Acromioclavicular joint - The best first aid measures for acute injuries!
- Mar 29
- 5 min read
Updated: 2 days ago
The acromioclavicular joint (AC joint) is usually given little attention until it is injured or torn after a fall.
In this article you will learn:
This results in a separation of the acromioclavicular joint.
This will tell you how severe the injury is.
What is meant by a piano key phenomenon?
These are the best first aid measures for acute injuries.
Conservative or surgical: This is the right therapy for you.
What happens when the acromioclavicular joint is dislocated?
The acromioclavicular joint connects the collarbone (clavicle) to the acromion. It is the only joint connecting the arm and the rib cage and is therefore subject to extremely high loads. The AC joint is surrounded by a taut capsule and interwoven ligaments, allowing it to withstand considerable stress.
The acromioclavicular joint often becomes noticeable after a fall (e.g., while cycling or playing football), when the joint capsule or the ligaments between the collarbone and shoulder blade are injured.
This most commonly occurs with a direct impact trauma to the acromion, the upper outer bony protrusion of the shoulder blade. This can lead to overstretching or tearing of the ligaments that normally stabilize the two bones in the joint.
How do I know the severity of the injury?
In types III, IV, V and VI, both the capsule and the ligaments between the clavicle and shoulder blade are torn and there is a separation in the AC joint.
If only the joint capsule is injured, it is referred to as a type I injury according to Rockwood.
If the ligaments between the collarbone and shoulder blade are overstretched or partially torn, this is a type II .
In types III, IV, V, and VI, both the capsule and the coracoclavicular ligaments (CC ligaments) are torn, resulting in a tear in the AC joint. Typically, the acromion protrudes below and slightly in front of the clavicle, resulting in instability in the joint. This instability can be very painful and lead to impaired shoulder function.
What is meant by the piano key phenomenon?
In a complete acromioclavicular joint dislocation, the clavicle protrudes upward from the shoulder girdle. This position is favored by the pull of the sternocleidomastoid and trapezius muscles on the clavicle.
Over the years, the piano key phenomenon has earned its place in textbooks. This involves the outer end of the clavicle being pressed downward like a piano key, but immediately springing back up when the pressure is released. The severity of the piano key phenomenon is an indirect indicator of the extent of the ligament injury.
Upon closer inspection, however, it becomes apparent that during a complete AC dislocation, it is the acromion that, following gravity, moves under and in front of the collarbone. Thus, following this analogy, one would actually have to lift the entire piano and rotate it slightly backward.
This is, of course, much more complicated and would certainly never have found its way into the books so easily!
However, in the piano key phenomenon, the collarbone protrudes under the skin.
These are the best first aid measures for injuries to the acromioclavicular joint (AC joint)!
In acute situations, cooling and immobilization are the best first measures. A cool pack from the freezer, for example, can help. Short-term immobilization of the arm can be achieved with an arm sling from an orthopedic specialist or a triangular bandage from a car emergency kit.
A graze, which often occurs slightly behind the acromion, should be disinfected and covered with a sterile dressing.
If necessary, a painkiller such as ibuprofen or paracetamol can be taken in acute situations, provided there are no other illnesses or allergies present. (If in doubt, consult your doctor or pharmacist beforehand.)
Numbness and paralysis of the arm require clarification by an emergency doctor or in an emergency room.
If you notice (e.g. in the mirror) that your collarbone is rotating upwards compared to the opposite side, go to an emergency room or to a specialist in orthopaedics and trauma surgery to have an X-ray examination performed.
An X-ray and a physical examination can accurately diagnose the severity of the injury. The decision as to whether conservative or surgical treatment is best can be discussed in detail with a shoulder specialist.
Then conservative (non-surgical) treatment after acromioclavicular joint injury is sufficient.
In most cases after an injury to the acromioclavicular joint, conservative (non-surgical) therapy is completely sufficient.
The arm should be rested for a few days. The above measures will lead to a reduction in pain after a few days to weeks, and you'll quickly be able to return to full activity. Sports activities can be resumed after about 3-4 weeks.
In some cases, treatment by a physiotherapist is advisable to train the movement of the shoulder blade.
Acromioclavicular joint dislocation: In this case, surgical treatment is advisable.
The situation is different with a complete AC joint tear. If the ligaments connecting the collarbone to the acromion are completely torn, there is instability, causing the bones to shift against each other. Shifting of the bones under the skin leads to pain during movement, which can persist for a long time.
A complete tear of the types III, IV, V, and VI ligaments is referred to as a dislocation of the acromioclavicular joint. In this case, the collarbone dislocates from the joint and protrudes upward under the skin. This misalignment is easily visible on an X-ray.
Until a few years ago, surgical treatment for a complete AC joint dislocation was performed through an approximately 8 cm long open incision across the acromioclavicular joint. This involved either implanting a hook plate or stabilizing the joint with wires.
Modern surgical treatment of acromioclavicular joint dislocation.
A new procedure now allows the injury to be treated using keyhole surgery through very small skin incisions.
A very strong suture is inserted between the clavicle and the coracoid process and held in place with two small titanium plates. This allows the position of the clavicle to be stabilized for a long time while nature takes care of its work and forms a stable scar between the torn ligaments.
Initially, this procedure was performed as a "tight-rope" technique. The further development of this surgical technique is called "dog-bone" and works according to the same principles. However, the drill hole diameters are now significantly reduced and the small titanium plates have been optimized with regard to their contact surface.
Postoperative result of the patient after "dog-bone" stabilization. The clavicle is correctly positioned relative to the acromion. The small titanium plates that fix the connection between the clavicle and the coracoid process are shown.
Aftercare and what happens after stabilization of the acromioclavicular joint.
In the first few weeks after surgical stabilization of the acromioclavicular joint, the arm is supported on a shoulder pillow to limit the load on the newly inserted implant.
The ligaments need about 6 weeks to form a stable scar.
During this time, the shoulder is moved daily, allowing most patients to regain full use of their arm after just six weeks. The titanium plates can be removed after one year at the patient's request.
Conclusion:
A fall on the shoulder can damage the ligament connecting the clavicle and the acromion. Severe injuries are referred to as a dislocation of the acromioclavicular joint.
Acute and chronic instabilities of the acromioclavicular joint (AC joint) can cause pain and dysfunction of the shoulder.
The best first aid measures for acute injuries include cooling, immobilization, rest and painkillers.
Early X-ray diagnosis and manual examination are useful in order to correctly classify the severity of the injury to the acromioclavicular joint.
Modern keyhole surgical procedures enable early resumption of physical activity and return to sport.
Do you have any questions?
Then make an appointment with our shoulder specialist :
Specialist in orthopedics
and trauma surgery,
Sports medicine
