Thanks for having me at this seminar. I think it's something I take home pretty immediate to use after every one of these sessions, so I appreciate being able to participate. I want to talk about the far lateral microdiscectomy. I think that this is, you know, there's always the, how many are using tubular access ports for their operations, generally? And the, I have a lot, my colleagues will say to me, they're like, you know, you're a little microdisc, it's not much different than mine, and they wouldn't say there's not, but I think there's an ocean between an open far lateral microdiscectomy and a minimally invasive microdiscectomy. This is what the access port is really at its greatest strength, and it is the reason from my standpoint, these are my disclosures which have absolutely nothing to do with my talk. This is where I, a concept that I have attributed to Kaspar. Kaspar was very critical in 1977 when he wrote about the use of the operating microscope in the use of a microdiscectomy. He says, you know, the operation that we have is very good. We're doing, we're taking a disc herniation off of a nerve root. However, our approach to get there is very bad. The ratio of what we expose to what we, to the actual surgical target is not a good one. And so I've called that the Kaspar ratio, and I've used that to kind of look at every procedure that I do and define the surgical target and see if I cannot create a Kaspar ratio of one to one. And I do that every single procedure regardless of if it's cervical, if it's lumbar, if it's anterior, if it's posterior. I'm striving for a ratio, surgical target to surgical exposure of one to one. I think we all should. And if we do that, then we have abided by the tenets that Kaspar preached when he introduced the operating microscope. So when you look at the early reports, I think the history, I'd love to just have a presentation on just the history of the far lateral microdiscectomy because when you read these early papers, Dandy was actually one of the first to describe the far lateral microdiscectomy or the far lateral disc extrusion. And it wasn't, he wasn't actually describing it, he was describing the ten percent rate of negative explorations. Because before MRI and CT, they would put some lipid diol and they would inject it into the fecal sac and get an x-ray. And what you could see is what, that's what you'd get. And so you wouldn't see the far lateral recess. But someone would have a classic L4 radiculopathy, this guy's got to have an L3-4 disc. They'd go and take the patient to the operating room. They would go and move the nerve root, no disc. He called it a negative exploration. He was looking, the neurological examination was correct. The patient did have an L4 disc herniation. It just wasn't at the L3-4 level. It was in the far lateral recess at L4-5. And it wasn't until a later generation with the CT where they say, hey, this is how you do it. And the way it was surgically managed was from medial to lateral, which endangered the PARs and would result in PARs fractures. So this is a, this is from Joe Maroon's article. This is in the mid-90s. And this is the exposure for a far lateral microdiscectomy. And so I, again, we want to, we want to see what is, what is the surgical target? So let's, let's try and define that. So I want to go through the first part. When, when I, when I talked to the, to the fellows in residence about this, I said, let's, let's really define this because one of the things a minimally invasive spine surgeon needs to know is the, these measurements. We need to have these measurements off the top of our head because we have to reconstruct the anatomy at depth in order to do these operations proficiently. If we, if we're, if we're trying to explore and find, we don't have the midline elements because this is the one time that we are furthest from our, our anatomical bearings. When we, what is difficult about minimally invasive surgery, in my opinion, as far as teaching residents and fellows, is that the midline is the basis of our orientation in surgery. When we do not have the midline, thus our disorientation. And so we have to find a new north star. And that north star in this sense is the pars interticularis, which is the center point of what we need to be looking at. So the first thing is obviously defining the neuroforamen, the component parts, and becoming familiar with the pars. And I think if there's one operation that taught me the far lateral microdiscectomy proficiently, it has been the T-lift. The T-lift made me comfortable approaching lateral, getting the pars, identifying the lateral aspect of pars, comfortable with the foramen. Because then I became comfortable with recognizing the superior aspect of the inferior articular process and getting my bearings there. Because again, I'm going to be working only, only on the basis of the surgical target. So this is the, obviously the neuroforamen, the contributions from the disc, the contribution from the pedicle, the pedicle, it's a pedicle, the pedicle defines the neuroforamen, as we all know. Not much of a contribution from the pars, but the pars is our access to the neuroforamen, and that's what, that's what I use. Obviously in this case it's not so much foraminal compromise from degeneration as it is from a disc extrusion. And so, what I need to know is, what is that distance? So if I know that distance and all of a sudden I can begin to make the argument for what kind of access port I'm going to use. So there you have an extrusion that's displacing the nerve root up into the pedicle, which is how, typically how I find them. So what I went through, we built a three-dimensional model, I call this Gilgamesh, it's my three-dimensional model with which I do, we're trying to work on some AR and some VR projects in our shop. We use the Punjabi papers in order to define exactly what these foramen are, the dimensions of them. And again, this is what we use as the basis of our, to establish what we're going to use for our access port. So, now what I need to know is what that, what that ring is. I need to know the dimensions of that ring so that I can make my, make my argument. There's a beautiful paper written by Rulin in the early 90s that really defined all of these parameters, and he actually wrote a paper for the anatomical basis for a farolateral microdiscectomy, which I think is, I give that, that PDF to the fellows, I say, look, you've got to read this. The pedicle, which I put in blue here because that really, after we get to the PARs, the next step, you got to find the pedicle. Because you do not want to be, you've got a small exposure, a limited area, the pedicle will lead you straight to the nerve root. And the, I don't know why, there's like a sense of humor because the disc and the nerve root can look exactly the same when you're in these, especially when, with a nerve root that's completely displaced. I cannot tell you how many times, if it wasn't for the pedicle, that I would have taken an 11 blade and gone right into the nerve root. But it is just finding that pedicle, using a right angle ball tip probe, and pushing down, and then unequivocally you can find that nerve root. So these are the dimensions, this is what Rulin in his paper called the operative window, and that is the distance from the inferior aspect of the transverse process to the superior aspect of the superior articular process from the level below. So at L3-4, I put the most common measurements that we're used to, or most common levels that I'm used to dealing with. I don't see a lot of far lateral herniations at L1-2. At times L2-3, sure, but more common L3-4, L4-5, and L5-S1. And L5-S1 has its own tricks. So 10 millimeters, and again we're trying to build the argument for what size access port to use. Here it's 7 millimeters with a range of 3-14, and then at L5-S1, very small window, very small window. As a matter of fact, I see Dr. Fessler in the back, he wrote a really nice paper about the far lateral microdiscectomy at L5-S1 and having to drill the sacral ala in order to get access to it, which is, if you're not prepared to do that, then it's going to be a long day in the operating room. A far lateral microdiscectomy at L5-S1 is not always an easy task. So I assembled all of these measurements, took it into my model, and I said, okay, I am now going to define my surgical target. My surgical target is not going to be any greater than 16 millimeters by 16 millimeters. I've extracted it, and this is how I approach it, so therefore, what should my access port, it should be a 16 millimeter access port. And so the surgical target defined is 16 millimeters by 16 millimeters. That's what I'm going to use to do this procedure. If I put the access port in the right place, as Nelson Oisiku would say when I was a resident, Bob's your uncle and Fanny's your aunt. So this is what it would look like if I've got, if on a good day, this is what I should be looking at. Now this is the one procedure where I see Mike Wang in the back, and I know Dr. Fessler has got his experience at the endoscope. So this is one of the times where I think that I'm interested to see if this, that's all the exposure you have, and in endoscope and get there, is that, do I parlay my knowledge of the anatomy here into the endoscope? And that's a question I haven't answered myself yet. I can tell you there's something very heartwarming to me to find the nerve root first, and I haven't had that confidence with my experience with the endoscope in the lab and the nerve root. One thing is piercing the nerve root or digging the dorsal root ganglion in a cadaver, it's entirely a completely different thing to have done that on an individual. So, OR setup, nothing, I mean, I set it up just like a microdisc Jackson table, Wilson flame, put the fluoro, the image intensifier opposite my, the symptoms, and I used the, put the operating microscope, although I'm interested to hear what Charlie has to say about some of the more eye in the sky technology, because my neck doesn't feel good at the end of the operating day anyway. So planning the incision at four or five, I'm going to plan an incision four centimeters lateral. And again, I've superimposed the model here. I want a converging trajectory onto the pars. Now the pars is a difficult thing to target from the surface of the skin. So I, and right on the other side of the pars is the nerve root. So I don't want to be driving a needle down into the pars. What I want to do, and this is my anatomical basis for the way I do on a four. So at L3, four, I'll move into 3.5, at L2, three, I'll move into three, and at L1, two, because the pars gets closer and closer, narrower and narrower. So I don't target, the Mac never projects very well. I remember my boards were administered on a Mac and I couldn't see the images very well, and I don't know why that is. So, but there you can't see it very well. The, but the needle is targeting the inferior articular process, which I think is a safer target. We're more familiar with that. That's what, it's a bigger target. It's a safer target. And then from there, what I, what I use is I slide that onto the pars and I want that access port onto the, or my first dilator, I want that docked firmly onto the pars. And so what I do is I start onto my target of the inferior articular process. I'm conscientious of the fact that there is a facet capsule there that I do not want to disrupt. So I'm, I'm, I'm being very ginger with my, with my dilatation, but then I slide it up. I can feel the, it's, again, I'm reconstructing the anatomy at depth. I know the anatomy there. I just slip off the pars. I just closed my eyes and the nurses say, Oh, you're using the force now. Huh? So I just know I want to, I want to eliminate any, I just want the tactile sense of slipping off of the pars. And then I know exactly where I'm at, because again, when you have 16 millimeters, you don't have a lot to, you got to be in the right spot. So then that's a 16 millimeter access port positioned right over in the pars. Now, the one thing is that there is a, there's a gap here. See if I have, there's a distance here that's going to be no matter what you do, because this can easily reach the pars, but the TP and the inferior articular process are going to keep a centimeter or so of soft tissue that's going to be in the way. So you're not going to see what, not like doing a laminectomy, minimally invasive laminectomy where if you wand everything correctly and anchor the access port on there, you should just be having some wisps of muscle, but you should be looking at the unmistakable ivory of bone. Or like when you're dilating over a facet for a T-lift, on a good day you should be looking at almost nothing but joint if you've done it right. Here because of the anatomy, the topography is not as favorable. About a 20 degree convergence onto the far lateral disc, and then here you can see it in surgery, and I do put quite a bit of convergence on there and then I'll have the patient rotate away from me to give me an ergonomic, optimize my ergonomics into the disc. And then an AP image for microdiscectomies or laminectomies, helpful, not necessary. For a far lateral microdisc, I get an image right down the, in line with the pedicle. I want the alzhei, and when I see this, I know where I am, I know where the pedicle is, therefore I know where the nerve root is, and I'll find that disc, and I can feel very confident about where I am. And this is where I tell the fellows, I go, when you have that image, you've got to start reconstructing the anatomy, you should have something like this in your mind. And so this is the anatomy at depth at a minimally invasive spine surgeon, I think, our skill set is different than our open colleagues because they get to see everything. They can find, identify, they have to have recognition memory, right? So we, they activate the, I recognize, all right, we have to have recall memory, reconstruct the anatomy at depth, that's a skill that's actively developed and it happens by these sort of exercises that I tell my fellows and residents to practice. So that's what I want to see when we're down there at depth, but this is what I see. So I, my, under the microscope I see this, but my brain is seeing this. My eye sees this, my brain sees this. So now I know, based on this image, where I am. And from there I'm very confident and I can go about exposing. This is going to be, I'm going to give you, see if we've, should be some video here. So then that's, that's the equivalent of the exposure, and again, there's always going to be a, some soft tissue there, but you can see the, the lateral aspect of the PARs, the, this is the PARs, this is going to be obviously the inferior aspect of the transverse process that I'm very conscientious to keep cautery away from the facet joint. And then this is the bone work that I intend to do. I don't always have to drill the, the superior aspect of the superior articular process, but I, I find it very comforting to enter the foramen, certainly this, the junction of the transverse process and the PARs always gets me to the pedicle, and that is, that's my north star. I, the more of this I do, the less bone work I, on occasion, I get the exposure and everything seems to fall out and I don't have to drill any bone at all. Other times, I need to get that to that pedicle, and again, I want to find that nerve root safely and you can see under the extension of the ligamentum flavum from the midline is the intertransverse process ligament. This is the exposure. Let me see if I can get this to play. So I take a, so I take a, the drill width of, of the PARs. So, a two millimeter burr, I'm going to just drill, just to be able to get into the foramen, and that's the bone work that's done, and so now I'm going to be able to access, and this is, again, the right angle ball tip probe. There's always the unmistakable perineural fat, and so I have to be able to feel that, this is not video, so we're going to, and so I, there's a video capturing that. I think it's the next slide. So the ball tip probe, this is, I think, the first thing that needs to be done. When I do this, all of a sudden I know exactly where I am. There's the perineural fat. I want to be able to go medial to the pedicle, lateral to the pedicle, and then you can see the nerve root is right there. I can't tell you how many times I've been convinced it's the nerve root and it's the disc. Other times, I thought it was the disc. It was the nerve root, so I've always find the pedicle, sweep down, and that has not, that has always met with a reassurance that I know exactly what I'm dealing with. Okay, so now I'm working within that cube, and I know I want to get a, take my suction retractor and I pull that nerve root up against the pedicle, and then now I'm looking at the disc there, and so now it's, now we're pedaling downhill. Once we've identified the anatomy here, this is an L4-5, far lateral disc herniation, and the nerve root is being protected with the suction retractor, and then out comes the fragment. Always satisfying when it finally comes out, and then I've always make it, there's always more than you think, and then there's even more. You explore, and the nerve root just doesn't, it's not relaxed, and then this fragment comes out and then we have a relaxed nerve root, so. Then some sort of hemostatic agent, the, I've never had to go chasing too many veins, I just, a little bit of pressure, the more I cauterize, the more it bleeds, so I just pack it. It's like a nosebleed. Just hold it for a few moments and then closure. So, I don't know what your experience is with the far lateral, I don't, I see six a year, as it turns out, and that's about consistent with what Dandy described when he initially wrote about the negative exploration. He said about 10% are negative explorations, I think those were far lateral disc extrusions. I remember one of my residents who's currently on staff, she was doing a far lateral micro disc ectomy with me, and this was one of the times, they don't always go your way, but there was one, and that was the one that was 47, and she's like, wow, that's an easy operation. I said, don't leave here with that impression, don't leave, because this is not, this isn't how they, everything went our way, it's one of the times where the disc kind of jumped out at you, but they can take quite a while while you're sorting things out. I think Kevin Foley, he says he hasn't had any re-herniations, I've went back in preparation for this, I've had 7% of my patients, as it turns out, have gone back to require a T-Lift, I don't, I mean, they don't re-herniate, I guess they don't re-herniate at the same rate, but if they re-herniate 10% of the time, then I've got, that's statistically where I'm at. I've had to convert one almost immediately, this one never cleared the trees, I mean, she was coming in, of course she's the radiologist's wife, she comes in, has a far lateral microdisc, and she never cleared the trees, and I just, I said, look, we just have to do a fusion. I think it's the beginning of a degenerative process, and I don't think that this is the end-all be-all, and I always tell them, I said, look, the most definitive way for me to handle it, it's like doing a posterior cervical foraminotomy, I said, look, this is a great operation, we're going to decompress the nerve root, but it does not stop the degenerative pattern that is happening in your neck, and you, at some point, you may need some more definitive procedure. But it's an outpatient procedure now that I routinely do, I saw these in residency doing the Wiltie approach, I was never oriented, they were bloody, all the Toradol and Ketamine in the world didn't make these patients comfortable, they were miserable, and I would say that this is, and going from the inside out, I think, when the disc is far lateral just makes no sense in my opinion. I do not revise any of these, some people will, I have had a patient who had a fragment completely removed, they put another fragment right in there, the MRI looked actually worse than their preliminary one, and I'm glad I keep operative video, because I was able to show them, look, this was your disc, we took it out. But I don't revise those, because I think that at that point, you just need to, I don't give them three strikes like I would in a microdisc, I don't know what everyone else is experiencing there, you get one shot at the far lateral in my hands, because I've tried to go back in there, and it's very perilous, in my opinion, and I stretch the dorsal root ganglion, it's just a lot easier, so that is, that's my thoughts on the matter, and we talk about this and a lot more at the spine section, so if you guys do spine, come check us out, the meeting has evolved, yes? I see a lot of patients that have initially improvement in the pain, but then they have an aching type of pain, probably from banging the ganglion over with a glass wall. Yeah, you know, this is one of the, we heard earlier about gabapentin, if there's one thing that I have done, and I picked it up from one of these breakfast seminars, having this sort of conversation, everyone, because of the dorsal root ganglion, and you saw me with that suction retractor, I'm twerking on it, and I'm very conscientious of what's going on with the heart rate, this is one of the times where I have the monitor, and I have them turn it up, because if the heart rate really shoots up, I just relax. Do I do interoperative monitoring? I'm a cost-conscious guy, I don't see the, I don't monitor every anterior cervical procedure, and these are procedures that I perform at a surgery center where we would absorb the cost of, I'd get voted off the island by my partners if I- Do you do monitoring? I just use ENT for the technicians that are going to have to do the stimulator. Okay, yeah, I don't do that, so, but I do put them all on Neurontin for, I tell them, we'll talk about it at your first month post-op. This is a great talk, and great images, thank you very much, this is very, very, it's a challenging problem to retract the right anatomy that we're not familiar with, because it's not surrounded by bone, there's half of it that's bony, and then half of it that's soft. There are two actions that we added to this, I didn't actually publish this, but I did One is intraoperative navigation. Now, when I went from doing this with fluoroscopy, where you're zapping yourself, you know, a lot to find that sweet spot, to using navigation, where you dock a PRF on a really high pressure sometimes, just take this location, do a spin, do a spin completely without fluid, and then add direct hand stimulation, it really makes it, in my hands at least, you know, compared to my older men and others who were exposed, it's much safer operation. The anatomy is much better defined, you know, if you go right down into Hamlin's triangle, which can be very variable, or sometimes non-existent, that exiting nerve, and sometimes actually most patients, which we push down all the way down to the lower pedicle, and you go in, find it with navigation, and then find it with stimulation, and you know exactly where you are, it makes it a great operation. But you're right, you get in there, your first look is exactly what you see, and you have to start reconstructing the anatomy in your mind. But, yes, that's a much more expensive way of doing the operation, as you mentioned, probably not something I want to do. But you're adhering to the, again, the Caspar ratio, you're putting, the name of the game is getting that access port in the perfect spot. And that's an art form in it. However, L5-S1 is a whole different... L5-S1 is very challenging to go to far lateral distance. With navigation, you can come as far lateral as you want, almost like an endoscope is a drill, and it can improve. This is great, it's a great sort of segue into the next couple of talks.

far lateral microdiscectomy

tubular access ports

Kaspar ratio

surgical techniques

reoperation

intraoperative navigation