Dr. Cannova: The creation of the implant that matches the anatomy perfectly is a complete change from anything we’ve seen before. We’re actually putting in a knee replacement that is specifically designed not only from an instrument standpoint but also from the implant standpoint to that person. The thing that we are looking at most as we advance knee replacement and, for that matter, joint replacement surgery in general is we want patients to ultimately forget that they have a joint replacement. The way we are able to do that is by essentially creating a stable knee that feels like their native knee. This technology and this advance I think is probably the biggest thing so far that allows us to do that. There are a lot of implants out there on the market, there are a lot of implant companies that put a tremendous amount of research behind looking at different designs to recreate normal anatomy. Nothing to this point has been able to recreate exact anatomy like this really has.
Off-the-shelf implants traditionally have high success rates, so why are 20% of patients still dissatisfied with their results?
Dr. Cannova: We’ve always talked about success rates in the 95-98% range after total knee replacement. What we’ve realized now when we quoted those studies is that objective findings, the motion, the stability, ultimately the longevity of those implants in general had very high success rates in the 95% to 98% range. When you actually ask patients what they feel is happening with their knee, up to 20% of patients feel that they still have problems with the knee; it doesn’t feel like their normal knee. Part of the reason we think that they aren’t satisfied is because we’ve changed the anatomy, we’ve changed the way that knee works and responds. And the hope is with a technology like this, if we’re not changing that anatomy and we’re not changing the balance of their native knee, then patients will have a higher success rate, feel like this is their normal knee, and essentially forget that they had a knee replacement.
How does the ConforMIS system help you address the issue of mid-flexion instability?
Dr. Cannova: One of the other issues that we always work around from a standard offthe-shelf knee replacement is what we call, as surgeons, mid-flexion instability. Midflexion instability is when we test the knee at the time of the operation, we typically test in essentially a straight knee or zero degrees as well as a flexed knee to 90 degrees. We want to see that the stability and the balance are correct at those two positions. What we often under-appreciate is what happens through that, what we call mid-flexion area as the knee comes through into 45 degrees and beyond, what happens because the ligaments and the anatomy does change at that point. One of the big problems that we’ve seen is that the knee can be balanced in those two positions, but become very unstable in the mid-flexion zone. We also think that as part of the reason why people ultimately have problems after knee replacement is that what we call mid-flexion instability. As we look at a more patient-specific solution, if we can match that anatomy perfectly throughout the range of motion and not just in those two positions, then we really feel that we can eliminate that mid-flexion instability. We can eliminate those subtle problems that patients get afterwards, and those subtle problems can be swelling in the knee, pain in the knee, difficulty going up and down the stairs, which are common things that we see that we often under-appreciate that are likely coming from midflexion instability. This solution, I think, addresses that, because we are matching anatomy so well.
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