DCR and Nasolacrimal System (Cadaver)
Alright so, I’m just going to show some of the anatomy of the nasolacrimal system, and do a dacryocystorhinostomy to demonstrate that. The first step I guess is to evaluate your anatomy. So middle turbinate here. I’m holding a sickle knife, and I’m operating on the right side of the patient, using a thirty degree camera. So key landmarks are the axilla of the middle turbinate, the vertical attachment, the inferior turbinate, superior edge, here. The uncinate is also going to be used as a landmark for this. Sometimes it’s kind of flexible in this case; it’s kind of rigid. You get the sense that it probably ends right around there. Other sort of virtual landmarks are where you imagine the lacrimal sac to be. And it actually begins up to a centimeter above the axilla. It can be quite high. And then of course, from there it comes down, siphoned to the nasolacrimal duct, and it will exit the inferior meatus. You saw how high it goes, and often you have to remove the anterior wall of the agger nasi in order to get to the lacrimal sac. The other thing when you do a real one is to evaluate your septum too. This one is really nice. And if septum is over and can see - I can technically get in there. Don’t hesitate to take the time to do a little septoplasty, get it out of the way.
So I make my incision, and what I’m going to do, for this next step, is create a mucosal flap. So I’m going to start roughly a centimeter above the maxilla and come forward. And this can bleed in real life, so you want to inject ahead of time, best you can. We’re going to use a needle tip bovie to do this. Then I’m going to make a vertical incision. You can use a scalpel for this or a beaver blade or again the cautery. In this case, I’m just going to drag the sickle knife, so it might not be the nicest incision here. Going the best I can right down to bone. And then lower horizontal incision is going to be somewhere on top of the inferior turbinate, and it’s going to bleed a little bit too. And I want to attach those. Alright. I’m just trying to stay right on bone.
Now I’ll take my freer. Do you always do the mucosal flap? Pretty much. Because then I’ll try to - kinda using PJ Wormald’s technique. And try to preserve that because you can use that it later to cover some of the exposed bone that you create. I find that it creates a lot of - I mean we didn’t preserve the mucosal flaps, because it would just get destroyed. I also like... But I think it is a good idea because it does scar a lot. Even if I do - even if I do wind up removing some of it, I like to preserve it initially, because I can use it to protect the middle turbinate, even if I do end up taking a few quarters of it later. See a lot of really good exposure of the nasolacrimal duct to the bone. That’s the kind of exposure you want to get.
You can even make that incision more anterior. Right. I almost take it back to where I sort of- to the uncinate. Here I think I’m right at the uncinate there. I need to release that down here. And this actually is an avascular plane if you get into it right. Alright. Now unfortunately, the thickest bone around the nasolacrimal duct is right where you’re trying to get to it. The thinnest part is in the posterior part, which you can’t access surgically.
Now I’m taking a kerrison. My next step I’m going to expose the nasolacrimal duct - lacrimal sac. So I’m taking my kerrison and I’m just insinuating back here, trying to get behind the uncinate. Well, actually the bone is in front of the uncinate really. And I’m taking this off. And I’m kind of cracking it and letting go, pulling it. Do you drill or-? I’ll drill later, yea. What drill do you use? I just use a DCR drill, 20 degree, guarded DCR drill. What I used in fellowship - what I used in fellowship was the Sonopet, fancy, expensive. I mean, it was because Alex was using it. He was doing the DCR.
So again, anyways. I’m crunching it, letting go a little bit. The reason I let go is because there’s a chance I can nag the nasolacrimal duct. I don’t want to tear that. I just want to get the bone. As you get higher, you kind of lose the advantage of your kerrison. You really can’t - just cause of the angle you can’t really get much more. Now in theory, we’re probably looking at the sac of the duct there, lower part of it. I can push from the outside, and there we go. You see it kind of move there. You ask yourself, “Could that be the orbit? The periorbita?” Well not really, look how far interior you are. I’m not pressing that deep, so.
My next step is to take my drill and drill away the part that I couldn’t get to with the kerrison. Twenty degree angle on there. It’s got a guard on it. He’s drilling the area of the nasolacrima - the lacriminal sac. You see it’s pretty high up there. You see how the DCR burr has a guarded tip? That’s the DCR burr right? Right, it's got a guard on the back here to protect my mucosal flap and middle turbinate. Again this is the thickest part of your dissection - of bone dissection. The frontal process of the maxillary bone.
I’m releasing my flap, just a little bit more to get it out of the way. This is very dense hard bone. Sort of skeletonizing the bone here, trying to thin it out. Minimize my drill on the sac mucosa or the mucosa itself. I’m just exposing more and more of the sac. Alright so a little more drilling, and I’ll just puncture through here. Alright. So you can see we went a little bit too far. So this is - that’s not lacrimal sac, that’s actually skin, or the periosteum. So I actually went too deep there. No harm done, but that’s when you can just come back and check the lacrimal sac moving area up there or not.
Alright. Now from the outside, I try to put a probe into the lacrimal duct, the lower canaliculus. I’ll try to advance that here. I can see it moving. Again, nice confirmation that we’re in the right spot. And lower canaliculus joins with the upper one to form a common canaliculus, and that’s what enters the sac. And I’m really not trying to torque this probe at all. It’s just sitting right there naturally. I’m getting confidence that I’m in a good location, and I can also - also put my flap back. There’s a middle turbinate. I can see where the middle turbinate axilla is, which is right there. So I can probably actually go higher. I think for the purposes here, I’ll just stop, but you can go higher. So I’m going to make a little incision in the sac. The anatomy is kind of set. From here on out, it’s just technical things to get the right instruments to make these incisions.
The lacrimal sac is here. This is going to be more tough than you think it should be. Because it’s often been infected. So that’s kind of a...there’s nice movement. You can tell that I had to go through several layers to get to that. You can be mislead and think you’re in the sac but you’re really not. Just extending this down. So this flap, you can just lay back, and you can imagine that’s going to heal. Really that’s one of the advantages of the endonasal approach over the external approach. The external approach they don’t preserve this flap. Plus they’ve made a hole on the other side of the sac. They have very good results too, but that’s kind of the theoretical advantages of our technique. So you kind of see how it does go higher. I probably would take a little bit more time and drill this away. Even before I made an incision I could do that, because I already knew from where the axilla of the middle turbinate is right here. I’m still a little bit low. This is probably good enough for most cases.
There we go. So you might have seen I had a little difficulty getting through there, and there’s actually a little valve right here and sometimes that valve cannot be cooperative to you. But this is really nice, so I didn't have to tear, of course it’s not going to bleed here, but I didn’t really push through or tear, it fell in by itself. Now you could in a case like this you might argue not even have to put in, you just over canalicular tubing, guibor, something like that, usually I will for revision cases, at least.
Alright and now your flap, still here, and it’s not so important for the anatomy here, but I would just trim this flap, so that it would cover this bone - cover this bone up here. That’s a great dissection there. Yeah it’s nice. Now I probably didn’t cut that the best, but you can get the sense that it’s mucosa you can lay back down here. It looks like it went too high but again I didn't - it turns out I didn't really have to go higher, but I could go higher. Alright. If you guys look at the monitor, there’s a probe going through the common canaliculus. You got to identify that. That’s how you know how high you are. If you don’t see that then you got to go higher. Right. That looks great. Alright.