Okay, so looking at this eye view, I see it’s a left knee. First thing I want to look at is the first image on the tibial page of the eye view. I’m looking to see if we have a lot of osteophytes that will serve as good reference points during this custom knee replacement to make sure that the jig is sitting in the proper location.
I want to see if there’s anything out of the ordinary that may inhibit proper seating of the jig. On this one right here, nothing seems off to me, but I will use this eye view during the procedure to show you a picture of how we believe the jig should be seated.
The next image I’m looking at is the lateral view, the sagittal. I am looking at the patient’s native slope. I see it’s 10 degrees. So in an instance like this, I’d want to give you a heads up that you’re probably going to have a pretty thick cut anterior, and a minimal cut posterior because we are making a cut at zero degrees. On the next image, it’s the tibial bone resection.
What I’m looking for here, first thing is this L-L cut. That stands for lowest point to lateral. If this number is greater than or equal to seven millimeters, then I’m going to recommend considering a minus two cuts on the tibia. This is just to help ensure that we can use the thinnest poly possible, and have the least amounts of change in the joint height. On the next image, I could just go back a second.
Also with this image, after we make the cuts, if we want, we can measure this and compare it to the eye view, to make sure that our cut values on the patient are the same as what the eye view had.
If there’s any deviation that’s significant, we can go back and check out cuts and make sure we fine tune it, to get it to where it’s supposed to be. On the next image, I’m looking at the tibial base plate placements. Essentially, just going to put it where it fits. There shouldn’t be any under coverage or overhang of the implant.
It should be a near perfect fit. This is to help make sure that we don’t malrotate the tibia. This is useful intraoperatively when you’re placing the trial, because we do give you about a millimeter and a half to play with it. But usually, you’ll just go by what you see in the picture, and that’s usually pretty spot on.
Next thing I’m going to look at is the keel size. I see on this one, it’s 12 millimeters. So before we do anything in the procedure, I’ll make sure that this is set up beforehand because there are three different keels, 10, 12, and 14 millimeter.
I want to ensure that the correct one is on the field and ready for the surgery so there are no delays. The last image are the poly thicknesses. It’s going to change for every patient on the lateral side. So how it’s going to work, you’re going to be given four polys. Each poly is going to be either six millimeters, eight millimeters, 10 millimeters or 14 millimeters on the medial side.
And then the lateral side is going to be the medial side plus the patient’s natural distal femoral offset. On this one here, I see it’s 1.6 millimeters thicker on the lateral side. So the medial side is 6.1, the lateral side is going to be 7.7. Now on the next page, I’m looking at the femur.
First thing I’m looking at is this first image. I want to see again, how many osteophytes we have here to make sure that we have good reference points. The more osteophytes, the easier it is to find the sweet spot of the jig.
Intraoperatively, I’m going to show you this image to make sure that if there are any questions as to where the jig should sit, you can see these referencing arms here, and those should hug the osteophytes.
So if it is an instance where you feel like it’s sitting well in more than one place, you’ll know which location is the correct one based on this image. Next I’m looking at the distal femoral cut. This particular image, I see there’s a step cut, so I know that we’re going to need a reciprocating saw blade here, and two separate sagittal cuts. The reason conformance does this is when the patient’s offset is more than two millimeters, they will add the step cut in order to preserve the most amount of bone.
Next image is showing you the cut angles for the anterior cut and the distal femoral cut. This is more of a reference. So when you have the next jig on, it gives you an idea of the angle that you’re going to be cutting out anteriorly.
Next image is all three in one block. First thing I want the surgeon to be aware of is that this medial profile lines up with the medial profile of the bone. So if it’s a perfect match, then the jig is in the right location. If it’s not, then you know you have to make some adjustments.
I’m also going to make sure the surgeon is aware of these femoral cut values, because just like in the tibia with all these femoral jigs, after you make the cut, you can measure the cut thicknesses to make sure that your cut values are around the same as what conformance said they should be.
The last images, this is going to show you how the final implant is going to set and how it should work. It’s going to show you the appearance in extension, both posterially and anteriorly, and it’s also going to show you the placements of the implants and how it looks inflection and also 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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