Dr. Jones: ConforMIS has three lines of implants available. The partial replacement replaces either the medial or lateral aspect of the knee. It’s been very effective, particularly in once again the lateral compartment, where there’s a difference in radius of curvature. The iTotal replaces medial, lateral, and patellofemoral areas of the knee, and the difference is really the flexion angle, the ability to flex the knee better. And secondly, the difference from the standard knee replacement is the ability to have that stability in mid-range motion, where they don’t have that play that they have on the other side. In addition, ConforMIS has an iDuo or a customized patient-specific implant that replaces the medial and patellofemoral area of the knee, or the lateral and patellofemoral area of the knee. There are very few implants that address what is a very common scenario, which is where medial or lateral wear with additional patellofemoral wear or knee cap wear. In those patients, they’ll have a normal, lateral or outside medial part of the knee, but the other parts of the knee are very damaged. They want to maintain the anterior cruciate ligament, the posterior cruciate ligament. If their lateral compartment is normal, they want to keep that lateral meniscus. They want to keep that lateral radius of curvature, lateral cartilage, as normal. The iDuo, that has been one of the biggest innovations in the knee replacements realm of treatment, and I think it’s a very effective way to treat bicompartmental disease of the knee.
Can you compare your experience using ConforMIS implants vs Off-the-shelf when it comes to mid-range stability?
Dr. Jones: So, mid-range we call about 45 degrees of bend in the knee. And in that range with the standard knee replacements, you would have some slop, some play, and patients, younger patients in particular would hate that. So, what the patient-specific implants allow is stability in that middle range motion aspect of their movement. When you try to put pressure on your knee with your knee bent, you like stability, you like support. That’s what these patient-specific implants provide. The other implants, the standard implants did not provide that stability. So, it was one size fits all. They had play at the middle ranges of motion. They had loss of flexion. They couldn’t bend as well. A lot of people couldn’t get past 115 degrees. I mean you can’t even get out of a chair without having to use your arms if you can’t bend past 115.
The other thing that can happen if an implant isn’t patient-specific for our knee, you’ll have some implants that are too big for people. If there’s metal pushing into the ligaments, these things called collateral ligaments in the knee. So for women in particular, there are some companies that have come out with female-specific knee replacements, and they try to address that issue. But typically, it’s just hard. Their anatomy is different. They’re smaller boned individuals than males, and so it’s tough to get an implant off the shelf, a standard implant that’s going to fit their knee. It’s a very tough thing to do. And then that tends to leave these boggy or kind of puffy-looking knees. They’re stiff, doesn’t look cosmetically-appealing to them, but more importantly it doesn’t function well, because the tissues are tight then you’re going to have pain in that motion of the knee, when you move the knee back and forth, when you put pressure on the leg, and that’s going to cause swelling, cause pain, cause dysfunction, and a constant kind of ache in the knee, which is obviously not going to be good for patient satisfaction.
You have referred to ConforMIS implant surgery as being more of a resurfacing than a replacement. Can you explain why?
Dr. Jones: ConforMIS differentiates itself from the standard knee replacement by its patient-specific aspect in particular. So, when we use a CAT scan, a CT scan, to make a model of the knee, we have an implant that is then directly made based on their anatomy. And that implant is then allowed to recontour directly to that patient’s anatomy. So, a standard replacement, you’ll make these box-type cuts, these big standard cuts, and you remove a lot more bone first of all, but also you’re not particularly resurfacing, you’re then contouring the patient’s knee to the implant versus basically in this case we’re taking the implant, which is contoured to the patient’s knee, and just kind of trimming things back, and then putting our implant on. So, it basically resurfaces their normal bone contour, but basically avoids any overhang, any edge loading, any areas where the implant might, in other cases, standard cases, be pinching the soft tissues.
So, these implants, when you put them in, you look at a post-operative x-ray, it’s perfect. It looks like you’ve just resurfaced the knee. There’s metal on the end of the knee now, but the contour is the same as the other knee, the size is the same as the other knee. There’s none of this overhang on the femur, the top part or the tibial side, the bottom portion of the knee replacement.
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