Moderator Berry: Michael, you know the concept is appealing. That said, when we look at the best prospective randomized trials on this, and Simon Young is probably the best, it has failed to show any demonstrable benefit of that concept. Why is that?
Dr. Dunbar: Unfortunately, I think it’s the metrics as Meneghini was alluding to. We’re using subjective outcomes. Survivorship data takes a while. I think we need measurement stats from EMG [electromyography]; fluoroscopic getting in and out of chairs; gait analysis, etc., which show proportional distributions. These randomized controlled trials by definition are small numbers of patients, so the averages can be misleading.
Moderator Berry: If we just had a little better way to test it, more numbers, you’d see a difference?
Dr. Dunbar: I think so, but I also would like to say that the other important caveat is that we didn’t see any increased complications or problems. I agree with David that the gold standard is neutral mechanical alignment, but I do think it’s safe to explore this topic.
Moderator Berry: Fair enough. Dave, there seems to be some relative degree of safety in exploring the idea and none of us like to do huge releases. As this topic has come up, would you admit to cheating just a little tiny bit and letting that tibial component slide into a degree or two of varus just so you don’t have to do that extra huge release that you might have had to do to get that last couple of degrees of neutral alignment on the tibia. Or would you just never do that?
Dr. Lewallen: No, I would agree. And I think they are on to something because within the range of pathology that we see in total knees, there’s a subset of patients that have this valgus on the femur, varus on the tibia, joint obliquity, straight leg…people look at the X-ray and they think it’s a varus knee, but it’s not really. Also, in my opinion, there are some rotational problems in those joints too as they’ve developed.
Moderator Berry: It reminds me Rob Trousdale’s humorous quip. Somebody asked him, “How do you decide whether you’re going to do kinematic alignment on the knee?” He said, “On the post-operative X-ray.”
Thank you both very much for an informative debate. I think this is one to stay tuned on. Emerging information. Controversial, but an area that has the potential to make a big difference to our patients.
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