“Twenty-five years of implant retrieval has shown that we definitely have a solid attachment with cementless devices, ” argues Aaron Hofmann. Aaron Rosenberg counters, “The literature and registries clearly show that it sometimes is just silly not to cement (patients with osteopenia, patients with significant bone defects, the elderly).”
This week’s Orthopaedic Crossfire® debate was part of the 31st Annual CCJR – Winter meeting, which took place in Orlando this past December. This week’s topic is “The Cementless Knee: Lifetime Guarantee on Parts and Labor.” For the proposition is Aaron Hofmann, M.D., of the Hofmann Arthritis Institute in Salt Lake City, Utah. Aaron Rosenberg, M.D. of Rush University Medical Center is in opposition. Moderating is Steven J. MacDonald, M.D., F.R.C.S.(C) from the University of Western Ontario.
Dr. Hofmann: “Let’s talk about an implant that I first implanted in 1985: it was the first asymmetric tibia, has a deep trochlear groove, and has 3D titanium coating. Over one million have been implanted, but it’s less popular now; there were about 6, 000 implanted last year.”
“Recently a new patient came to me and it turned out that she needed a poly exchange. She is 55 years old, but she had a cementless knee put in 27 years ago. I think the philosophy of it having to be equal or better than cement holds. The only problem is the cost.”
“I use something called cancellous structured titanium, a 3D porous coating. We learned a lot about this years ago while doing implant retrieval. One patient with rheumatoid arthritis had a cobalt-chrome implant on one side and a titanium on the other; the bone seemed to favor the titanium (even in this patient who was on methotrexate and prednisone).”
“We did a study comparing a titanium to a cobalt-chrome plug. You get attachment to both, but you get a deeper, more diffuse attachment if you’re using an implant made from titanium or trabecular metal. I’m still looking for the ideal implant.”
“From a technical standpoint, you have to replicate the normal slope. If you have a kinematic mismatch then the implant is going to be toggling around. And you can’t smoke your way through the bone.”
“The real problem has been on the tibial side. Take a case with a 1/8 slice of the proximal tibia…we know from our experimental work that it’s 78% space and only 24% bone. So this is the real challenge. How do you get attachment to the proximal bone? We do that by increasing surface contact. We use a bone slurry that we call ‘biologic cement, ’ and place it on the cut surfaces of the bone (primarily the tibia). There is science behind this showing that you get 72% initial contact with the implant versus 92% if you use the bone slurry. It’s biologically active, and with a double tetracycline labeling there was a 67% increase in biologic activity. And they can be removed if the porous coating is flush with the implant.”
“In one of our clinical series (Hofmann, Evanich, et al., Clinical Orthopaedics and Related Research), well, sometimes when you have a hammer everything looks like a nail. I was doing 89% cementless—way too much. But I was making a point that it can work in the young, the old, and in rheumatoid patients…and we had 98% survival of the metal parts (not the poly).”
“In another paper that shows the young, active patient (Hofmann, Evanich, et al., Clinical Orthopaedics and Related Research), we had 75 patients who had an average age of 42. There was a minimum of nine years’ of follow-up. We had 98% survival of the tibia and the femur (that’s because there were two infections). This is the patient we should help with a cementless device.”
“Twenty-five years of implant retrieval has shown that we definitely have a solid attachment. If we look at past, present, and future, I think that there have been very successful implants that we can learn from. But we are still looking for the perfect implant…but we need something that has a non-porous coated pegs and a stem-able tibial base plate. Give cementless devices a chance!”
Dr. Rosenberg: “First of all, the data pretty much shows that cementless fixation, being a biologic phenomenon, is subject to some increased variability compared to the mechanical fixation that is obtained with bone cement. An outstanding study by Ritter and Meneghini (Journal of Arthroplasty, 2010) included 73 cementless total knees and a minimum 10-year follow-up (with none lost to follow-up). They had 15 failures; 12 were metal-backed patellae and 2 of the tibias loosened at 1 and 2 years. The 20-year survivorship for aseptic loosening of any component was only 75%.”
“A study by Park and Kim (The Journal of Bone and Joint Surgery-British, 2011) looked at simultaneously cemented and cementless total knees using the same components (one in a cemented fashion and one in an ingrowth fashion). There were 50 patients and multiple high level measurements (radiological results, etc.). Femoral survival was 100% in both at 14 years. Tibial survival with cement was 100%, whereas it was 98% with cementless.”
“Fehring et al. (Clinical Orthopaedics and Related Research, 2001) looked at 440 revision total knees; 63% were revised within 5 years of the index arthroplasty (38% because of infection, 27% due to instability, and 8% because of patellofemoral problems, and 7% from wear or osteolysis). However, 13% were from ingrowth failure; only 3% were revised early for cemented implant loosening. They noted that if all arthroplasties in the early failure group were cemented routinely and balanced carefully, the total number of early revisions would have decreased by 40%, and overall failures would have been reduced by 25%.”
“A 2003 study by Barrack et al. (Journal of Arthroplasty) looked at 82 cementless mobile bearing total knees and compared them to consecutive series of 76 cemented knees with the same indications, implant, technique, and follow-up. They found an 8% tibial revision rate for subsidence and failure of ingrowth with the cementless group…versus 0% in the cement group. The cementless group had lower Knee Society Scores and a higher percentage of pain > mild (23% versus 7%).”
“A 2013 study by Meneghini and de Beaubien (Journal of Arthroplasty, 2013) looked at the highly-touted tantalum monoblock tibial components; they had 106 consecutive tibias with a posterior stabilized design. There were nine failures at a mean of 18 months, with a medial tibial collapse noted…occurring predominantly in tall, heavy males. The mean height in the failed group was 73 inches versus 66 inches in the well-functioning group. And the mean weight was substantially higher in the failed group than in the well-functioning group (260 lbs. versus 204 lbs.).”
“The Swedish registry shows a higher percentage of uncemented patients that fail at the 100 component-year follow-up (about 40% higher). The UK registry (2011) reported the revision rate at 5 years was about 20% higher. The Australian registry showed that cementless fixation did worse at 100 observation-years; at 10-year follow-up the cumulative percent revision rate was substantially higher.”
“As Aaron has mentioned, we can’t use this type of fixation in all patients. Let’s agree to respect each others’ opinions…no matter how wrong yours may be.”
Moderator MacDonald: “So comment on the registry data on cementless total knees.”
Dr. Hofmann: “You’re not cementing in a cementless device. So if you don’t use that surgical technique and do something on the tibia…and the tibia is at risk to increase the surface contact and the biologic activity then you’re going to be in that 10-15% loser range. I think it’s very technique dependent.”
Moderator MacDonald: “Obviously, the results and registries reflect some older designs—both cemented and cementless. We’re in an era now of enhanced fixation and ingrowth. Is the future brighter for cementless?”
Dr. Rosenberg: “I think it is, but the problem is that we’re stuck with biology. In some respects I prefer to be a carpenter rather than a biologist…in part because I don’t always have the tools that I want. The next era will probably bring us some other biological modifications of the ingrowth surface with protein modifications and other bone-stimulating mechanisms that will help us consistently achieve bone ingrowth.”
Moderator MacDonald: “What percent of your knees are cementless now?”
Dr. Hofmann: “I went from 89% to 8% cementless; it’s a cost issue. If the implants cost $1, 000 more per part we know that’s crazy because it only costs $100/$150 per part to coat them. If the manufacturers were offering something that would equal the cement and the cementing time—less than $1, 000—I bet everyone in this room would jump on the cementless bandwagon.”
Dr. Rosenberg: “I think we can separate patients into two cohorts: one where it’s silly not to cement (patients with osteopenia, patients with significant bone defects, the elderly). Then there are the patients in whom you have greater concerns about the long-term survival of the implant. I think it’s fair to say to the patient, ‘This may offer you something that is biologic, and the interface will survive over a longer period of time than cement would.’ But we don’t have the data to support that.”
Moderator MacDonald: “Is it sometimes an intraoperative decision? To help the audience, what should they be looking for?”
Dr. Hofmann: “I make the decision ahead of time. You can look at the X-rays and know that the bone quality is good enough. It’s based on the age and activity level of the patient (individuals around 55 years old are great candidates). Otherwise, I’m cementing the majority of my patients.”
Moderator MacDonald: “Like cemented knees there are going to be some design features that are critical to predictable success. What do you look for in a well designed tray?”
Dr. Hofmann: “It should have peripheral pegs of some sort—and a central stem. In patients with soft bone you can add a stem extension.”
Dr. Rosenberg: “We know the principles that are required for ingrowth, namely, an appropriate mechanical environment and a minimization of micromotion while the ingrowth process occurs. The more rigidly you can initially get component fixation the greater the likelihood that it will withstand the micro stresses that occur during the rehabilitation period.”
Moderator MacDonald: “Thank you, gentlemen.”
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