Acromioclavicular dislocation is a dislocation of the lateral end of the clavicle towards the acromion with injury to the stabilizing capsule/ligament apparatus of the acromioclavicular joint.
The most frequent cause of a dislocation of the acromioclavicular joint/acromioclavicular joint dislocation is a fall on the shoulder with direct force application on the acromioclavicular joint. More rare is the indirect injury caused by a fall on the outstretched arm. This often results in a collarbone fracture.
A frequent cause of accidents is falling from a bicycle, horse, or while skiing.
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Symptoms of acromioclavicular dislocation
An acromioclavicular dislocation manifests itself mainly in three symptoms:
- Pain directly above the shoulder joint
- Swelling of the shoulder area
- Gentle posture
Typically, an acromioclavicular joint dislocation manifests itself with immediate, shooting pain. The affected person often adopts a relieving posture, as any kind of movement of the shoulder or arm increases the pain, such as:
- Overhead movements
- Lateral lifting of the arm
- Arm lift against resistance.
For example, turning the arm inwards prevents pain and movement. As a rule, the arm is angled as a gentle position, held in front of the body, and supported with a healthy arm. The relieving posture immobilizes the acromioclavicular joint (which is also what one would like to achieve, for example, during therapy with a backpack bandage), which leads to a significant reduction in pain. As an immediate measure, the arm can be stabilized with a bandage or sling in front of the abdomen.
The consequence of an acromioclavicular dislocation is often a rupture of the capsule in the shoulder area.
If the acromioclavicular joint dislocation occurs during sport, the pain usually forces the person affected to stop the sporting activity. Exerting pressure on the shoulder region also causes additional pain, so lying on the injured shoulder can be extremely uncomfortable. When the acromioclavicular joint is dislocated, the arm can be moved relatively well passively, which means that another person (e.g., the examining doctor) can perform movements with the injured arm and shoulder without the active assistance of the person affected. This excellent passive mobility in an acromioclavicular dislocation is an important distinction from a dislocation of the shoulder (dislocation); passive mobility would also be limited. Active mobility and the movement possibilities of the affected shoulder or arm are usually considerably restricted and can only be performed with great pain. Under certain circumstances, a partial or complete instability of the shoulder can be determined by the acromioclavicular joint dislocation.
Shortly after the injury, there is usually a swelling that extends to parts of the shoulder and upper arm. Sometimes a bruise (hematoma) also forms. Cooling with ice can prevent a more severe tissue swelling and, thus, even greater pain.
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Depending on the severity of the injury, not only the symptoms of pain, swelling, and relieving posture occurs. In some cases, the clavicle can shift in position due to the acromioclavicular joint dislocation, which can be explained by a tear in the affected ligaments of the acromioclavicular joint. The outer end of the clavicle may protrude upwards and form a bulge under the skin. However, it is only apparently a raised position of the clavicle; actually, a low position of the arm or shoulder joint due to the weight of the arm and gravity is the reason for the protrusion of the clavicle. If all ligament structures are completely torn apart, the full picture of a shoulder joint disruption is given.
On physical examination, the “piano key phenomenon” is evidence (pathognomonic) for the presence of a complete acromioclavicular dislocation, since the displaced clavicle can be pressed down with the finger-like a piano key. Still, when the pressure is released, it immediately springs back up again. Sometimes it can be heard that the bones rub against each other (crepitation). This usually painful symptom can be masked by shoulder swelling when the collarbone is slightly elevated. The extent of the piano touch phenomenon is an indirect indication of the severity of the ligament injury in the case of a shoulder joint dislocation.
The diagnosis of an acromioclavicular joint dislocation can often already be suspected due to the very typical symptoms. The swelling in the shoulder area, relieving posture, and a localized pain under pressure over the shoulder joint are indications of an acromioclavicular joint dislocation. As a rule, movements between the upper arm and the shoulder blade do not cause pain when the shoulder blade is stabilized. To confirm the diagnosis, an X-ray examination of the shoulder joint is necessary in addition to the typical symptoms.
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When the acromioclavicular joint is disrupted, the various ligament structures around the joint and the collarbone often tear as a result of a fall on the shoulder.
Depending on how many ligaments are injured and what type of injury is involved, the pain can also vary in intensity. Especially in the area of the acromioclavicular joint at the outer end of the collarbone, severe pain occurs, which can then radiate into the arm. Often the pain is already so severe that the patient is no longer able to move the shoulder or arm. Often, even the mere hanging off the arm hurts very much, which is why patients usually support the shoulder on the other hand.
Also, swelling can occur around the shoulder area, and the shoulder is very sensitive to pressure.
Another typical symptom of a complete acromioclavicular joint dislocation grade III, according to Tossy, is the so-called piano key phenomenon. Due to the rupture of the ligaments, the collarbone protrudes so far down that it can be pressed down like a piano key and rises again. To relieve the pain, the patient can take medication such as ibuprofen or paracetamol.
Diagnosis of acromioclavicular dislocation
After taking the patient’s medical history and physical examination, an x-ray is regularly taken when the acromioclavicular joint is disrupted. In the event of a fall on the shoulder, the shoulder is x-rayed in two planes (from the front (a.p.) and laterally), and additionally, if there is a corresponding suspicion of a fall on the shoulder, a target image of the acromioclavicular joint is taken.
To further intensify the piano touch phenomenon, the X-ray target image can be taken under load and in lateral comparison. For this purpose, a weight (20 lb) is slung around the patient’s wrists, whereby the acromion is pulled further towards the foot, and a possibly unrecognized piano touch phenomenon is displayed.
Sonography (ultrasound) can also be used to diagnose an acromioclavicular dislocation. In the case of ligament injuries, bleeding in the joint area can be detected (low-echo area), and the 3-4 mm joint space can be enlarged in the frontal plane.
An advantage of sonography is also that the shoulder tendons (rotator cuff) can be examined simultaneously for an injury. Older patients, in particular, are more frequently affected by an injury to the rotator cuff.
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The classification, according to Tossy, is a graduation of the acromioclavicular joint dislocation. It includes different degrees according to which the severity of the injury is assessed. Besides, this classification is also used to determine the indication for surgery. It depends on the number of injured structures.
In Tossy I, a strain or partial rupture of the capsule and ligament is located in the acromioclavicular part of the shoulder. The other ligaments of the clavicle are not injured, and the clavicle is not higher. There is a widening of the joint space of the acromioclavicular joint.
Tossy II is a complete rupture of the capsule and the ligament between acromion and clavicle. Even more, the ligaments of the clavicle are torn. This shows a slight elevation of the collarbone in the outer area.
Finally, in Tossy III, all the ligaments at the acromioclavicular joint and the clavicle are torn, resulting in a visible elevation of the clavicle according to the piano key phenomenon. In the x-ray image, a clear widening of the joint space becomes visible.
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In most cases, grade Tossy II and III injuries are treated surgically to avoid the following damages in particular, such as chronic instability of the joint and also the ligaments.
The operation is performed endoscopically, which is why only small skin incisions are usually necessary to insert the instruments. The patient is given a general anesthetic. There are various techniques to choose from.
In many patients, the ligaments are sutured together again and also additionally stabilized by a tendon (augmentation) from the leg (gracilis tendon). The joint capsule is also reconstructed. The duration of the procedure is often around 60 minutes, and the patient can usually leave the hospital on the first or second postoperative day, depending on the patient’s condition.
To guarantee good healing of the joint, the entire shoulder is subsequently stiffened with an orthosis. This is worn both during the day and at night so that the sutured ligaments can heal well and also become stable.
Over the next three months, the movement is then rebuilt and increased through targeted physiotherapy, whereby the shoulder must not yet be subjected to heavy loads. Light jogging is allowed after about six weeks.
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Healing of the acromioclavicular joint dislocation
An acromioclavicular joint dislocation is usually a benign injury. In the vast majority of those affected, no discomfort or pain is left behind in everyday life or during sports. How much time an acromioclavicular joint replacement takes to heal depends on the degree of injury. Without surgery, healing usually takes between 2-12 weeks until the injured ligament structures are restored.
The more extensive the damage to the acromioclavicular joint is, the sooner an operation must be performed to straighten the acromioclavicular joint. This can significantly increase the healing time. Wires or plates that are inserted into the joint during the surgery for stabilization can be removed after 6-10 weeks. This is followed by a physiotherapeutic follow-up treatment to achieve complete healing. In most cases, the shoulder is fully resilient again about 12 weeks after the acromioclavicular joint is dislocated.
The healing process can be improved by conservative treatment methods such as
- Immobilization of the joint through various bandaging techniques
- Physiotherapy in the form of lymph drainage
- Manual therapy
be promoted. Physiotherapeutic therapy strengthens the muscles surrounding the shoulder joint and improves the ability to bear weight. After consultation with the treating doctor or physiotherapist (shoulder-friendly), sports activities can be resumed as soon as the pain subsides in the event of a slight acromioclavicular dislocation, often after 1-2 weeks. In the case of moderately severe acromioclavicular dislocations, no sports should be taken for 5-6 weeks to allow the partially injured ligaments to heal. Types of sport in which the shoulder is strained or in which the hands are raised above the head (e.g., volleyball) can only be performed again after about three months. Strong pulling and pushing forces on the shoulder should be avoided if possible to prevent setbacks in the healing process.
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