Gustke v. Thornhill: The Cementless Knee: The Emergent Game Changer

This week’s Orthopaedic Crossfire® debate was part of the 19th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “The Cementless Knee: The Emergent Game Changer” For is R Kenneth A. Gustke, M.D., Florida Orthopaedic Institute, Tampa, Florida. Opposing is Thomas S. Thornhill, M.D., Harvard Medical School, Boston, Massachusetts. Moderating is Paul F. Lachiewicz, M.D., Duke University Medical Center, Durham, North Carolina.

Dr. Gustke: I’m certainly in favor of cementless total knees under certain circumstances.

The cemented total knee is the gold standard. The literature reports 15-year survivorship, which is excellent. The problem with cement is, however, it is a grout. Not an adhesive. It relies on interdigitation into the bone and the interface is doomed to fail biologically at some point in time.

Post-mortem retrieval studies (Miller et al.; CORR 2014) support this loss of the cement interlock. Trabecular bone initially interlocks. It resorbs, leaving cavities in the cement layer. And you get less bone contact over time.

The problem we have today is that our total knee patients are younger, more active and heavier than in the past (Kurtz et al.; CORR 2009). By 2030 more than half are going to be under the age of 65. We know that the younger the patient is the worse their survivorship (McCalden et al.; JOA 2013).

Obesity is common (Odum et al.; JOA 2013). In 2002 only 6% of total knees had BMIs [body mass index] over 30. In 2009, it was 20%. And most of us estimate in our practices that 40-50% of the patients have BMIs over 30.

A meta-analysis looking at patients with BMIs over 30 showed that there was a 1.23 odds ratio for revision for aseptic loosening (Kerkhoffs et al.; JBJS 2012).

It’s even worse if the BMI is over 40—only 88% 5-year survivorship in one study (McElroy et al.; J Knee Surg 2013).

These young, obese, active patients are going to have increased stress on their prosthesis-cement-bone interface (Odum et al.; JOA 2013).

The theory behind cementless fixation is it’s better able to handle this increasing stress because it’s a biological interface. You have repair potential. The interface actually may strengthen with increasing loading.

A Cochrane Database System Review looking at RSA [roentgen stereophotogrammetric analysis] (Nakama et al.; 2012) to compare cement versus cementless surgeries, showed that the future risk of aseptic loosening was actually 50% less with cementless fixation.

Another study using RSA shows that what happens is the non-cemented total knees may migrate in the first 3 months, but then they stabilize (Henricson et al.; JBJS Br 2008). Whereas a cemented total knee continues to migrate.

Yet, the common perception is that cementless total knees are inferior to cemented total knees. And it’s based on old literature. A study out of the Mayo Clinic (Duffy et al.; CORR 1998) looking at PFC knees showed only 72% 10-year survivorship with cementless total knees.

A study looking at Miller Galante I knees (Berger et al.; CORR 2001) at 11 years showed problems with metal-backed patellae, tibial component loosening and osteolysis around screws.

I think these poor results reported with cementless total knees are design related. They had cobalt-chrome porous interfaces. Poor initial tibial component stability using metal-backed patellae and use of poor polyethylene.

My personal experience with cementless knees is over 1,300 of them done in the last 30-something years. This still represents only 20% of all the total knees I’ve performed because I use cementless knees in patients who are young, active and heavy, where I am looking for durability over 20 years. My average age in this population is 57.

We recently reviewed my database and developed Kaplan-Meier survivorship curves over the various different designs of cementless knees. The implant that I used had a bimetal femoral component with titanium porous coating for reliable bone ingrowth and a cobalt-chrome articular surface for better wear. The tibial side was an asymmetrical baseplate with continuous porous coating. Early on they had no central stem. And then later we added a stem, all had 4 peripheral pegs.

The patellae used were metal-backed in some and all-polyethylene in others. And the poly design initially was non-highly crosslinked and later on highly crosslinked.

And the titanium surface that we used was consistent throughout the entire series, about 60% porosity, which is very similar to normal bone and also very similar to the trabecular metal-type interfaces that we use today.

Here’s what happened when we eliminated certain design aspects over the years. Eliminating stemless baseplates improved the survivorship. Eliminating metal-backed patellar components significantly improved survivorship. Eliminating tibial screws that offered travel pathways for particulate and the potential for osteolysis eliminated some bad results. And now with highly cross-linked polyethylene my results over 10 years are better than 99.5% survivorship.

If I look over the last 1,000 cementless total knees that I used, I’ve had 1 revision since 2002.

And this is supported in the literature. Studies like Buechel’s report, 18-year, 99% survivorship (CORR 2002). Ritter’s study (JOA 2010) if I eliminate the metal-backed patellae they have 97% survivorship. Hofmann’s study (CORR 2002) in young patients at 9 years had no revisions for loosening. And Whiteside’s study (CORR 2007) looking at both heavy patients and young patients, had no loosening at a 5- to 10-year period.

In summary, cemented interfaces eventually fail biologically because the cement-bone interlock loosens over time. We have concerns for these young and heavy patients. RSA studies support the premise that cementless fixation maybe better for the long term. Biological fixation, I think today, is more reliable because we have made improvements in implant design and polyethylene.

Cementless fixation, I feel, is the preferable method for total knee replacements in the young, active and heavy patient.

Dr. Thornhill: Let me just remind you that this debate is called “The Cementless Knee: The Emergent Game Changer.” What is the game changer in total knee replacement?

Right now, 15-20% of patients with total knees are not fully satisfied. Will cementless total knee designs change this? I think not. Now that I’ve won this debate, I’d like to thank you.

But I have a little more time.

There are some advantages to cementless total knees.

First, it’s a shorter operative time. You don’t have to use a tourniquet. I use a tourniquet when I cement.

It’s probably better for MIS [minimally invasive surgery], but that to me is like having a two-handed strangle hold on a loser.

Now the concerns of cementless knees are captured in the history of it, which Ken so nicely covered to support my point. In our first 10-year PFC study cementless femurs did uniformly well—in fact the bone looked better than the cemented ones (Schai, JBJS-Br 1998).

I think the fact is, as Ken pointed out, that the data is old, but if you look at 10-year survivorship, 92% for cemented; 61% for cementless (Rand et al.; JBJS-Am 2003).

Some of the problems were screw fixation, component breakage. The Gordian Knot of this argument is the patella.

Variable substrate. The fact is that in the tibia you have to worry about different kinds of substrates because you can have sclerotic bone on one side and osteoporotic bone on the other. In that case, cement creates a uniform proximal tibial mantle to support tibial fixation.

Surgical cut precision. You have to be more precise in the cementless design. Matter of fact, the old expression is “A little putty, and a little paint makes a carpenter what he ain’t.”

Cost is an important issue here. And you can work those data any way you want in terms of the cost of the cementing, the cost of the operative time, versus the increased implant cost. And as you all know, different institutions pay different prices for the same implants.

The new material technology. I think there are three companies—at least three companies—that have material available with improved coefficient of friction, surface roughness, the ability to cut it, porosity, and ultrastructure.

The tipping point will be the new material technology, solving the patella issue and cost effectiveness.

Moderator Lachiewicz: So, Ken, let me ask you this. How precise do the bone cuts have to be with cementless total knees? Do you think this is for every man, every surgeon, or are we going to need robotics to do this correctly? What do you think?

Dr. Gustke: I think it’s important. If you’re doing cementless total knees, there’s definitely a difference in your surgical technique so that your surfaces are perfect, and your press fit is perfect. No different than what we have when we prepare an acetabulum for a press-fit acetabular component or the femoral stem for a total hip.

Moderator Lachiewicz: Okay, great. Tom, let me ask you. Do you think there are any patients that nowadays you would select a cementless total knee? What do you think should be the patient selection criteria?

Dr. Thornhill: The first problem for me, Paul, is I resurface every patella. And I don’t have a good metal-backed patella.

Moderator Lachiewicz: Ken, can you take on the question of do you think cementless knees have more pain or more dissatisfaction than a cemented knee?

Dr. Gustke: Having done this now for 30 years, I think there is a little difference. There’s more discomfort in the cementless knee. I can perhaps attribute that to the fact that there is more migration of the tibial component in the first 3 months or so. That may be the reason for pain. There’s more potential for blood loss because you’re not sealing the interfaces. I don’t think that has presented itself as a problem for the long-term, nor as an issue that has made me not choose to do uncemented knees. I think there is a difference, but it’s minimal.

Moderator Lachiewicz: Tom, do you think there’s a difference in quality in terms of pain relief, satisfaction, ambulation between those two fixation methods?

Dr. Thornhill: There has been reported in the OPCA series more blood loss in cementless. But now we’re much better at the blood loss. And if you account for patient selection, there’s probably no difference.

Moderator Lachiewicz: Ken, one last question for you. Do you think we’re going to have a reliable cementless patella in the future? Do we have one now? Do you leave those un-resurfaced when you do a cementless knee?

Dr. Gustke: My experience with metal-backed patellae was terrible. But never for the interface and never because they didn’t gain biological attachment. It was because of polyethylene wear. We have different polyethylene today than we had in the past, but it’s still thin. The real question is whether today’s polyethylene will be able to tolerate the stresses if it’s still only 3mm or 4mm in thickness. I don’t have an answer for that. I’m still doing cemented patellae in the majority of the cementless knees that I do.

Moderator Lachiewicz: Okay. Thank you to both of our speakers.

Please visit www.CCJR.com to register for the 2019 CCJR Winter Meeting, – December 11 – 14 in Orlando.