By Jonathan Chu, MD

Interventional Pain Medicine

PM&R

So today, let’s talk about the subacromial injection, which is one of the most popular types of steroid injections used to treat shoulder pain, particularly pain caused by injury or dysfunction of the rotator cuff. It’s an excellent option if your shoulder pain just isn’t responding to oral or topical NSAIDs, and you’re just not able to get enough pain relief to do your physical therapy and home exercises properly.

In this video I’m going to go over everything you need to know about the procedure, including the relevant anatomy, who’s a good candidate for the injection, how the procedure is done, potential adverse effects, and how to integrate the injection into your overall treatment plan.

So first, let’s talk about the anatomy. And as I always say, when it comes to pain medicine, knowing the anatomy is half the battle.

Now first of all, it’s important to note that this injection is most commonly utilized to treat rotator cuff tendinitis, which is a painful inflammation of the rotator cuff, usually due to a tear or injury to the rotator cuff. Now, if you’ve seen my previous video on shoulder pain, you’ll remember that the rotator cuff is made up of four muscles, known as the SITS muscles:

Supraspinatus

Infraspinatus

Teres Minor

Subscapularis

The most commonly injured structure is the tendon of the uppermost muscle of the rotator cuff, which is the supraspinatus. This is the muscle that helps you abduct your arm, which means bringing it away from your body. If you study the anatomy, this makes a ton of logical sense, because during overhead activities this muscle will often rub up against the acromion, which is the bony shield right above the shoulder joint, and is the bony structure that you can palpate whenever you touch the upper and outer part of your shoulder.

Now, since the injection is called the subacromial bursa injection, let’s talk about what that is, exactly. Bursas are fluid filled sacs that help to allow smooth movement of a certain body part. The subacromial bursa sits right between the tendons of your rotator cuff and the bony acromion, serving to cushion the area and also facilitate smooth shoulder movement. Of course, the problem is when there is a rotator cuff injury, oftentimes this bursa will fill up with painful inflammatory chemicals, which makes it really tough to move your arm and shoulder properly. This painful inflammation of the bursa is known as subacromial bursitis. This is why doctors will often use the terms subacromial bursitis and rotator cuff tendonitis interchangeably, because though they are technically two different things, they are closely interrelated.

If you have suffered a rotator cuff injury, it’s important to note that in terms of your term recovery, your physical therapy and your home exercise program really are the keystone to returning to normal function and activities. However, a lot of times, if your rotator cuff is acutely inflamed, it’s just too painful to be able to do the exercises properly and consistently.

Most of the time, assuming that you don’t have any stomach, heart, or kidney issues, you can actually quell the painful inflammation with a Non-Steroidal Anti-Inflammatory medication (or NSAID), either over-the-counter or a prescribed by your doctor, usually for a one to two week course to calm everything down in your shoulder.

Examples of common over-the-counter NSAIDs would be ibuprofen or naproxen, and a common example of a prescription NSAID would be meloxicam, which I personally really like because it is a little gentler on the stomach and kidneys, and most insurances will cover it.

Of course, if these NSAIDs just don't cut it, or for some reason you aren’t able to take oral NSAIDs, then you can talk to your doctor to see if you're a candidate for a subacromial injection for your shoulder.

It’s a very easy, simple, and effective procedure, and actually one of my favorites to do. I’ve done hundreds of these injections both with and without ultrasound guidance, and they’re really a piece of cake. Also, more importantly, usually very effective in the properly selected patients. Most primary care doctors, orthopedic surgeons, PM&R physicians, sports medicine physicians, and pain physicians do this procedure very regularly.

Now, as far as how the procedure is performed and what to expect, first your doctor is going to mark the site of injection after palpating the bony landmarks. Next, they are going to prep the area  to sterilize the field; I usually prefer to use chlorhexidine, but 70% alcohol also works well, of course. Next, your doctor may or may not anesthetize the skin with a small amount of lidocaine. If they’re using a small gauge needle, like a 25 gauge, you really don’t need to anesthetize the skin first, and you can avoid having to stick twice.

Your doctor will inject the subacromial space via one of two approaches: the posterior approach, which is from the back of the shoulder, or the lateral approach, which is from side. I personally like to use the lateral approach, but that’s just a preference; there’s actually been a study in the journal Musculoskeletal Care in 2019 that demonstrated that the two approaches have equal efficacy.

The injection will be a mixture of a steroid, such as triamcinolone, and a local anesthetic, like lidocaine or marcaine. When I’m doing this procedure, I like to mix 40mg of triamcinolone and about 4-5cc of 1 percent lidocaine, which is a fairly typical medication combination.

Both the steroid and local anesthetic are quite important for the efficacy of the injection. The local anesthetic will work to numb the entire region almost immediately, but will last only for about 2-3 hours. That being said, it still serves a very important role, because it can help to decrease wind up and central sensitization by “resetting the system,” so to speak. You see, in long-term painful conditions, the repeated stimulation of pain receptors actually makes them more sensitive and hyperactive over time, through changes in neurotransmitters all the way up in the spinal cord. Now, by numbing the entire area for a few hours, it can help to “break the cycle,” allowing hyperexcitable neurons to return to their normal state, almost like when you turn an electronic device off, and then back on again. Lidocaine, in itself, actually has a mild anti-inflammatory effect, as well.

Of course, the steroid is even more important than the local anesthetic, since it acts as a very strong anti-inflammatory agent by decreasing the production of numerous inflammatory chemicals, such as prostaglandins and cytokines. The steroid usually takes 3 to 7 days to take full effect, and then the pain relief usually lasts anywhere from a few weeks to a few months.

Now, most commonly this injection will just be done using bony landmarks for guidance. This is perfectly acceptable, and is really quick and easy, and is actually my preferred method for patients who have uncomplicated anatomy.

You can also use ultrasound guidance to help with accuracy, and with this method you can visualize the needle entering the bursa and the medicine filling the bursa. I’ve done hundreds of shoulder injections this way, and it definitely helps with increased accuracy, and also really confirming that the medicine is getting right on target, but it is not a necessity in most cases.

Now in terms of risks, the rate of adverse effects is exceedingly low, and if done properly, this is a very safe procedure in general. Obviously, as with any injection, swelling, bruising, or a temporary increase in pain are all possible. Very rare potential complications would be a rupture of the rotator cuff tendons or an infection; however, in general, these are exceedingly uncommon.

In fact, along these lines, the American Society of Regional Anesthesia, or ASRA, classifies this procedure as a low risk for bleeding, and their guidelines state that in most situations, this procedure is safe to do even for patients who are on blood thinners, such as clopidogrel (which is also known as Plavix). Of course, if you do happen to be a blood thinner, such as Plavix or Eliquis, you should talk to your doctor about the potential risks and whether they feel comfortable with the procedure before moving forward.

Another safety factor to consider with this injection is blood sugar; if you happen to be diabetic, you should know that steroid medications can temporarily raise your blood sugars. Thus, if you are someone who does suffer from diabetes, you’ll want to talk to your doctor and have a discussion regarding the risks and benefits of the injection. If your diabetes is under good control, a single steroid injection is usually okay. However, if your diabetes is poorly controlled, you probably want to work with your doctor to get it under proper control, first.

Now, a common, and excellent question that a lot of patients have asked me is: if these injections typically last an average of 3 months, do you need these injections over and over again forever?

And the answer is, no.

In my opinion, the subacromial injection is an awesome injection, because in the properly selected patients, it is both very easy and very effective. However, it is definitely not the be all, end all; it is just one part of your comprehensive treatment plan.

Overall, I would say that the most important part of your recovery from a rotator cuff injury is actually the rehabilitation and physical therapy, and I’m not just saying that because my background is in PM&R.

In general, it’s just extremely important to get your shoulder moving again after a rotator cuff injury. This is because if your shoulder is immobilized for too long, there is a chance that you could develop a painful condition called adhesive capsulitis, otherwise commonly known as frozen shoulder, in which it becomes extremely difficult to move your shoulder at all, and it’s a scenario that you definitely want to try your best to avoid.

Thus, it’s really best to think of the subacromial injection as a powerful tool that helps control your shoulder pain for a certain period of time, giving you an approximate 3 month window to really rehabilitate your shoulder properly. This rehabilitation typically involves restoring the passive range of motion of the shoulder, then restoring the active range of motion, then strengthening the shoulder, and then lastly, returning to normal activities and function. Hopefully, after that, you will no longer need any more injections or NSAIDs.

Anyway, that concludes my summary on subacromial injections for rotator cuff pain. Hopefully, you found it valuable and educational, and if so, please consider liking and subscribing. Also feel free to check out the official 360 Pain Academy site, which has a lot of free articles and educational resources. This is Dr. Chu with 360 Pain Academy, take care until the next video.

References:

Benzon, H. T., et al. (2018). Essentials of pain medicine (4th ed.). Elsevier.

Braddom, R. L. (Ed.). (2010). Physical medicine and rehabilitation (4th ed.). Saunders/Elsevier.

Cuccurullo, S. J. (2004). Physical medicine and rehabilitation board review. Demos Medical Publishing.

Hoppenfeld, S. (2014). Fundamentals of pain medicine: How to diagnose and treat your patients. Wolters Kluwer.

Netter, F. H. (2006). Atlas of human anatomy (4th ed.). Saunders/Elsevier.

Waldman, S. D. (2012). Pain management injection techniques (3rd ed.). Saunders/Elsevier.