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Ask the Experts: All-polyethylene or metal-backed tibia?

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KOLOA, Hawaii — During a panel discussion at Orthopedics Today Hawaii 2011, Douglas A. Dennis, MD, asked a panel of knee arthroplasty experts whether they would choose a metal-backed tibial implant or an all-polyethylene tibial component for a 72-year-old woman who exercises moderately.

Starting off the discussion, Dennis said that the reported advantages of the modular metal-backed tibial component are surgical flexibility, great survivorship, the need for less inventory and the opportunity to later perform a liner exchange.

Douglas A. Dennis

“If we look at an all-polyethylene tibia: It is cheaper, there is excellent survivorship in the literature, there is no backside wear so osteolysis is rare, it gives you increased polyethylene thickness and is easy to revise,” Dennis said.

“The downside for the metal-backed modular is there is more cost, there is backside wear and the possibility of osteolysis, and it has a decreased polyethylene thickness.

“The downside for the all-poly is there are fewer intraoperative options, you can’t do a liner exchange, it requires more inventory and it does not lend itself well to bone defects which may require shims or augments,” he said.

“The modular-backed component will cost about $600 to $700 more than an all-polyethylene tibia. What would you do?” he asked.

Wayne Paprosky

The following are the panel’s responses:

Wayne Paprosky, MD: Certainly, from the economic standpoint, there is a cost factor. The problem is, what is everybody used to? And how many times would a community orthopedist decide he wants to change the polyethylene after he puts a knee in? From that point of view, I think you are giving that up. From my point of view, I prefer to use a modular tibial base plate and, until I am shown that there is a definite advantage other than cost to it, I am not going to change.

Thomas P. Schmalzried

Thomas P. Schmalzried, MD: I just want to emphasize that you don’t have constraints with the mono-block poly. Recognizing that there is a learning curve, it doesn’t take many bad outcomes due to laxity to offset the economic advantages. In our training program right now, the modular tibial component is one of the most commonly used. So, there will be economic conditions that will drive the shift [to all-polyethylene], but there will be issues related to the all-poly components because of the lack of training. – by Lee Beadling

Reference:

• Dennis DA et al. Panel discussion: What technology merits additional costs of knee replacement? Presented at Orthopedics Today Hawaii 2011. Jan. 16-19. Koloa, Hawaii.

Disclosures: Dennis is a consultant for and receives research grants and royalties from DePuy. Paprosky is a consultant for and receives royalties from Zimmer. Schmalzried is a consultant for Stryker and receives research grants from DePuy and Stryker

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