BackTable / MSK / Podcast / Transcript #22

Podcast Transcript: Genicular Nerve Ablation

with Dr. John Smirniotopoulos

In this episode, host Dr. Michael Barazza interviews Dr. John Smirniotopoulos about genicular nerve ablation, an innovative treatment option for the management of osteoarthritis. You can read the full transcript below and listen to this episode here on BackTable.com.

(1) Predictors of Genicular Nerve Ablation Outcomes

(2) Getting Started with Genicular Nerve Ablation

(3) Knee Pain Management with Genicular Nerve Ablation

(4) Patient Selection for Genicular Nerve Ablation

(5) Procedural Anatomy & Pain Management Considerations

(6) Genicular Nerve Ablation Probe Selection & Techniques

(7) Complications & Exercising Caution

(8) Navigating Patient Expectations & Outcomes

(9) Expanding Nerve Ablation Beyond the Knee

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Genicular Nerve Ablation with Dr. John Smirniotopoulos on the BackTable MSK Podcast)

Ep 22 Genicular Nerve Ablation with Dr. John Smirniotopoulos

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[Dr. Michael Barazza]
This is Michael Barraza returning as your host. I'm excited to welcome Dr. John Smirniotopoulos to share his experience performing genicular nerve ablation. John is an assistant professor of clinical radiology in the IR department at MedStar Georgetown University and at MedStar Washington Hospital Center in DC. Did I get that right, Dr. John Smirniotopoulos?

[Dr. John Smirniotopoulos]
Yes, that's right.

[Dr. Michael Barazza]
Thanks for joining us, man.

[Dr. John Smirniotopoulos]
Thank you for having me.

[Dr. Michael Barazza]
Of course. For our listeners, Dr. John Smirniotopoulos and I already talked about this, Dr. John Smirniotopoulos has been helping me start a program doing this in Baton Rouge. John, how long have you been at Georgetown?

[Dr. John Smirniotopoulos]
I've split my time between Georgetown and New York. I went to med school at Georgetown, did my residency at Cornell. Was a fellow at Georgetown, went back for my first job at Cornell, and came back to Georgetown a couple of years ago, so April 2021.

[Dr. Michael Barazza]
That's right. You worked with my guy, Bill Brown, in Cornell.

[Dr. John Smirniotopoulos]
That's right. Yes. Exactly.

[Dr. Michael Barazza]
Can you tell us a little bit about the training program there in DC? A lot of our listeners are med students and trainees.

[Dr. John Smirniotopoulos]
Absolutely. We were one of the first programs to adopt the new IRDR residency program back in 2016. We've obviously grown that and built that out. We currently have two independent spots for residents that are matching in, and we have ESIR available to those who match in as diagnostic but maybe you want to decide they are going to go into IR a little bit earlier. Additionally, we do have residencies available after people graduate traditional residency and maybe want to go somewhere else for a year.

We typically have four PGY-6 spots for IR, meaning four equivalent fellows or what it used to be back in the day. They split time between Georgetown University Hospital, Washington Hospital Center, which is my primary clinic site where we do a lot of these procedures we'll talk about today. In addition, they do some of their diagnostic training elsewhere at Children's National and in Baltimore at Shock Trauma.

[Dr. Michael Barazza]
Nice. That's awesome

[Dr. John Smirniotopoulos]
It's a robust clinical experience for the residents. Their IR is at Hospital Center and at Georgetown's, and it's pretty evenly split between the two sites. At Georgetown, a lot of cancer volume, liver transplant, those complex pediatric patients. At Hospital Center, a lot of very sick heart patients where level one trauma, a 1,000-bed hospital, so tons of trauma, some PAD work, complex IO work, vascular reconstruction. Between the two sites, it's a nice breadth of variety. I have a lot of bias because I train there and I'm an attending there, but I think it's a great program.

(1) Predictors of Genicular Nerve Ablation Outcomes

[Dr. Michael Barazza]
That's awesome. You guys, your crew just presented some of your data on genicular nerve ablation at the recent SIR annual meeting, and it was selected as a newsworthy article and had a press release for it. Can you give us a little bit of details about the study and what you guys found?

[Dr. John Smirniotopoulos]
Yes. We started doing the specifically genicular nerve ablations and treating these patients a little over a year ago, and we wanted to analyze our early data to see how our results were. A lot of the data that is available is in the pain literature, which is good data, but we haven't really seen a lot come from the IR literature, so we thought, let's see how our patient population is doing. Specifically, we wanted to see if we have a way of predicting outcomes. Who is going to do better from this procedure? Does it help with selection?

What we did is we did a prospectively-collected, retrospectively-reviewed study of the patients that we had performed the procedure on. Specifically genicular nerve ablation. We looked back at their baseline WOMAC scores and their VAS pain scores, and then we called them for follow-up and try to get updated scores on them. We had help from a couple of our residents and very, very hardworking medical students to accomplish this. Was great. In total, by the time we submitted it to SIR, we had 36 patients that we had collected enough data on.

Of those 36 patients, 47 knees. What that means is several patients had both knees treated over the time period. That also means that they were able to give us a VAS score for each separate knee and a WOMAC for each separate knee because the treatments are done on different days. We'll get into that in a little bit. What we did is a multivariate analysis. We tried to, again, see what we can glean from our data to predict outcomes.

We looked at BMI, age, race, gender. We looked at prior surgical history. We also looked at inflammatory diseases such as rheumatoid or fibromyalgia. We essentially found that the biggest predictor of outcomes, and all patients had a significant reduction of their pain, but the biggest predictor of outcome was age greater than 50. Again, everyone, all comers had significant reduction of WOMAC and VAS, but that was our only real predictor of who was going to respond more than maybe another population.

[Dr. Michael Barazza]
Super interesting. I was wondering if there was going to be something like BMI, or whether or not the patient had an arthroplasty, but that was the big one, was age. I'll be interested to see if you guys have any ideas about why that is.

[Dr. John Smirniotopoulos]
That's a great point. That actually got brought up while we were giving the talk at SIR.

[Dr. Michael Barazza]
I bet.

[Dr. John Smirniotopoulos]
Someone asked the audience, why do you think that happens? We thought BMI actually would be the main predictor, and our orthopedic colleagues who refer us these patients, also thought BMI would be the biggest predictor, and it wasn't. We think that age greater than 50 likely pertains to a higher number of patients with maybe an increased grade of their OA compared to age.

If you look at some of the prior data that's out there, they look at their Kellgren-Lawrence scale, which is a degree of OA of 2 and 3. Certainly those above 50 are likely to have that. Also, to be honest with you, I think the population under 50 maybe has more sports-related injuries such as meniscal tears, things of that nature, but maybe there's also that expectation that's there. If you're younger than 50, you think maybe I'll get this treatment, I'll go run a half-marathon.

[Dr. Michael Barazza]
Right, I'll be back to normal.

[Dr. John Smirniotopoulos]
I tell everyone this is not a time machine. I think it's managing expectations that maybe has a bias in there as well.

(2) Getting Started with Genicular Nerve Ablation

[Dr. Michael Barazza]
You said you've been doing this for about a year. How and why did you start doing this? Where did this come from?

[Dr. John Smirniotopoulos]
That's a great question. We wanted to start getting musculoskeletal procedures involved in our practice. We had an interest in genicular artery embolization, which we had already done some work on, in addition to a lot of vertebroplasty, kyphoplasty, and then malignant ablations, things like that. We do a lot of that at baseline, and then we had started incorporating more pain interventions, and we thought, we like the MSK field, what else can we bring to the table? I, again, went to a medical school where 20 people in my class went into ortho by Georgetown, and a lot of them, like myself, have moved back over the years.

When I came back, we started talking about what procedures IR can help them with, just because in IR, I feel that we learn a procedure, learn a disease pattern, maybe get bored, and then try to find something new to do. We started talking with our ortho colleagues, and I reached out to some of my friends and said, listen, what about controlling some of the joint issues that you guys are facing with your patients?

We presented ablation. We looked it up, read some papers in the pain literature, talked to the local rep for the specific company we use, which is Avanos COOLIEF, and started evolving the practice that way. It was out of interest in seeing what other specialty we can help with patients and maybe grow a clinical arm of our practice directed towards those ortho musculoskeletal patients.

[Dr. Michael Barazza]
Was there much information out there on it to research and learn as you started to take this on?

[Dr. John Smirniotopoulos]
That's a great question. A lot of the data in pain management in general, right, is going to come from the pain literature and then PMNR as well. That's where the bulk of it does come from. Certainly in the knees, it's probably the most studied compared to all the joints of the body. There's plenty of randomized control trials, again, from the pain literature, comparing specifically radiofrequency ablation to other conservative modalities of treatment, such as intraarticular corticosteroid injection, hyaluronic acid injection.

That data has existed now for several years, and it was something we could piggyback off of to learn about the disease process, the treatment paradigms, have those conversations with our ortho colleagues to say, this is what the data shows, this is what's out there, here's how we can help.

[Dr. Michael Barazza]
John, you mentioned that you guys are also doing genicular artery embolization there, and that's building steam as well, particularly in the academic world. I'm wondering if it was hard to carve this out as a second treatment when you guys are already doing something for knee pain there.

[Dr. John Smirniotopoulos]
The GAE is interesting. It's certainly recognized amongst our ortho colleagues as a modality to treat hemarthrosis, recurrent hemarthrosis, and that's primarily what we're doing those for. We have very good anecdotal results from that. It's clearly borne out in the literature. Treating primary osteoarthritis of the knee with GAE is in our literature, in IR literature. I've noticed that from the orthopedic side, it is taking a little bit of buy-in for the primary OA population. I think they have a very interesting rationale behind that. It's not just don't cut off the blood supply to the joint.

Their thought and their concern is if there is a chance the patient may have a knee replacement within 12 months, they are concerned about wound healing globally, and so when we presented the ablation as potential minimally invasive therapy, they jumped on that and they really enjoyed that as an alternative. Now, the question is where do you work GAE in into the treatment pattern? It's tricky. My algorithm for this, and the algorithm we're trying to really push forward at our institution in the appropriate patient, of course, is we'll start conservatively with the nerve block for the nerve ablation.

If that works, we'll do the ablation. If a patient has limited response, meaning under six months of treatment effect, which is the standard of what you would want to see after ablation, and at six months is also what insurance limits you in terms of a global period to perform a second ablation, but maybe if they have a short response, then we can consider GAE and going in an algorithm and in a very appropriate fashion that makes not only the patient happy because we have alternative treatments, it makes us happy because these patients will come back to you and they'll talk to you, and they'll say, my pain came back sooner than I thought it would. It makes our orthopedic surgeon colleagues also happy because we're trying to be as gentle as possible on the joint that they may eventually want to replace.

(3) Knee Pain Management with Genicular Nerve Ablation

[Dr. Michael Barazza]
My first two patients that I saw for this were patients who are ultimately going to be candidates for a knee replacement. They just can't get it for about 10 months because they had coronary stents. That makes a lot of sense. You mentioned there are lots of injections, there's arthroplasty, there are tons of procedures for knee pain. Why is there a role for a nerve ablation? Is there a gap in the existing therapies that we need to fill?

[Dr. John Smirniotopoulos]
The biggest reason we get referrals for genicular nerve ablation from our orthopedic surgery colleagues is a patient is not ready for a knee replacement. Either they don't want it yet or they just haven't been convinced enough that they need it, or they're not suitable medically. BMI plays a big role into that and they need to lose some weight. Or there's some other reasons such as, again, we have a liver transplant center, so they've had a recent transplant and they should not have an operation yet, and so they need something to kind of bridge the gap, but certainly, there's a patient population that doesn't want the surgery.

Or you have the post-operative patients, the post-TKA patients, where their joint hardware looks great. It's not loose, there's no infection, they've tapped them, it looks fantastic. There's no hemarthrosis, they just have pain. That's where that really plays a role is those scenarios. The nice thing about the nerve ablation is that it does not inhibit or prohibit any future therapy, whether it's an injection or a surgery. That really helps round out and comfort the patient and the orthopedic surgeon. That's where our role is. You mentioned, is there a gap with other injections?

Certainly, there's a lot of data in the orthopedic literature globally now for reduction of corticosteroids into a joint space. There's concern for tendon rupture there. There's concern for wound healing. Some of our orthopedic surgery colleagues are not wanting any corticosteroid, whether it's a hip or a knee, in the joint space within six months prior to an operation. If that's the case, we need something to bridge that gap for a patient for pain control. This is a good modality to do that.

[Dr. Michael Barazza]
John, you've been doing it for about a year now. Any major changes in how your practice, how it's evolved since then? Are they all coming from ortho?

[Dr. John Smirniotopoulos]
The majority are coming from ortho. It's an interesting paradigm how the orthopedic practice can filter into an IR practice. I feel that when we have clinic, we have clinic half day a week for us. When I was at Cornell, it was a full day a week. If you talk to your orthopedic surgery colleagues, they probably have clinic two to three times a week, and they may see 30 to 60 patients in that clinic. Maybe that orthopedic surgeon only does joints, and so, that person is seeing however many patients, 90 to over 100 a week just for a joint.

[Dr. Michael Barazza]
I just can't imagine.
[chuckling]

[Dr. John Smirniotopoulos]
When we started offering this procedure, I was the one that initially spearheaded it, which was great because I felt like I know the surgeons that are referring to me, there's four of them and they're my friends, so this is easy. Go ahead, just send me patients. Before you know it, your floodgates are opening and then they're sending a ton of patients. Our practice rapidly started recruiting patients for this intervention. I've talked to other colleagues throughout the country and it's the same story. When you start doing it, they'll keep sending you more and more from ortho. I had my partners then buy into it.

[Dr. Michael Barazza]
Of course. Now you're seeing you get all the patients. It does make a lot of sense, especially the way you lay it out for a lot of these patients, this is a bridge. They may ultimately get an arthroplasty at some point in their lives. And so, you're not directly competing with them. And you're really helping them with the challenging patient population. It's almost like pelvic congestion syndrome patients for OB. It's not like a UFE. You're helping them get to where they need to be with or without a knee replacement. It makes a lot of sense that they'd be happy to send them.

[Dr. John Smirniotopoulos]
One other thing about that is that we got eager with this when we started it. We had our orthopedic colleagues and I said, this is great. Why don't we go ahead and start giving talks to some of the primary care groups? So, we started doing that. Then we set up our website so people can self-refer on a form. Yes, majority are ortho, but we do get a lot of self-referrals and primary care that send it too. Once you start doing it and people start knowing you do it, you're going to start getting a lot of patients coming [crosstalk]

(4) Patient Selection for Genicular Nerve Ablation

[Dr. Michael Barazza]
My first patient actually came from-- I gave a talk to a primary care doctor's group. An ortho doctor, a guy had reached out to her just out of blue, he's like, do you know any interventional radiologists who might do genicular artery embolization? She's like, yes, actually, I got a guy. That was a pathway where I started getting my first ones. Then now the ortho is just sending them directly. Let's start getting into the details of genicular nerve ablation. To start, we've already kind of covered some of this, but what are the general indications, and how do you decide who's a candidate?

[Dr. John Smirniotopoulos]
I think the best question is how do you decide who's not a candidate at this point. Because it's almost like you could do this for anyone, and that's what we see here. I think the most appropriate candidates are candidates with some degree of osteoarthritis. Now, if you look at data from the randomized control trials for this procedure, look at the sham trial for GAE, and a lot of the published data that's out there, the Kellegren-Lawrence scale is typically mild to moderate OA. We do not restrict that in clinical practice, and I'm sure other people do not restrict GAE or ablation for that.

Really, anyone who has any degree of OA, who does not want surgery, is not a medically surgical candidate yet, who has had prior surgery. It's a wide variety of patients there. The ones where you have to temper their results, and they may still want to go forward with it, are the ones who have maybe meniscal tears or recent sports-related injury. We do get those referrals certainly, and we will try the block for them. If the block works, that's fantastic, meaning that they get 50% decreased pain control, and then we'll go for the ablation. I think the biggest thing is making sure your patient that you see is going to be compliant with a physical therapy regimen after you're done.

Chances are they've tried PT and have stopped PT because they'll say it didn't do anything for them. If you can reduce their pain by half or more, then have them go back to physical therapy, because ultimately, that's what's really going to have the biggest long-term effect, strengthening the muscles around the knee joint, getting their flexibility, getting their stability. You're teaching some people how to walk again, because they've been relying on other muscles. Really getting those patients. Who not to do this on, it's almost that you leave that up to the patient, because this is such a relatively benign procedure. If they fail the block, then that's okay. They don't get the ablation.

[Dr. Michael Barazza]
Talking about the workup, you mentioned the WOMAC score. What all do you do in your workup to figure out how they're going to do and monitor their improvement after?

[Dr. John Smirniotopoulos]
When we first started this back in, I think, February is when we did our first ablation of 2022, we were just doing VAS, the visual analog score, so the scale of 0 to 10, and just saying if they got a 50% reduction of their VAS pain scale after their block, and you can do that, usually we do it 30 minutes or greater after their block itself, then they qualify in. Now, while that is how we decide who to ablate, we do collect WOMAC scores and KOOS, K-O-O-S. What we're looking for is not only, yes, pain is controlled, we want to look at the functional status.

The WOMAC is particularly good at that, because it does have a pain component in the survey, it has a stiffness component in the survey, and you may find patients complain about stiffness as their primary issue, and you think to yourself is this going to actually do anything for stiffness? Maybe not, but it somehow does because they will go to PT. Then it has a functional component to it too. We grade their WOMACs at baseline, so they'll come in for their block. I don't do it in clinic, I would do the day of their block.

We grade their block and then we grade it at follow-up. We try to follow up these patients at different intervals, and then we can see how they're improving. Now, all of this is subjective at the end of the day, so that is a component to it. We have discussed with our orthopedic colleagues of looking at range of motion, we haven't adopted that yet. Again, for us, VAS score, WOMAC, and then KOOS are the easiest surveys and by no means does anyone have to do all of them, but that's what we do in our practice.

[Dr. Michael Barazza]
Do you have any imaging that you require?

[Dr. John Smirniotopoulos]
Oftentimes, they do come in with some radiograph. However, if it's an injury like a meniscal tear or something like that, they'll probably have an MRI associated with it. I don't behold them to it, especially the self-referral patients, it may be difficult for them to bring over their imaging, and we have a discussion that yes, of course, we'll be looking at their X-ray under fluoro, we do these under fluoro in our practice. It's not a standing X-ray to really show degree of OA. However, it is appropriate that yes you can still see what's going on there.

(5) Procedural Anatomy & Pain Management Considerations

[Dr. Michael Barazza]
Your nerve block. Let's talk about the anatomy. What nerves are you targeting and where do they run?

[Dr. John Smirniotopoulos]
Probably the biggest takeaway from this is this is all based on cadaveric dissections, the whole anatomy. They've actually gone back and looked at the cadavers again as recently as two years ago and found there are more nerves than they probably initially thought. This plays into the conversation I have with a patient. We're targeting four major nerve trunks here. We're targeting the supramedial genicular nerve, supralateral, inframedial, and then the fourth nerve is the suprapatellar which some people advocate doing, some people don't.

Those are four trunks of nerves. Those are not all the nerves that are innervating the anterior compartment of the knee. I stress that to patients because I tell them your pain is not going to go to zero, I'm going to try to cut it in half, I'm targeting the major players that are here. We do this based on landmarks if you're doing it under fluoro, and what you're looking for for the suprapatellar is about 5 centimeters just midline above the patella. That is a branch that comes down off the vastus and then the idea is that it innervates the kneecap and goes into the knee joint itself.

The supramedial and supralateral, you're targeting that transition, the diaphysial transition where the femur fans out under fluoro. Then the inframedial, you're targeting that transition of the tibial plateau to the tibial shaft there. Obviously, you're not targeting the fibular branch. Foot drops are negative style points. We do this under fluoro, some people do it under ultrasound as well.

If you're doing it under ultrasound and we've done this, it's easy to do in clinic if you have that operation set up where you can bring an ultrasound machine in and you're targeting, again, that transition of the bone from a wide to narrow junction, so to speak, 50% down the width of the shaft to 60%. You're looking ideally for a neurovascular bundle. Sometimes you can actually see the genicular artery and then you're targeting around the genicular artery.

[Dr. Michael Barazza]
Don't inject in there.

[Dr. John Smirniotopoulos]
Exactly.

[Dr. Michael Barazza]
Do you take it all the way down to the bone?

[Dr. John Smirniotopoulos]
Yes. You start in your AP view. You take your needles down and you take it just adjacent to the cortex, to the periosteum. Then when you're happy with your AP view, I usually get all four needles in place. Again, those four that we talked about, I'll transition to a lateral. You're ideally having the affected knee propped up with some pillows or something so you can get the other knee out of the way on your lateral projection. Then you're going to go ahead and if you're on the bone, walk off the bone or be adjacent to the bone.

You're going to push your needles down until you're heading 50% to 60% distance. I tend to go a little bit on the deeper side, again, based on some of these cadaveric studies. Then you're going to inject your 1 to 2 cc's of local medication. We use 0.5% bupivacaine. Some people use lidocaine. The idea is you're creating a spread of a local medicine that's there, local anesthetic. You take your needles out, put band-aids on, and then you reassess them at some time point after the procedure.

[Dr. Michael Barazza]
Dr. John Smirniotopoulos, you're looking for about 50% pain relief, right, in order to proceed with the ablation?

[Dr. John Smirniotopoulos]
Exactly.

[Dr. Michael Barazza]
You don't get anybody who doesn't get that 50% pain relief?

[Dr. John Smirniotopoulos] Yes. It's rare. I actually appreciate those patients that don't because in my mind, they're not trying to convince themselves. It's like, okay, you didn't get it. That's fine. That's okay.

[Dr. Michael Barazza]
We have other things.

[Dr. John Smirniotopoulos]
Exactly. Then we start talking about GAE for those patients. I'd rather have that patient that says, didn't hit 50. Maybe I went from a 10 to an 8. I'd rather have that than someone try to convince themselves they got 50 and then you do the ablation. It's on the rare side that you don't get that 50% response. It's less than 10% of our population, certainly, but it happens.

[Dr. Michael Barazza]
So far, we've had 100% success with the nerve block. That must be really good. How long after the nerve block do you do the ablation?

[Dr. John Smirniotopoulos]
There's no time period that we need to wait, especially from an insurance standpoint because that may play in a role for an authorization. You could do it the next day. We do have some patients that schedule the block and the ablation after our clinic visit. It's more so to guarantee their spot. Then if they don't have that relief, we'll just cancel their ablation. Then if you're doing two knees, and this is probably an important feature here, I tend to block both knees in the same setting to save the patient a trip, but I separate the ablation of the knees.

The ablation of the knees, I'll separate three to four weeks. That's purely based on allowing them to recover, go to PT, get that established. Then some patients, you'll see, their pain started on their right knee. Then six months later, they're like, oh, my left knee starts hurting. They may just be compensating. If you take care of one of the knees, they may start to ease up on the other side.

[Dr. Michael Barazza]
That makes sense. For the actual treatment, do you do local anesthesia again or do you do sedation, or anesthesia?

[Dr. John Smirniotopoulos]
No, we do sedation. Especially our patient population. Sometimes, to be honest with you, with the blocks, we'll do sedation as well. I always ask a patient, how do you do with needles?

[Dr. Michael Barazza]
I wish I had asked that on my last one. The first one was super smooth. Then the next one I did, there was a lot of screaming.

[Dr. John Smirniotopoulos]
You can always tell when it's nerve block and ablation day, because sometimes the screams are heard down the hall. We're shutting down the doors in our angio room. I always have the conversation in clinic before I do anything, how do you do with needles? If they'll look at you and they'll say, needles are not my friend. Okay, let's just give a little bit of twilight, not a lot, a little bit, and then get them through the first procedure. At that point, I make the conscious decision not to ask them how their pain was right after, 30 minutes after. I'll call them the next morning. That way, guarantee that whatever was in their system has worn off or set in fentanyl.

Now, for the ablation, every one of my patients, except for, I think, two, have been with moderate or anesthesia. The patients that require anesthesia, you'll absolutely know from the block if you're giving twilight and conscious sedation and saying, this is not going to be enough for the ablation date. They just need an extra bit of support. Patients with fibromyalgia, I would just book right off the bat with anesthesia. Those are the ones that you're prepping their leg and they're already complaining of pain just from the chloroprep. It's, again, not the majority of minority, majority of ablations we do with conscious sedation, but it happens.

(6) Genicular Nerve Ablation Probe Selection & Techniques

[Dr. Michael Barazza]
Let's talk about equipment. There are tons of different RFA probes of different types. You mentioned the one that you use. How do you choose an RFA probe for this and what are you looking for in terms of the type of RFA and ablation size?

[Dr. John Smirniotopoulos]
There's a lot, as you said, that's out there. There's a lot that has been studied historically out there. We use Avanos cooled RF. It's COOLIEF, that's the name, even though it's heat. The idea, similar to OsteoCool, there is some saline that's being circulated around the probe tip. It is reducing the amount of char that's formed. Therefore, it's not as self-limiting as traditional RF and you get a more uniform, about somewhere between 0.5 to 1 centimeter ball of heat to cause that ablation. It's just more uniform and more guaranteed.

If it's superior to just standard pulsed RF, that is not really worn out yet, it hasn't been studied yet, but conceptually that makes sense that you have a larger ball of heat. You're probably going to capture some of that variability of the genicular nerves based on those anatomic studies I was talking about. That's why we use it. It's also where a lot of the data has come from using that specific probe. If you trust the data, then I would go ahead and use the product that's been shown in the data to work very well. That being said, people also do cryo for this as well.

Other institutions, they'll use a cryoprobe. The thought behind the cryoprobe is you can visualize it under either ultrasound or CT. You can see your ablation zone. You may have a theoretical decreased risk of damaging any muscular structure or tendon because of that control. Again, you are using a cooled device to cause the destruction of the nerve. Plus, you're likely to get some more layering degeneration using cryo than you are heat, so that backtracking of the nerve dying. There's some argument to be used for that too.

That has its own pros and cons associated with it. If you do a lot of cryo in general, you're going to use up your argon gas. How much do the probes cost? Some of the kits that we use come in two or three-probe kits. You can go ahead and ablate three spots at once, and you're in and out of there as opposed to doing one at a time. It just really is up to your comfort. It takes a while.

[Dr. Michael Barazza]
Do you do just one spot with each needle, just burn?

[Dr. John Smirniotopoulos]
That's a really good question. That's how we started. We had those four points, and one of my partners, because I got all of us trained up to do this once the volume got too high, he likes doing the three spots, and there's data to suggest from the pain literature that four spots is superior to three spots in our own unpublished sub-analysis, that's not borne out yet. In any case, we start off with doing one probe at each location. Again, suprapatellar, the superior lateral, and supramedial genicular nerves, and inframedial. Since that cadaveric study came out and I read about it, there was also another study in the pain literature suggesting improved outcomes from doing more than those four spots.

In particular, a pullback technique for the superlateral and supramedial. It's a study that came out, I think, last year, and they had very good results. The idea, again, is that you have variability in where those nerves lie, and specifically the superior genicular nerves. They come from both the sciatic and the common femoral, and so there's just variability on the patient where that's going to go. I, myself, have been doing the pullback technique, meaning I'll go ahead, I'll ablate the suprapatellar, and I'll ablate the inframedial at the same time, so we have a two-probe kit for our purposes, two-and-a-half minutes of RF ablation, reaching 80 degrees temperature.

[Dr. Michael Barazza]
That's not bad.

[Dr. John Smirniotopoulos]
Yes, not bad. Depends on your patient. It might feel longer than it is if they're not that asleep. They'll be squeezing your nurse's hand, that's fine. You do those, then you take those probes out, and then I ablate the superomedial-superolateral at the same time. I'll go deep with it, so you're trying to get the distal tip of your RF probe about two-thirds the way down. That's because it's going to generate a ball of heat that's distal to the probe tip itself by about 4 millimeters. Some of these probes, especially the COOLIEF probe, it comes with a radiopaque marker on it.

The ablation zone starts actually a couple millimeters distal to the radiopaque marker, and then it extends beyond the tip itself. You want to get the tip about two-thirds depth, do your ablation for two-and-a-half minutes, and then pull back to about one-third depth. Repeat the ablation there. I think what's important to take away is that prior to every ablation, we do a motor stimulation test on these patients. The probes allow us to do that.

There's a actual stimulation function on the screen. You hit that, you turn it up 2 volts, and you're looking for any muscle twitching. Sometimes you'll see the probe beat on its own. That's okay. If you see the muscle twitching, it's not subtle, it's very obvious, and then you adjust. More importantly is that I repeat that test when I do the pull-back technique just to make sure I'm not hitting anything superficial that's there.

[Dr. Michael Barazza]
Do you do that with all of them, or just the superior, the motor test?

[Dr. John Smirniotopoulos]
Oh, the motor test, I do for all of them. The suprapatellar is where you definitely see it the most, in the knees. Now, we also do this procedure for the hips. I have seen it for the obturator, and we have to adjust. For the knees, the suprapatellar is where you see it the most. If you do see it for the suprapatellar, my recommendation is to adjust a little caudally, not cranially, because you're going to get off the motor neuron for the vastus, and get more on the sensory motor neuron. Now, if you go too caudal, then you start flirting with the capsule there, and you do risk ablating the capsule, and causing a transient synovitis there.

(7) Complications & Exercising Caution

[Dr. Michael Barazza]
Aside from motor nerves, are there any other structures in the area you really need to worry about?

[Dr. John Smirniotopoulos]
The joint capsule is probably the biggest one. If you read enough of these kind of case reports that are out there, you'll see some people that have had a complication with a transient synovitis, or some type of maybe hemarthrosis. I do warn the patient that that's one of the potential risks, is having some inflammation there that may require arthrocentesis, or something of that nature. The motor neurons are absolutely the biggest concern, and frankly, I haven't seen much fasciculation, except for that suprapatellar, but I still test everything. It is the conversation I have with a patient that it is transient, it won't be permanent, but that is a potential risk factor.

[Dr. Michael Barazza]
Any other complications that you've seen frequently, or that you worry about?

[Dr. John Smirniotopoulos]
No. Occasionally, we're doing this under fluoro in our practice quite a bit. You may put in your 17 gauge trocar needle for your ablation, and you may pull that inner stylet out, and you're going to start seeing blood come back. If you do it enough, you'll see it. What that means, in my mind, and comparing this with ultrasound, is you're probably on the neurovascular bundle for the genicular nerve.

Some of the guidelines will say, put the stylet back in, adjust. I don't think you have to necessarily do that. My thought is that if you're ablating it, you're going to have some type of thermal coagulation at that point, and it might actually make you feel that you're actually close to where the nerve is a little bit more so than if you're doing it just based off markers, but you can develop a potential hematoma with that being said.

[Dr. Michael Barazza]
It's not in a challenging spot to control, I would think, and we're not talking about ablating the popliteal artery.

[Dr. John Smirniotopoulos]
Exactly. It's relatively safe. I think all of us in IR are very comfortable messing around with blood vessels. A lot of the other physicians in the country that do this maybe are not. When the reps train you, they're probably used to training those other types of physicians, and then if we see blood, we're like, I can stop this pretty easily. That's just our specialty.

(8) Navigating Patient Expectations & Outcomes

[Dr. Michael Barazza]
Let's talk a little bit about follow-up. One of the most important things, I think, for pain intervention is setting reasonable expectations, and so I'm curious how you counsel these patients before genicular nerve ablation on what they should expect in terms of the degree and the duration of pain relief.

[Dr. John Smirniotopoulos]
I think the counseling and setting expectations might be the most important part of any pain procedure that we do. It's all about setting up expectations. I tell the patient, for the block, we're looking for a 50% or more reduction. They're likely to have something similar to that when we do the ablation if they're a candidate. Again, we're not a time machine. I'm not reversing their cartilage damage or their loss. Certainly, if they're post-TKA, I'm not taking away their hardware or whatever's irritated there. I think that's very important to really hammer in.

Again, I tell them, look, if I can reduce your pain by 50%, cut it in half, and start getting you to a level of activity that you want, that's going to be the biggest benefit to you. Again, that's where the physical therapy comes in. I really do hammer in the physical therapy. We don't have one particular physical therapist we send people to. However, within our institution, we have so many PT offices in the DC metro area. My referral form, it's a physical form that I actually give them where I can write down their ICD-10 code. It's a script, but I can also circle what I want the physical therapist to ideally focus on.

Range of motion, strength, stability, gait training. Then I will write a indefinite number of sessions with them, but they may ultimately need a referral. More importantly is that I'm the one giving them the script. I'm not asking whoever referred them to give the script. I think that helps the patient really, one, see you as the person taking care of their pain right now until they may or may not need surgery down the road, but also, once they have something in their hand, it might make them a little more compliant with it too. More importantly, though, I tell them whatever pain benefit they're going to have, they're going to see the maximum benefit at six weeks.

Not that it's going to go down, but it's going to take about six weeks or so to really calm down any inflammation and see how much of the nerve was destroyed, see where their functional status was. Beyond six weeks, I doubt that they would improve on their pain. Hopefully, they're not going to get worse with their pain, it won't come back, but that's the maximum benefit. I've seen that with several patients now because we try to follow up with them at six weeks after the ablation, just a phone call, not necessarily a clinic visit, see how they're doing.

That's what we're seeing, is six weeks that it really did start to improve after day two of the procedure, once that soreness from the needles going through the muscle has gone away, because they fixate on that. I tell them it's like a flu shot. You're going to go down the muscle, hit the nerve, and then that'll ease up in two days. Some of them will say even like two weeks after, they noticed a change from one week after, and so they start seeing that.

Our follow-up is a phone call at six weeks. Ideally, I have an e-visit or some type of follow-up at three months just to see where they are, and then again at six months, and at six months is when we start saying, are you doing okay? Do we need to repeat it at this time? If someone says, yes, pain's back. It worked great. It just came back a couple weeks ago. That's fine. They don't need to have the block again. If they have the block and the ablation, they can just schedule the ablation.

[Dr. Michael Barazza]
If pain comes back and it's after six months, you would repeat an ablation, whereas if it happens significantly sooner than six months, that's when you consider GAE or something else?

[Dr. John Smirniotopoulos]
Exactly. GAE has that nice role to play there, and it's a little easier conversation to have, especially some of these patients. Again, they're a little apprehensive about anything, and you start talking about their blood vessels. They might say, what else can we do that's not that first? I think if you trial things out and you set up that paradigm there, it makes the conversation easier to have.

(9) Expanding Nerve Ablation Beyond the Knee

[Dr. Michael Barazza]
Dr. John Smirniotopoulos, we've covered most of what I wanted to on genicular nerve ablation. You mentioned you're doing nerve ablations in different parts of the body. The hip, I know you're doing spines. Could you just tell us a little bit more about what you guys are doing and what your experience has been?

[Dr. John Smirniotopoulos]
I would also preface this by saying the majority of people doing these procedures in the country are not interventional radiologists. There are a lot of pain doctors that are doing this, a lot of PM&R, and they're fantastic at it, and that's where the data is. This is a newer field for IR over the past several years to get into, but there's clearly a national interest in it, and I think we're at a nice position to help with these patients because, one, we typically do this in a hospital setting, meaning that it can actually get reimbursed for the facility. This doesn't get reimbursed at an OBL.

If you work in a hospital setting, it's easy to do, but also we're not really taking away from ortho's business, but it gives us an avenue to work with our orthopedic colleagues. My thought is that if someone can do something with image guidance in a different specialty, we should be able to do it. Maybe we could do it better. Ideally, and the reason we're really pushing this forward is we want to have the data for this to have these nice studies that come out. Again, there's plenty of data out there. It's in the pain literature, but I think we can have our own.

I think we can expand upon what's out there. It does transition to the other procedures that we do. Like you said, yes, we work all over the body as we do with everything in IR. When we first started doing the knees, the Avanos rep said, there's also hip, shoulders, SI joint, facets. We said, okay, I could probably learn that. You'll realize that your ortho colleagues, they'll send you a knee, and sure, maybe the knee hurts. You talk to the patient a little more, then they'll start talking about some other part of their body that hurts. We wanted to be able to offer that.

I think the easiest transition was to adopt the hip. A lot of other specialties don't enjoy the hip. The reason is for the hip, there are two nerves you target. You target the femoral articular nerve. That's twelve o'clock on the acetabulum, easy to target, not a lot of real estate there that could be dangerous. The one that people shy away from is the obturator articular nerve. That's because it's medial, it's the incisura. You are going near blood vessels, so that gets some people nervous. In IR, we try to go into blood vessels most of the time, so we know how to avoid them.

We started doing the hips, and the hips actually work very well. It's a similar process. You do the nerve block, 50% reduction of pain, they can go ahead, have the ablation. We found the hips have a great, great response. One of the things that I tell patients too is, listen, if you don't want a hip replacement, we'll do this. However, if you can get a hip replacement, you should probably get a hip replacement because the hip replacements also do very well. We have a certain number of patients that we do this post-THA. Again, we're not taking away from anything, and we're adding to something that's there.

Now, you may find your knee patients have actually a hip issue and they're coming to you for your knee. Let's say you do the block and the block doesn't work, but you have evidence that they have a way of their hip, so maybe if they have knee pain is actually from the hip and you can start talking about the hip, so we started doing the hip. Then we started doing the shoulder because our sports colleagues, our sports orthosurgeons, they see a lot of the shoulder patients. Maybe they've had a chronic rotator cuff or a rotator cuff repair with residual pain.

They started referring us the shoulder patients. Shoulder patients, you target three nerves. You target two on the posterior aspect of the shoulder. You're going for the suprascapular nerve, axillary nerve, which is going to be the lateral humeral head. Then you're going to be targeting the lateral pectoral nerve, which is anterior. You have to either prop the patient up on a wedge. You wedge the patient up and you rotate the II, or just I found it's actually just easy. Start them prone, do a towel prep on the back, hit the two spots on the back, just flip them.

The shoulder patients do very well also. Now the hip and the shoulder, 100%, I see stimulation of the motor neurons. Be very careful. You have to adjust. Even a couple millimeters lateral to where you see fasciculations is probably going to get you off it, but that's where you see it. So the shoulders, hips do very well. And then we expanded to include SI joint. I'm not sure if you saw kind of in the news after SIR that several Medicare groups throughout the country are not going to reimburse for sacroiliac joint nerve ablation.

That's the L5 dorsal ramus, that's S1 through S3 primary dorsal rami. Interestingly, they are reimbursing for the nerve blocks at those sites, not the ablation. Not sure why, but depending on your location in the country, you may be more limited with the SI joint than others. I would say just like the other, if it's SI joint pain, if it's really SI joint pain, those patients need a 70% reduction of their block, but man, that ablation works well for that particular group.

[Dr. Michael Barazza]
Huh. You're doing basivertebral vertebral nerves too, right?

[Dr. John Smirniotopoulos]
Yes, we are. So we started offering that about eight months ago in June of 2022. We do a good number of kyphoplasties and we certainly do OsteoCool ablation of cancerous lesions. A lot of our friends who sent us SI joint patients are the ortho spine surgeons, so we started talking to them about, what about this procedure? We're getting the ablation game, I guess, for all non-malignant osseous issues. The orthopedic spine surgeons actually see a large number of patients with what they call discogenic back pain. We call it vertebrogenic back pain.

That's axial loaded back pain with associated modic type one or type two changes on MR, symptoms worse with forward flexion, things like asking the patient, okay, does it hurt when you tie your shoes, unload loaded dishwasher, go from a sitting to standing position or just sitting for a long period of time. Different than facet pain. Facet pain, the example I like to give is if you're walking around Target or grocery store and you feel better when you lean over the shopping cart, that's more facet.

Different modality. Again, they have their different procedures that can help them. The base of vertebral nerve ablation really helps for that axial loaded, we call it anterior column back pain, that vertebrogenic pain that the orthopedic surgeons typically, unless there's something truly anatomically wrong with the patient, don't want to operate on because there's no radiculopathy or anything like that. Those referrals come in primarily from our spine surgeons.

[Dr. Michael Barazza]
You've had really good results though with them now.

[Dr. John Smirniotopoulos]
Yes, we have. And if you look at the data that's out there for-- there's a five year SMART trial, there was a sustained reduction of pain over five-year time point. The thought being that these nerves are not myelinated as they enter the bone. That's what we're seeing from our patient population as well. The biggest issue with BVN, basivertebral nerve ablation, is actually the insurance authorizing it right now.

Because it has a CPT code. It's been shown, but getting them to buy into it has been a little bit tricky. I've spoken with colleagues across the country who are doing this. It's the same story everywhere. You know, it is what it is, similar to other procedures that we started doing, like Y90, where you had to fight to get authorization, and then eventually the dominoes start falling.

[Dr. Michael Barazza]
Man, this is awesome. I think we covered just about everything. Hats off to you for building this from the ground up. I really look forward to seeing some more of the data come out from your group. I think you said you're presenting again coming up. It's a very controversial thing if you're supposed to call it guest or jest. That's coming up pretty soon. Anybody going there, look out for Dr. John Smirniotopoulos's group. They're going to be presenting again.

[Dr. John Smirniotopoulos]
Great. Thank you so much for having me. I really encourage anyone who's interested, feel free to reach out to me. It's a fun part of our practice that we have built out. It's a nice change of pace. We certainly do a lot of oncology, you know, a lot of trauma. It's just a different way to treat patients.

[Dr. Michael Barazza]
Absolutely. All right, man. Thank you. We appreciate you sharing your Sunday and expertise with us.

[Dr. John Smirniotopoulos]
Thanks so much for having me.

Podcast Contributors

Dr. John Smirniotopoulos

Dr. John Smirniotopoulos is an assistant professor of clinical radiology in the IR department at MedStar Georgetown University and MedStar Washington Hospital Center in DC.

Dr. Michael Barraza

Dr. Michael Barraza is a practicing interventional radiologist (and all around great guy) with Radiology Associates in Baton Rouge, LA.

Cite This Podcast

BackTable, LLC (Producer). (2023, July 19). Ep. 22 – Genicular Nerve Ablation [Audio podcast]. Retrieved from https://www.backtable.com

Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.