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Coronal Approach (Cadaver)

Transcription

CHAPTER 1

The coronal approach is very helpful when it's necessary to expose the upper or middle facial skeleton. When we make the incision, we will also be looking for the superficial temporal artery, which is commonly accessed to get a temporal artery biopsy. The need for the coronal approach is often due to facial trauma, such as a frontal sinus fracture, orbital fractures, or zygoma fractures. The relevant anatomy that we're going to be looking for today is the specific layers of the scalp, and we'll be looking for more bony architecture than anything else, which includes the orbits and the zygomatic arch. The key parts of the procedure, are the dissection down to the subgaleal plane, and dissection anteriorly to important structures such as the orbits and zygomatic arch.

CHAPTER 2

Alright, so, the coronal approach is helpful when access to the, upper middle-third of the facial skeleton is necessary. Obviously, it can also be helpful when attempting to harvest a cranial bone graft or to deal with some sort of cranial or vault trauma. When the incisions are drawn out, they should normally be in- both a male and a female, about 4 to 5 cm behind the hairline, perhaps even further back in a male, as you have to account for the possibility of male pattern baldness as life progresses, and in a child, it should be even further back to account for growth of the child. In a patient with hair, you could use either twist ties to create a part and then cause a separation of the hair, it's generally frowned upon to shave the hair, although that's possible. You can again use twist ties, or you can use a jelly to just matte the hair and create a part. In a patient who's bald, obviously, we can make the incision wherever we want. So we'll start by making the incision, with a preauricular incision, we're also going to try to identify the superficial temporal artery and vein today. So let's make- just make like a pre- like a crease incision and do it down- so you bring the incision all the way down to the lobule in the preauricular fold. We'll do the same thing on the other side. And then we would pass in the hairline, up into the hairline there. And the incision can be staggered. It can come anteriorly in the midline as you approach the vertex. So bring it a little bit more anteriorly like that. Yes. There you go. And then again, it'll drop here into the preauricular skin crease, down as far as the lobule. And normally Lidocaine with epinephrine would be infiltrated for bleeding. We're going to start in the midline and we're going to basically dissect out laterally as far as the superior temporal ridges, specifically to not get into the temporalis muscles and encounter bleeding. So, the layers that we're going to go through initially are under the acronym of SCALP, which stand for skin, connective tissue, aponeurosis and muscle, loose areolar tissue, and pericranium, or periosteum as it would be known in other bones. When making this incision, initially we'll make hatch marks so we know exactly where to- to realign the- scalp upon closure. So let's make like 3 vertical little hash marks. And this can go through skin down to the connective tissue. Helps us realign things when we close the- the incision line.

CHAPTER 3

And then we'll start in the midline, and we'll be going through- first we'll be going through the skin and the connective tissue and through to the galea, down to the loose areolar tissue. The skin and subcutaneous tissue are really not separable. It's in this plane that one would encounter… Let me have a gauze there. Yes, thanks. That one would generally encounter sweat glands and hair follicles. And this would be normally done with a- a 15 or a 10 blade. So, our first layers will be skin and connective tissue, we're going to go through the galea and we're going to look for that loose- areolar tissue, loose fatty plane. Normally, you would encounter bleeding at this point, if- if electrocautery is used, there would be concern of damaging hair follicles, and then leaving a fairly- prominent and obvious scar. So as we try to find our plane in the cadaver… If this was a live patient, we would be applying Raney clips- to control bleeding, and usually over a sponge. So with each step a Raney clip will be placed to control the bleeding at this stage of the game. So it looks like we've encountered our fourth of 5 layers, which is just above the pericranium.

And we'll carry this out to the superior temporal line. And we'll do that specifically so that we don't get into the temporalis muscle, which would result in fairly significant bleeding. So if we can carry the incision lateral to the superior temporal line, then we can basically, bluntly dissect inferiorly, and then place a scissors, and spread the scissors, and cut down between the scissors, so that we avoid cutting into the temporal muscle. So let's try blunt dissection, see if you can come under there, and try to get it down- somewhere down into here. Try turning it like that, yes. And come flatter, like that. See if you can get it under. I don't know that you can. So we're now dissecting- superior- to the superior layer of the temporalis fascia. Taking down pretty well. Yes. So, with the introduction of a scissors, then we can then extend our line- Is that- can you see our line there? I can't see it. Want to redraw that? If you can see it, that's fine. By using the scissors, we protect the temporalis muscle- and decrease our risk of bleeding. And this can be carried down all the way to the zygomatic arch. So let's come here. And now, I'm at the- basically the root of the zygomatic arch. I'm going to carry it down as a preauricular. You want to come right in the preauricular crease there. And so, the preauricular incision can come as far down as the lobule of the ear.

So again, we'll bluntly dissect- in the subgaleal plane- to protect the temporalis muscle. And often at this time, one would note the glistening layer of the superficial layer of the temporalis fascia, which at the superior temporal line is contiguous with the pericranium. And again, this dissection can be taken all the way down to the zygomatic root, right in the prearicular area. One can note the- what appears to be a vessel, which would be here, which would be the superficial temporal artery. We'll try to dissect that out.

Great. Okay. And then preauricular incision will be made right in the preauricular fold. Down to the lobule of the ear. Now, if we try to find the superficial temporal artery… And you can see the stranding of the, the loose areolar tissue in the subgaleal plane. So one can note the- what appears to be the superficial temporal artery in the subgaleal plane. Okay, and if I close this up, it's about a centimeter behind the wound margin, right in this area here.

CHAPTER 4

So we'll continue now with our dissection, so we're going to dissect bluntly, come from the crest, here. Let's come at this- the top. So we're going to dissect bluntly, and this can be either done with back cutting with a scalpel blade, it can be done with fingers, or the Beaver end of a- of a number 9 malt, or Tessier. So we'll try now to raise the flap, come bluntly there. So come underneath, and we'll get it down. And we're going to take this down to about 4 mm superior to the supraorbital rims. In a live patient, this plane is very clear and dissects very readily. And try coming- come from here, and try coming like even- yes, just like that. So through the skin cadaver, that thin cadaver skin, you can see how readily that plane is developed. And again, this will be taken to about 4 cm above the supraorbital rims. So let's say to about- yes, it's probably fine right there, and just come straight across all the way. Okay. So you can see the glistening layer of the superficial layer of the temporalis fascia, and deep to that, you can see the temporalis muscle. The superior edge of the temporalis muscle is found at the superior temporal line. And again, this fascia is contiguous with the pericranium.

CHAPTER 5

Okay. At this point, we would make an incision in the pericranium from the superior temporal line on one side to the other superior temporal line, and we'll do that now. Why don't you take that, go from here to here, and come right through, straight across. Just come straight down, right into the bone. Okay, and then…

CHAPTER 6

So, if you look carefully, you can now see the pericranium as we've dissected it. So this then is the periosteum. Keep going there. And as we dissect above the root of the nose, we will start to identify the nasofrontal suture.

CHAPTER 7

So our next step to further release the flap is to make an incision from the root of the zygoma, up to the superior temporal line connecting with our initial incision. And this will be done through the superficial layer of the temporalis fascia, and dissection then will be made just deep to that layer. So come just through the fascia, no more. It's important at this point to be very careful of cutting into the muscle, to prevent bleeding. So I'm trying to identify here- that's the superficial layer of the temporalis fascia, and our incision will be just through that. You can see here, this- these are the fibers of the temporalis muscle. And this is the- the superficial temporal fat pad. So we're going to come just through- the superficial layer of the temporalis fascia. And basically it's from the root of the zygoma just to where- to the lateral aspect of the obrit- to the lateral aspect of the supraorbital rim. And then we'll make dissection- just deep to this layer. All the way down to the root, or all the way down to the zygomatic arch. There you go, perfect.

CHAPTER 8

So now we've come through the superficial layer of the temporalis fascia. We'll encounter the superficial temporal fat pad. If we went through the muscle, we would encounter the- the deep layer of the temporalis fascia, and on the other side of the deep layer of the temporalis fascia, we would have the- the temporal extension of the buccal fat pad. And deep to that, we would- be at the temporal bone. So again, this dissection is carried out down to the superior aspect of the zygomatic arch. You feel it? Yes, might connect it to preauricular there. Okay, go for it. By staying in this plane, we avoid the- temporal branch of the facial nerve, which should be in the- basically the galeal plane, or in the temporal parietal fascia. So we'll now come and ex- we'll- connect to our preauricular incision, and our coronal incision. Here, we're coming through the preauricular muscles and staying- just anterior to the external acoustic meatus. Okay, then let's connect- see this right there? Let's connect those guys up. Great. Now, let's dissect here a little bit more- are you down to the arch? In fact, you're anteriorly down to the arch. So if you feel… Take that down? Yes, go for it. Okay.

CHAPTER 9

So we'll go to the- to the right side. So again, you can note here, temporalis muscle, superior temporal line, temporalis muscle, and you can see the superficial temporal fat pad through the superficial layer of the temporalis fascia. Yes, so we're going to now make an incision from the root of the zygoma up to just the superior aspect of the superior orbital rim. We're going to be doing that just through the superficial layer of the temporalis fascia- you're going to come here as your target. In a live patient, this is a fairly, dense, white, glistening layer that's fairly easily to identify. And again, we'll dissect down to the- to the superior aspect of the zygomatic arch. So, we're just lateral to the orbit here, and we're staying just deep- to the superficial layer of the temporalis fascia, and we're encountering the superficial temporal fat pad.

CHAPTER 10

So we're now at the superolateral aspect of the orbit. And we're about to expose the frontozygomatic suture. Let's come, let's do the arches first. Okay, yep, just come right down. So again, in this flap, we would find- lateral to where we're working, we would find the temporal branch of the facial nerve and the temporal parietal Fascia. Can you feel it right, right there, right there, you're right on it. So, there's a periosteum that overlays the zygomatic arch, and we're trying to dissect down on the deep surface of the superficial layer of the temporalis fascia, down to the superior aspect of the arch. And once we're fully at the arch, we'll then make an incision along the superior aspect of the arch to fully release the flap. Can you kind of just try to stand-by, and just kind of feel the tip, and just stand-by. So we're now at the superior aspect of the zygoma, and we're dissecting down onto the zygomatic arch. So this is the frontal process to the zygoma, we're going along the arch, back to the temporal process. And we'll now- sharply dissect the periosteum off of the arch, to get further release of the flap. Try coming anteriorly and just working back rather than start in the middle. You got it. Come through a little bit more tissue there? Okay, go for it. Sorry. Come right there, cut right there. See right here, there's like a- drop in right there. Yes, so here is the frontozygomatic suture. I think we're probably fine, right? And now, if we notice, we see the supra- supraorbital neurovascular bundle.

CHAPTER 11

And as I dissect down inferiorly, I'm right on the nasal frontal suture. This here is the nasal frontal suture. An instrument can be placed, can be- advanced all the way down- to the junction of the cartilaginous and bony nasal support.

CHAPTER 12

This then is the superior aspect of the orbit, and we will dissect out the lateral orbital rim, looking for the lateral canthal tendon. In a live patient, the bone inferior to the supraorbital neurovascular bundle can be released with a chisel- to allow for further exposure of the orbit. So as you can see, the- the coronal approach is excellent for a fracture of the zygomatic- zygomaticomaxillary complex, that would involve the zygomaticofrontal suture or the zygomatic arch. So where there's a comminuted zygomatic arch, it can be fully exposed, reduced, and then rigidly fixed. As we dissect medially through the orbit- let's do this, so that I can do that. The structures that we will encounter are the medial canthal tendon, and then about 24 mm posterior to the anterior lacrimal crest and the medial wall of the orbit, we'll find the anterior ethmoidal neurovascular bundle, about 36 mm posterior to the anterior lacrimal crest, we'll encounter the- can you take that down? We'll encounter the posterior ethmoidal neurovascular bundle, and about 42 mm posterior, we'll encounter the optic nerve. So there's the medial canthal tendon, inserting into the anterior lacrimal crest. And then, posteriorly- we would encounter the anterior ethmoidal neurovascular bundle. And here we note the, the posterior ethmoidal neurovascular bundle. It's also interesting to note the periorbital fat, which again is also periosteal, but the periorbital fat, which becomes, important in suspension of the orbit. If we were to go back to 42 mm, we would then encounter the optic nerve and there's usually at least 3 mm between the posterior ethmoidal foramen and the optic nerve. Now, if we were to have a frontal sinus fracture, we could reduce that, if we had an orbital fracture, with further dissection, we can expose the entire inferior orbital rim and allow for plating of that. We can plate the frontozygomatic suture, we can plate the arch. This obviously gives a, a fairly significant amount of exposure for reduction of fractures. If at this point, we- we wanted to take a cranial bone graft, then we have excellent exposure in which to do that.

CHAPTER 13

So if we were to close this, then we would basically pexy the periosteum at the- at the level of the superior temporal line. We'd do that a little bit superior, we would essentially oversew that so that we have good suspension of the mid-face, and then we would close- We would close our- our wound with a 2-0 resorbable sutures in the connective tissue layer, and we would either do staples or 2-0 sutures for the skin, and we would take those out in 7 to 10 days if we did either- either sutures or staples.