Name: Endoscopic Approach to Thoracic Discectomy
Uploaded: 2025-01-08T00:00:00Z
Channel: Arthrex
Description: Raymond J. Gardocki, MD (Nashville, TN), demonstrates targeting and resection for a transforaminal endoscopic thoracic discectomy procedure.

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<p>Raymond J. Gardocki, MD (Nashville, TN), demonstrates targeting and resection for a transforaminal endoscopic thoracic discectomy procedure.</p>

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VID1-006058-en-US | A | Endoscopic Approach to Thoracic Discectomy

Raymond J. Gardocki

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Endoscopic Approach to Thoracic Discectomy

Hi, my name is Ray Gardocki. I'm an associate professor of orthopedic surgery and neurosurgery at Vanderbilt University Medical Center in Nashville, Tennessee. And I'm here to talk to you about the transradial approach to the thoracic spine. So we have a cadaver draped out here in the lab, and we're going to try to make some markings on it so we can identify the midline, the line coplanar with the disc, and determine our distance from midline. To start our approach. So we've got the center line marked. Now we're going to try to get a nice orthogonal view with the disc which you can see on the x ray is already squared up. And there's our center of our disc. So here we have the lateral line drawn to the front of the disc space. Also a nice orthogonal view of our disc. We're going to mark that line on the body. So that depth to the front of the disc from the midline is typically a good starting point. Another clue on the thoracic spine is where the rib cage starts to roll over. You don't want to go too far lateral, otherwise you're going to go through the lung and into the chest cavity to get to the foramen, which is not ideal. So on the AP we've drawn a line orthogonal with the disk, and on the lateral we found the depth to the front of the disk space. Well these lines define a square. So if you insert at the corner of the square and go in at 45 degrees, you would end up at the front of the disk space. Since our target is the foramen, we're going to flatten out to about 35 degrees. And that's going to put us directly into the foramen. We're going to make an incision around the needle tugging on the needle slightly. You can get a gap between the skin and the needle. And if you cut from the needle away, you'll prevent having a dog eared piece of tissue and make a nice clean cut. I like to make the incisions in Langer's lines because they heal very nicely with without tension. The stylet comes out, the guidewire goes down the needle, and then the needle comes out, being sure not to pull out the guidewire. So here you can see that the guidewire is now in the same place that the that the needle was in. There's now a series of dilators that slowly expands the tissue. This way we don't disrupt any of the paraspinal musculature, but we dilate through it to advance into the foramen. That's the first dilator. Here's the second dilator. Rotating. This allows it to pass through the fascia. You can see that it's docking all the way onto the disc, onto the floor of the canal. Based upon the fact that it's going all the way to the end of the guidewire, there are times when the foramen is a little bit small and the dilator will hang on the lateral aspect of the superior articular process, and that just means that there's some drilling that will need to be done, either with a reamer or high speed burr, to open up the foramen, to allow space for the endoscope and cannula to pass through the foramen. This is the final dilator. And now we're going to insert our cannula. For this I like to use a scalloped cannula because it fits very nicely on the facet joint and cradles it. Again, rotating the cannula allows it to pass through the soft tissues. I'll turn it with the open side down first and see that on that image. The tip of the cannula is hanging on the facet, so it's not completely seated into the foramen. And if I then turn this in advance the cannula, you can now see the tip of the cannula goes all the way to the end of the inserter. That scolloped tip of the cannula is now inserted into the foramen. So as we remove the dilators we'll then be prepared to insert the scope. Quick pro tip here is make sure you remove the dilators one at a time, because if you pull them out nested, they will fall on the floor and it will delay your case. So I like to hold the endoscope with my left hand. For that reason I put the inflow on the right portal. This way it doesn't interfere with my grip. So we'll turn the water on. And insert the scope. Rest your ring finger on the tang and let the scope rest on your thumb. That allows you to zoom in and zoom out at will. The image on the camera, on the scope. There's a little carrot, and that has to be at 6:00 to make sure that your camera is oriented properly. As you turn this, the camera turns and you can easily get disoriented. So you always have to be sure that that's at the 6:00 position. So the position you want to be with your scope is you always want a little bit of metal on the end of your cannula visible. That means that you're not too zoomed in and you're not too zoomed out. So right there is about perfect. So first thing you do is take a small straight pituitary and feel. And I'm going to go dorsally with the cannula and feel I'm going to feel the facet joint. And I'm going to pass ventral to the facet and feel the foramen. So I know that this soft tissue needs to go with the cautery. I can feel bone here and I can feel it sliding off. So I know that's my superior articular process. And this thickened white tissue is going to be facet capsule. Typically when you're in the foramen in the thoracic spine you want to create some space for maneuverability. As you can see here I have bone to my left that's going to limit access to the inferior portion of my disk space. So I'm going to use as a diamond bit to resect the upper portion of the pedicle and slightly expand my foramen. So we have working space to maneuver in the foramen and access what we need to in the spinal canal. The beauty of the diamond bit is it burnishes the bone as you drill. So it's very good about preventing bleeding. It cuts best on the equator of the ball. So if you place the equator of the ball where you want to go, you can drill very precisely. Also the diamond. Bur since it does more of a burnish than a tear of the bone, there's very little debris. So your visualization is better. So here you can see the inner cortex of the pedicle. That's that white looking bone right there. And we can basically place our drill right on top of that and trim it back down to the floor of the canal. So there's basically a little knife edge of bone that extends upward from the pinnacle that blocks your access to the disc slightly. That needs to be resected. You can see this does pretty quick work as long as you're cutting on the equator of the drill. Sometimes when you have this loose connective tissue, you can use the bipolar. And it does a very nice job of shrinking the loose seaweed, as I call it, to be out of your field of view. So now you have a very clear picture of the pedicle. This is the arch. That's the superior articular process. Here's our disc space. And the spinal cord is going to be right here. So you can see the resected edge of the pedicle. And you can see how it comes down and actually blocks access to the inferior portion of the disc. It's helpful to use the drill to sculpt this inferior portion of the pedicle into the back of the vertebral body, so that you have a flat plane with access to the dorsum of the floor of the canal inferior to your disk. So here you can see the inferior portion of the disk, the superior portion of the disk, and the back of the vertebral body cranial to the disk. And here's the disk space itself. You can see it's a little squishy. This thickened white tissue here is going to be the lateral aspect of the posterior longitudinal ligament. And the spinal cord is going to be just in there just on the other side of that epidural fat. Now I'm going to reach up here on the endoscope and touch the vertebral body above the disc. So now we know where our disc is. It's right here. Top border. Bottom border. We know this is about where our medial particular line is. We know the thickened white structure on the floor of the canal. Just medial to that is going to be the PLL. And the spinal cord is going to be just distal to that. Typically when there's a disc herniation the disc herniation protrudes dorsally and actually displaces the cord, so the disc herniation works as a retractor for you and gives you a safe place to work underneath the cord. So you can see here on the scope video the articulation of the superior articular process and intra-articular process. This is the lateral part of the facet joint. That's because we resected a portion of that arch. Here's the top of our pedicle that I can hook around. This is some pseudo dura here. And then the cord is going to be just deep to that. Normally when you're working in the frame in a thoracic spine, you don't look for the exiting route, which would be way up here. So this white tissue you see above us is the inner transverse ligament where it attaches to the capsule. And again you can see our our joint right here. If I remove this you can find the exiting route. There is no need to touch the exiting route in the thoracic spine. It's well above the disc space. In fact, what you have to do is resect the caudal pedicle slightly the cranial end of the caudal pedicle to allow full access to the disc space. So there's no need to go finding the existing route or mess with it. That also means that even if you have a primary arterial contributor at the foraminal level, you should still be able to do the procedure safely at that level because the exiting route is not at risk. If you stay parallel to the disc space, if it's a soft herniation, you can you can go into it with a punch and start to resect the angular fibers. And then you can reach in to the disc space. And grab the disc material and pull it out. As you can see, I can already reach to the midline ventral to the spinal cord within the disc, and my annual otomy is right at the medial particular line. So that's a safe place to open the disc Disk and still allows you access across the midline ventral to the spinal cord. Sometimes you need to create a trough ventral to the cord to have safe working zone to reach to the midline, and that's done by resecting the floor of the canal. Cranial and caudal to the disc. So if you create a trough in the vertebral body. Just below the disc space. And we'll go from that trough and drill right through the endplate into the disc. And that defines the inferior portion of the disc space. So here you see the endplate of the vertebral body above and the back of the body above. So this is the top of the disc. So we're going to take our drill and create a trough above the disc as well. So to try to clear some of the soft tissue out so you can see that we're cutting a trough into this vertebral body as well. So I see this trough cut into the body here with the end plate. The trough cut into this body here with the end plate. Now I'm going to connect those two dots. If this is a calcified disc you'll literally drill right through the disc so you can place your your drill into the trough. Drill through the end plate. Drill through the disc and connect to the next opening. I'm now under the lateral part of the cord with my drill. So basically the idea at this point is to create the safe working channel with troughs, resect the disc in between that extends dorsally. And if you need to go to midline or even across midline, you can just continue to drill the troughs across the floor of the canal. And that gives you a safe space to work underneath the cord as you grab disc material and calcified fragments ventral to the cord. You can pull them down away from the cord and then out. And that's an important point, because the trap here is to get target fixated on the structure you're trying to remove and pull it straight out. And if it's displacing the cord and you pull it straight out, you will drag it across the spinal cord like a guitar string. And that is unadvisable. So creating a ventral space to pull material downward and then outward is the key to being able to do this safely. And being able to get across the midline from a single side. So once you're happy with your decompression, you turn off your your fluid. You suction out the water from your surgical field. You remove your cannula, one subcutaneous stitch in the skin, a dab of dermabond. The patient can shower the day of surgery and goes home without narcotics.