Acromioclavicular joint dislocation: Description
The acromioclavicular (AC) joint, along with the sternoclavicular (sternoclavicular) joint, connects the trunk and arms. It is important for the position of the shoulder blade while moving the arm. If one rests on the arm, the force is transmitted to the trunk through the acromioclavicular joint. The acromioclavicular joint is supported vertically by the coracoclavicular ligaments (ligamentum coracoclaviculare) and horizontally by the capsular strengthening ligaments (e.g., ligamentum acromioclaviculare). In acromioclavicular joint dislocation, these stabilizing ligaments are injured, sometimes completely torn off.
Tossy classification
Depending on the severity of the force involved, a distinction is made between three degrees of severity in acromioclavicular joint dislocation according to Tossy (old classification):
- Tossy classification I: The capsule is overstretched without displacement of the clavicle.
- Tossy classification II: The joint capsule is torn together with the acromioclavicular ligaments.
- Tossy classification III: The acromioclavicular ligaments are completely torn, and the clavicle is displaced by more than one shaft width.
Rockwood classification
Furthermore, in acromioclavicular joint disruption, there is the Rockwood classification (new classification), which distinguishes six types:
- Type II: The joint capsule and the coracoclavicular ligaments are torn. On an x-ray stress radiograph, the clavicle is elevated relative to the acromion.
- Type III: In this acromioclavicular joint dislocation, all ligaments are torn. The clavicle has stepped one shaft width higher than the acromion.
- Type IV: This type of injury is when the clavicle is unstable in the horizontal plane in addition to Type III because the fascia (deltoid fascia) is partially torn. The attachment of the deltoid muscle to the clavicle is torn, and the clavicle is displaced posteriorly.
- Type V: The fascia (deltoid trapezoid fascia) and all ligaments are completely torn, while the lateral end of the clavicle is massively upward.
- Type VI: The lateral clavicle is hooked under the process of the scapula (coracoid process) (very rare injury).
Acromioclavicular joint dislocation: symptoms.
A acromioclavicular joint dislocation is typically accompanied by significant tenderness and swelling. In addition, a bruise (hematoma) is often seen. The affected person can no longer move the shoulder joint completely. In most cases, the lateral end of the clavicle protrudes upwards, creating a protrusion above the acromioclavicular joint. Patients therefore often adopt a protective posture.
Acromioclavicular joint dislocation: Causes and risk factors
The acromioclavicular joint dislocation is usually a sports injury: it is mainly caused by a fall on the shoulder when the arm is extended to the side, which causes a leverage effect on the shoulder girdle. This can happen during soccer or skiing, for example.
Acromioclavicular joint dislocation: Examinations and diagnosis
If you suspect an acromioclavicular joint dislocation, you should see a doctor of orthopedics and trauma surgery. He or she will first ask you in detail about the accident and your medical history (anamnesis). Possible questions are:
- What exactly happened in the accident?
- Did you fall on your arm or shoulder?
- Can you still move the shoulder or arm?
- Do you have any pain?
- Was there any previous discomfort in the area of injury such as pain, limited motion, or a previous dislocation?
This is followed by a physical examination. Sometimes the clavicle shifts upward in a acromioclavicular joint dislocation, which is then already visible to the naked eye. If the physician presses on the higher end of the clavicle (which is very painful for the patient) and it springs back up when released (piano key phenomenon), this indicates a Tossy III injury.
For further diagnosis, X-rays are taken – a panoramic image in which both shoulder joints are taken with a weight of 10 to 15 kilograms on the arm hanging down. A side-by-side comparison can then be made to determine whether the outer end of the clavicle is dislocated.
Acromioclavicular joint dislocation: Treatment
A mild acromioclavicular joint dislocation can be treated conservatively. This involves functional exercise of the shoulder in the case of Tossy I. In the case of Tossy II and Rockwood I to II, the shoulder is first immobilized in a so-called Gilchrist bandage for about two weeks. During this time, the patient receives pain medication. In addition, the shoulder area can be treated with cold (cryotherapy). Subsequent physiotherapy can have a positive effect on healing. However, the shoulder should only be moved to the horizontal plane for four to six weeks.
Acromioclavicular joint dislocation: Surgery
Acromioclavicular joint dislocation: Course of the disease and prognosis
After conservative treatment, the prognosis is good for a Rockwood type I to II. However, in the Rockwood type II injury, painful osteoarthritis can develop due to an incompletely dislocated acromioclavicular joint. This can also occur with the type III injury, as the acromioclavicular joint can partially dislocate over time as the scars have shrunk. Sometimes this must be corrected surgically.
Generally, there is rarely pain with movement or weight bearing on the shoulder after a acromioclavicular joint dislocation. Immediately after the accident, the clavicle is initially noticeable as it protrudes upwards. However, after only four weeks, this is no longer visible.
Like any surgery, the surgical procedure for acromioclavicular fracture can have complications. The fracture may be displaced even after surgery in rare cases. Furthermore, pain may persist. Sometimes the cosmetic result after surgical treatment of a acromioclavicular joint dislocation is unsatisfactory if excess scar tissue has formed.
