The Cementless Tibia: A Viable Fixation Alternative

This week’s Orthopaedic Crossfire® debate was part of the 35th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “The Cementless Tibia: A Viable Fixation Alternative.” For is R. Michael Meneghini, M.D., Indiana University School of Medicine, Indianapolis, Indiana. Opposing is Gwo-Chin Lee, M.D., University of Pennsylvania, Philadelphia, Pennsylvania. Moderating is Robert E. Booth, Jr., M.D., Jefferson Health 3B Orthopaedics, Philadelphia, Pennsylvania.

Dr. Meneghini:  Cementless fixation is a viable alternative on the tibial side. My disclosures are relevant because I have multiple implants that I’ve designed that are on the market and receive royalties for them.

Why cementless knees?  Why is there a debate where we’re talking about it?  We all know that there’s established long-term success by way of biologic fixation. We have now improved our biomaterials for fixation and wear. Regarding cementless failures from years ago, we corrected those mechanisms and we do have the ever-increasing demand for operating room efficiency. Patients are younger and more active. I’ll argue that cement is not the durable interface for those patients.

If you look at multiple survivorship studies, Rich McCalden in over 6,000 consecutive knees (McCalden, et al., JOA, 2013). The California database, over 120,000 knees (Meehan, et al., JBJS-Am, 2014), both studies showed conclusively a decrease in survivorship with aseptic loosening in younger, more active patients using cement.

Cement is not a durable interface long term. A published retrieval study showed that the bone pulls away from the cement over time. (Miller, et al., CORR, 2014).

We originally looked at this with Merrill Ritter years ago, looking at a small group that he had performed cementless originally back in the early 1980s, and followed those patients out to 20 years. He only had two failures and had a 97% survivorship at 20 years. That equaled his survivorship in the cemented AGC cohort, and there was a selection bias. Those cementless patients were younger by over a decade. And when we looked at those x-rays out to 20 years, we were impressed with the pristine radiographic interfaces (Ritter, et al., JOA, 2010). We saw them over and over again. Biologic fixation stood the test of time even in those young patients.

Mike Dunbar gets a lot of credit for helping us understand how these implants behave early, and using RSA data, we can risk-assess these patients for their longevity. He looked at 28 porous tantalum tibias and showed that at 2-year follow-up none were at risk for failure compared to the cemented counterparts where 4/21 were at risk. When he performed a 5-year follow-up on the cementless cohort, there was no further migration (Dunbar, et al., JBJS-Am, 2009).

A Cochrane database review followed up on that and looked at a meta-analysis showing the exact same thing (Nakama, et al., Cochrane Database Review, 2012). We know that press fit knees, particular to the tibias, will settle up to 1mm or 2mm over the first 2 years and then stabilize. Once they stabilize, it is a much more durable interface than cement. This is shown over and over again in RSA data. I would argue that cementless fixation is appropriate for younger patients.

The Mark Coventry Award paper out of Mayo Clinic looked at a porous tantalum design involving 397 patients in a randomized controlled trial. There were no failures at a minimum of 5-year follow-up in that cementless tibial design (Pulido, et al., CORR, 2015).

We are in the era of improved biomaterials—hydroxyapatite, peri-apatite, porous tantalum, and porous titanium.

I believe there is sufficient evidence to support cementless fixation. How do we continue expanding that and doing it safely?  I do believe that patient selection is important. There are gender differences. An older female, I think cement works great. Probably no reason to do a cementless fixation in that particular patient. But younger people, people with good bone, I think are appropriate. And you’ve got to be a little bit cautious in those who have poor bone quality.

We have biomechanical support for that. We looked at this in a biomechanical model and regardless of the design, if the bone quality is poor the mechanical integrity may be less. I would just use caution in the older, osteoporotic patients (Meneghini, et al., J Knee Surg, 2011).

I also believe there are critical implant design factors and surgical techniques.

I think now we understand what makes a successful press fit tibia. You either have a robust central keel or post and peripheral fixation of some kind. It can be a cruciform peg or screws, whatever your choice is. But that will be a successful design or central hex pegs which have also been shown over and over again to be successful. Modern testing has evolved, which is why we have more confidence in these modern designs.

We published some work where we introduced shear, compression and torsions forces into modern testing, to look at a more complex endeavor such as stair descent. Those were not looked at in the earlier designs. That’s why we have a lot more confidence in our future designs and we can actually look at the difference between two designs (Bhimji, et al., JOA, 2012). So modern testing has improved our confidence.

We can’t forget the technique. I think it’s really important to use the 4-Corner test—this I learned from Leo Whiteside—to make sure your tibia is cut flat. This is the critical point of making sure a press fit tibia works. So, you’ve got good designs now. Make sure that tibial cut is flat. And when you go to put your real implant in, it’s important that when you impact it that you allow your central pegs or your keel to maintain that stability. So, make sure the tibial implant and the tibial cut are co-planar as you go down. That maintains your mechanical integrity.

In summary, I believe cementless total knee replacement is the choice for the younger, more active patient. I do think patient selection is important. The principles of cementless fixation remain — adequate mechanical stability, maximum contact with viable host bone. Modern designs, I think, you can have a lot of confidence in the modern press fit designs. They’re very successful and surgical technique is critical.

Dr. Lee:  Debating Mike is always a tall task. But ability is not reliability. Devices not only need to be viable; they also need to be durable, reliable, reproducible. Cemented fixation remains a gold standard even in the young, active patient.

I think desire for uncemented fixation is because we feel that biologic fixation is better than cement. Obviously, Mike already showed the biomechanical studies associated with that. The question you really need to ask yourself is, “Is cement really the weak link?”  Or is cement breakdown the cause of failure and loosening over time (Sharkey, et al., JOA, 2014)?

If you look at the Australian National Registry, the risk of aseptic loosening or revision for aseptic loosening is about 2% at 15 years (AOANJRR Annual Report 2018). I think of young patients undergoing revision are not undergoing revision for loosening of implants because of cement breaking or failure. They are undergoing because of things like infection or instability.

Institutional series have shown that basically at 5, 10 and 15 years, large series of consecutive, cemented total knees arthroplasties have high survivorship and you don’t see this survivorship decreasing even at the 15-year mark (Vessely, et al., CORR, 2006).

In fact, if you do a good cemented total knee arthroplasty, and this happens to last over 8 years, there’s a greater chance of dying than the implant loosening. And even if you have the luck of having a good design, even in the very young patient, particularly with the IBI monoblock design, at 30 years very low rates of tibial loosening in this group of patients (Ritter, et al., JOA, 2016; Long, et al., JBJS-Am, 2014).

In my mind, cement is really not the root cause of aseptic loosening.

Cementless tibias, cementless total knee arthroplasties, you’ve seen are less forgiving, technically demanding, there are bone quality constraints, and they are costly. Which is not necessarily compatible with today’s environment.

Undoubtedly with older designs, cemented fixation was superior to cementless fixation (Duffy, et al., CORR, 1998). But even with contemporary comparative series, there was no difference in clinical outcomes but more aseptic loosening and more revisions in the cementless groups (Behery, et al., JOA, 2017).

I think a registry is actually useful to look at this question. If you look at the Australian Registry, you see the cemented utilization going up and the cementless utilization going down over time. At every time point—5 years, 10 years, 15 years—cementless revisions outnumber that of cemented revisions.

Whether using a PS implant, CR implant, medial pivot implant, cementless fixation performs inferiorly at 1 year, 3 years, 5 years, and even 17 years to the point where the conclusion was basically cementing the tibial component gives the best outcome for minimally stabilized and medial pivot design prostheses  (AOANJRR Annual Report 2018).

If you move next door to New Zealand, cementless fixation performed inferiorly compared to cemented fixation. Again, the comparison was that tibial loosening was the main culprit for an increased revision rate in this cohort of patients (The New Zealand Joint Registry Annual Report 2017).

Other countries such as Scandinavia showed no increase in cementless fixation utilization (Swedish Knee Arthroplasty Registry Annual Report 2016). Maybe because cementless fixation is associated with increased risk of all causes of revision, increased risk of pain, increased risk of aseptic loosening (National Joint Registry 13th Annual Report 2016). Higher revision rates at every point even beyond 10 years, which is when you would expect the curves to simply diverge if cemented fixations were also going to fail at that time. And they’re not really…the curves are essentially parallel in terms of survivorship.

There’s no doubt that improved designs and reliability make cementless fixation viable, but I would propose that just because commercial space travel is viable, doesn’t necessarily mean I’m going to do it. All these studies show comparative performance and not superior performance (Pulido, et al., CORR, 2014; Harwin, et al., JOA, 2017).

This is an older study. The 5-year results were actually presented at AAHKS, again, showing no difference in clinical outcome scores. No difference in survivorship. And the cementless group had more radiolucent lines (Fricka, et al., JOA, 2015).

In a study also presented at AAHKS that was subsequently published showed that cementless fixation doesn’t decrease operative time. Doesn’t decrease blood loss. And doesn’t decrease a change in hemoglobin. This was actually interesting as the cementless group had a higher patient satisfaction compared to the cemented group (Nam, et al., JOA, 2017).

Meta-analysis showed no difference between cemented and cementless fixation in total knee arthroplasty even in the young patients (Franceschetti, et al., Knee Surg Sport Traumatol Arthrosc, 2017), albeit I’ll admit the level of evidence is relatively low.

Michael alerted us that basically he can’t necessarily use these in every patient population. Many of our patients are obese and early tibial failure has been reported in this cohort of patients (Meneghini, et al., JOA, 2013).

Some studies have not necessarily found these differences…very short-term studies…but other studies following these patients out to a longer term clearly see a difference in survivorship compared to non-obese individuals (Boyle, et al., JOA, 2018; Lizaur-Utrilla, et al., JOA, 2014).

I think he shared some of the RSA data. In terms of mobility, cementless total knee arthroplasties move more than cemented total knees early on, within the first 2 years. I think the difference is beyond the 2 to 5 years (van Hamersveld, Bone Joint J, 2017).

Clearly you should not use this on every patient. Bone quality matters (Andersen, et al., JOA, 2017).

There are things about technique-dependence…Michael showed on the tibial side…precision is needed for achieving perfect implant stability (Conlisk, et al., Knee, 2017).

And the question really:  Are you all ready to abandon the cement?  What about the patella?  Is this the age of the unresurfaced patella among us?  I think a lot of these things lack clinically relevant evidence and many fall under the same category as those proposed with PSI, which we’ve already gone through this exercise.

A lot of the appetite for cementless fixation also is commercial and economic, largely because total knee arthroplasties are now being performed in ambulatory surgery centers and there’s an appetite for speed and elimination of cement. But the evidence is that cementless fixation does not provide improved survivorship, improve patient outcomes, better reliability, nor is more cost effective.

So cementless total knee arthroplasty is not a game changer and cemented fixation is and will remain the gold standard for the foreseeable future.

Moderator Booth:  Michael, those are some compelling numbers and the registry data is interesting. I don’t have the skill to do that little feathering that you showed Leo doing to get that prosthesis flat. How do you deal with it?

Dr. Meneghini:  I think skill may not be the right word. Patience could be the right word. At the end of the day, registries are very valuable, but they lump data and the finer detail aspects can be lost. Registries also take time to show results. Some of the data is 2 decades old now. Some of the patients in the studies are 20-year follow-up studies that were published 10 years ago. That means those were implanted 30 years ago. The patients we see in our clinics now are very different from what we saw 30 years ago in terms of age, activity level and the demands on their protheses.

Moderator Booth:  You supported doing it in women less than men. What’s the gender data?

Dr. Meneghini:  It’s a bone quality issue. There’s no doubt that when women hit menopause their bone quality can decrease.

Moderator Booth:  Age. You advocated most for the young. Why would we do less than the best in the young?  A revision, for me, of a cemented tibia is easier than a cementless tibia.

Dr. Meneghini:  That depends on the design. There are cementless tibias that are easier to revise, some that are less so. I think in terms of age…we approach it as physiologic age. In the Midwest you can have a 70-year-old farmer who is a heavy laborer and that person’s bone is as good as you’ll ever find in a 45-year-old female potentially. The one issue we’ve always seen in orthopedics—I’m sure you’ve experienced it—you do a reconstruction and you’re like, “Oh, this will do fine for 5 years. The patient probably won’t be alive by then anyway. It’s a tenuous situation.”  And then they show up in your clinic 10 years later and you thought for sure, “Well, they surely won’t live that long.”  But they do. Increasingly, a 70-year-old could easily have a 30-year life expectancy.

Moderator Booth:  Gwo, people who make the decision to do a cementless knee want to preserve the cruciate, not resurface the patella, do a lot of things. Are those decisions additive, do you think, over time?  Are they interrelated?

Dr. Lee:  If you go down the path of abandoning cement, not resurfacing the patella would be the next logical step. I do think a lot of the impetus is commercial. Working in the outpatient setting, there’s an incentive to get rid of the cement. To Michael’s point about registries; the reason patients younger than age 65 have lower revision rates is the use of computer navigation, better alignment and better balancing. It has nothing to do with cement or no cement.

Moderator Booth:  Thank you both for a good debate.

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