Acromioclavicular Joint Dislocation Specialist Singapore

MBBS (SINGAPORE) MMED (ORTHO) FRCS ED (ORTH)
Acromioclavicular joint (ACJ) dislocations are injuries often experienced by athletes. They are often mistaken to be glenohumeral joint dislocations (see section on shoulder dislocations).
However this certainly does not mean some who is not an athlete cannot suffer such an injury. Majority of ACJ dislocations occur in males in their thirties. Although many patients with untreated ACJ dislocations do well and eventually suffer few functional deficits, more severe untreated ACJ dislocations can result in chronic pain.
Some knowledge of the anatomy of the shoulder is required to understand ACJ dislocations.

What is Acromioclavicular Joint Dislocation?
Acromioclavicular (AC) joint dislocation occurs when the clavicle (collarbone) is displaced from its normal position at the acromion (part of the scapula). The AC joint helps connect the shoulder blade to the collarbone. Typically, dislocations result from a fall onto the shoulder or direct impact. This injury is common in contact sports but can also affect individuals from various backgrounds.
While both AC joint and shoulder dislocations involve the shoulder region, the key difference lies in the joint affected. AC joint dislocation involves the separation of the clavicle from the acromion. On the other hand, a shoulder dislocation occurs when the ball of the upper arm bone (humerus) leaves the socket of the shoulder blade. AC joint dislocations may be less severe than shoulder dislocations. However, the condition can still cause significant pain and limited mobility.
What Causes A Acromioclavicular Joint Dislocation?
The common causes of acromioclavicular joint dislocation include:
Falling Directly onto the Shoulder
One of the most frequent causes of AC joint dislocation is a fall onto the shoulder, particularly when the arm is not in a protective position.
In this scenario, the force of the fall directly impacts the shoulder, causing the clavicle to be forced upwards and out of alignment with the acromion.
This type of injury is common in activities such as cycling, skiing, or any other sport where falls onto the shoulder are likely.
Violent Blow to the Shoulder Area
A direct, violent blow to the shoulder, such as being struck by a heavy object or during a collision, can cause the AC joint to dislocate.
This can occur when an individual is hit by an object like a falling piece of equipment, or during high-impact activities like martial arts, rugby, or boxing.
The intense force from the blow may cause the ligaments around the AC joint to tear or stretch, leading to the dislocation of the clavicle.
Sports Injuries
Contact sports such as football, rugby, hockey, and wrestling are particularly prone to causing AC joint dislocations.
These sports often involve tackles, falls, and collisions where the shoulder is exposed to sudden, high-impact forces that can cause displacement of the AC joint.
Even non-contact sports like cycling, skateboarding, or skiing can result in AC joint dislocations. The risk increases if the athlete falls awkwardly or is involved in a crash.
Types of Shoulder Separation Injuries
Shoulder separations occur when the ligaments connecting the collarbone (clavicle) to the shoulder blade (scapula) are damaged, typically at the acromioclavicular (AC) joint. These injuries are classified into types based on the severity of ligament damage and the displacement of the clavicle.
Shoulder Separation (AC Joint Dislocation):
Occurs when the clavicle (collarbone) displaces from the acromion (part of the shoulder blade).
Classified by the Rockwood Classification system into six types (I-VI) based on severity.
Types of Shoulder Separation:
Type I (Mild): Sprained AC ligaments, minimal displacement. Treated conservatively.
Type II (Partial): Partial tear of AC ligament, some displacement. Treated conservatively or with immobilization.
Type III (Complete): Complete tear of AC and CC ligaments, significant displacement. May require surgery.
Type IV (Posterior): Clavicle displaced backwards, typically requiring surgery.
Type V (Severe): Significant elevation of the clavicle, requiring surgery and extensive rehabilitation.
Type VI (Inferior): Rare, severe injury with downward clavicle displacement, requiring surgery and complex rehabilitation.
What Are The Symptoms Of Acromioclavicular Joint Dislocation?
Common symptoms of acromioclavicular joint dislocation include:
- An obvious deformity of the shoulder
- Intense pain in the AC joint
- Inability to move the shoulder joint
- Decreased range of motion
- The end of the collarbone may appear to be sticking up under the skin

How Is A Acromioclavicular Joint Dislocation Diagnosed?
During a physical examination, your doctor may inspect the affected area for pain, tenderness or any deformities. Furthermore, they may test your shoulder’s mobility by asking you to perform specific simple exercises to determine whether or not the AC joint is dislocated.
An X-ray of your shoulder joint may also be performed to reveal the dislocation and other damages to your AC joint. An MRI scan may be required to fully assess the extent of the injury.
It is essential to avoid attempting to put the joint back yourself because of the risk of aggravating the injury. Also, the joint will not stay in place because of the pull of gravity on the arm.
How Is A Acromioclavicular Joint Dislocation Treated?
For Type I and Type II injuries (mild to moderate dislocations), non-surgical treatments may be performed. These methods focus on managing pain and inflammation, promoting healing, and restoring function gradually.
1. Rest and Ice Therapy
Resting the shoulder and avoiding movements that may exacerbate the pain (such as lifting or overhead activities) is crucial in the initial stages.
Applying ice to the affected area can help reduce swelling and alleviate pain. Ice packs should be applied for 15-20 minutes every 2-3 hours during the first 48 hours following the injury.
2. Sling or Shoulder Immobilisation
A sling or shoulder immobiliser is often recommended, especially in the early stages of recovery. Besides restricting movement and supporting the injured joint, this method also prevents further irritation.
Immobilisation typically lasts for 2-4 weeks, depending on the severity of the injury.
3. Physical Therapy
As healing progresses, physical therapy becomes an essential part of the recovery process. A physical therapist will guide the patient through exercises to:
- Improve range of motion.
- Strengthen the surrounding muscles, including the rotator cuff and shoulder stabilisers.
- Prevent stiffness and improve flexibility.
- Prevent the recurrence of injury once healing is complete.
For Type III injuries or more severe dislocations (Types IV, V, and VI), surgery is recommended for younger and active patients.
1. Surgical Repair for Severe Dislocations
For types IV-VI injuries, surgery is typically required to stabilise the joint and repair torn ligaments. The procedure may involve reattaching the acromioclavicular ligament, repairing the coracoclavicular ligament, or using screws, plates, or suture anchors to hold the bones in place.
2. Open Reduction and Internal Fixation (ORIF)
In cases of severe displacement, an open surgical approach may be needed to manually reposition the clavicle and secure it using plates, screws, or other hardware. This approach is typically used for Type IV, V, and VI injuries.
After surgery, patients are usually required to wear a sling to limit movement and allow the joint to heal.
3. Arthroscopic Surgery
In certain cases, minimally invasive arthroscopic surgery can be performed. This involves the use of small incisions and a camera to guide the surgeon in repairing the torn ligaments or reattaching the dislocated joint. This approach may be less invasive than traditional open surgery.
Prevention Strategies:
Maintain a Healthy Weight: Reducing excess weight to minimise joint strain.
Stay Active: Engaging in low-impact exercises like swimming and walking.
Nutrition: Consuming omega-3 fatty acids, vitamin D, calcium, and joint supplements.
Early Diagnosis: Regular monitoring to catch symptoms early and prevent further damage.
Anatomy of the Shoulder Joint
The shoulder joint is made up of 3 bones: the shoulder blade (scapula), the humeral head and the collar-bone (clavicle).
Movements around the shoulder involve 3 separate articulations: the glenohumeral joint, the acromioclavicular joint and the scapulothoracic articulation. When the arm is raised, the majority of movement occur at the glenohumeral joint and the scapulothoracic articulation.
The ACJ is a rather small joint between the clavicle and a part of the scapula known as the acromion. The acromion forms a roof over the glenohumeral joint which is often regarded as the “main” shoulder joint.
When we raise our arms, majority of movement occurs at the glenohumeral joint and scapulothoracic articulation. Only small gliding and rotatory movements occur at this joint. Despite the fact that such little amount of movement occur through this joint, this small joint has to deal with large forces.
The joint is held in place by several structures:
1. The joint capsule (the covering of the joint)
2. Ligaments found within the capsule of the joint (known as the AC ligaments)
3. Ligaments that are attached, on one end to the coracoid process (part of the scapula) and on the other end, to the clavicle. These ligaments are called the coraco-clavicular (CC) ligaments.
Sports injuries are the most common cause of ACJ dislocation. Often times it is the result of direct impact on the point of the shoulder.
The most common scenarios I see are when patients trip while running fast causing them to tumble “head over heels” or when cyclists pitch over the handlebars after having hit a pothole or a branch on the road. In almost all of these scenarios, the patient lands hard directly on their shoulder.
Frequently Asked Questions
When should I visit a doctor for acromioclavicular joint dislocation?
If you suspect you have a dislocated AC joint, you should seek immediate medical attention. This is because treatment is much easier and you have a much better chance of excellent recovery if the injury is treated early.
What will the doctor do?
The first thing is to confirm the diagnosis. This is easily done with a simple x-ray. Often it is prudent to do x-rays of both shoulders to compare both sides. This is because some patients’ clavicles naturally sit slightly high giving the appearance it could be slightly out of place.
Comparing the uninjured side with the injured side allows your doctor to not only confirm the injury, but also allows him to grade its severity. This is important because milder injuries will do fine without any invasive surgery to fix the joint, but more severe injuries may require surgical fixation.
Besides x-rays, some doctors may also recommend doing an MRI scan. This mainly useful for looking for other associated injuries. A number of patients with ACJ dislocations may also suffer concomitant injuries like labral tears. Please refer to the section on Investigations to learn more about MRI scans.
What does surgery for ACJ dislocations entail?
The objective of surgery is to put the ACJ back in place and keep it in place. Many techniques have been developed to achieve this over the years. Many failed and have become historical. Many shoulder surgeons will treat acute injuries differently from chronic injuries. I generally regard injuries less than 2 weeks old as acute.
For acute injuries, I usually use one of 2 methods, depending on patient preference and size of the patient. For large and heavy-set patients, I use a strong hooked plate which levers against the inferior surface of the acromion to push the clavicle down and keep it in place.
This is an excellent and extremely strong method of holding the ACJ stabilized, but a big drawback is the need to remove the plate after a period of about 5 – 6 months. By that time, the ACJ and CC ligaments would have healed.
If the plate is not removed, it may cause irritation and pain when patients lift their arms overhead by impinging on the underlying rotator cuff tendon.
For smaller patients, I use a suspensory type fixation, where a hole is drilled through the clavicle and the base of the coracoid process. The ACJ is then brought back into place and held by passing strong suture tapes through the holes, secured over the clavicle and under the coracoid with small metal buttons.
This surgery is done via keyhole surgery and there is no need for a second surgery to remove the metal buttons. Please see section on keyhole surgery if you would like to know more about keyhole surgery.
Finally for chronic injuries, I use either one of the above techniques, but I loop a tendon graft around the clavicle and the coracoid process so that the body can, over time, convert the tendon graft into a new ligament to help hold the ACJ in place.
A tendon graft is a tendon which is either harvested from the patient’s leg or a commercially prepared tendon procured from deceased donors.
The need to loop a tendon graft increases the complexity of the surgery and there is some evidence that ACJ injuries which are treated early (acute injuries) tend to do better thanchronic ones.
Will I be able to participate in sports after the surgery?
Absolutely. The aim of the surgery is to restore stability to your shoulder, not just during daily activities, but also during sports.
How to prevent acromioclavicular joint dislocation?
Unfortunately acromioclavicular joint dislocations are often accidental injuries and there is not a lot you can do to prevent it from happening.
What are the common symptoms of an acromioclavicular joint dislocation?
Symptoms include pain, swelling, bruising, tenderness over the shoulder, and a visible bump or deformity on the top of the shoulder.
What are the different types of AC joint dislocations, and how do they affect treatment options?
AC joint dislocations are classified into different grades. Grade I may require rest and therapy, while Grade IV and above often necessitate surgery.
What are the risks of untreated AC joint dislocations?
Untreated dislocations can lead to chronic pain, joint instability, and decreased shoulder function over time.
Are there any lifestyle changes or modifications required during recovery from an AC joint dislocation?
It is important to avoid overhead movements, heavy lifting, and activities that strain the shoulder during recovery.
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