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Grand Rounds-Mini Open Transpedicular Thoracic Corpectomy

Jean-Pierre Mobasser and Dean Chou

April 25, 2011

Transcript

- Hello ladies and gentlemen, welcome to another session of the AANS Operative Grand Rounds. We have an exciting new series of sessions related to technical nuances for complex spine procedures. Our first session is on Mini-Open Transpedicular Thoracic Corpectomy, Dr. Jean-Pierre Mobasser, one of my colleagues will be the moderator for the following sessions. We hope that you find these sessions instructive and at the same time enjoyable, thank you.

- Grand Rounds and our topic today is a complex spine surgery. With us today we have Dean Chou from University of California at San Francisco, and I'm Jean-Pierre Mobasser with Goodman Campbell Brain and Spine in Indianapolis, good afternoon, Dean.

- Good afternoon Jean-Pierre, thank you very much for inviting me.

- Thank you for joining us today. We have an interesting topic, Mini-Open Transpedicular Corpectomy. Dean, tell me, how long have you been working on these?

- We started doing this for about three years, off and on and this sort of evolved from an open technique.

- Great, and let's go through our disclosures and state that none of these disclosures had any influence on what was done here today. So let's start with indications. Can you give me an idea of the types of patients you believe are good candidates for Mini-Open Posterior Corpectomy?

- The greatest indication is probably those with the tumor or infection, but also trauma and deformity patients would be appropriate for this.

- Great, and how do you decide whether or not to go anterior versus posterior when you're doing these kinds of operations?

- I think a lot of it depends upon surgeon comfort level and the anatomy of the patient, if they've had previous thoracic surgery and also the patient's physiology.

- Okay, are there patients that you believe are not candidates for a posterior, who would still be a candidate for an anterior approach?

- I think those patients would be patients in whom one would be concerned about wound healing, such as patients who've been on chronic steroids or patients who've been radiated. You probably want to avoid the posterior approach because the general is a higher infection rate from a posterior approach.

- Okay, and in your discussion in this, we obviously see that there's less blood loss and less operative time doing a posterior approach. But one thing that you mentioned is better neurological outcomes with the posterior approach, can you explain that?

- Yes, we've looked at 80 patients and about half underwent an anterior approach and half under what a transpedicular approach, and we found a statistically significant difference, and that the patients with the transpedicular corpectomy at greater recovery. And we're not exactly sure why we postulated maybe a circumferential bone removal, immediate stabilization, and that you don't have to ligate the stegmentals like you do from an anterior approach. But we're not exactly sure why it happened, but that's what we saw.

- Okay, and choosing an anterior approach versus a posterior, we also have to discuss the ribs and what you do with these. And I understand that this has been something that you've written about, whether to just cut the ribs and move them out of the way versus remove the rib completely. And a lot of that has to do with the pleural effusion problem that you've seen in removing the rib heads.

- Yes, that's one thing I noticed that I would take your rib head out just doing a standard costo-transversectomy and the patients would be fine and then post updates, really. They de-saturate and get an x-ray and there's a pleural effusion there. And so what I did was I set it to just cut the rib and not remove it.

- Okay, while we get straight to it and let's discuss an open procedure and make sure that everybody's comfortable at the anatomy and discussing before we move on to a Mini-Open. In an open procedure, we have to have a good exposure, and it actually has to be a wide exposure to expose those ribs in order to get lateral enough to place the cage. Obviously localizing is going to be an issue and making sure that you have good localization is critical to these types of surgeries. Dean, tell us how he preferred to localize in performing these operations.

- I tend to localize some T1 down with an AP x-ray, just because S1 is so far away and T2 is so far away, and a lot of these spines with the upper thoracic spine is so difficult with the shoulders. And I don't use the 12th rib because some people have 14 ribs and some people as well have 11 ribs. So I tend to just go from T1 down.

- And I think it's also important to mention that radiologists tend to count differently, so I think when the radiologist labels a certain number in the thoracic spine, it's critical to understand how your radiologist arrived at that value when you're determining where you're going to operate. Luckily a lot of times these fractures are obvious enough that on a plain lateral image, you can see the fracture itself or the metastatic collapse of the vertebral body. So in the open procedure, first, we want to place our hardware and you can see instrumentation has been placed. In general we're looking at probably two segments above and two segments below. If somebody is osteoporotic, you may extend that out one or two segments beyond that. Next stage would be to perform the laminectomy and do a wide decompression, expose the spinal cord and the exiting nerve roots, and control bleeding while exposing down the lateral side of the vertebral bodies. And Dean, you tend to use some sort of hemostatic agent when you're exposing down the lateral aspect of the body?

- Yeah, sometimes you'll get into the segmental vessels and if you just stop that just by using hemostatic agents, pour it down there and pack it off.

- Yeah, I think we tend to also have little clips available, if that isn't doing a sufficient job for us. And then we get to the corpectomy now, obviously this is an incredibly de-stabilizing procedure with the spine when you're removing all the supporting structures all the way around circumferentially, therefore the temporary rod placement is critical to holding everything in alignment. Do you want to walk through how you do your corpectomy? This is something that we're going to discuss both for an open-end minimally invasive.

- Yeah, so after I do this, the laminectomy and remove all the pusher elements like you stated, I put a temporary rod in and you can switch that back and forth. And then I moved the pedicles and then you can take one of the nerve roots if you want to, to the thoracic spine. I usually take one or two, if it's just one level, and then I go down with the drill and take out all the body and then identify the disc above and below, I leave the discs for the very end, and then identify the PLL and using a Woodson instrument cut the PLL. At the very end there I move the disc and the PLL at the same time.

- We need to talk about the potential troubles you could face in an operation, such as this. We tend to use navigation, which helps us know where we are in the vertebral body, where the aorta is in relation to where we're drilling. Do you have some sort of AD you use in assessing the critical structures surrounding the surgery?

- A lot of times what I use is... because I use a matchstick for the blunt bur, I tend to just sort of go by feel and it feels softer then I stop and I just use Alo's ligament to protect me from the antrum visceral structures. And if I know the aorta's there, then I'm much more vigilant than on the other side.

- Okay, and then the cage placement, do you wanna walk through your placement of this cage and the issues you can run into in trying to reach around the code in placement?

- Yeah, it's sort of a conflicting thing between getting the biggest cage you can possibly get in there and then your size of your opening. So I tend to use a sizer first, try the sizer, see how it looks and then get a caliper to see how large of a cage to put in. And then I just continue trial down and see whether or not I can get that cage in.

- Do you use a monitoring for this portion of the procedure?

- Monitoring for the entire procedure?

- Yeah, and I think that's an important point is that when you're doing these kinds of operations and have the spinal cord exposed, I think monitoring is a critical component of this operation. So the other thing we need to discuss which allows you that access is the rib heads and what you do regarding the ribs. And I know that this is something you've written a little bit about, and you can see this trap door osteotomy procedure. Why don't you walk us through that real quickly, cause I think it's a very beneficial part of what you've done with this procedure.

- So what I did was... cause when you put the cage in, this rib is in your way, and so what I did was just make a cut and the thing swings open out laterally and that's all it is. Just pushing the rib up and then pull it away and you can put the cage in without dissecting the pleura.

- And do you need to do that in two segments in order to place the cage or is one rib sufficient?

- Usually one, but what happens is this rib doesn't just stick to the vertebral body that you've taken out, but it also speaks to the one above. So you actually have to dissect it away from the vertebral body above also.

- Okay, and this is a nice picture of the cage sliding down with the rib hinging away from the spinal cord, allowing you a little bit more room. Have you found that there are some technical limitations with the instrumentation and accessing this space and getting the cage placed centrally?

- Usually the straight holder makes it a little bit more difficult sometimes, actually we'll see what the Mini-Open technique, but otherwise I just take an APM model x-ray to confirm placement to make sure it's midline enough.

- Before you expand the cage?

- I usually expand it so it doesn't move, I put it in and expanded it so it doesn't move anywhere and then I take an x-ray and then if it looks good I take the holder out.

- Okay, and here's a nice CT scan which shows excellent placement of the cage, and you can also see there have been two cuts in the rib on that side, is this that you required more room in order to get the cage in?

- Yeah, you can see that when I tried the first, which is not very big, I couldn't get the cage in. So I actually had to make a much bigger cut and that's about three centimeters to get that cage in there.

- And have you found that this point that three centimeters is roughly the space you need in order to do this repetitively?

- Yeah, three centimeters seems like a good number.

- Okay, so let's move on now to Minimally Invasive. So we've, discussed the open procedure and I think walked through it quite nicely, now we've got to incorporate the Minimally Invasive aspect to this procedure. Dean, I would say that there's two different components to performing an operation like this. You have to first be comfortable with the posterior corpectomy, which in of itself is a very significantly complicated procedure, but then you also have to have some facility with the Minimally Invasive approaches and be very comfortable in doing these types of things, would you agree?

- Yeah, I think so. I think the requisite for doing these procedures is really being very comfortable with the open first, because essentially it's the same operation.

- Okay, so in this slide here, we have an example of a metastatic carcinoma to the thoracic spine. And I think we're gonna walk through one of the earlier on many opens that you did for this type of surgery. So localization being obviously critical and key. Once the localization's been done then we can see the percutaneous instrumentation being placed over guide wires. Another important note with Minimally Invasive, one of the pitfalls of Minimally Invasive being the guide wires and how they can migrate. Very critical to make sure that your guide wires aren't migrating on you. And so I think surgeons have a whole bunch of different tricks to keep those guide wires in place. Dean, is there anything you do specifically to control the guide wires or miss portion of the operation?

- I always put the blunt side down into the patient and never the sharp side. And then I always... anytime there's a passing of any instrument, it's always held that I take a lot of to make sure it's not migrating.

- That's right, and we always have our assistants hold the K-wires and I will always mark them with a marking pen to make sure that as we're tapping or screwing over them, that the cage wires not advancing with the screw. So here you can see the instrumentation has been placed percutaneously and then a incision has been made midline around the instrumentation to give us access to the lamina. And this portion of the operation, the laminectomy then perform the spinal cord's been exposed, and this is all being done through a Mini-Open retractor system. And then the temporary rod placement to provide the stability while the corpectomy is being done. When looking at your picture here, it seems like there's a pretty good exposure and adequate room. I'm sure though that this retractor sort of limited you in some aspect, hasn't it?

- Yeah, it has. You see the retractors now put to the table, and so when you putting your cage in, it actually limits the access to the cage and we can see that shortly.

- Okay, and is this what you're talking about? This portion right here?

- Yeah, but see how the holder is straight and you're trying to get in a curve fashion, so with the straight holder it's a little more difficult to get it in with this retractor.

- Okay, so it appears at the top end of the attractor is really limiting your ability to rotate out laterally with your instrumentation.

- That's right.

- Okay, but we can see the cage going in and being placed around the dura. Obviously we can see that you've done two different procedures, one with the nice midline incision, and then one with multiple stab incisions. Was the multiple stab incisions early on in the case series that you've done?

- Yes, the multiple stab incisions was basically true, minimally invasive or cutaneous screws and a minimally invasive attractor. And what happened with this patient on the left was that his wound dehisce and he got infected because of the multiple parallel incisions. And so in speaking with Rick Fester, he had a great idea of just doing a midline incision, but do your actual opening in a minimally invasive way.

- Okay, and so in this picture I think we're showing the benefits of a minimally invasive exposure of the muscles and fascia itself. On the left we have a picture of a open procedure, which I think looks fairly typical of how these surgeries go and then on the right we have the same skin incision. However, the muscles and fascia are all intact at every level except where the corpectomy is being done. And so I think we can see there's a significant difference in these two muscular exposures or dissections. Dean, one of the arguments surgeons have had against doing posterior corpectomy have been the damage to the muscle and the ischemia that's done in such a wide exposure of the muscles. Do you think that these minimally invasive approaches help reduce that risk?

- Yeah, I think so. I think they've got a lot of studies to show that in the lumbar spine and I think that the same probably holds true with doing this in the thoracic spine.

- Okay, well let's move on then to another case, and we'll just see a Mini-Open approach. This is for a Metastatic T12 renal cell carcinoma and obviously we know this to be a very vascular lesion. Do you find that these vascular type lesions are something that make you more nervous to do a Mini-Open and not have control, or is that really not a limiting factor?

- Our original thought was if it's Mini-Open, maybe there's gonna be less blood loss because they've showed that with T lists and other minimally invasive procedures. But in this case, it's still very very bloody and it needs quite a bit. So I personally didn't see that significant of a difference in terms of blood loss.

- We've had a tendency to embolize these the day before surgeries and reduce some of the blood flow to the tumors and have seen that that's helped significantly with our blood loss and surgery.

- Yeah.

- Are you doing that at your facility?

- Yeah, we tend to embolize these preoperatively also.

- Okay, so at this, we're doing localization again. Now here we've shown that the skin incision has been opened, but the fascia is still intact. And then we can see the Jamshidi needle placement into the pedicles under fluoroscopy. Dean, do you guys use navigation at all for placement of these screws?

- I think you can, I've used it a few times, but I tend to just go straight back to neuro.

- Okay, so I think that there's a wide range of how this can be done and I think that's more of a factor of how comfortable you and your facility are with navigation versus using the traditional methods. But regardless, we can see that the pedicles have been cannulated and then a percutaneous screw placement over the guide wires through there. And at this point it looks like all your screws have been placed and now we're opening the fascia only over the segment that we want to expose. So at this point the laminectomy has been done and now we're starting to do the corpectomy. Now I see a different retractor, do you wanna comment on why you switched over to this retractor?

- Yes, because originally we put the minimally invasive attractor, and again it's so rigid with the table mount. And we've found that using a plain old cerebellar retractor gives you the same amount of exposure as the other one, yet that's much more mobile.

- And I think it allows you that ability to rotate your instrument or your hand laterally to push the instrument or the cage underneath, whereas that other attractor really blocks you from that maneuver, would you agree?

- Yeah, that's absolutely right, it gives you much more wiggle room.

- Okay, and so at this point, we can see the temporary rod being placed to provide some sort of stability at this point in the procedure and then the rib head osteotomy. So this is the... what I think you've you feel to be, sort of a key portion of the operation is by performing that trap door rib head osteotomy, having access and more room for that cage to then fit down along the way. And here we can see that you can push those ribs laterally after they've been cut. And you have a lot more room laterally to do that. When sizing your cage, is there any specific goals you have in mind?

- Again, the main principles to get the biggest cage you can get, I tried to get it as interior as possible, and those are the big principles. And then the other thing is that because of these expandable cages can expand on you, you don't need such a huge cage to put it in initially, but you can get it much bigger once you get it inside the patient.

- And I think this x-ray really shows nicely what you just described with a nice cage, a very good sized cage, centrally placed in all the way ventrally so that it's up against the apophyseal ring. It looks very nice on this image. And then you tend to cross-link after you've placed the rest of your hardware, do you find this to be a critical portion of the surgery, or a surgeon preference issue?

- Yes, just as you said earlier Jean-Pierre, that this is such an unstable or de-stabilizing operation that is very very unstable and that's why I think the two cross linkers are important. And the other thing like you mentioned is the temporary rod, I think it's really important to do that also.

- And so some people would argue who aren't big supporters of Minimally Invasive, that this incision is no different than a open surgery. I think the point being that it's not really the skin incision when it comes to minimally invasive spine surgery, but rather what you do to the muscles. And I think that the pictures we saw showing the opening just around the level of surgery is a significantly less morbid procedure for the pair of spinal muscles. So we'll move on to this next case and the importance of this case is I think in addition to the cancer and the fracture is the kyphosis and can you correct a kyphosis like this? Did you have concerns or doubts the first time you were trying to do this as to whether you would be able to get an adequate correction?

- Yeah, I think it's someone like this we use the same principles of in an open procedure, really looking at what's causing the problem. It's the kinking and the spinal cord over the apex so if we didn't correct it, we really would have a problem.

- And I think this picture really shows that dura and spinal cord how kinked it is right there at the fracture level.

- Yeah, that's right. That's right before we did any procedure right there.

- Okay, and so at this point now the corpectomy has obviously been done in the dura doesn't look half as kinked as it did on the previous slide. And now we can see the cage being placed ventrally, considering the kyphosis, it looks like we're probably gonna have a much smaller cage just trying to access that space, would you agree?

- That's right. Originally I was planning on taking out three levels, but I only took out one in this case because the other two levels actually felt pretty good. So I just did one level corpectomy, even though we instrumented over nine levels.

- And, your estimate of the bone quality had to do with when you're cleaning off the desk and evaluating the end plates.

- That's correct. And then the other thing is that we did three above and three below because it's a kyphosis correction versus two above and two below.

- Absolutely, and so at this point in the procedure, we're working on the kyphosis correction and it looks like you're reducing your rods down.

- Yes, in this case we're just doing a simple to liver technique put the rod at the... engage it into the upper screws, lock it in, and down and push it into the inferior screws.

- Do you think it makes any difference whether you're a cancer laboring to the superior or inferior screws?

- Probably not so critical. I think it's probably, it depends what you think is more mobile, but I tend to do either.

- Okay, well, this x-ray the postoperative x-ray on the right shows a very nice correction of that kyphosis, compared with the MRI image in the middle. So at this point, why don't we go to the videos and show some pictures and videos, and we'll walk through these together of the techniques that we've been describing. So this first case is a Metastatic Colorectal Cancer T6 and here's the MRI showing the imaging findings with the spinal cord compression. So we're gonna go through the procedure similar to what we've shown in the pictures, and you can see the localization with the correct levels. We're gonna make the skin incision at this point of the surgery, but yet preserve the fascia, just like we have previously. Now this looks like a smaller skin incision so is this just a two above and two below procedure.

- That's right, as you know, the upper thoracic spine tends to be much smaller than the lower thoracic spine.

- Okay, so we can see the Jamshidi needles being placed into the pedicles that I assumed was done with fluoroscopic guidance. And now we're placing the guide wires and then we're gonna go through the normal steps that we do for this procedure, where you dilate through the paraspinal muscles in the fascia tap over the K-wires and then place the pedicle screw instrumentation and the percutaneous fashion. Any concerns in this portion of the case, other than the K-wire, which we previously described.

- Yeah, I think that's the main thing, like you said, you don't care, the K-wire is really critical in this case.

- And I think you're showing a nice live view there so you can see that wire as you're passing the screw over the K-wire, which is another way to control it and have good visualization. We also tend to use navigation for our screw placement, which helps us in controlling where the screws are going and making sure that we've accessed, and particularly in those cases with difficult pedicular anatomy. And it's a very nice picture showing the screw going in under a live fluoroscopic view over the K-wire and making sure they don't advance. So once all our screws have been placed, we're now at the portion where we want to do the corpectomy and expose the vertebral body. And it looks like we've identified and localized the correct area and just open a scene... opening the fascia along the appropriate level. So we can see the initial retractor and this is the Mini-Open retractor that you had initially for exposure to the lamina, so we can form a laminectomy. And I think that any surgeon can do their normal laminectomy type approach, there's not a specific way to do this. And you can see a nice, generous exposure. And I assume at this point you've done your rib, had osteotomies so that you have room to place that cage. Does seem like there's a little bit of tension on the dura as that cage goes by, is that something that you're watching very closely during that portion of the surgery?

- Yeah, that's a great point. There's gonna to be some tension on that it's so free that there's actually some time for you to... there's actually space for you to push gently because if the circumferential decompression.

- Yeah, so I think that the ability of the spinal cord to move to the other side as you're placing the cage is critical and that's why that wide decompression is so valuable. And here's the postoperative image with the drains in place and the nice skin incision. So now we'll move on to another case which shows this, and this is a T5 Corpectomy. And this was I believe one of your earlier cases where we saw that separate skin incision, is that correct?

- Yeah, that was with the true minimally invasive with percutaneous everything and you can see how difficult is it for that occasion there.

- And then we can see those skin incisions where there was a breakdown due to probably poor vascularity after the multiple incisions.

- That's right.

- Okay, and then we move on to the lumbar spine and this is interesting because we bring in another factor, which is the nerve roots. Obviously we have room to work through the nerve routes in the lumbar spine, but they're not as easy to sacrifices as the thoracic spine. So you can see here manipulating that cage around the nerve root, now it's very nicely done. Do you have trouble now re-accessing that cage and expanding it when it's loose like that in the disc space?

- Yes, it's very difficult to meet a device that can grab the cage and then expand it separately, not in a single unit. So it's very difficult to re-grab that cage and expand it, but it can be done.

- And I think one thing we may want to point out for people undertaking these procedures is that these are some edited videos and that sometimes the placement of the cage, the manipulating it around to the center, expanding it, that can sometimes take 20, 25 minutes to do. It's not something that takes five seconds necessarily. Would you agree with that Dean?

- Yeah, absolutely.

- So we don't want people to sort of undertake this and be frustrated that it doesn't go in quite as smoothly or simply as they hoped it would. And then we discussed O-Arm Navigation and any sort of image guided navigation and how beneficial it can be. And that also tends to be something that varies from institution to institution because your scrub techs need to be facile with it, the x-ray technologists, and this just shows a three dimensional image of your hardware that can be rotated with some of the software programs these days. And I think this is one of the points of the procedure that is meaningful to you. And I think also a great help to surgeons is doing this Trap Door osteotomy technique. And we can see at this point that you're drilling over on the rib and creating that osteotomy so that we then have the ability to move that rib. And I think that's an excellent example of how you can push on that wall and move it out of the way to buy that extra space, to replace the cage. And I think that technique also allows for a placement of a larger cage, as you can see here, because without that you wouldn't be able to fit something so large in that space. And at this point, again, the skin incision with the drain placement. Now we'll look at how you disarticulate the rib head as you set out and get stuck. And this is just done by a maneuver with the cub and you can sort of see it pop free when you do that. Is it all, is it a tactile feedback situation?

- Yeah, tactile feedback and it's usually what happens is that rib is stuck into the body above. And that just gives you that little room to move it more laterally.

- Well, I think those are some excellent videos of the technique and they really provide the ability to feel more comfortable in performing these surgeries. It give you an idea of what you can do. So let's talk briefly about complications, I think this is a critical part of this. There are gonna be complications when you're doing complex surgeries, such as this, what are some of the complications you've run into and how have you then altered the procedure to deal with these?

- The first thing that if you looked at those videos, there were two cases of the screws placed one level above and one below, and one of those patients completely fell apart. So much of the early literature shows that nearly a short segment station. I no longer do one above, one below. And it's really important to at least two above two below, because again, it's so unstable, the thing would just fall apart completely. I was lucky with one of them, she was a young woman that L1 burst facture. She still does nicely, but I think for most people, one above and one below is simply not efficient for this type of feature. The second thing that's really important, it's a very important caveat, is if you know your patient does not have a terminal disease such as metastatic cancer, there's so much bone removal, a complete bone removal, and you really have to make sure that patient has every chance with you. And so if you're gonna do say something like osteomyelitis or something like that, it's really important. I use autograph from the iliac crest, but it's really important that if you think this patient is gonna have it's probably not gonna be the operation to do. And then the last one is the patients with osteoporosis. As you know, osteoporosis doesn't accept implants very well and this is so unstable. If you were to do this in an ostial products fracture, it could be a complete disaster because the implants would rip right out pseudoarthrosis rate would be incredibly high. So I'd be very, very careful in osteoporotic patients. I personally do not do this procedure in patients who have osteoporosis, it is so unstable.

- And I think earlier on, we sort of mentioned the pleural effusions that you were having to deal with. And were there any intervention required early on for these pleural effusions, such as a drain?

- Yeah, a lot of them they need to pick up catheter test tube type thing to drain up those blow up fusion, because your surgical drains, the drainage up it comes down, but the drainage is all going to their chest.

- So I think in looking at the poster corpectomy and minimally invasive, there's gonna be risks in either side of this procedure. With the Posterior Corpectomy, you need to know how to manage those risks, with the Minimally Invasive, the risks such as the K-wires, what you have to be very wary of are also critical. So it seems to me in looking at this procedure that this is a very viable option, that it is not a lesser surgery than doing an open surgery. And I think that's a critical component for minimally invasive spine surgeries, making sure you're doing the same adequate operation, not less of an operation, just to achieve a minimally invasive procedure. There's gonna be less blood loss, there's gonna be an improvement in the patient's length of stay. And according to some studies, there's maybe some improved neurological outcome, although we're not quite clear on why that may be. So at this point, Dean, I'd really like to thank you. I think it has been fascinating. And I'm actually looking forward to trying this procedure when the next patient presents itself.

- Well, thank you very much for having me Jean-Pierre, nice talking to you.

- Okay, all right. And this concludes our AANS Operative Grand Rounds.

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