What is Acromioclavicular Joint Injury?
Injuries to the acromioclavicular joint, located in the shoulder, are common in athletes and young people. In fact, these injuries make up over 40% of all shoulder-related issues. While minor injuries typically don’t lead to significant health problems, serious ones can result in a notable decrease in shoulder strength and function. Other potential complications from an acromioclavicular injury can include a broken collarbone, shoulder impingement (when shoulder muscles rub against the top part of the shoulder blade), and in rare cases, damage to the nerves or blood vessels.
What Causes Acromioclavicular Joint Injury?
The acromioclavicular joint is the point where the outer part of your collarbone meets a part of your shoulder blade known as the acromion. This joint is mainly held stable by a bundle of strong tissues known as the acromioclavicular ligament. This ligament has different parts, and the top part provides the main support to the joint. Additional support comes from two other ligaments, the trapezoid and the conoid, which help keep the joint stable, particularly in an up and down direction. There’s also another ligament called the coracoacromial ligament.
Minor injuries to this joint don’t usually cause significant issues, but serious injuries can lead to considerable strength loss and reduced function in the shoulder. Injuries to the acromioclavicular joint could be associated with a broken collarbone, shoulder impingement syndromes, and less commonly, nerve or blood vessel damage.
Risk Factors and Frequency for Acromioclavicular Joint Injury
Injuries to the acromioclavicular joint, often called “AC” injuries, are common in active individuals. These injuries usually occur as a result of sports events, car accidents, bicycle falls, or activities like skiing. They make up a large portion of all shoulder injuries and are particularly common in high-impact sports, such as football, lacrosse, and ice hockey.
- AC injuries often occur after sports events, car accidents, falls from bicycles, and skiing.
- These injuries represent around 40% of all shoulder injuries.
- They also account for roughly 10% of all injuries in high-impact sports like football, lacrosse, and ice hockey.
Signs and Symptoms of Acromioclavicular Joint Injury
If someone hurts their acromioclavicular joint (a joint in the shoulder), they usually feel pain in the front and upper part of their shoulder. This kind of injury often happens because of a hard hit to the shoulder while it’s raised, or because they fell on an outstretched arm. They might also feel the pain traveling to their neck or shoulder, and it often gets worse when they move or try to sleep on the hurt shoulder. When a doctor checks them out, they might notice swelling, bruising or some changes to the shape of the acromioclavicular joint, depending on how severe the injury is. The patient may feel sore in that area and may find it painful to move their shoulder fully. They might show the “Piano key sign”, where the collarbone lifts up and then goes back down when it’s pressed from underneath. Lastly, it’s important for the doctor to also check the entire collarbone for any breaks or injuries at the sternoclavicular joint (where the collarbone meets the breastbone), and to ensure the nerves and blood flow in the injured arm are working properly.
Testing for Acromioclavicular Joint Injury
: If your doctor suspects you might have an injury in your acromioclavicular joint, which is a joint at the top of the shoulder, they’ll typically start by taking regular X-rays. Although these can help to rule out other potential causes of shoulder pain, this type of injury might not always show up on typical X-ray views.
To get a better look at the joint, your doctor might take a few extra X-ray angles. One such angle is the Zanca view. For this, the X-ray machine is tilted 10 to 15 degrees upwards (towards the head). Your doctor may also take two straightforward X-rays, one of each shoulder, to compare them.
In cases where the injury isn’t clear cut, weighted stress views might be used. This technique applies some weight to the joint to see how it reacts. If there’s still uncertainty, other imaging techniques like ultrasound or MRI scans may be considered for a deeper look.
When looking at the X-rays, your doctor may use the Rockwood Staging System. This method involves comparing your injured shoulder’s X-ray to the X-ray of your healthy shoulder. This will help in planning the treatment, particularly by checking the space between the coracoid (a small hook-like structure on the shoulder) and the clavicle (the collarbone). This distance is crucial in deciding the best treatment option for you.
Treatment Options for Acromioclavicular Joint Injury
Acromioclavicular joint injuries are characterized using the Rockwood system, which groups them into six categories.
Type I usually involves a minor sprain where the acromioclavicular ligaments are strained but there are no visible changes on an X-ray.
Type II is more severe with torn acromioclavicular ligaments and partly damaged coracoclavicular ligaments. This can result in a slight collarbone elevation but not higher than the shoulder bone. Both Type I and II injuries are generally treated using non-surgical methods, which include wearing a sling, medication for pain relief, applying ice, and attending physical therapy.
Type III injuries involve damage to both the acromioclavicular and coracoclavicular ligaments, leading to the collarbone lifting above the shoulder bone. This can be seen on an X-ray as a 25 to 100% increased gap between the collarbone and shoulder blade. This type of injury is often treated like Type I and II, using non-surgical methods. However, if the collarbone is displaced by more than 75%, or the patient is engaged in heavy labor, a top-level athlete, cares about the cosmetic impact, or doesn’t improve with non-surgical treatments, then surgery might be considered.
In Type IV, the end of the collarbone is displaced towards the back, into a muscle called the trapezius.
Type V injuries involve the end of the collarbone moving upwards above the shoulder bone by more than 100% compared to the uninjured side.
Type VI, a rare injury, involves the collarbone moving downwards in front of the shoulder blade’s muscles. The methods for managing Type IV to VI injuries typically involve surgery necessitating a referral to an orthopedic surgeon.
If a patient presents with an acromioclavicular joint injury within 6 weeks of injury, this is considered an acute case. The treatment aim is to stabilize the acromioclavicular joint. Several stabilization techniques are employed, such as the use of a hook plate, Bosworth screw, tension band wiring, or endobutton. Long-term repeated cases are handled differently, with strategies focusing on joint clearing, ligament restructuring, and securing the joint. This could involve procedures like the Modified Weaver-Dunn procedure, the Mazzocca technique, the Neviaser technique, the Rockwood procedure, the Docking technique, or the Mumford procedure. The chosen treatment is dependent on the specifics of the patient’s case.
What else can Acromioclavicular Joint Injury be?
When a doctor is trying to diagnose an injury to the acromioclavicular joint, which is located at the top of the shoulder, they might consider a number of possible conditions, including:
- Damage or disease in the joint itself, causing pain and inflammation (acromioclavicular osteolysis or arthritis)
- A fracture, or break, in the nearby bone extension, called the acromion
- Frozen shoulder, or adhesive capsulitis, which is stiffness and pain in the shoulder joint
- A slight shift or subluxation of the humerus bone at the front
- A type of limb injury known as Erb-Duchenne
- Complex pain syndrome, a chronic pain condition that can affect the shoulder
- A tear in the shoulder’s soft tissue parts, known as the glenoid labrum or rotator cuff
- A condition known as Os acromiale, where the acromion, a part of the shoulder blade, does not fuse properly
- Superior labral tear, which is an injury to the ring of cartilage (labrum) in the shoulder joint
- An infection in the joint, known as septic arthritis
- Dislocation of the entire shoulder joint
Doctors could consider these possibilities and recommend tests to determine the correct diagnosis.
What to expect with Acromioclavicular Joint Injury
Typically, people with injuries to the acromioclavicular joint have a good chance of recovery. Most of these injuries don’t need surgery, and patients usually regain usual movement within 6 weeks and return to their normal activities by 12 weeks. If surgery is needed, the recovery period is longer, often involving 6 weeks of immobilization and a gradual return to full activity around 6 months.
Possible Complications When Diagnosed with Acromioclavicular Joint Injury
The main complication seen with the separation of the acromioclavicular joint, which is a joint at the top of the shoulder, is ongoing pain. This lasts in about 30% to 50% of people. Another known complication is arthritis in the acromioclavicular joint itself, which is more commonly seen in patients who have had surgery. There can also be issues with the surgical hardware, infections, adhesive capsulitis (a condition where the shoulder becomes very stiff), and fractures in the coracoid and clavicle, which are bones in the shoulder. The use of a hook plate can lead to irritation of the acromion (another part of the shoulder), impingement or compression of the subacromial area, and osteolysis, which is destruction of bone tissue.
Common Complications:
- Ongoing joint pain
- Acromioclavicular joint arthritis
- Hardware irritation
- Infections
- Adhesive capsulitis
- Fractures of the coracoid and clavicle
- Acromion irritation with hook plate use
- Subacromial impingement with hook plate use
- Osteolysis with hook plate use
Recovery from Acromioclavicular Joint Injury
The process of recovery after a shoulder injury can be divided into multiple stages, each with its own set of actions:
In the first 1 to 6 weeks:
- The arm is rested in a sling
- Ice packs are applied to the shoulder for relief
- Patients start moving their elbow and wrist
- Personal hygiene care is given
- Pain relief medication is provided
During weeks 6 to 12:
- Movements lifting the arm above 90 degrees are limited
- Patients gradually stop using a sling and begin pendulum exercises
- Passive movements are initially started, followed by active movements
- Patients begin with isometric exercises, moving on to strengthening exercises for the rotator cuff
- Moving the elbow and wrist continues
In the 12th week onwards:
- Patients start to do full range movements of the shoulder above 90 degrees
- Exercises for enhancing position sense and strength are allowed
After a period of 6 months following this routine, patients can usually go back to playing sports.
Preventing Acromioclavicular Joint Injury
Acromioclavicular joint injuries, which often cause shoulder pain, are typically seen in athletes and individuals experiencing traumatic injuries. If someone suffers from this type of injury, it’s essential to have it assessed by an orthopedic specialist or a sports management physician. Initially, keeping the shoulder immobilized in a sling, applying ice, staying rested, and using anti-inflammatory medicines generally forms the basis of the treatment for these injuries. However, it is important that the patient resumes their regular activities only after being given the go-ahead by their doctor.
