The clavicle is a small, S-shaped curved tubular bone that connects at one end to the sternum (the sternoclavicular joint) and the other end to the acromial process of the scapula (the acromioclavicular joint). Traditionally, three parts are distinguished in clavicle: the sternal end, the diaphysis (middle part) and the acromial end.
Dislocation of the acromial end of the clavicle is a fairly frequent injury. The main mechanism of injury is a fall on the shoulder. In this case, the ligaments connecting the clavicle and scapula are torn, and after that, the clavicle is displaced upward by the action of muscle traction.
A typical ACJ damage mechanism
Various tearing options are possible. For example, only the capsule of the acromioclavicular joint can burst – in this case, the dislocation will not occur or there will be a subluxation, since other ligaments will hold the collarbone. If other ligaments rupture will be occur (conical and trapezoid ligaments), it will be the dislocation of the clavicle in this case.
Incomplete (left) and complete (right) dislocation of the acromioclavicular joint
When the acromial end of the collarbone is dislocated, the function of the arm is impaired – most often it is impossible to raise the arm above the shoulder, pull the arm to the side.
Immediately after injury, pain in the shoulder girdle occurs. If the dislocation is complete, then collarbone sticks out, and, in some cases, it is possible to identify symptom of a «key» when you press on the collarbone, it sets in its place (falls), but if you stop the pressure, it will immediately dislocate again. The absence of «key» a symptom does not mean that everything is in order with the clavicle. Firstly, it is not always possible to simply check this symptom because in some patients pressing the collarbone causes severe pain. Secondly, swelling develops in several hours after the injury. Thirdly, in obese people, collarbone can generally be poorly defined.
An X-ray examination helps to establish the final diagnosis. In an X-ray, with dislocation of the acromial end of the clavicle, significant diastasis in the acromial-clavicular joint is determined due to the displacement of the distal end of the clavicle up. In particularly dubious situations, often present with incomplete dislocation of the acromial end of clavicle and insufficiently expressed clinical symptoms, an X-ray of the healthy acromioclavicular joint is produced for comparison. Pictures are taken on a single film in standing position of the patient. In doubtful cases, functional radiography is sometimes performed – a load is taken in the hand, which pulls it down and dislocation becomes more obvious.
X-ray of a patient with ACJ dislocation
In the first days after the injury, cold is applied, which reduces swelling and pain. The hand is in a special bandage. With severe pain, pain medications are taken.
Optimal treatment depends on the type of dislocation. Conservative treatment is indicated for incomplete dislocation (subluxation) of the clavicle. In this case, a patient is recommended to wear a special dressing for 3-5 weeks. Next, control X-ray is performed and the decision is made on the need in rehabilitation: to remove the bandage and begin physical exercises.
Fixative dressing for the treatment of ACJ dislocation
Surgical treatment is indicated for complete dislocation of clavicle when its acromial end has completely shifted up.
A fairly large number of options for operations were proposed. The most modern methods today are considered fixation with two metal buttons and a very strong thread (the so-called MINAR technique) and synthesis with a hook-shaped plate.
ACJ fixation with buttons (left) and hook-shaped plate on the right
For chronic and repeated dislocations, other operations are performed (resection of the acromial end of the clavicle, plastic surgery of clavicular ligamentous apparatus using other ligaments, etc.).
After the operation, the hand is immobilised with a scarf dressing for some time (in different operations and indifferent reliability of fixation, this time varies), after which rehabilitation begins.