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Grand Rounds-Transforaminal Lumbar Interbody Fusion (TLIF)

Charlie Branch and Jean-Pierre Mobasser

September 23, 2011

Transcript

- My name is Charles Branch and I'm at Wake Forest, university of neurosurgery. And with me this evening is Jean-Pierre Mobasser from the Goodman Campbell Brain and spine Institute in Indianapolis. And we're here with the AANS Grand Rounds where we're going to discuss minimally invasive approach to TLIF, Transforaminal Lumbar Interbody Fusion, using image, guidance, and navigation. I think this is a great technique that's developed and has a utility for those of you that are really looking to advance your technology with lumbar spine fusion. As you'll see on the slide here, on my disclosures include both a consulting agreement and a royalty stream, with Wake Forest University from and some of the products that you're gonna see here are in fact products that we've helped develop and for which Wake Forest received the royalty Dr. Mobilizers. So Jean-Pierre. Welcome. Tell us a little bit about, what we're gonna talk about this evening.

- Thanks Charlie. We're gonna go over a minimally invasive navigated TLIF and go through the basics of how to do this and the nuances and pitfalls and make sure everybody has an understanding of how you can get into trouble doing these procedures, but also how you can help people. And I thought we do a case example as I always find that one of the best ways to learn.

- Who's the best? Give us some pearls before we get started, you know, for the person watching, when should they sort of think about doing a minimally invasive image guided TLIF as opposed to a more conventional procedure?

- Sure. I think that you have to be comfortable with every aspect of the surgery before you put them all together. So I think you need to be proficient with minimally invasive surgery and need to be proficient with a open TLIF fusion procedure. And then I think you have to have a fair amount of experience with navigation to know what can get you into trouble and what to avoid. And what's problematic before you try and put all three of those things together in one procedure.

- Great, what about the optimal patient? I mean, this isn't for every patient who might need a fusion. So if you were gonna give us some advice on two or three conditions, that would be the best to start on, what would they be?

- I think starting with somebody who has a fairly straightforward problem, a grade one spondylolisthesis at L4-5 with a little bit of instability who presents with radicular apathy, foraminal stenosis is an excellent starting point for a procedure like that.

- You got a case here that you wanna count it over with us as a great example of how to do that. Why don't you tell us about this ?

- Okay. This is a 40 year old engineer who presented to our clinic with a two-year history of right L5 radiculopathy, and been able to manage it pretty well over the years. But the symptoms started to become progressively worse. He had been through injections in the past, but they had started to not provide the same benefit he had had previously. He's seen a couple of other surgeons, but was looking for something more minimally invasive, I think partially because of his engineering background on physical exam, he's a pretty healthy guy, 5' 9", 160 pounds. Non-smoker really not complaining of a lot of back pain. This was more L5 radiculopathy and traced it out in a pretty classical distribution of significance. He had some mild EHL weakness and then some numbness in the dorsum of his foot.

- All right. And so I know this is not about non-operative therapies, but how someone like this and how long do you make them wait or what non-operative techniques do you put them through before you both agree that you're going to a fusion is the right thing to do. Is there some, .

- Well, I think we all sort of use the same standard treatments to try and make people better. In this case, this guy had been dealing with this for two years. So by the time he got to me, he was at a point where he was looking to get this fixed. And I think that tends to happen to us a lot as the people get to us at a point where they've already failed conservative treatment. And when people start to have weakness and numbness, I tend to spend less time with the conservative treatment to that point and more time saying, okay, we need to get this pressure off the nerve before we suffer nerve damage. But in general, I tend to use therapy, injections, all those sorts of things to try and get people, to see if they can get to a point and avoid surgery, if possible.

- But I think your key point is, someone who has started to develop weakness, especially if an MRI or imaging study shows foraminal compression or some significant pathology, you know, it's time to move away from the non-operative care, and do a structural correction. So what does the MRI

- Well, you can look at this, a sagittal, not quite a midline, but paracentral MRI shows a grade one spondylolisthesis with disc space, moderate disc space collapse in a central herniation at the 5-1 level. If you then look at the foraminal view, you can really see that there's significant narrowing and compression almost flattening the cell 5 nerve root here in the foramen between that bulging disc and the pedicle itself.

- And that's such a great view just to remind everybody that the five root is pretty vulnerable. When if in fact there's a radiology report that shows and somebody balking at letting me do this, reminding the insurance company or the radiologist or whoever is that this is significant neural compression out of the foramen certainly helps you get, this guy taken care of appropriately.

- And I think another point with this, is this is not something that's gonna get better, a time therapy, all those things. The bottom line is this nerve is being smashed by bone and disc. And the only thing that's gonna help, that really is to decompress that nerve.

- The rationale for interbody approach is in fact to restore that foraminal heights to actually get the disc space restored so that the foraminal compression is relieved. Yes, we can do that with a dorsal decompression, but, it sure is neat to see when you got that height restored. Does the axial view help you much?

- For me, the axial view just shows that on that right side, you can see there's crowding around that lateral recess and foramen on the right compared to the left.

- Okay. So here we got a guy who's failed his non-operative therapies. He's, got a progressive weakness and pain and imaging that shows a significant compression of his 5 roots bilaterally in the frame and collapsed disc space. So, you know, I would go ahead and say, it's time to, you said, it's time to move on to an intervention. I think the challenge now is, which intervention makes the most sense. We can sit here and say that TLIF is the best, but honestly, we've got to acknowledge that the goals of decompression and stabilization may be accomplished in a host of ways. And the surgeon needs to pick the way that works the best for him or her and their patient. But I think tonight we'd like to show your way or today, we'd like to show your way, that you can get this job done with very little tissue trial with this minimal invasive approach. So let's see if we can move on forward through that.

- So this is just a picture showing our patient positioning. I tend to use a Wilson frame at some times for these 5-1 cases as I can tend to realign that 5-1 disc. So it points a little more vertically, which makes it a little bit easier than if you have them more in the anatomic position. I also then can raise the head of the bed and tilt the table so that I can make the tube that I'm gonna be working through point more towards the ceiling, rather than pointing laterally and towards the head of the bed. So in the minimally invasive procedure, the first step's gonna be finding the PSIS cause I'm gonna need to dock the reference arc to the patient, in a fixed position. And with the percutaneous manner I can do this adequately. Another option is they have these spinous process clamps that you can use, that work just as well. So you can see in this position, I placed the percutaneous hip pen solidly in position. And then I attach the reference arc to it so that the camera can see it for navigation purposes.

- I'm gonna ask you to give the viewers some pearls regarding this particular step. Obviously this antenna or array, that becomes the reference for the image guidance is really key and protecting it and getting into the right position are absolutely a must. How do you make sure that this thing doesn't get disrupted during the case or constantly get blocked when you're trying to view the reference balls during your navigation.

- That's a critical, actual component of the surgery. If you look down here, I sort of tend to push it down the alium in parallel to it so that the frame is more central. And I also tilt it backwards. So the frame is more towards the feet rather than straight up. This moves the reference array a little bit out of my way and prevent some of the line of sight issues you can get between the camera and your instruments. There are other ways to place this. You can place this from a lateral position across the alium and place it more by cortical in nature. But then I tend to struggle more with the S1 screw on that side as it really does tend to block it. Also critical is making sure your scrub techs learn never to go anywhere near this, and to avoid touching it as much as possible.

- Of course, for those that are still getting used to it, being sure those balls are snapped onto the antenna and not covered with blood, certainly separate . Well, a lot of pearls on that. Okay. So we've got our antenna on, now what?

- Now the O-Arm's wheeled into the room. They spin an image and then they remove it and then we're ready to start working.

- How long does this normally take you to get that from the time you got your antenna docked, to the time you're actually looking at images to navigate? What's something we can shoot for?

- If they've already got the machine up and running in your room, so it's been turned on and it's ready to bring into the room. The whole procedure will take about two or three minutes to bring it in, the image and pull it out. It takes about five minutes to boot the machine up. So we tend to call them ahead of time, have them come in. But the days of point registration and FluoroNav, and an additional hour or two to the case don't exist anymore with this technology.

- So you're pretty happy with this O-Arm, even though it's pretty large and cumbersome to get around the O-Arm.

- Well, the good thing is once you've taken your image, it doesn't have to stay in position anymore. So we actually push it out at this point. And in our hospital, there are three or four spine surgeons so it'll go to another room while I'm using it for navigation.

- Fantastic. All right, show us how you actually use navigated images to get your screws in.

- So once we have the image information up on the stealth station, I use a image guided navigated dilator to plan my skin incision so that I can get my incision, placed over the pedicles and the disc space that I will wanna work on. This way, I'm not fighting the fascia or soft tissues to achieve the angles that I need to. And this is a good example right here that shows the navigated dilator and how that translates to my position over the L5 pedicle, so that I can mark it and know that, that's gonna be part of my skin incision.

- I noticed there's not beam's eye or pedicle view, are , some pitfalls things that the viewer needs to sort of be wary of when he's starting this initial docking and tapping?

- So there are a lot of different views that you can use with this navigation software. I tend to favor the trajectory of views that you see in the top left and right of the screen. And those give me an axial and sagittal view, but in the line of, however, I tilt my hand, if you did an actual true axial view, then the way you tilt your hand, doesn't affect the image as much. So I wanna see how my tilting affects my position. So that's why I choose the trajectory views. But if you're comfortable with a fluoro, AP and lateral, if you're comfortable with the probe's eye view, you can have those options too, in the software.

- The first time you do this, it's important that you get some practice, even with some open cases, would you advocate the sense of even using this navigating system on an open case So you can reference , with what you're seeing on the navigation.

- Absolutely. I think that, this technology doesn't replace your mind in all the things you've spent 10 years learning how to do this is something, a tool to avoid radiation and to improve accuracy. But you have to confirm in your brain that what it's showing you make sense. And so I have my own fail, safes that I utilize to make sure that everything that I'm seeing makes sense to me.

- Very good. And that's, I think that's certainly important. And I think other issue we're bringing up at this point is this image that we have, is the spine as it is right now. And once we've manipulated the spine in any way, this image set is no longer actually entirely accurate. So something to remember as we're starting to navigate, okay, show us how we go ahead and get the screws in here's that technique.

- So this is showing once we've decided where we're gonna make our incisions, we've made the incisions open the fascia, and then this is a placement of the awl tap, and there's a tissue protector around it to protect the muscle. And so you can see how it looks in the patient. And then in the bottom, right image, you can see the awl tap as I've docked in, in position over the L5 pedicle, before I start to advance it so that I'm comfortable with the trajectory. And also the trajectory shows how long a screw I'm gonna wanna put in so that I can start to estimate what it's gonna be.

- point is pretty hard at cortical bone, sometimes hard. How do you get through that cortical bone without awl tap?

- Yeah, the awl tap is pretty sharp. So it's similar to, if I had an open case, if I can penetrate it, then it'll work. However, sometimes you get some pretty dense cortical bone you can attach some sort of navigation to a drill, and there are different techniques for doing this. And I'll actually drill a pilot hole down through the pedicle so that I can pass my tap much easier through that bone and deflect the spine less than affect the accuracy of the navigation less.

- Guidewires. Are you using guidewire still? Or what's that, is that good thing or is that.

- So I think this picture shows the traditional technique with any percutaneous screw system of placing a guidewire and using it as an exchange to re tell, find your hole. I think there's, this is a very good way to do it. It helps make sure that you're going back where you wanna go. It's very safe in that respect. There are some significant risks with guidewires where you could actually advance them through the anterior vertebral body into a vascular structure or a navel. And if you go off access at all with the tab or the screw over that, guidewire, it will start to advance it. So control of that, guidewire is probably one of the most critical portions of this procedure that I emphasize. And because there can be such problems with it. I've tried to look for another technique that doesn't involve the guidewires.

- Is the system gotta navigate. Is there a ball or something that can go on the guidewire to help use it as a navigation tool yet? Or is that still in development?

- I think that's still in development. They are certainly looking at ways to be able to know where that guidewire is, because as a surgeon, when you're trying to focus on what you're doing, it's very easy to forget about these other things going on at the same time, while you're still learning these technologies. And there have been numerous instances of guidewires causing nitrogenic injury. So I've actually moved away from the guidewire at this point, and don't use it anymore for these percutaneous procedures.

- So, you've made your tap let's get our screws in. We're on the contralateral side at this point. Is that correct?

- So, yes, I put my screws in on the contralateral side first, what I wanna do is utilize my navigation when it's most accurate. So you can see here, the placement of the L5 screw on the contralateral side, you can see the placement of the screw here in the sacrum, on the contralateral side. And then we go to the ipsilateral side and tap those holes and prepare them for the screw placement.

- It's better to tap the contralateral hole first or the ipsilateral hole. What does it matter?

- The caudal screw or the caudal hole, which is closer to your navigation, if you think about the ilium and the relation between the ilium and the sacrum, it's always gonna be fairly constant. So which order you tap these in isn't as critical, but I always try to do the work on the level that I think is least accurate or furthest away first, while I have the most accuracy.

- Okay. So we have our screws in the contralateral side, our holes ipsilateral, and now we're gonna dock a dilating tube onto the set, and you can use your navigation to help you

- Yeah. So once I've made my holes, I tend to fill the holes with some sort of hemostatic agents. So they don't bleed during the procedure, then I'll use a navigated dilator, as you see here to find the fossette and find the angle down the disc space. So I can dock my tube in the exact trajectory I want down that space so that I'm not fighting against the soft tissues in the fascia.

- Now I see here in this slide, you're illustrating it with, a solid tuber close to this is a 22 millimeter tube, I guess, I think, would you advise the, sort of the early users to consider the tubes that extra split open or expand just to give them a little more working room at first?

- I think so. I think that when you go down a fixed tube, it's almost like a horse with blinders on it, and you have to be very comfortable working in that narrow corridor. I think for people that are used to looking at their anatomy for a reference point, this can be very daunting. So I tend to recommend people start with a little bit more of a mini open so they can see their surrounding anatomy and have that comfort available to them. If over time they want to move towards this, they certainly have the option.

- Okay. So how do you take off that sort of facet joint and really decompress the brain?

- So here's a view looking through the microscope down the tube that shows the fossette after we've taken off the soft tissues, and you can see the lining of the synovium. I tend to use a drill to drill in that synovium and also create a space so I can fit my Kerrison in there to harvest bone.

- All right. So when you say harvest bones, you're taking with your Kerrison, or you're drill, you're saving all the bone you take out and using it as local autograph.

- Correct. Once the facetectomy is going to be completed. You can see at this point we have a camben's triangle exposed. This is the traversing nerve root, the S1 nerve root. This is the exiting L5 nerve root. This is the disc space where the annulotomy has been performed, and you can see the disc space has been cleaned out fairly generously.

- And do you feel like when you're doing this technique that previously on operate on patient, you're gonna get enough bone to fill up that disc space, you know, really get a good .

- I tend to do sometimes a laminectomy, hemi-laminectomy in combination, while I'm doing this, I typically have more bone than I can fit down there sometimes.

- Okay. And so we've got that bone good central decompression. You take off the entire facet joint. Is that fair statement?

- Yes. And that for me is more, the critical part of the TLIF is that I rarely have to retract the traversing nerve root. We put a retractor down there more to protect the dura and the nerve root than to actually retract it.

- And that's a great looking view. And I think certainly something that everybody ought to aspire to, which is seeing the pedicle below the axilla, the nerve root above and this way, you know exactly where you are and where the critical structures are. Now what? so we've got this exposed and then you're gonna pack that . How many CCS of bone you think you get in an average disc space?

- You know, I don't think I can give you a number that would be accurate. I just continue to pack a disc space until I can't get much more in there. I think it's gonna vary from how tall a disc is, how collapsed it is, the size of the circumference as well. Do you have a feel for how much you put in?

- a funnel that looks like, I'm amazed at how much I can get in, you know, it's probably 15 CCS of bone that you can actually pack in. Again, depends on how granular, how much you've grounded up. But unlike you, I like to get that space packed full above before I put my device in. And now I'll go ahead and put this the spacer in.

- Yeah. And you can see in this case that we had a fairly low line nerve, that was somewhat covering the disc. A lot of times, I won't even see this nerve if it's higher up, I wasn't surprised to see this, given the slip and narrowing and the isthmic , this tends to be more recurring theme, but it certainly can make passing that inner body device a little more difficult. And I'll sometimes have a retractor on that, more to protect it as that cage is passing past it.

- All right. So, and we talked to sort of different people sort of try to push that device on down anteriorly. And sometimes it gets wedged in good and that sort of angled trajectory. But if I can get it to push up front, I will. All right. So now we've got our interbody device screws in. Now what?

- So now as the trickier portion of this operation is going back and then finding the holes that we made before and putting our screws down into them, typically that sacral hole and the trajectory I've mapped is gonna be unchanged because it's in a fixed relationship to the ilium but if you look here at L5, you can see because we've lifted that disc space up. If you look at that trajectory to the top, right image, you can see that the screw now looks to be above the blue line, which was the trajectory we mapped before doing our inner body work.

- All right. So, any tricks that you need to know to get those in, or, I mean, is that pretty straightforward?

- Well, so in general, if you're using a guidewire and you have that, then it'll help guide you back to that whole. When you go to a guide wireless system, I will actually place my screw down on the transverse process. And then while I'm using live navigation, I'll match over the superior side of the transverse process and inferior and see how much different it looks and what the screen is showing me almost. So I can, in my mind recalibrate what the navigation is supposed to be to help me find where that hole should be.

- Fantastic. All right. So we've got those in now. We need to get our rods in about how long do you think you normally would arrive for like the 5-1 level would be what's your sort of average length?

- I think my average for 5-1 is probably 30 or 35.

- And you try to put your graft in compression when you put these rods in?

- I do there's one, you're putting the set screws in, you can squeeze the handles together and compress that area. And I like to do that as well. These extenders also have the ability to reduce a spondylolisthesis. So if you have a good bone, you can tighten down the set screw in the bottom S1 screws and then hold the L5 screws back towards the rod.

- Okay. All right. So rod in, there's a device, there you can see there that measures or gives you a sense of, how long the rod is. what that device tells you is different from what your brain says ahead of time, then you really better sort of check and make sure things are set up correctly. Cause you've already sort of said 35 or 40 millimeter rod, and this thing says 60, make sure you're not on backwards or whatever.

- Absolutely. I think you've gotta continue to use your mind when you're doing these procedures, and double check mentally that everything you're doing makes sense to you and is not different than normal.

- Okay. So you get your rod in and you got those screws locked down. I think you say here, it says check with fluoro. So at this point you're gonna bring a fluoro machine in just to make sure that everything is as it should be.

- Yeah. This is the only portion of my procedure where there's radiation utilized is to check those rods, to make sure they're through properly the proper length. And then also to see if I've reduced that spondylitis basis with all the inner body work I've done, or if I need to utilize the reduction device extenders in order to realign it further.

- Fantastic. All right. So we've got those in, you got, reduced and compressed. How well are you able to actually reduce a with this technique?

- You can actually get a significant amount of reduction. The extenders will go up to about 16 millimeters of reduction at its maximum. Now you have to basically have things pretty loose in order to achieve that. So if I need to do a significant reduction, I may need to have a bilateral facetectomy and decompression to really achieve that kind of reduction, unless there's a lot of laxity in the facet joint or an isthmic spondylolisthesis.

- Okay. So we've got this locked down and out and you know, very little tissue trauma, you know, couple of three little incisions, and certainly at least in my experience this lets the patient get up and get going and recover more quickly.

- Yeah. I think these patients do return to work narcotic use all the studies that have been out there. My experience tends to mimic the only area where I've had a slightly different experiences. My patients in the first week or so have, I think more back pain than what other people have reported. And I tend to see a lot of muscle spasm, and I attribute that to the fact that these muscles are capable of spasming that they're alive, and they haven't been damaged to a point where they've been stretched so much that they can't do that. So I've had a little bit more muscle spasm and back pain for the first week after these procedures, but it drops off fairly quickly. And then they really advance.

- I will with that. So don't get disconcerted when people actually sort of feel like they're a little bit worse, that first layer too, cause those muscles are actually still alive and so are the nerves. In contrast to our OpenTech a little harder on our nerves and muscles. All right. So now you've got, you know, show us a newer technique where, you know, we skip a step or two, and certainly as we develop our technical expertise and the tools, this is an opportunity to actually shorten the time, and improve the accuracy of this technique or at least the safety of it.

- Yeah. We had to develop some tools to help us do this. So we develop these awl tipped taps in order to have the ability to put one device in that will make a hole, tap the pedicles. So it can then receive the screw. And we've been through three generations or iterations of this to this point, you can see on top the first one, and you can see the length of the awl before you get to a screw thread. The problem I ran into with this, as you had to put a significant amount of force to engage this, and you have to be almost a centimeter in before you had two threads that could then pull the tap down the pedicle and in the hard bone, it was very difficult to do. So the second generation, we brought the thread a little bit closer to that tip and it made it a little bit better in those cases. What we then found with the third generation is by bringing that thread all the way up to the awl tip and taking that aggressive fluid all the way up, it's really almost made it much easier where once I get engaged to about this point, which can be done with force in this slight twist, I can then back off and let this tap pull itself down the pedicle.

- It looks little bit wicked, but actually it's actually safer because you don't have to use as much force to get into that pedicle entry zone.

- That's right. And then we use a tissue protector around it to protect that muscle as we're pushing our tap down and twisting it into the hole. So really we've turned this now into a two-step process where we tap the pedicle and place the screw. And what I thought we'd do is show a video of this live in an operating room. So at this point, we now have the video that shows us doing, we now have the video showing us doing the new placement of the pedicle screw. So the O-Arm is taking it's image, and it's now being pulled out of the patient field. And we are now gonna sort of redirect the camera, get the drapes off that we use to keep the field sterile while the images are transferred across. We obviously have two options for draping patients versus the machine. If I'm pulling the machine out, I tend to just use a drape over the patient to protect the field rather than drape the machine. So at this point, we're gonna register our instruments and you can see me register the navigated dilator. If you remember, we use that to plan our skin incisions. That's the all tip tap, which we're registering. And then lastly, we're gonna register the navigated screwdriver for the screw placement. So this was, as we did earlier, you can see live how now the navigated dilator, I can sort of use to plan this, the trajectory and the placement over these pedicles. This is a different case. This is showing the 4-5 level, and you can see the spondylolisthesis here. We didn't have this technology when I did the other case. So this is a newer technology to show that video. And so I've marked the skin incisions, and then I'm gonna make those incisions so that we can then use the awl tip tap to place the screws. Charlie are you using navigation at Wake Forest?

- We are, we actually late adopter, I guess I've been making sure that the alarm or the navigation software really got to the point when shoot or plug and play. And so we've actually acquired an alarm and have the navigation system. And it's a lot easier than it was two or three years ago when the first views came out.

- So you can see at this point, I am not mapping my trajectory down the pedicle. I'm passing the tissue protector down over the pedicle. And then that yellow line that you see there in this area, is the trajectory that I'm gonna use over that L5 pedicle. So once I get the tip seated, I then mark it in a position I want. And you can see, I have to apply a little bit of force to that, to get the tip, to see. And you can see the tip has gone in that blue tip is now seated in the bone. And that's when I get him to mark my trajectory. Cause now I know I'm anchored in place. At this point, you can see the tip advancing and now I can get it to pass with minimal effort. The threads will almost pull the tap down the trajectory. So I'm just making sure I like my aim, but you can look at my hand and see that I'm not applying any force at this point. I'm just twisting it and going down the pedicle with live navigation and seeing exactly where my instrument is at all times.

- Yeah, live navigation.

- And no radiation, that's right. Zero radiation. And I'm not wearing led if you notice during this procedure. So at this point, I've backed my awl tip out and you can see my assistant is holding that tissue dilator in position until the very last minute, I wanna make sure my screw is loaded. The virtual screw is on the screen. Now watch at this point, he pulls the dilator out and I pushed my screw right back down the hole, through the muscles, into the screw hole. And you can see immediately the tip of that screw dropped right into the hole that I created in the bone. And it will do that nine out of 10 times if you keep that tissue protector and cause the muscle opens up like a channel and pushes you right back where you were about one out of 10 times, I'll actually have to feel around a little bit before the tip will drop back into that hole. This shows on the virtual.

- Jean-Pierre, I think you're gonna have to acknowledge that you're really good at this. And so the early adopters, might not find that to be quite as easy as you've made it look on this image.

- So I think you're right. Let me back up and say that I've been doing this technique for about two years. So it certainly took a lot of trial and error to get to this point where it worked as well. This was not something that I was able to do so easily the first time. And there was actual several cases where I'd have to then put the navigated dilator down into the hole and drop a guidewire to work over in order to find it. So this has not been without its trial and errors over time, but at this point, finding that hole has become a whole lot easier. And this is now a good representation of how it goes nowadays.

- And certainly something that people could, that they can do with a little practice.

- Yes. I think that there's nothing that I'm doing that other individuals couldn't do with practice. And you can see at this point I'm doing the exact same procedure to L4. So I am tapping down that pedicle while using live navigation with no radiation exposure. And now I'm backing it out. There is a software upgrade now where they can do a reverse projection. So you can actually mark your trajectory when you're all the way down. So it's an actual, true trajectory rather than a projected trajectory. And that has an increased accuracy. So at this point, same procedure, you can still watch my assistant has the dilators, they pull it out and I immediately put my screw back down and you can see it drops right back into the hole. This is a pretty good representation of how it works. We have not had significant problems doing this. I haven't had to go back and revise any hardware at any point. So at this point, I'm gonna move ahead a little bit with the video. We've got this screw in, now we're gonna go to the other side and you can see, I am tapping those other sides and preparing those holes. And at this point you can see that I'm tapping that LFI pedicle. We're gonna save that trajectory that you can see down the pedicle so that after I've done my TLIF, I can come back and find that hole. As we said earlier, that you can see me passing the hemostatic agent down through that tube, into the pedicle, to achieve hemostasis. And now we're gonna go and perform the exact same thing at the L4 level. And you can see me finding the trajectory. I want making sure I'm away from the facet joint, docking that tip. And then I'm gonna apply a little bit of force, get it to engage, and he's saving my plan now and you'll watch it all. Initially apply a little bit of force right now. I'm crashing the tissue protector down and you can see now I just basically can twist that tip in and the threads now get engaged. And now it's going down the pedicle without any effort.

- I noticed that you changed hands there when you're doing that at the beginning. Now tell us about the antenna on the device. Is that a nuisance or any tricks on keeping that So it doesn't sort of fall out of the field of view.

- Yeah. Great question. So right here, you can see the reference arc, which is attached to the instrument and it tends to rotate. And if you don't hold on to it, it will slide away and you'll lose your navigation. We've talked to the company about creating a little more friction in that so that it won't fall so easily to the dependent gravitational side, but that's an excellent point and a good question. And I had to change hands so I could control that while I was doing it.

- Now this point, you're just feeling to make sure you're in the right spot.

- So at this point we've made both our holes on this side, we've got our screws into the other side. I'm sort of denuding that facet and stripping some of the muscular attachments away. And then I'm gonna try and achieve my trajectory. So you can see I take off the navigation portion and I can now pass my dilators down right over the navigated dilator. And we'll go up to a 22 millimeter dilator and tube. And then I'll put that navigation attachment back on to make sure my tube hasn't moved. What I love about this navigation is I can always see that my tube has moved significantly in the process of what I'm doing right here. And without it, I'd have to take another image to put it back where I wanted it to be. So if you look here, we're attaching the bed rail attachment and articulating arm to the tube before I lock it in position, I will put that arc back on the dilator and see if I've moved out of position. So you can see I'm now more over that L5 pedicle. And then I moved up. So you can see I'm looking at this to make sure I'm happy with where I'm docked. And now I look at my trajectory across the facet and down the disc space to make sure I'm happy with where I am.

- So, is that reference arc that goes on your small dilator? Is that available on everybody's kit or is that some special tool, .

- That is commercially available. And at this point now we just go to our TLIF, which we've already done. For a little over two years now. So we've been doing this for a little over two years now, and we haven't had to return anybody to operating room for screw misplacement. The toughest problem I've encountered is that dense sclerotic bone, or I can't really penetrate with the awl and the amount of force I'm having to apply, is too much. So that's when I go to a navigated drill and I drill a pilot hole down that pedicle so that my tap can then be utilized.

- You know, I think it's a great technique. Certainly the capacity to limit or minimize tissue trauma is real. I think we got accepted. You make it look easy because you've done a lot and certainly fit the term expert. But, I think we've gotta remind everybody watching that we need to approach this in a very step wise or methodical fashion, starting with developing your comfort skillset with the TLIF with an open technique. And then with the mini open, retractors the expandable tubular retractors, really developing the TLIF and screw placement techniques, and then sort of move on up to this next step. I think that's a safest way to do it better for your patients. It gives you a level of comfort and competence that'll make you successful and allow you to get the full benefit of this, really neat navigated TLIF technique. Thanks so much, for sharing this with us Jean-Pierre it's great to spend this hour with you and share a really neat way of doing spine fusion with .

- Okay. Thank you very much, Charlie.

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