade I - III AC separations are treated successfully with non-operative treatment that may include:
ice to reduce pain and swelling.
rest and a protective sling until pain subsides. This usually takes about 1-2 weeks.
pain and anti-inflammatory medications.
A rehabilitation program to restore normal motion and strength is begun as soon as tolerated with gentle exercises and progresses as healing allows.
Depending on the grade of injury, most patients heal within 2 to 3 months without surgical intervention. The patient is allowed to return to sports when there is full and painless range of motion, no more tenderness when the AC joint is touched, and manual traction does not cause pain. This usually takes about 2 weeks for a grade I injury, 6 weeks for a grade II injury, and up to 12 weeks for a grade III injury.
Surgery may be necessary for AC separations that do not respond well to non-operative treatment. If, after 2 to 3 months, pain continues in the AC joint with overhead activity or in contact sports, surgery may be necessary. There are some physicians who offer early surgery for a select group of Grade III AC separations based upon the activities and demands these patients place upon the shoulder.
These patients include:
In a distal clavicle resection, about 10-15mm of the clavicle is removed through a two-inch incision above the joint. The AC ligament is then transferred from the bottom of the acromion into the cut end of the clavicle to replace the torn ligament.What types of complications may occur?
Complications of AC joint injuries are persistent instability of the shoulder girdle or residual pain with activity. These complications can be present with either non-operative treatment or operative treatment. Failure of the acromioclavicular ligament and coracoclavicular ligaments to heal can lead to pain and a sense of instability with overhead activity. If the end of the clavicle remains unstable because of lack of scarring, contact sports or overhead tasks may be painful.
Other complications associated with the reconstruction of the AC or CC ligaments are related to hardware failure. Fixation of the clavicle to the coracoid process is difficult because of the rotation of the clavicle with all overhead activity. The screws used to fix these two bones together can pull out if the patient does not wear a sling after surgery as instructed.
Most surgeons today will securely fix the clavicle to the coracoid with dissolvable sutures or with a screw that is removed at about three months.
Patients with lower energy AC joint injuries that respond to conservative non-operative treatment can recover in as little as one week for a Grade I injury to an average of twelve weeks for a Grade III injury.
Specific recovery programs following surgical reconstruction of the AC joint vary depending on the type of surgery performed. General care recommendations include:
Do all AC separations require surgery?
No. In fact the vast majority of AC separations do very well with conservative treatment of the symptoms. Most AC injuries are grade I, II, or III and these generally do not require surgery. Usually the joint remains sore for two to six weeks and then full return to activity is the norm. Only unstable grade III injuries and high-energy AC separations, which are often the result of motor vehicle accidents, require surgery for full recovery.
Will the "bump" ever go away?
The clavicle will become stable in its newly elevated position, but without surgery the "bump" will remain. The joint will function normally and will not remain tender to touch or movement. This minor cosmetic deformity will persist but will not interfere with overhead activities or participation in sports.
Are there downsides to a resection of the AC joint?
An AC resection is a procedure in which the end of the clavicle is removed and the acromioclavicular ligament in reattached into the end of the clavicle to replace the ligament torn during injury. Once the initial injury has healed and the clavicle has regained stability from scar tissue there is no functional loss with an AC resection. In the rare instance that the AC joint remains painful after a separation, but does not require stabilization, an AC resection is very effective in relieving pain without sacrificing function. If, however, the clavicle is unstable at the time of resection, a full reconstruction of the coracoclavicular ligaments is necessary to maintain the stability of the upper extremity. Will I be able to return to athletics if an AC injury is not treated? Absolutely. Most athletes in contact sports have had a low energy AC separation at some time in their careers. Except for the slight deformity that remains, there is no clinical significance to a healed AC separation. Occasionally high-energy AC separations that have disruption of the AC and CC ligaments will require surgery, but these injuries are usually apparent early on with a correct X-ray evaluation. Grade I, II, and most grade III AC separations will heal without treatment and a full return to sports can be expected.
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