The Conformis iView I will be discussing for this custom knee replacement is a left knee. The first page of the iView is the tibia. The very first image on the tibial page of the iView is going to discuss the tibial cutting jig or T1. This image will show us where the jig should sit on the bone.
What we’re looking for are any major landmarks or large osteophytes that the jig is going to reference to help us make sure that we get it in the right place. The next image is going to show us the patient’s native slope, as well as the slope of the actual tibial cuts.
In this image, the patient’s native slope is 10 degrees and we are making a straight zero degree cut. What this means is that the front or anterior portion of the bone is going to be a lot thicker than the back or posterior section of the bone.
That is not a concern. It’s just something that we want the surgeon to be aware of. So after he makes this cut, he knows it looks as it’s supposed to. The next image of the tibial iView is going to give the surgeon the actual cut values of the resected bone.
So after the surgeon makes his cuts, he’s going to take this resected bone to his back table and measure the thicknesses and ensure that it matches with the resection values that Conformis provided. If there are any discrepancies, the surgeon can go back at this stage and make adjustments to his cuts as needed. The next image is going to show the tibial tray placement.
This is to help make sure that the final tibial implant is put in the best location for the patients without any malrotation. Also, avoiding any overhang or under coverage of the implants. Since the tibial implant is customized to fit the shape of the placement’s knee, the risk of a mal-rotated or poorly covered tibia is significantly reduced.
The final image on the tibial page of the iView is going to give us both our poly thicknesses, as well as the patient’s native distal femoral offset. The four polys that are given with each knee are going to measure on the medial side, 6.1 millimeters 8.1 millimeters 10.1 millimeters or 14.1 millimeters. On the lateral side, thickness will be the thickness of the medial side plus the patient’s distal femoral offset.
So in this instance, the patient’s offset is 1.9 millimeters. So if the medial side is 6.1 millimeters, then the lateral side will be eight millimeters. This offset poly helps us to achieve a neutral mechanical alignment, meaning the knee is straight.
The second page of the Conformis iView shows us the femoral images. The very first image on this page is going to show us the proper location for the distal femoral cutting block. The surgeon will take notes of any osteophytes that Conformis has outlined in order to ensure the proper placements of the jig. The next image is going to show, again, the placements of the distal femoral cutting block, as well as the section values for the distal femoral cut.
After the surgeon makes his cut, he will take the resected bone to his back table and measure it to assure that the cut values match the numbers that Conformis has provided. If is a mismatch, then the surgeon can make adjustments at this very moment without having to back track later on in the procedure.
The next image is going to provide the cut angles for both the distal femoral cut, as well as the anterior cut. The fourth image on the femoral side is going to show us the 3-in-1 block, otherwise known as the F4. The one thing to note here is that medial profile of the F4 block should match up perfectly with the medial profile of the patient’s femoral bone.
Once the surgeon has found the proper placement or has confirmed the proper placement of this jig, he will pin it in place and make his resections. Conformis provides the resection values for the anterior and posterior cuts. The surgeon can take these resections to his back table and measure it to confirm that the amount of bone resected matches the amount of bone Conformis recommended.
If there are any mismatches, the surgeon can go back to this jig and make his adjustments to assure that correct values are obtained. The final set of images on the femoral page of the iView is going to show us how the final implant will sit. We’ll get an image of how the final implant sits with the knee bent and with the knee straight, both from the front and the back, as well as an 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.
You can see my full CV at my profile page.
