Abdel v. Schmalzried: The Cementless Knee: Emergent Game Changer

This week’s Orthopaedic Crossfire® debate was part of the 34th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “Abdel v. Schmalzried: The Cementless Knee: Emergent Game Changer.” Affirming is Matthew P. Abdel, M.D., M.S., Mayo Clinic, Rochester, Minnesota. Opposing is Thomas P. Schmalzried, M.D., Joint Replacement Institute, Los Angeles, California. Moderating is Jay R. Lieberman, M.D., Keck Medical Center of USC, Los Angeles, California.

Dr. Abdel: I’m going to talking about the cementless knee in the affirmative.

We’re all aware that the literature for cemented total knee replacements reports good long-term results with 90% survivorship at 15 years. However, if you really look at that, we’re talking about patients over 65 years of age, usually females, BMI [body mass index] under 30 and not highly active.

Today, this is not our patient population and we need long-term biologic fixation.

There are multiple differences in our patient populations compared to this historical, institutional and registry-based information. Our patients are younger, more active and living longer. Obesity is a worldwide epidemic. The CDC reports that the United States by the year 2030, 51% of the U.S. population will be considered obese.

That is not what the reported literature is discussing.

Finally, why the longevity differences between hip and knee? In North America, hip uncemented components are standard, but not in the knee. I would contend that, today, we have different materials, manufacturing, and designs that allow us to have cementless fixation in the knee.

Why is cementless fixation in the knee attractive? Multiple reasons. First, our patients are younger and we need improved longevity. Second, obesity is here and it’s only going to increase. And finally, cost. The decreased operative time and supplies help your workflow and save money.

Why now? We’ve had innovations like highly porous metals, designs that focus on the keels and pegs for biologic fixation with rigid initial fixation, and 3D printing that allows us to do this more precisely, more accurately, and more reliably.

So, let’s go through some of these points in greater detail.

Longevity. I’ll draw your attention to one article by Nakama, et al. (Cochrane Database Syst Rev 2012); 5 randomized controlled trials (RCT) in 297 patients. The risk of future aseptic loosening with cementless fixation was half of cemented fixation. One study included Ritter and Meneghini (J Arthroplasty 2010) with a 20-year survivorship of 98% for cementless fixation. Multiple studies with 98% survivorship at 10-20 years, with historical designs reporting 95% survivorship.

What about cemented fixation? Our own internal Mayo Clinic data shows that cemented fixation starts out great but decreases over time to 80% at 20 years in thinner, less active patients. In the Australian National Joint Registry, at 5, 6 and 7 years you can see increased loosening and lysis in young patients. A disaster.

Contemporary implant designs can mitigate this. We looked at a Level I clinical trial completed between 2003 and 2006 which took a randomized look at cemented modular, uncemented monoblock and cemented monoblock designs (Pulido, et al. CORR 2015). The data showed no difference in survivorship at 5 years. You say, “Okay, no difference.” But, remember, we anticipate the cement fixation to only get worse from the first, to second, to third decade of use. By contrast, biologic fixation minimizes early failures and you get that ingrowth which, we anticipate, will last the lifetime of the patient.