“In my experience CoC bearings are incredibly reliable in young patients, ” states Steve Murphy. “It’s expensive, ” avers Bill Maloney. “And use is based on the theoretical long term benefits in young patients.”
This week’s Orthopaedic Crossfire® debate is “Ceramic on Ceramic: A New Standard.” For the proposition is Stephen B. Murphy, M.D. from Tufts University School of Medicine in Boston; against the proposition is William J. Maloney, III, M.D. from Stanford Hospital and Clinics in California. Moderating is Robert T. Trousdale, M.D. from the Mayo Clinic.
Dr. Murphy: “My job is to explain why I think ceramic-ceramic (CoC) are the best for young patients and perhaps for patients that aren’t so young. I started using them and went to uncemented ceramic-ceramic in 1999. In our 2012 study we had 103 patients that are minimum 10 years with 7 lost to follow up; mean age was 42 years. Most of these patients were part of a prospective FDA IDE [investigational device exemption] study. These were all uncemented components with flush mounted liners and no elevated metal rim; the metals were titanium with the alumina ceramic with an 18 degree taper.”
“Of these patients, 17% had had prior surgery, many having had multiple previous surgeries, including hip fusions. Regarding soft tissue technique, all of these surgeries are done with preservation of the posterior capsule and short rotators…either with a transgluteal, trochanteric slide, or superior capsulotomy. Most of these were small bearings. There were 4 revisions out of the 96: two liner fractures, one stem in a medically complicated patient didn’t stick, and one cup did not stick. There were no dislocations, no revisions for infection, no osteolysis or pseudotumors.”
“In a 2013 Journal of Arthroplasty study by Babovic and Trousdale there were 104 hips with only 7 lost to follow up; patients were under 50 and had 100% survivorship at minimum 10 years. There were 4 mechanical failures and 1 revision for recurrent instability. But they excluded 70 of the patients from the study, which was more than they included in the study…and there was a 6% dislocation rate in the 70 patients they excluded.”
“So why would a surgeon not recognize the superiority of ceramic-ceramic bearings? Possibly cost, or fracture, squeaking, or dislocation. As we see these metal-on-polyethylenes getting trunionosis, more accelerated wear, pseudotumors, the trend is going away from metal heads. When you’re comparing CoC and ceramic-poly (CoPoly) the cost is almost identical and in some cases of enhanced porous coatings the non-ceramic-ceramic hips are actually more expensive at our institution than the ceramic ones.”
“Regarding fracture, we’ve had young males doing very risky things, falling from heights or bicycling into a tree. Fracture in poly could be much more common than fracture in ceramic. And with the newer ceramics this issue may go away.”
“Squeaking is an old issue and I find it tedious that in the 15+ years that I’ve used CoC I’ve never had a YouTube-worthy patient making a squeak. I think it’s the orthopedic equivalent of tabloid sensationalism. People do get rare squeaks, and most of the time they go away; this is not a clinically relevant thing for a flush-mounted liner.”
“There were no dislocations in all of these patients at a minimum of 10 years. Clearly, the fact that you have fewer options can be made up for with other things, including soft tissue technique and component placement.”
“As for crosslinked poly (XLPE), I’m concerned that they seem to change every year: they were ‘great’ and now they are ‘greater.’ I think we’ve learned a lot, including that lipids and stress changes the poly. It would be nice to see minimum 10 year results in patients under 50 that have fewer patients lost to follow-up or excluded. Certainly with XLPE the strength has decreased, the fracture rate is still high, and we are now seeing pseudotumors with these constructs with metal heads. And they all oxidize in vivo; every one that has been retrieved has evidence of oxidation. Then there’s vitamin E poly…there are concerns that the wear rate is actually higher than the current XLPE.”
“So I hope that XLPE are good bearings; ceramic on XLPE could be a very good bearing, but I know from my experience that CoC bearings are incredibly reliable in young patients.”
Dr. Maloney: “The topic is ‘Ceramic on Ceramic: A New Standard’, and Webster’s defines ‘standard’ as something established by authority, custom, or general consent. This is clearly untrue for CoC THA [total hip arthroplasty]. Why the interest in CoC THA? It has an incredibly low wear rate. But is this relevant with today’s bearing surfaces? Probably not.”
“If you look at data from 2002 (Laurent et al., Society for Biomaterials) you find wear with cobalt chromium, alumina, and zirconia on poly without radiation, on conventional poly, and on XLPE. With XLPE it almost doesn’t matter what you put on it. It’s been said that the height of the XLPE does poorly against scratched heads, but that’s not been our experience. In a study we did using retrievals from revision surgery. With conventional poly against the scratched heads you got more volumetric wear; when we did the same study with the same heads against XLPE it was still extremely low: less than 0.1mg per million cycles.”
“The biggest downside to CoC THA is cost per outcome (value); CoC are significantly more expensive. And at our institution there is a significant ‘upcharge’ for a CoC bearing. Kevin Bozic has looked at this. To justify the cost, there would have to be a substantial reduction in revisions. From Dr. Bozic’s 2009 data on a nationwide inpatient sample we see that 14.2% of the bearing surfaces going in in the U.S. were ceramic (it’s probably higher now). There are a disproportionate number of these done in the northeast…probably related to Dr. Murphy’s practice.”
“When you look at the complication rate comparing metal-on-plastic and CoC there is no difference. The revision rate for both was about 1%; mechanical loosening was very low in both groups. So both of these are pretty good bearing surfaces, but CoC had a significantly higher cost.”
“From the Australian registry we see that metal on poly, metal on ceramic, and CoC all do pretty well; metal on poly tends to do a little bit better. But when you take a technology (CoC) and put it in an everyday surgeon’s hands it is not doing better than metal on poly. If you are going to use CoC it appears that the larger heads are better than smaller heads.”
“Steve is an excellent surgeon and he’s been doing this for a long time. But there are less options, even with the newer heads, in terms of neck length and liner options. As for breakage, it doesn’t always occur in high activity patients. While the new ceramics are better, we don’t have a good feel for what the clinical fracture rate is; I think it will be relatively low, but not zero.”
“You can squeak by with CoC THA, but it’s not a new standard for THA. Any use is based on the theoretical long term benefits in young patients.”
Moderator Trousdale: “Steve, the one undeniable benefit of CoC is that in the lab it wears better than any other bearing. So Bill’s point is, ‘Are all the other negatives worth the theoretical wear benefits in light of the fact that in 10-14 years highly XLPE looks pretty good.”
Dr. Murphy: “When I discuss CoC I’m talking about minimum 10 year results in my own patients. You’ll notice that when people talk about XLPE they show wear rates, penetration rates, incidences of osteolysis. What you don’t see are clinical outcomes in young patients at 10 years. You have the only article in the literature now on that topic and that’s a complicated article because most of the patients were excluded from the study. The only real experience I’ve had with fracture are with these guys falling from heights. Poly fracture is quite common, and people don’t talk about that either. The other concerns I have are continued oxidation of all of these things, and continued changing of these polys for some reason…probably because they are not good enough.”
Dr. Maloney: “I don’t think that fracture in highly XLPE is common. I did the first one in 1988 with Longevity. After doing a couple thousand of these I’ve had one that’s broken…and that was probably my own fault because I put a 36mm head in a very thin liner. If you look at the clinical outcomes, I have a group of patients under 50 that have twice been reported in the literature. Robert Barrack and his group are following them at Washington University (where I did the cases). The patients are functioning at a very high level with a low revision rate. It’s technically more demanding to do ceramic-ceramic…and it’s more expensive.”
Moderator Trousdale: “Bill, what bearing surface would you use in a 20-year-old that needs a total hip?”
Dr. Maloney: “I did a THA on an 18-year-old recently and we used highly XLPE and a cobalt chrome femoral head.”
Moderator Trousdale: “Steve, in that case you would use CoC?”
Dr. Murphy: “Yes. We see these articles about XLPE and how people aren’t seeing problems…but at our hospital we’re having pseudotumors with wear and trunionosis in hips that have metal heads. And it’s being seen in Chicago. You don’t see pseudotumors with CoC bearings and titanium metals. If you’re going to use XLPE and someone is going to be around for awhile than you probably ought to use something other than metal on the femoral side.”
Moderator Trousdale: “From these large databases it appears that pseudotumors with cobalt chromium heads and highly XLPE are relatively rare.”
Dr. Murphy: “For some reason we’re seeing it so much more often now. Josh Jacobs just published a study last year showing pseudotumors in cobalt-chrome on cobalt-chrome. Now we’re seeing it in cobalt-chrome on titanium.”
Dr. Maloney: “But that’s a function of the taper. In our own experience we’ve not had any cases like that at our institution. We’ve operated on six at our institution, but like Steve’s institution we’re a referral center.”
Moderator Trousdale: “Steve, comment on fracture. Is trauma an etiology in fractures of ceramic?”
Dr. Murphy: “I saw an atraumatic ceramic fracture eight years ago. The only ones I’ve seen since then are men getting picked up by an ambulance after a fall from a large height. These are easy fixes: no synovitis, no bone resorption, and in about 20 minutes they can be on their way.”
Moderator Trousdale: “Thank you both.”
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