Moderator Trousdale: In hip surgery we’ve certainly migrated away from cement for the most part. Do you think 10-15 years from now the same will be true about our total knees or is it going to take longer than that?
Dr. Callaghan: Leo’s been working on it for 20 years, but I think he’s getting close to the halfway point. So in 15 years I think we’ll be there.
Moderator Trousdale: So, Leo how would you argue…John showed some really compelling registry data. So, certainly in your hands you show 99% 18-year survivorship with one design that you use that was pretty impressive. How would you argue in the masses, certainly in large registries whether it’s the Norwegian, Scandinavian registries, the Australian registry or the other registries in the UK, that cementless fixation seems to lose in a large group versus cemented fixation. How do you address that?
Dr. Whiteside: When you look at some of the recent registry data, segmented, stratified data, what you find was the Profix knee in the UK done cementless had the highest survivorship. Likewise, in the Australian registry when you stratify and look at different implants, the Profix knee done cementless had the highest survivorship. Now the registries are like the Bible, you can use ‘em to prove anything, but you certainly can’t use registries to show that cementless does not work in total knees, at least with modern day registries.
Moderator Trousdale: John, you said you’re going to migrate towards cementless fixation. So, what are the optimal design characteristics of a cementless total knee?
Dr. Callaghan: I think you have to have something that absolutely fixes to the bone. So, in that regard you have to make sure that you have a porous surface that has a track record to be able to do that. But I also think that you have to have more than that to prevent lifting up of the front of the device. He’s using screws to do that. I think you can do some of that with pegs. I think maybe you can do some of that by taking the load off of that surface. I use a mobile bearing to do that. I think you have to abide by the principles that Leo showed, if you’re going to have a chance.
Moderator Trousdale: Yeah, if you have live bone, good ingrowth surface and you make it stable, it will probably work. So, Leo what are your tricks?
Dr. Whiteside: You need a stem that actually presses bone and gives you an elastic grip on the stems to begin with. And you need a stem that has gross contour to it as well to accept that grip…that press fit that you get. You need a surface at the top that is very well done. I mean done so it’s not a round surface. Remember it’s soft on one side and hard on the other. Always going to be like that, so it’s always going to try to sink into the soft bone. That’s why the screws are necessary to hold it down. One thing that John said that I think is very true, destressing the interface is very important.
Moderator Trousdale: To elaborate on that. Do you do cementless in everybody? So, 350-pound male?
Dr. Whiteside: 350 pound male.
Moderator Trousdale: 90-year-old woman with osteopenic bone?
Dr. Whiteside: Yes. But I do have a Morse taper on that tibial component and I can add a stem that goes clear down to the diaphysis if I want to.
Moderator Trousdale: You ever sneak a little cement on that stem, Leo, to hold it in?
Dr. Whiteside: Jesus, no, no.
Moderator Trousdale: Fair enough. Last question to the audience. How many are routinely using uncemented total knee replacements? There’s three of them out there Leo. I agree with you that’s going to change. Thank you, gentlemen.
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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.
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I have been using cementless total knees for almost 14 years now. I admit I don’t do the large numbers as the presenters, but I have had great results. The only ones I had to revised was due to surgeon’s error. I placed too small a tibial component and it settled. I have used cementless in 90 year old female and a 95 year old male and 400lb males.