Overview of Acromioclavicular Joint Injection
The acromioclavicular (AC) joint, located on top of the shoulder, is a common source of shoulder pain in patients. It’s estimated that about half a person in every 1000 will experience AC joint pain each year under routine healthcare. Pain in the AC joint can come about either through injury or over time without a specific injury.
When the AC joint pain is caused by an injury, it’s typically because of a hard hit to the top or side of the shoulder. The resulting injury, often called a separated shoulder, involves a tear in the ligaments that hold the joint together. This type of injury can happen frequently in contact sports like football and hockey. If you have a separated shoulder, you might see a noticeable bump on top of your shoulder and feel pain directly on the AC joint. This pain can be treated in one of two ways: by resting the shoulder and supporting it with a sling, or going through surgery if the damage is severe.
On the other hand, if the AC joint pain isn’t caused by a specific injury, it’s usually seen in patients over 40 years of age. The pain starts slowly and gets worse when you try to stretch the shoulder across your body. You could also feel a grinding sensation in your shoulder. The source of the pain is usually on the top of the shoulder. A good way to feel the pain is to ask the patients to stretch the injured arm across their body.
The most frequent causes of this type of AC joint pain are from overusing the shoulder, wear and tear, and breakdown of the end of the collarbone. The first step to treating this pain is through conservative management, which includes physical therapy, modifying your activity levels and over-the-counter pain relief drugs known as NSAIDs.
In cases where the AC joint pain continues regardless of initial treatment, we can inject medication into the AC joint to help relieve the pain. Both as a way of diagnosing the root cause of the pain and for providing significant relief. Doctors must stay updated on who should receive this treatment, possible risks, and the best way to carry out this procedure to give the most relief to people suffering from this condition. This detailed description discusses AC joint injections and the importance of the healthcare team in implementing this procedure.
Anatomy and Physiology of Acromioclavicular Joint Injection
The acromioclavicular (AC) joint is a part of your shoulder that links the outermost part of your collarbone to a part of your shoulder blade known as the acromion. This joint contains a fibrocartilaginous disk, which is a type of cushioning tissue, and a synovial membrane, which helps to lubricate the joint.
The AC joint is held in place by two important sets of ligaments. The stability from side to side is managed by the AC ligament, while the vertical stability is maintained by the coracoclavicular (CC) ligament. This consists of the trapezoid and coronoid ligaments.
There’s another ligament, the coracoacromial, that helps to stabilize the AC joint, along with the deltoid and trapezius muscles. These are two major muscles in your shoulder and upper back that assist in movements and maintaining posture.
Why do People Need Acromioclavicular Joint Injection
Joint injections into a part of your shoulder known as the acromioclavicular (AC) joint can be considered if more common treatments like exercises, painkillers, and changes in your daily activities haven’t worked. These injections can help diagnose or treat shoulder problems, such as osteoarthritis (a type of joint disease that results from breakdown of joint cartilage and underlying bone) in the AC joint.
Another situation where this type of injection might be needed is when you have ‘distal clavicle osteolysis.’ This is a condition where the end of your collarbone (near your shoulder) wears away, typically due to an injury or from repeatedly lifting heavy weights.
It’s important to note that if your shoulder is separated (the ligaments around your AC joint have torn), these injections aren’t usually the go-to treatment. However, they might be used if your separated shoulder leads to other issues like osteoarthritis.
When a Person Should Avoid Acromioclavicular Joint Injection
There are times when a doctor might decide not to give an injection into the AC joint, which is in the shoulder. These conditions are when:
If there’s an infection in or around the joint, which could get worse with an injection. This infection is known as septic arthritis.
If a patient has a hypersensitivity or known allergy to the solution that will be injected, the injection could cause a harmful reaction.
If the skin over the place where they would put the needle in is broken or damaged, the injection might not be safe.
If there’s a fracture (a broken bone) at the injection site, an injection could cause more harm.
And lastly, if a patient is taking blood-thinning medications or has a bleeding disorder, an injection might cause them to bleed too much. Therefore, doctors will proceed with caution in these cases.
Equipment used for Acromioclavicular Joint Injection
For this treatment, the doctor will need the following tools:
- A small syringe about 3 to 5 mm in size
- A needle roughly 1 to 1.5 inches long and 25 gauge in thickness. The gauge of a needle refers to its size—the smaller the gauge, the larger the needle diameter.
- Half a milliliter of a pain-numbing medicine, typically lidocaine or bupivacaine
- Between 0.25 to 0.5 ml of a type of medication called a corticosteroid, which reduces inflammation. The preferred type is methylprednisone as it has a smaller risk of causing fat to shrink.
- Gloves for hygiene and safety
- A skin cleaning solution such as chlorhexidine to ensure the area is clean before the procedure is carried out.
Who is needed to perform Acromioclavicular Joint Injection?
Healthcare professionals like doctors, nurse practitioners (advanced nurses who can diagnose and treat illnesses), and physician assistants (professionals who support doctors in providing care) can carry out injections into the AC joint, a joint at the top of the shoulder. It’s beneficial to have a nurse there to help get the patient ready.
Preparing for Acromioclavicular Joint Injection
The doctor should have a chat with the patient about the potential risks and benefits associated with the procedure. It’s important that the patient, the doctor, and a witness all sign a form to show they agree to the procedure. Additionally, before starting the operation, a pause or ‘time-out’ should be carried out to ensure everything is in order.
How is Acromioclavicular Joint Injection performed
For this procedure, the patient should sit with their arm relaxed and hanging down. We first locate the AC joint by feeling along the collarbone until we reach its end. There’s a slight depression just to the side of where the collarbone ends – that’s the AC joint. Once we’ve found the AC joint, it will be cleaned with a solution like chlorhexidine to prepare it for the injection.
The injection is given from the top front, aiming downwards. If there’s any resistance, the needle will be slightly adjusted until it enters the joint. The solution is then slowly injected into the joint. If we have access to ultrasound technology, it can greatly help in making the injection even more precise.
After the injection, the patient should remain seated for a few minutes just in case they feel faint or dizzy. This is known as a vasovagal response.
Once the injection is complete, we’ll check on the patient and gently move their shoulder to see if there’s any improvement. The patient should be aware that their pain might increase over the next 48 hours due to a steroid flare-up. If this happens, using ice and nonsteroidal anti-inflammatory drugs (NSAIDs) can help manage the pain.
Possible Complications of Acromioclavicular Joint Injection
Although it is rare, some problems can occur after the procedure. These may include infection, which is when harmful germs invade and multiply in your body. Another potential issue is that your pain might not get better or could even become worse. In some cases, the skin above the treated area might lose its color, a condition referred to as hypopigmentation. Lastly, there’s a possibility of fat atrophy, where the fat layer under your skin starts to shrink or degrade.
What Else Should I Know About Acromioclavicular Joint Injection?
Injections into the AC joint, which is a joint at the top of your shoulder, can greatly aid in understanding and treating the source of shoulder pain, if done properly. These injections can both help determine what’s causing the pain and provide relief from it. The length of pain relief varies among individuals and could last anywhere from several weeks to months.
The injections contain a steroid, a type of medicine that reduces inflammation and pain, and they can be given again if needed. However, doctors need to be careful with giving too many injections because over time, they could damage the joint’s cartilage, which is the tough, flexible tissue that covers the ends of your bones in a joint.
