On this patient’s left knee, eye view, first image I’m looking at is the placement of the tibial cutting jig. This image is going to show you exactly where the image, where the jig should sit during this custom knee replacement. This is important because every once in a while, during the procedure, you may have a hard time finding the jigs exact sweet spot.
Referencing this picture will give you an idea where the jig should sit based on the shape of the patient’s anatomy. The next image I’m looking at is the patient’s slope. So with this knee, we’re going to be cutting at zero degrees as a straight flat cut.
The patients need a posterior slope is 12 degrees, which means as we make the cut the anterior portion of the bone, it’s going to be a lot thicker than the posterior section. No red flags there, but you just want the surgeon to be aware that way they’re not surprised when they see the variance.
With the next image you’re going to see the cut values for the tibia at five different locations. What we’d like to do with this is after the patient, after the surgeon makes the cuts. We can take this cut bone on the back table and measure it at these five reference points to make sure that the amount that we cut is the same as the amount we should have cut. This way if we did not cut enough bone, we can go back and make the adjustment at that very moment. Instead of having to backtrack later on.
The last thing I want to look at on this image is the LL cut LL stands for lowest points to lateral. If this number is seven millimeters or greater, we’re going to usually recommend that, that the surgeon take a minus two cut on the tibia, meaning they’re going to cut two millimeters less Bone.
The reason we do that is to ensure that we’re using the thinnest possible polys. Also, since this eye view is available weeks before the actual surgery, if the surgeon sees cut values that are really higher than they normally are, he may wish to order additional thicknesses of polys. And because conformance is customized, that is an option that he has.
The next image is showing the placements of the final tibial implant. The surgeon will typically reference this picture when putting the trial on and making the holes for the implant to sit. This just ensures that the rotation is perfect, which usually it will be anyway, because this is a custom made implant and is designed to fit the exact shape of the patient’s knee.
The last image is going to show you the poly thicknesses with each knee, you will receive four, the surgeon will receive four polys. This is the plastic that’s going to fill the gap between the tibia and the femur. Every patient’s medial side is going to meet either 6.1 millimeters, 8.1 millimeters, 10.1 millimeters or 14.1 millimeters.
The lateral side is going to be the thickness of the medial side, plus the patient’s distal femoral offset. So on this one, the patient’s offset is 0.5 millimeters. So that means the lateral side needs to be half of a millimeter thicker than the medial side. So the thinnest poly will be 6.1 medial and 6.6 lateral.
The next page is the femoral side. The very first image is going to show exactly where the distal femoral cutting block should sit. I’m going to look to see how many osteophytes the patient has for the jig to reference. The more osteophytes, the better it just provides more landmarks to make sure we’re putting the jig in the correct Location.
If, we are ever in a situation where you can’t find the exact sweet spot where the jig could sit, should sit. You can reference this image, looking at these outrigger arms over here, ensuring that they’re hugging the correct osteophytes and helping to guarantee correct placements of the jig.
The next image I’m going to look at is the distal femoral cut thickness. Just like with the tibia, we can take this cut after it’s completed to the back table and measure it to make sure that we are where we should be. If there are any mismatches, we can adjust it at that very moment.
Instead of having to backtrack later in the case, which would add substantial more time to the procedure. The next image shows the knee from the side. It shows the angle of the distal femoral cut that we just made. And the angle of the anterior cut.
The fourth image is the placement. What’s called our three in one block. This image is going to show the patient, the surgeon where the jig sit on the bone it is important to note that the medial profile of this jig matches up with the medial profile of the patient’s bone. So if the jig is put on and the profiles don’t match, then the surgeon knows that the jig needs to be adjusted. It’s just an extra reference point and safety check to make sure everything is done accurately.
This jig will also tell you how much bone you are going to be resecting anteriorly. And then at the bottom here, it’s showing you the two posterior cuts, just like all the other ones. After these cuts are made, we can take this cut bone to the back table, measure it to ensure that our cuts are accurate and make any adjustments if they need to be made.
The last images of the eye view are going to show the final implant fitting as the knee is in full extension from the back. Full extension from the front as the knee is flexed at 90 degrees and one image from the side.
I am fellowship trained in joint replacement surgery, metabolic bone disorders, sports medicine and trauma. I specialize in total hip and knee replacements, and I have personally written most of the content on this page.
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