So we're gonna go on and talk about C1-2 fixation. I'd like to acknowledge my current fellow, Coy, who helped me put some slides together for this. And I have disclosures, they're here. I think this is a CME course, so we're obligated to disclose. I do some work with DePue and Globus and some publishing work. So we talked about causes of high cervical myelopathy and instability, and you've seen some very common indications for that between what Eric showed you and what Michelle showed you. For those of you who are seeing things like those guidelines things that Michelle showed, a lot of the upcoming questions on your written boards will be pulled from there. So I would strongly suggest you actually look through and at least memorize the little boxes that come like that because it's likely to come up later on. And at the end of our day today, after Mike Wang speaks after me, we are gonna have a little oral board style question and answer session. So we talked about some of these fixation options at C1-C2. There is options including wiring, there's clamping, there's trans-particular screw fixation, and then there's a C1-2 goal harms technique. And we'll review each of these as well. And these things are also, again, likely to show up in the future and things that you should probably know for exam type things. So, C1-2 clamps, these were used when I was a resident, should have been some time ago now, in the 90s. So basically they're not great in rotation, requires the laminate to be intact, so largely are not utilized nowadays. I've seen maybe just two in the last 10 years of someone trying to do this, and they were both from outside the US. What are the types of C1-C2 wiring? So, Brooks starts with a B, gets bilateral separate wiring, so that's easy to remember. Galley is pictured here. You get a piece of bone wrapped, put on the back of the arch of C1, and then you wrap it around C2. And Sontag put the piece of bone in between C1 and C2 and then squeezed it. And so this is why Michelle was showing you those other pictures, because that's where you get your fusion. It's all well and good to put your screws in, right? If you don't get a fusion, then what happens to the screws over time? And the green shirt. It'll work on fusion. Federal fusion, non-union. Non-union, that's right. So then your hardware will become loose if you don't get a fusion. This is why we incorporate bone graft often between C1 and C2 lamina. Now, if you do not have a lamina of C1, so you had a Jefferson's fracture next to you in the dark shirt, what's a Jefferson's fracture? A fracture of C1, a break in the ring of the lateral anterior and posterior fraction of C1. Okay, if you have that fracture, can you do one of these wiring techniques? Cannot. So where are you going to put your bone graft? You wouldn't be able to do the wiring without the other part of the C3? Yes, you could not do a wiring, but you could put screws. So where would you put your bone graft to support your fusion? Laterally. Laterally where? Facet. Into the facet, okay. What's between you and the facet when you're doing a posterior approach? There's a structure in between you and there. Or C1? No, that's not the structure. Next to you in the pink shirt. C2 nerve root, okay. So what do we do if we want to pack bone graft into the joint? Okay, and then you could pack bone to the joint if you took the nerve root, that's fine. If you take a nerve root, out of curiosity, would you take it before the ganglion or after the ganglion, and why? Okay, let's ask the person next to you there. You guys can take it after the ganglion? No, you take it before the ganglion. Otherwise, you can set up, just as he said, in theory, a neuropathic pain syndrome. Okay, so we can also do mogrel screws. Probably Rusty and Pat are the only two in this room who still use that technique, I'm guessing, since they probably were the only ones facile enough to do it for so many years. Most of us have moved away from this because there is a blind pass between the C1-2 joint and you can hit the vertebral artery rarely. So if you choose this technique, you need to really investigate where the vertebral artery is and if there's anatomic variation in it. What is the advantage of using this technique versus the goal or harms technique? We're going to ask there in the striped shirt. There is an advantage. It's very important in today's day and age, too, when we talk about cost. And that the advantage is that you can get the thing done with two screws rather than four and two rods, plus set screws. So in other countries, when I go and visit, I often will see them using mogrel's technique with the transventricular screws because it's cheap and it's very effective and then they'll supplement with wiring. What is the one technique that captures four cortical layers of bone? That's right, four cortices. What are those four cortices? Let's ask right behind you, Rusty, here in the check shirt. It would be the outer cortex where you enter on the interstitial surface. Okay. And then you have the articular surface of C2, superior articular surface, and then the inferior articular surface of C1. Yep. And the anterior cortex of C1. Very good, excellent. Okay, so if you hit the vertebral artery on one side, which side, by the way, do you think you should do first? Here in the glasses. Andrew, please go for the non-dominant side. Okay, which side is that, usually? Usually right, okay, good. If you do hit it, don't go to the other side. You can, and I say this, but there are patients who they hit on both sides. If you hit it on both sides, that's deadly. That's massive posterior fossil stroke. You hit it on the non-dominant side, there's a reasonable chance that they may not have a deficit at all if they have a patent circle of Willis. So, very important to think about that. So, this is the anatomy of the vertebral artery. Here it's coming off the subclavian. It goes into the formant transversaria. Which formant transversaria does it typically enter first? Next to you there. C6, I'm right in the middle. Yep, good. And sometimes it can enter in C7, so we have to think about that too when we put lateral mass screws in C7, for example. If you look at the distance from the vertebral artery from the midline, it's very important if you're doing a transoral odontoidectomy. So, at the level of C2, it's 14 millimeters from the axis. At the level of C1, it's 22 millimeters from the axis. So, if you're doing a transoral and you have a one centimeter little paper ruler, you drop it there and you stay in the middle, then you're not gonna be far enough, wide enough to be hitting the vertebral artery. So, it's important to note that. So, this is the path of the vertebral artery. And that is the position of the what screw? Right there, with the beard. Andy from Iowa. So, that's the starting point of the tripoticular screw? Yes, that is correct. And it is also the starting point of another screw. C2 bar screw? That's correct. Okay, good. Next to you there in the red, that is the starting point of a? C2 medical, Andy from Northwestern. Okay, good. And then next to you, that is the nerve root, which you would have to go through that to get to the facet joint to pack a full bone. And that, of course, is a C1 entry point. And what entry point is this? That's right, that's a translambar entry point. Very good. All right, so if you see CT scans of axial cuts that look like this, you do not want to do a PAR screw, because that vertebral artery is sitting in the middle of the PARs. You probably don't also want to do a transverticular screw, because you might have problems with that. If you see subluxation like this, and you're going to do a magro type screw, you don't want to do that, because it's not reduced, and you can even see that this person has the vertebral artery sitting at C1, right in the pathway of where you might want to go. So, it's very important to look for aberrations in the anatomy, and figure out if there's going to be something in your way. This is why the C1 lateral mass screw was thought of. Initially reported by Gold, using little plates and small screws. And then Melcher and Harms talked about using rods and polyaxial screws afterwards to make it a bit easier. So, we all talk about all kinds of fascinating anatomy of the thalamus. You know, there's 15 different lines that come here and there. But, if we talk about the fascinating anatomy of C1, C2, there's plenty to be known there, too. So, here you can see all the little grooves and things. This is a very important groove to know about. What sits in this groove here, with the glasses there? That's right, that's the vertebral artery. So, you're looking at this C1 from the top down. So, the vertebral artery comes out of here, and then courses here, and will sit right there before it enters into the formant magnum, to form what? The two vertebral arteries joined together to form the same person? Basilar artery, right, okay, good. And then you can look at the lateral masses. Here's the anterior tubercle of C1. This is very important to look at the shape of C1, because if you're putting a C1 lateral mass screw, and you put the screw there, and on the lateral fluoro, you line it up so it's at the front tip on the lateral fluoro of the anterior tubercle of C1, then a lot of the screw will be extraneous into the soft tissue here, and what structure sits right here next to you there? Carotid, that's right. So, you go a little too deep, and you hit something else red that you weren't thinking about. So, when you do this on C1 lateral mass screw on the lateral fluoro, you want to stop your screw at the back of the tubercle of C1, and not come out too far anterior. This is the side view of the C1. Again, the vert comes out of here, swings over, and sits in the soft arteriosus, and then comes up into the form of magnum. It's very important to notice where that vert is, and if you're taking a bovie and you're exposing C1, you don't want to take your bovie on the top surface of C1, otherwise you're going to meet something red that you don't want to meet. So, this is intraoperative basic anatomy, but you basically put your starting point here in the lateral mass of C1. You're going to go through the lateral mass of C1 with your drill, and then ultimately with your screw, and you want to stop the screw here at the posterior aspect of the tubercle on the fluoro, and not come too far out anterior, and then you put your screw in. You do not need to sacrifice the C2 nerve root. If you're doing a wiring technique to put your bone graft in, you can push the root down and put the screw in, which is what I do, but some people take it and they pack their bone into the facet joint, and then that bone gets into here. So, this is the harm's variation of Gohl's technique, where he put the screws on rods and made them polyaxial to make it easier to line up, and again, if you do this, you don't have to sacrifice the root. You can see that you can pull the screw you can pull the root down, and then put the screw there, and then put the construct there, and then bone graft here. What do you do for hemostasis on your C1? So, I like to use a little bit of gel foam, or a little bit of powdered gel foam type stuff, and then I pack it there when it starts bleeding, and then I go to the other side. When I come back, it's usually dry. But if you keep trying to sit there and bipolar it, it can be a bit painful. Okay, over here in this row here, question mark, the big question mark, what is that structure? This is now looking at C2 from the top down. Is that the pedicle? That's the pars, okay. What's the second question mark? That's the pedicle, good. And which one is this? Same person, oh, I don't know your name. What's your name? Joe. Joe. Pars. Pars, yeah, good. So, this is the difference. The pars connects the superior and inferior articulating processes. So, the pars is there in green. The pedicle basically connects the vertebral body to the superior articulating facet by definition. So, the pedicle is in red. So, those are two separate structures. So, when you say that there's a C2 screw, it's not interchangeable to call one a pars and one a pedicle. They're actually separate different constructs, separate different screw positions and separate entry points. So, make sure that you call a spade a spade. These are the entry points for the pars screw versus the pedicle screw. So, the pars screw entry point from the medial C2-3 facet joint is basically three millimeters up and three millimeters lateral. So, that first little red dot here, there. And the pedicle screw entry point is more superior and more lateral to the pars screw entry point by two millimeters because the pedicle screw is gonna go like that and the pars screw is gonna go like that. So, they have different entry points. And this is a very classic question that you might get asked later on if you were taking some kind of exam. So, here is the pictorial representation of that. Pars screw is number three entry point. Pedicle screw is number two entry point. You can see the differences in trajectories and the C1 lateral mass screw is the white arrow, number one entry point. There's the pedicle, there's the pars. Pictorially, again, represented here with C2 pedicle screws compared to this picture which is C2 pars screws. You can see less lateral to medial than the pedicle screw. So, we reviewed a lot of different techniques here. I'll show you a little surgical video of a C1, C2 lateral mass screw with a translaminar screw now. But you can clamp it. That's really sort of fallen out of favor because it's not good in rotation. You can wire it. We talked about the three different kinds of wiring. So, if you wanna be a star, you can tell people now what the three different kinds are. And we talked about Mogrel's trans-particular screw and then we talked about the C1 lateral mass screw introduced by Gol later finalized by Harms with a polyaxial screw. So, this is the operative view. So, here you can see the Penfield 4 is pulling the C2 root down. I made a small little opening in the back of the C1 lateral mass and I drill a pilot hole. Then I tap the pilot hole. Now, again, where is the sulcus arteriosus? This is here. The vertebral artery sits here. So, I'm on the bottom surface of the C1 lamina. Here's the root here being held by the Penfield. Now, typically, this is hard cortical bone. So, I usually do tap it because if you don't tap it, usually the screw doesn't wanna go sit in there. When you measure the screw size for this, what is the typical screw size? Let's ask here with the sweater tied around you. That's exactly right. 34 in a smaller person, 36 in a bigger person. That's a pretty long screw and the reason is because you're leaving the head superficial to the C2 root and that's why it ends up being long. Some people put smooth shank over the C2 root. I usually thread it all the way down. Know that it makes much difference, but that's why it's such a long screw. So, it's good to tell your scrub person before you start what two sizes of screw to have ready so they don't sit there and fumble about in the back table while things are oozing from the little plexus that sometimes sits there. Here's the translaminar screw entry point. So, a little hole there, we take the gear shift or you can use a drill. The issue with the translaminar screw is if people have a big thick neck, then the tendency is to put the translaminar screw at a more steep angle and that's where you end up in a canal. So, you really gotta think about on the translaminar screw that you have to end up in the lamina on the other side. If they got a big thick neck, it's gonna be a hard screw to get. So, you can practice that when you get into the anatomy lab too and then you can put in translaminar screws. And the other issue with the translaminar screw also is this is not my first go-to screw. This is the screw that I use if for some reason I cannot get a par screw or a pedicle screw in because the vertebral artery anatomy is off or someone has already tried a pars pedicle screw that got loose. And the reason is that there's been some instances where people have really thin bone in the pedicle and these screws in the back here are not crossing the instantaneous axis of rotation. And so, what can happen is the pedicles can fracture and the whole posterior element complex can just be loose. So, this is not the number one go-to technique for me. I'd rather have screws that go more anterior through the pars of the pedicle. So, what do you do if you have vertebral artery injury, Dario? You put in a short screw to go to angio, you don't have to do the other side. Okay, so the scrub tech hands you some kind of powdered gel foam stuff. You gonna shove that in there? No. Okay, why not? It'll embolize the nerve. That's right, that could embolize, that could cause stroke. So, if you hit it, you can always stick your finger in there first, stop the bleeding, but you wanna get gel foam and you wanna get a patty. You don't wanna put flowable hemostatic agents because they can get sucked into the vessel and cause stroke. And then, that creates more of a problem than if you just had the bleeding stopped. And you could put a screw in to tamponade if you need to. And then, where do you go post-op, Nathan? Angio. Angio to do what? Well, they have a couple of options, but they may need to take down the vertebrae and convert it to tamponade. Now, if the vertebrae is in a location where you could get proximal and distal control, it is possible to get proximal and distal control, then you could potentially try to repair it. That's not easy to do, but if it's something like this, where the vertebrae is hit in an area that's in sulcus arteriosus, then you potentially could put temporary clips and stitch as another option. But, for the most part, it'll get hit in a blind spot where you can't see. And so, you need to figure out a way to tamponade and get them to Angio. So, I'll stop there. I didn't make it all the way through the front row. If any of you have any questions, don't hesitate to ask.

fixation techniques

C1-C2 spine injuries

surgical options

fusion

anatomical structures

vertebral artery injury