Appropriate follow-up studies have been done by Professor Tibesku as well as looking at some other data. No differences between the medial uni and the bi-cruciate total knee, but the PS knees were actually worse than both.
The early clinical data reflects variations in outcomes. Implant stability is achievable based on RSA, but I think requires a meticulous cementation process.
I would say, in summary, my patients report that they do feel good, it does feel stable, and I’m proceeding with vigor, enthusiasm and a sense of optimism.
Moderator Sculco: Okay, so Mark…you’re a kinematic kind of guy. Does this then have some appeal to you that perhaps the kinematics—if the kinks are worked out—could make it a better knee?
Dr. Pagnano: Well I think that’s why I started with the presumption that it is conceptually appealing. There’s no mystery if you can save the ACL and PCL that’s at least one step closer potentially to getting better knee kinematics.
It’s just that the whole three-dimensional architecture of the knee becomes so distorted as soon as you switch to a total knee design.
Again, where you’re trying to make an incremental gain in function, you have to weigh that against the potential that you can have some short-term catastrophic problems. That’s my problem right now with bi-cruciate as it currently stands.
Moderator Sculco: So, Adolph, tell us a little bit more about the technique and your patient selection because balancing the cruciates—anterior or posterior—is involved in the deformity. So how technically difficult is it to do this well?
Dr. Lombardi: First of all, the indication is going to be the patient that, in my hands, I can’t do the uni on. These are minimal deformity and correctible usually. This is the type of patient that I’m approaching with a bi-cruciate.
As far as balancing these knees, it’s really a resurfacing technique. You’re removing that amount of bone and putting back with the metal and plastic. Another nice feature is you can put a different thickness medial versus lateral because they are separate components. We do that to catch up with a bit of that lateral laxity instead of releasing on the medial side.
You can take this one step further if you decide you haven’t taken enough bone and it’s too tight, the first thing that goes is the anterior cruciate ligament. At that point you can switch to a tibial tray that has a keel and you can use different bearings on either side and even a more stabilized bearing, let’s say, on the medial side if you want a not as stabilized bearing on the lateral side.
Moderator Sculco: Mark, as you look to the future where do you see us potentially moving to advance the state of what we’re doing in design and knee replacement? Do you see us in an area where we could be much better than we are?
Dr. Pagnano: We’re probably, from an implant design standpoint, fairly close to the asymptote of what we can do. Anything further runs the risk of introducing unforeseen problems.
We’re probably pretty close to the peak as far as implant design goes. And I think more of the potential impact on improving function and patient satisfaction is going to come from surgical technique and finding for groups of patients or for individual patients, what is a better target.
If hitting that target is very, very important, then using some type of enabling technology to hit that target whether that’s navigation or robotics or some other imaging modality.
That’s where I think the next step comes.
Moderator Sculco: Let’s get a big round of applause and Bon Natale.
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Senior Editor: Jay D. Mabrey, M.D., whose 35 year career in orthopedics included residency at Duke University Medical Center, service in the United States Army Medical Corps, Fellowship at the Hospital for Special Surgery and a long, distinguished career at Baylor University Medical Center where, in addition to his overall leadership at that institution, developed the Joint Wellness Program that helped patients get up after surgery more quickly, developed the first virtual reality surgical simulator for knee arthroscopy and chaired the FDA Orthopaedic Device Panel, is Orthopedics This Week’s newest contributing writer and editor.
