This week’s Orthopaedic Crossfire® debate was part of the 32nd Annual Current Concepts in Joint Replacement® (CCJR), Winter meeting, which took place in Orlando this past December. This week’s topic is “Ceramic-Ceramic THA in Patients <60: A New Standard.” For the proposition is Gwo-Chin Lee, M.D., University of Pennsylvania, Philadelphia, Pennsylvania. Opposing is Thomas P. Schmalzried, M.D., Joint Replacement Institute, Los Angeles, California. Moderating is Paul F. Lachiewicz, M.D., Duke University Medical Center, Durham, North Carolina.
Dr. Lee: My task is to support the use of ceramic-ceramic total hip arthroplasty in the young, active patient.
I’ll begin by saying that I routinely use highly cross-linked polyethylene, but I just don’t use it for everybody. I think supporters of polyethylene for everybody will say that polyethylene is better, it’s more reliable, it’s forgiving and we haven’t been able to demonstrate significant wear and therefore it’s good enough.
The fact of the matter is today we operate on patients who are often younger, more active. And more patients are expected to live into their 80s and their 90s and even into the 100s. The problem in my mind remains wear and osteolysis.
If you look at why revisions are being done in the United States, instability and dislocation are the main reasons. That has driven the use of larger heads, even with very small cups and thereby very thin poly.
One recently published study examining the clinical wear rates of 36mm ball heads on young patients found that even with ceramic ball heads, the linear wear is actually right at the threshold of 0.1mm/year. My question to you today is, while we think that it may be good enough at 15 and 20 years, can we really project these results out to last 30 years, 40 years, and even 50 years?
I’m not an engineer, but when I read studies where a lot of things measure no wear or even negative wear, I ask the question ‘do we really have the tools to actually measure wear?’ In my mind a lot of volumetric wear is actually a big issue. Fortunately, Paul et al. in his initial article published in 2009 showed that larger ball head sizes—36 and 40mm—exhibited more measurable wear volumetrically compared to the smaller ball heads. And while, at this time, they didn’t see any significant clinical osteolysis, once they extended this, the wear patterns continued to hold true—larger ball heads produced higher volumetric wear, and now they’re seeing small osteolytic lesions at 12 to 14 years follow-up.
Can we do better? I think we can for certain patients with ceramics. Ceramics trump all the other bearing surfaces in regard to wear. On top of that they’re hydrophilic which means they are wettable, and tend to be optimized for the use of larger ball heads in terms of wear. And finally, they’re biocompatible.
If you look at the results of the modern ceramics out there in the literature, they’re certainly competitive with very low failure rates and high survivorship at the mid-term follow-up. And these advantages are highlighted in the very young patient, showing very high levels of survivorship at 14.6 years follow-up.
Our institutional experience has been the same with a good experience in very young, active patients. We’ve had complications, but at very low rates. These are highly active patients who got their hips done when they were young. They remain very highly active into their 50s and 60s after 10 to 14 years, very low failure rates.
In every series that’s out there, ceramic-on-ceramic actually outperforms polyethylene with less osteolysis and less measureable wear.
So why not ceramics for everybody? In my mind squeaking remains the big unsolved problem in ceramic-on-ceramic bearings, but that rate of occurrence is actually relatively quite low and we’ll probably solve that in the very near future.
Polyethylene can fail as well. What happens to highly cross-linked polyethylene a decade or two afterwards? Will its material properties remain the same? These questions remain unanswered.
Ceramics today have better wear, they’re more reliable, have more options, and, I think, there needs to be a recognition that there is a role for ceramic-on-ceramic articulation in total hip arthroplasty. Modern ceramic-on-ceramic total hip arthroplasty should be the standard in young active patients.
Dr. Schmalzried: Everybody recognizes that ceramic-on-ceramic has low wear. But let’s look at different metrics. Survivorship. Function. Special risks. And cost. Of course, it’s all relative. Cross-linked polyethylene at 15 years – what are the relative benefits and risks?
What you didn’t see from Dr. Lee is the everyman Australian registry — which means not just single centers, not just specialty surgeons, not just surgeons that have an interest in a technology. The Australian registry is real world and ceramic-on-ceramic does not compare with cross-linked polyethylene in the hands of the everyman.
Ceramic-on-ceramic has comparable function but I have not seen anything that says ceramic-on-ceramic patients have better function. Bearing surface material is not determinant of function, so if you want to run the Paris Marathon with something other than ceramic-on-ceramic, you can do at least as well, maybe better than a ceramic-on-ceramic patient.
Squeaking. Look at the literature. Who does it occur in? Younger patients. Those that have a higher range of motion or higher activity levels. Clearly, it’s position sensitive. Have to get the center of the hip in the right place. So, the at-risk population is exactly the people that have been recommended to put ceramics in.
Now, I know that fractures don’t occur often. The problem isn’t that it’s a low incidence, the problem is those are hard cases to take care of. Everybody that’s looked at this problem is confronted with the residual ceramic particles. They’re hard third bodies. They result in accelerated wear of the subsequent bearing and then you get some significant osteolysis.
Now let’s talk for a minute about the osteolysis threshold because it’s a good thing to think about when we’re talking about what could happen down the line with young patients. We won a Hip Society award for the following analysis.
In our series, we looked at activity, because when your patients get older, everybody slows down. You can’t take the activity level of a 30- or 40- or 50-year-old and then superimpose that on their later years and say they continue to do this. Everybody slows down. The data indicates it’s a compounded decrease in activity of about 2-3% per year. So, if you take a life expectancy of a 50-year-old, which is 31 years, the total volumetric wear over 31 years using the formula where you factor in the decreasing activity for cross-linked polyethylene, it’s 305 cubic millimeters. So there is a low risk of osteolysis during their lifetime.
In summary, I recognize the low wear of ceramic-on-ceramic, but survivorship is not better, function is not better and there is a squeaking risk in the target patients. Lastly, throw in the fracture risk, low revision survival AND it costs more. I think the relative benefits and risks favor cross-linked polyethylene.
Dr. Lee: I think we all want the best for our patients in the long term. I think the main issue really here is who’s going to benefit from that ceramic-on-ceramic hip replacement. Not everybody’s going to realize the benefits and longevity of ceramic-on-ceramic hip replacement. The task was actually to discuss whether young active patients, potentially under the age of 60, 50 or 40 would benefit from that or not. And my concern is that in 2015, I don’t have enough convincing data to basically suggest a modern highly cross-linked polyethylene that’s going to last 30, 40, or 50 years.
Dr. Schmalzried: I’m unaware of convincing data that the current generation of ceramic bearings and the parts they’re associated with have 30, 40, 50 year data either. So both of us are speculating, right? I think my summary slide said it all. Until I have something that’s demonstrable, that offsets the cost and the fracture risk and the revision survival, I’m going to stick with cross-linked polyethylene.
Moderator Lachiewicz: So Gwo, let me ask you this. If a patient has a chip fracture and then a more complicated fracture, how do you handle those? And do you think revision of that will be not as good as the primary?
Dr. Lee: There’s no doubt that ceramic-on-ceramic is a less forgiving surface. I would say that on the ball head side, the fracture issue has been relatively figured out. With the latest generation of ceramics there have been only 26 reported fractures in the ceramic database in the last 13 years. And two-thirds of them were related to a taper design that’s no longer on the market.
We learned a lot about the use of ceramics using appropriate taper, appropriate impaction, and I think going forward head fractures will be a relative rarity. This is technology with no wear. So I think we need to basically figure out things like component position, individualized component position, how to insert these liners a little bit more properly so that we can realize the advantages ceramics offer the young patient.
Moderator Lachiewicz: Gwo, one more question. How do you answer Tom’s contention that based on the fact that the ceramic-on-ceramic bearings have actually changed since they were first introduced…what assurance can you give us that this will be a 20- or a 30-year hip?
Dr. Lee: I think the main change has really been in the material properties of ceramics and its toughness and fracture resistance. The wear properties haven’t really changed.
Moderator Lachiewicz: Tom, you mentioned highly cross-linked polyethylene… but what did you recommend for the head material for the young patient? I know you’ve written about trunnion corrosion with metal-on-polyethylene hips. Do you feel that there is a role for ceramic heads in these young patients?
Dr. Schmalzried: I do.
Moderator Lachiewicz: And do you use them routinely?
Dr. Schmalzried: In young patients, yes.
Moderator Lachiewicz: I want to thank Dr. Lee for quoting my papers and I just want to clarify that we did find some evidence of osteolysis, but these were only seen on oblique views. The clinical significance is unknown. We also have a paper showing that the risk of re-operation is much lower with highly cross-linked polyethylene. So what Tom said about clinical significance is correct. There is no clinical significance yet of that osteolysis.
I’d like to thank both speakers.
Please visit www.CCJR.com to register for the 2016 CCJR Winter Meeting, –December 14 – 17 in Orlando.
