“Ceramic-ceramic is probably the best solution in terms of safety, ” says Aldo Toni. “Too many problems with ceramic-ceramic, ” counters Stuart Goodman. “Point loading, the shell-liner interface, the femoral head-trunion interface, etc.”
This week’s Orthopaedic Crossfire® debate is “Ceramic on Ceramic Hip Arthroplasty: A New Standard.” For the proposition is Aldo Toni, M.D. from the Rizzoli Institute in Bologna, Italy. Against the proposition is Stuart P. Goodman, M.D., Ph.D. of Stanford University Medical Center in California. Moderating is Clive P. Duncan, M.B., F.R.C.S.(C) from the University of British Columbia.
Dr. Toni: “Our experience with ceramics started nearly 20 years ago, so we have gone through different materials and designs. The best material is probably Delta-Delta; it has the best mechanical properties. We have survival data on almost 10, 000 ceramic-ceramic, 3, 300 ceramic/metal-poly, 1, 400 metal-crosslinked poly, and 1, 100 metal-metal (this is about 16 years follow up). Up to seven years there is no difference in the materials; they are all fine.”
“After seven years standard poly starts declining. The problem is the second decade. Complications leading to revision related just to ceramics are low: 1.2% revision at 15 years. And there is no osteolysis.”
“The problem with ceramics is brittleness. We took the data from our original registry—ongoing since 2000—and found that out of about 5, 700 ceramic heads we only had one failure. With the Biolox Delta specifically, out of nearly 11, 000 cases there were no failures. Failure of the head is a forgotten problem nowadays.”
“There are still problems related to ceramic liners; the overall incidence is 0.13%. But this problem is mainly related to surgeons, not to materials. If you look at the causes for liners chipping or other damage, we find malpositioning, microseparation as a result of instability, and neck-cup impingement (often a problem of malposition too).”
“The cup being malpositioned in terms of anteversion…this is the main cause of fracture of this material. Even noises are related to this—81% of noises we registered were related to a malpositioned cup. So the take home message is, ‘Yes, ceramic may break, but this is very low; and only 0.5% complained about noise being a problem with ceramics (but never with the new Delta-Delta.)”
“There is no perfect prosthesis. The Australian registry showed us that using metal-metal—just switching from the smaller diameter to the 36 and 40 mm diameter, we had a jump in the revision rate…more than 20% after a few years. Bigger may be worse for metal, but maybe this isn’t true for ceramic. If you look at the results of 28 and 32 mm heads, we see that metal-metal and ceramic-ceramic are performing better than others. And we can safely go up in diameter with no risk in increase of revision rates.”
“As for poly, it’s been through a lot of improvements in the last decade; after 10 years it’s performing very well with the crosslinked poly. But we know that there is a tradeoff for this improvement: it’s mechanical impairment. So if we go with a larger head and thinner poly liner you may risk mechanical failure. With metal there is the risk of ions and ALVAL [aseptic lymphocyte dominated vasculitis associated lesions] reaction. So nowadays ceramic-ceramic is probably the best solution in terms of safety…and the capability to take advantage of this solution without paying any price. So I think that ceramic-ceramic is a good standard for demanding patients.”
Dr. Goodman: “We’ve heard all the advantages of ceramic-ceramic; the mechanical properties have also been shown to be very good. The newer materials give us a composite that is very wear resistant. But, do our expectations for ceramic-ceramic meet reality?”
“There are issues: difficulty with cup assembly, incomplete seating of the ceramic liner within the metal shell, liner canting and dissociation, as well as liner chipping and fracture. Then there is edge loading, striped wear, and squeaking, catastrophic head breakage (rare), and they’re expensive.”
“Issues with the liner: the titanium shell may deform, the liner can seat in a canted position, and it can lead to liner dissociation. These issues vary with different designs. Incomplete seating of the liner can happen due to soft tissues, bone, or hydroxyapatite particles, which can lead to asymmetric stresses, dissociation, or fracture. Chipping can also occur when you put the implant together.”
“Edge loading is secondary to this hard edge which is created where the lead-in surface intersects with the more ground and polished bearing surface. The edge of the bearing surface is recessed a few millimeters from the face of the implant. As that head runs over that hard edge onto the bearing surface you can get edge loading. When the contact area moves over this hard edge there is wear and potential damage leading to striped wear.”
“Microseparation can also lead to striped wear. During a gait cycle there is impaction of the head on the rim during heel strike; this can also cause striped wear. Ceramic-ceramic bearings are very sensitive to implant position. And squeaking? It’s an impulse where there is stick slip friction from the bearing surface. It’s probably due to a number of causes: lack of lubrication, edge loading, bearing damage, impingement, debris, and high contact stress. This can be amplified, especially with certain implants. Squeaking can also occur due to impingement.”
“In general, ceramic-ceramic bearings have decreased range of motion (ROM) compared to a metal-polyethylene. Issues with the femoral head: We’ve heard about catastrophic head breakage—it is very rare. But when it occurs it necessitates revision surgery. So, what bearing should we choose after that? If there are retained ceramic particles they can destroy a metal bearing surface.”
“Ceramic-ceramic bearings are susceptible to point loading if there is debris. There are issues with the shell-liner interface, the femoral head-trunion interface, and one must have a clean assembly. It can also lead to particulate disease. This is very rare, but has been reported.”
“I think we’ve already heard that highly crosslinked polyethylene seems to be doing very well—at least after 10-12 years. Crosslinking decreases the number of free radicals that are available for oxidation and degradation. And at least in one center with 15 years of data the results are spectacular.”
“There are many randomized controlled clinical trials that show a reduction in wear of 40-98% compared to conventional polyethylene. With conventional polyethylene the penetration rate was 0.137; with highly crosslinked polyethylene it was 0.042 mm per year. There are even newer and probably better polyethylenes that are currently not only in clinical trials, but are being used on a daily basis. Please consider the pros and cons of different bearing surfaces.”
Moderator Duncan: “Stuart, do you think that a nickel allergy exists? Are there patients in your practice in whom you must consider a ceramic head?”
Dr. Goodman: “I have never seen a case of nickel allergy. In the general population over 10% has a nickel allergy…and there have been millions of total hip replacements done over about 40 years. If it were as common as one might think, then we should see a lot more allergy. One must keep in mind that the skin macrophages are totally different than the deep macrophages. So whether someone has a cutaneous nickel allergy has very little bearing—that’s why patch testing is almost irrelevant.”
Moderator Duncan: “If the middle aged, anxious, female patient from California tells you she has a reaction to metal jewelry, will you convince her to have a metal on polyethylene or would you consider using a ceramic head against poly?”
Dr. Goodman: “I sit down with the patient and have a discussion, and I’ve not yet put in a ceramic-poly head for someone with a nickel allergy cutaneously. If they insist on it I would do it. As I tell my residents, I practice psycho-orthopedics.”
Moderator Duncan: “Aldo, this is a message to your colleagues in the audience who inherit a fractured ceramic-ceramic. Bring them through the surgical steps that are important in the analysis of that pre-op and intra-op, what they should do and what bearing surfaces they must consider.”
Dr. Toni: “They must take into consideration making a wide synovectomy because debris is going to be all over when they do the revision of the fractured ceramic case. Also, I strongly support the idea that they should not use metal-poly afterward because we’ve seen bad cases where the ceramic debris are entrapped in the new poly and it is grinding the new head. So if you have to do a revision of a ceramic fracture always use ceramic-ceramic or ceramic-poly…never metal-poly.”
Moderator Duncan: “If the cup is malaligned you would advocate that they change the cup in every case?”
Dr. Toni: “The CTs already show you if there is an anteversion, and during surgery you can check for any possible contact/impingement. Now we have an instrument that can give you the chance to take the cup out without doing any major damage to the bone.”
Moderator Duncan: “How about the trunion? What information do they need pre-op and how do they examine that and decide whether or not to remove a well-fixed stem?”
Dr. Toni: “If the trunion is severely damaged then you should not use any solution involving ceramic. The recent option—the titanium sleeve—should only be used only if the trunion is not severely damaged. Otherwise you only have the choice of metal-metal.”
Moderator Duncan: “Thank you both.”
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