Today, I would like to discuss the conformance eye view. The first eye view for this custom knee replacement that I am looking at here is of a right knee. The eye view is broken down into two pages.
The first page provides the tibial images. The first set of images on the first page of the eye view is going to show us the precise location that the very first cutting jig, the T1, should be placed upon the patient’s bone.
Preoperatively, the surgeon will look at these images to see if there are any noticeable landmarks that the jig has to reference. Usually, these noticeable landmarks are osteophytes. Intraoperatively, if the surgeon finds that the jig is sitting well in multiple locations, then what he will do is reference this picture to see which location is the best for this patient.
Next, the surgeon will pin this jig into place and prepare to make the tibial resection. The next image will show the surgeon how much bone is supposed to be resected at various points along the tibia. After the surgeon finishes this cut, he will take the resected bone to his back table, get a caliber, and measure the tibial cut at various points to make sure that the values that have been cut, that the amount of bone that has been cut matches with the amount of bone conformance recommended be removed. If there is a mismatch, the surgeon can go back to this jig and fine-tune his cuts to ensure that the numbers match up.
The next image is going to show the placement of the patient’s final implants. The surgeon will reference this image while placing the implant to ensure that the rotation is correct and that the implant is fully seated on the patient’s tibia without overhanging or any significance under coverage.
The final information provided on the tibial page of the eye view is going to show the patient’s medial and lateral offset. Each patient has a unique distal femoral offset. In this instance, the patient’s offset is 3.1 millimeters. What this means is that the lateral portion of the poly that is placed inside of the patient is going to be 3.1 millimeters thicker than the medial side of the poly. This allows us to respect the patient’s neutral mechanical alignments, or in other words, provide the patients a straight knee.
The next page of the eye view is going to show us all of the necessary femoral images as they relate to the procedure being performed. The first image of this page is going to show us the proper placement of the femoral iJig. Just like with the tibial iJig, you want to ensure that the jig is in the proper location. And we do this by placing the jig on the bone and seeing where it wants to sit, and then seeing if that location matches the location that conform is provided in the images.
The next image is going to show how much a bone is going to be resected for the distal femoral cut. After the surgeon has made this cuts, he will take the resected bone to his back table and measure the cut thicknesses and see if that measurement matches up with the amount of bone conformance recommended be removed. If there is a mismatch, the surgeon can go back with his saw blade and fine-tune the cuts to make sure that the correct amount of bone has been resected.
Next, we’re going to look at the F4 or 3-in-one block. What the surgeon will remember while doing this procedure is that the medial profile of this F4 cutting jig should match with the medial profile of the patient’s femur. Once the location has been confirmed and the jig has been pinned at the place, the patient will cut the anterior bone, as well as the posterior femoral cannula bone.
After the resection has been made, the surgeon will take the cut bone to his back table and measure the thicknesses of the cut and see if these thicknesses match with the thicknesses that conformance had recommended. And just as with the previous jig, if there is a mismatch, the surgeon can go back with his saw blade through this jig and continue to cut more bone until the proper amount of bone has been resected.
The final set of images on the eye view is going to show us how the final implant should sit inside the patient’s body. The images provided will show the final implants as it looks from the back of the knee while the leg is straights, as well as the front of the knee while the knee is straight and flexed at 90 degrees. Additionally, conformance will provide one image that shows how the side of the final implant will look with the knee flexed at 90 degrees.
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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