Learn About Spine Procedures

By Jonathan Chu, MD

Interventional Pain Medicine

Physical Medicine & Rehabilitation

So today, let’s talk about one of the most important and commonly performed interventional pain procedures, which is the lumbar medial branch block. Now, this procedure is actually a diagnostic procedure, which is part of a two-step treatment for lumbar facet joint pain, the second step being the lumbar radiofrequency ablation, or RFA.

Now, why is this procedure so important, and why is it done so frequently, especially if it’s only a diagnostic procedure and not designed to be a long-term procedure?

In this video, I’m going to not only answer that question, but also teach you everything you need to know about the procedure, including the relevant anatomy that we’re treating, how the procedure is done, and what the potential benefits and risks are.

So, with that, let’s get started.

First of all, it’s important to know what this procedure is intended to target and treat, and that would be the lumbar facet joints. I’ve actually done an entire in-depth video on just the facets, which I will link in the description below, but I’ll give a quick overview of the essentials here in this video.

Your lumbar facet joints are paired synovial joints located in the back of your spine. Synovial means that they are lined with hyaline cartilage and wrapped in a tough fibrous capsule, and in many ways they are actually quite similar to your knuckle joints in terms of size and structure. Even though lumbar facet pain is not really talked about a lot, it is actually the second most common cause of low back pain, and in any given pain clinic or rehabilitation clinic you are going to see a ton of patients who suffer from it, and in my own opinion, lumbar facet joint pain is one of the most underdiagnosed and underrecognized causes of low back pain.

Now, just like any other synovial joints in your body, these facet joints can degenerate over the years and decades due to wear and tear and the stresses of everyday life. This is a pathological process known as osteoarthritis, which involves the gradual breakdown of the joint cartilage, often along with the formation of bone spurs, thickening of the underlying bone of the joint, and swelling of the surrounding soft tissues. As these joints degenerate, they become more prone to flaring up with painful inflammation.

Now, when someone is experiencing a facet joint pain flareup, it typically presents as a dull and aching pain and stiffness that is predominantly localized to the lower back and buttocks, though it is important to note that it can mimic other pain conditions and radiate into the thighs, and once in a while, even as far down as the calves. Typically, this pain is worse with extension, which is back-bending, and also, lumbar facet pain is usually worsened by prolonged standing or walking.

So now, how do the medial branch nerves play into all of this?

Well, a medial branch is a very thin nerve, almost like floss, that comes off the back of a larger spinal nerve, and provides nerve supply to the nearby facet joint and also a little bit of the surrounding musculature, which is known as the multifidus muscle.

It’s important to note that each lumbar facet joint is supplied by the medial branch at the same level, as well as the one directly above. For example, the L4-5 facet joint is innervated by the L3 and L4 medial branches.

Now let’s apply this to the real world. The most commonly blocked medial branch nerves during this procedure are the L3 and L4 medial branches, and also the L5 dorsal ramus. The L5 dorsal ramus is a small technical detail that you really don’t need to worry about, you just need to know that it functions essentially the same way as a medial branch nerve. Now, by blocking L3, L4, and L5, your physician is going to be able to completely numb up the L4-5 and L5-S1 lumbar facet joints. These two joints are the two lowest facet joints in your lower back, and thus where most of the motion occurs when you bend and twist. Therefore, these two lower levels are usually the most prominent sources of pain when it comes to facet joint arthropathy.

Next, let’s go into detail about how this procedure is actually performed.

During the procedure you’re going to be laying on your belly in a procedure room that is equipped with fluoroscopy, or x-ray guidance, so your doctor will be able to visualize how to place the needle properly. Your low back will be prepped with chlorhexidine or another similar solution in order to sterilize the region and make a sterile field for your physician to work.

Next, your physician is going to use the x-ray guidance to place 3 spinal needles directly over the 3 medial branch nerves I discussed earlier. I personally have always used 25 gauge spinal needles for this particular procedure, because they are quite thin and easy to tolerate, but both 25 gauge and 22 gauge spinal needles work very well for this particular procedure.

In general, this procedure may seem intimidating, but it is actually usually quite easy to tolerate, especially compared the the radiofrequency ablation, since the needles are a little thinner with the block, and also, since it is just a diagnostic block, you don’t have to be quite as stringent with getting perfect placement as you would with the RFA.

Now, once your doctor has placed the needles and confirmed that they are in the proper locations via multiple x-ray images, he or she will inject a small volume of numbing medication over each of the medial branch nerves; most commonly this medication will be marcaine, which tends to last for a longer duration than lidocaine.

It’s important to note that during the next few hours after the procedure is over, it is very important to pay close attention to your low back and how much pain relief you get from the procedure. In most pain clinics your doctor will actually give you a pain diary so you can record how much relief you get in the hours following the procedure. During these few hours you can really test the block by walking around, bending, twisting, and doing your normal daily activities to really see if it is working for you.

Now if you do get significant pain relief from the nerve block, then that confirms that the lumbar facet joints are the source of your low back pain, and you can then move on to the radiofrequency ablation procedure, or RFA. In that procedure, special needles are used that actually heat up and burn the medial branch nerves, and thus can provide more than a year of pain relief, and is a much longer-term treatment. I will do an entire separate video on the lumbar RFA in the near future, because it is so important, effective, and one of my favorite interventional pain procedures. When that video is complete, I will link it in the description below.

Now, some doctors will prefer that you get at least 80% pain relief before they move on to the RFA procedure, while others only require 50% pain relief. Multiple retrospective studies have actually looked at this and have not found a significant difference between the two cutoffs, so you’ll just have to ask your doctor what they prefer.

It’s important to emphasize that the lumbar medial branch is primarily a diagnostic procedure, and is only designed to provide pain relief for a few hours. If the block is positive, then it will be the next step, which is the lumbar RFA, which will provide the long-term pain relief.

Interestingly, every once in a while, the medial branch block itself will actually provide months of pain relief. This can happen because of fascinating physiological mechanisms known as wind-up and central sensitization; this essentially means that when someone is suffering from a serious pain for a long period of time, the nerves themselves and the neurons they connect to in the spinal cord can become hyperexcitable and overactive, leading to progressively increasing pain responses, which is certainly not a good pattern. By numbing these nerves, even for only a few hours, sometimes this negative pain cycle can be interrupted and reset, almost like when you turn a computer off and back on again. Of course, while occasionally the medial branch block itself can provide long-term pain relief, this only occurs a small percentage of the time.

Next, let’s talk about potential adverse effects. Again, though any procedure involving the spine can be quite daunting, in general it is a very safe procedure when done properly. As with any spinal injection, there is a very small risk of potential bleeding, infection, or increased pain. Also, this procedure is considered a neuraxial procedure, which is essentially just a fancy way of saying that this is a procedure that is performed in or around the spine. This means that, according to the American Society of Regional Anesthesia, if you happen to be on a blood thinner, such as Plavix or Eliquis, you will need to hold that medication for a certain duration of time prior to the procedure in order to prevent any bleeding complications. The exact duration of the medication hold is different for every type of blood thinner, and also ASRA does change their guidelines every couple of years, so you’ll want to discuss this with your own physician, and really make sure to follow their instructions to a T, as you really do not want to take any chances when it comes to blood thinners.

So that pretty much covers all the essentials you need to know about the lumbar medial branch block. I have done this particular procedure thousands upon thousands of times, and I can say that in general, it is a very simple, safe, and easy procedure, and it is often very effective. Hopefully you found this information valuable, and if you did, consider liking and subscribing. Also, you can check out the official 360 Pain Academy website for a ton of free articles and educational resources, link in the description below. This is Dr. Chu with 360 Pain Academy, take care until the next video.

References:

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

Furman, M. B., et al. (2018). Atlas of image-guided spinal procedures (2nd ed.). Elsevier.

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

Rathmell, J. P. (Ed.). (2011). Atlas of image-guided intervention in regional anesthesia and pain medicine (2nd ed.). Lippincott Williams & Wilkins.

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