“This operation works well and I strongly recommend it, ” says Leo Whiteside. “Besides, we have major new developments in the area of osteointegration.” “What about the tibia?” says Thomas Thornhill. “There’s a really variable substrate…and don’t forget the cost and issues of revision.”
This week’s Orthopaedic Crossfire® debate is “Cementless TKA: A Worthwhile Resuscitation” For the proposition was Leo A. Whiteside, M.D. of the Missouri Bone & Joint Center. Against the proposition was Thomas S. Thornhill, M.D. of Harvard Medical School. Moderating was William J. Maloney III, M.D. from Stanford Hospital and Clinics.
Dr. Leo Whiteside: “This operation works well and I strongly recommend it. It’s highly dependent on all sorts of technical issues: design, porous technology, instruments, and technique. Intramedullary alignment was key to success; also, a stem on the tibial component…we quickly learned that we needed to enhance the stem to make it work effectively. As Bartel and Burstein showed, the stem does not stress-relieve; it protects and prevents failure and leads to appropriate stress transfer.”
“We looked at cementless total knee replacement (TKA) at medium term with 256 knees and found one loosening (and that was questionable). The rest of them had some trouble (one acute infection, four late-onset infection, etc.). We continued to follow them up long term and found less than 1% failure rate due to loosening…and we didn’t find progressive worsening due to pain.”
“I’ve looked at a Profix knee at medium term follow-up with a large number [over 1500 knees] and found none revised for loosening. With Robert Viganò I looked at heavy, active patients at 10 years and found no loosening…and looked at rheumatoid patients and found no loosening.”
“There are about 122 important studies; 10 are negative, 101 are neutral when comparing cementless to cemented, and 11 are positive. If you look at good comparative studies, 46 studies are pretty neutral (5 negative, 31 neutral, 10 positive). If you look at well done, controlled studies you see 2 negative, 3 positive.”
“Cemented studies: McKasie et al. did a randomized study looking at the PFC [press fit condylar] cemented versus cementless and they had a significantly higher percentage of radiolucent lines in the cemented ones. Ranawat’s study…not a big group [112 knees] but very well done there was 1.5% loosening at 10 years in cemented knees and 6% at 15 years. Something happens at about 10 years in the usual cemented knee. If you look at Ranawat’s tough cases, the bigger, active patients, it starts happening five years after surgery. And by 15 years after surgery there is more like a 70% survival rate in these tougher knees.”
“Li et al. found the survival rate at a general hospital of 92% at 10 years with 82% radiographic follow-up. That’s not wonderful. Lonner and a group of very good guys did tough cases and came up with 12.5% loosening at eight years with younger, active patients. That’s not wonderful. Especially when you look at Aaron Hofmann’s 0% loosening in a similar group at 10 years after surgery.”
“Nielsen has shown that there is progressive migration of these cemented components, not cementless. And recent studies by Mark Miller show that the interface—even though it looks good—is not bonded. I see this all the time in my practice.”
“The new developments are all in osteointegration. The thinner, more effective saw blades…this rigid metallurgy now makes it possible to make your bone cuts with less heat and to re-cut the tibia if need be. Screws aren’t new, but they’re getting better as we learn how to use them. Polyethylene sealing and locking are now much more effective and osteolysis isn’t likely to be an issue. New porous coated ceramic components are on the way. These are not appropriate for cemented technology because they’re made to last 20-30 years.”
“Advanced porous surfaces now make it much more likely that you have a strong implant that you can convert into a revision implant and be highly successful—even in tougher cases. These new porous coated technologies make it happen in many cases. But new technology has its issues. A lot of these are already coming out with inadequate fixation and stress relief that could lead to early or late failure.”
Dr. Thornhill: The advantages of cementless TKA are shorter operative time, you don’t use a tourniquet. It’s better for MIS because of the fact that cement extrusion you need to be careful of…every time I do a cemented knee I frequently find fragments of cement. Also, how often do we cement total hips now? I stayed with uncemented hips for a long time when Boston was still doing a lot of cemented femurs.”
“I did this type of knee for a long time: uncemented femur; I’d cement the proximal tibia but not the keel. I was concerned about metal-backed patellae, and I believed in resurfacing patellae. So this was my construct: it had the capability of being completely uncemented, but it had a cemented component. It also was suited for uncemented options.”
“When we first looked at our 10 year data on this—253 knees—we uncemented the femur in a porous coated technology in over half. We did a few uncemented metal-backed patellae and a lot of hybrids…but not many uncemented tibias. But our 10-year component survivorship was 100% for the femur, 100% for the few tibias, and the metal-backed patellae not as well.”
“The article from Mayo Clinic—and others—showed that cementless knees of that time did not do as well as the cemented knees. My other concern about the uncemented knees is predominantly on the tibias. There’s a really variable substrate, and cement creates a uniform proximal tibial mantle that I think—because tibial fixation is probably going to be the Gordian Knot of uncemented knees. Surgical cut precision…I think you can do it. Cost and issues of revision should also be discussed. The thing that has made more uncemented components at the present time has been this new material technology.”
“Tipping points: the new material technology will improve tibial fixation, the recent data on high flex designs is a bit of an unknown; I think it’s going to be cost. We are facing accountable care organizations and cost effectiveness…and we are going to be asked about value. You’ve got to be able to guarantee that these technologies are going to save the hospital budgets on an annual basis.”
Moderator Maloney: “Leo?”
Dr. Whiteside: “The cost issue is always there, and I recall when I used to have this debate about total hip. When you look at all the costs involved in doing a cemented knee versus a cementless knee, it’s maybe even a little in favor of the cementless—if you’re a good negotiator.”
Moderator Maloney: “Tom?”
Dr. Thornhill: “I think it’s a problem if you use loosening as a surrogate because our incidence of primary loosening of knee replacements—much of those loosening components are associated with malalignment, infection, other issues. But primary loosening is extremely small whether cemented or cementless. We revise knees for periprosthetic fracture, infection, and technical error. The American College of Rheumatology it says that joint replacement is the greatest thing to happen in the 20th Century in terms of musculoskeletal disease. So I think the vendors have tended to come out with new technology and charge a premium.”
Moderator Maloney: “Leo, you’ve been banging this drum since I was a resident—the market still hasn’t embraced cementless technology—why?”
Dr. Whiteside: “I think there are some political issues. There were a lot of poor technologies that were foisted on the market quickly. A lot of the long term studies seemed to show very low loosening rate and they were quite believable. But I’d say that people are underestimating the loosening in cemented total knees. All the time patients come to me with a painful swollen knee, and the doctor they came from didn’t recognize loosening, but I can see it.”
Moderator Maloney: “Tom, you quoted 100% well fixed implants and Leo quoted Chit Ranawat’s study, but that was with the PFC implant and I think they had a problem with polyethylene wear and maybe backside wear with a titanium base plate. So is that a fair comparison with modern technology?”
Dr. Thornhill: “I don’t think it is. Because of conflicts of interest at our institution I’m not allowed to report on my own cases. But I think primary loosening of cemented implants is a problem. And tibial fixation of cementless implants and getting non-metal-backed patellae or making metal-backed work is going to help.”
Moderator Maloney: “Leo, you have some principles you’ve developed and they involve stem design, spikes, and screw fixation. So you’ve ensured that the tibial component was rigidly stable. What about some of the newer designs that are getting away from those principles?”
Dr. Whiteside: “I think we’ll have another wave of higher failure and some disillusionment with cementless technology because people are tempted to do less than adequate fixation of the tibial component. The femur has enough complexity to the bone contact surface that it’s a lot less likely to loosen. A flat plate on the upper surface of the tibia is destined to fail unless it’s very well fixed with multiple technologies.”
Moderator Maloney: “Tom, you discussed the magic metals.”
Dr. Thornhill: “The attempt to make stems so short and so flat that you can get them in through very small incisions is going to be problematic and will have a higher incidence of failure.”
Moderator Maloney: “And the necessity of using screws as a secondary means of fixation?”
Dr. Thornhill: “I wouldn’t do it, probably just because of the history.”
Moderator Maloney: “Leo?”
Dr. Whiteside: “The screws are very helpful. If you have a well designed implant and a polyethylene that seals on top of them, then it’s hard to argue with them for security of fixation.”
Moderator Maloney: “What polyethylene are you using?”
Dr. Thornhill: “I’m using a moderately cross linked poly that’s melt annealed.”
Moderator Maloney: “Something in the 5 megarad area?”
Dr.Thornhill: “Correct—5.5.”
Dr. Whiteside: “I’m not ready to go to that. We have very well compression molded polyethylene now that’s EtO [ethylene oxide] sterilized that is very effective and is not as risky.”
Moderator Maloney: “Tom, we’re going to be held to a different standard as it relates to looking at outcomes at what cost. There’s still a price differential for cementless technology. Where do you see that going?”
Dr.Thornhill: “If you want to embrace cementless technology you’re going to have to take all the other facets of the cost of the knee—cement, time in the OR—and show because we’re certainly going to find for elderly people unless you have a lot of quality adjusted life years left that they’re not going to accept higher cost.”
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