This week’s Orthopaedic Crossfire® debate is “Ceramic on Ceramic Total Hip Arthroplasty: A New Standard.” For the proposition is Gwo-Chin Lee, M.D. of the University of Pennsylvania. Against the proposition is Robert L. Barrack, M.D. of the Washington University School of Medicine. Moderating is Aaron Rosenberg, M.D. from Rush University Medical Center.
Dr. Lee: “I use polyethylene in most of my total hip arthroplasty (THA) patients, but I think there is a role for alternative bearings. Work by Kevin Bozic et al. found that the most common reasons for revision in the U.S. are: instability/dislocation (22.5%), mechanical loosening (19.7%), and infection (14.8%). Because of instability we have seen a trend towards larger heads.”
“If you stick to 28/32mm heads then highly crosslinked polys will wear well in the long run, but that’s not what we are seeing clinically. We are seeing 36mm heads on small cups such as 50/52mm. As for volumetric wear, I don’t know if we can measure that accurately and I question whether we have the tools to measure wear sensitively.”
“There has been a recent resurgence of ceramics, primarily driven by the appetite for larger heads. There have been an increased number of head size options, and the reliability of ceramics in terms of fracture rate continues to improve. And the issue of trunionosis is driving the use of ceramic ball heads because there have been some reports showing that these heads may be more trunion friendly on these modern hip designs.”
“Ceramics are ideal because: they have the lowest in vitro wear rates, they are hydrophilic and wettable. And unlike metal on metal, it’s inert and biocompatible…meaning that there aren’t issues associated with soft tissue toxicity and local tissue reactions.”
“If we look at the clinical results of ceramic in THA we see favorable numbers (from 92-100% survivorship) with relatively low complication rates. A study by Kim et al. in patients 30 years old and younger found a 99% survivorship at a mean follow-up of 14.6 years. Our institution has had similar results with young, active patients, namely, high survivorship and low complication rates. When we discuss survivorship it’s important to stress clinically relevant durability. These patients will continue to be very active despite having THA.”
“In some studies where ceramic-ceramic has gone head to head against metal-polyethylene, the former have shown less osteolysis and less measurable wear. So why not ceramics for everyone? There have been fewer options (until recently), risk of fracture, risk of squeaking, it’s less forgiving, and in some instances cost is an issue.”
“The clinical fracture rate is actually relatively low. Taking into account 13 studies from 2008-2012, the fracture rate is low (0.6%). As for squeaking, a 2014 meta analysis by D.H. Owen et al. showed a 4.25% squeaking rate with only a 0.2% revision rate for squeaking.”
“Our group participated in a retrieval study looking at fretting and taper corrosion—using a matched control study with ceramic ball heads and metal ball heads. Ceramic ball heads showed less taper fretting and corrosion compared to matched metal ball heads.”
“I’m not advocating ceramic-ceramic arthroplasties on everybody…not everybody should be allowed to drive a Ferrari. Just ask Adolph Lombardi what happened last time he allowed me to drive one of his cars.”
“If the definition of ‘standard’ is that it’s a level of quality or achievement that is desirable, then I propose that ceramics are today’s standard. They show better wear, they are more reliable, and there are more options (particularly in the larger heads).”
Dr. Barrack: “There is a role for ceramic heads, and some of the advantages just mentioned are particular to the head; the head helps protect the trunion. But the debate is on ceramic-ceramic, not ceramic-poly; I frequently use the latter, but I never use the former. What we just heard was that it was not a standard…that it may be occasionally indicated. But I would even take issue with that.”
“Hard-hard bearings became popular in the first decade of this century. Since that time there’s been a major decline in enthusiasm for hard-hard bearings. There has been a renewed enthusiasm for ceramic-ceramic because of improvements in manufacturing, taper tolerances, higher strength, and a lower wear risk.”
“In spite of these major improvements, concerns were expressed with the new generation of ceramics. In 2004 I published a paper on this topic in Clinical Orthopaedics and Related Research with Dr. Corey Burak and Dr. Harry Skinner. Dr. Skinner actually has a Ph.D. in ceramic engineering and was one of my mentors. The concerns included the fact that even with these improvements we continue to see problems with modularity, fracture, taper limitations, stripe wear, limited surgical options…and squeaking and impingement in particular.”
“The conclusion [from our study] was: ‘Although ceramics show promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist.’”
“The proposed solution was to alter the ceramic, particularly a hybrid material called Delta ceramic, a composite material made of alumina and zirconia. The purported advantages were higher strength, fewer fractures, a lower wear rate, and more options for heads (not liners). As for squeaking, we thought it would go away; lower wear and the disappearance of squeaking have not come true.”
“In the current healthcare environment payers will not expend more for these expensive technologies without proof of added value. Also, we must account for variability in surgeon performance. You need more of a margin of error, which we don’t have with hard-hard bearings. The current legal environment, especially in the U.S., is unforgiving of failures of new, unproven options.”
“Michael Porter is a leading healthcare economist and is the architect of value based purchasing (i.e., that you have to either improve the outcome or decrease the cost in order to add value). I believe that ceramic-ceramic does neither. It doesn’t improve outcomes and it increases the cost. In the investigational device exemption (IDE) study from Johnson & Johnson they state definitively that they have ceramic liner fractures.”
“There is not a problem clinically with metal-poly (even in young patients). Metal-poly outperforms ceramic-ceramic. The problems are impingement, malposition, wear, squeaking, breakage, and mal-seating. A 2011 study by Lee et al. in the Journal of Orthopedic Research found that if the component is malpositioned then the wear rate goes up dramatically…even leading to cracking and liner damage. The problem is that there are a lot of outliers in hip replacement these days.”
“Massachusetts General found that half of their total hips are outside the ideal zone, many by 10-20 degrees. Metal-crosslinked poly is very forgiving of this; hard-hard bearings are very unforgiving. A very high percentage of these liners are mal-seated. Work from Hospital for Special Surgery and two other centers showed that mal-seating is a problem. And squeaking was shown as an issue in work by Andy Shimmin et al (Bone and Joint Journal, 2013), who found that 11% of patients experienced ‘noises’ and 13% experienced reproducible squeaking.”
“New generation ceramics are better, but the standard metal-crosslinked poly has improved even more. And the 10-15 year results cannot be improved upon. Sadly, ceramic-ceramic isn’t ready for prime time.”
Moderator Rosenberg: “Gwo-Chin, two minutes to respond.”
Dr. Lee: “I believe the main difference in our positions is that ceramic-ceramic accounts for about 20-25% of my hip practice. I offer it primarily to patients under the age of 50. The literature shows that when you’re comparing conventional bearings to ceramic-ceramic it is difficult to find that one is superior to another. But when you look at the issue of survivorship in the literature it is dealing with things retrospectively…our patient population is changing. The patients undergoing THA are under the age of 65 with perhaps another 30 years of life in them. They want to be active, so their usage rate of that material is going to be different than what we’ve previously seen. This does fall into the ‘theoretical advantages’ category, but we shouldn’t throw the baby out with the bath water.”
Moderator Rosenberg: “So you’re saying that with regard to ceramic liners you’re practice is about 20%? And are those predominantly patients in whom you don’t feel comfortable using a larger head because the plastic is too thin?”
Dr. Lee: “Correct.”
Moderator Rosenberg: “Bob, at what size plastic—if you want to use a larger head—would you be tempted to use a ceramic liner?”
Dr. Barrack: “The wear data show that if you have a properly positioned component then you can go down to 4mm of polyethylene. I do that in older, less active patients, but in younger, active patients I would probably do a dual mobility hip. The assumption is that in young, active patients crosslinked poly might have a problem, but there is no evidence of that. At our center we looked at patients under 50 with CT scans and with Martell software and we have virtually no measurable wear at 10 years plus in patients under 50.”
Moderator Rosenberg: “One thing that concerns me is that everyone is trying to do less invasive surgery and there is more tension on the soft tissues. I’ve seen that the hardest part of the case is getting the head on the trunion through a tiny incision. Gwo-Chin?”
Dr. Lee: “Proper implantation of ceramics is crucial and increases their reliability. My advice is to do the smallest incision possible without compromising your surgical technique.”
Moderator Rosenberg: “Bob?”
Dr. Barrack: “It’s a teaching point. If you’re bound to using a ceramic liner then it’s almost impossible to get concentric seating and impaction. It’s dangerous to have a cocked component at the time you seat it because there are many more intraoperative chips and fractures than postoperative chips and fractures. And if you make a small incision you may not even realize that you have chipped or cracked a component in the ceramic liner. So we’ve introduced a new failure mechanism, yet we’ve not demonstrated the benefit.”
Moderator Rosenberg: “Thank you, gentlemen.”
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