Initial total knee prosthesis had an all polyethylene tibial component. They went out of favour because of fears of subsidence and early failure. Metal backed components were introduced with claims of better load distribution to the proximal tibia and consequently less subsidence and loosening.
However advantages of the all polyethylene tibia cannot be ignored. The component is monoblock thereby completely eliminating backside wear. Moreover it is cheaper making the surgery more cost effective.
So what is the current status of the all polyethylene tibial component?
A ten year randomized controlled trial comparing all poly with metal backed components found no difference in the two components. They studied 566 knees.
Blumenfeld et al in a literature review recommended all poly components in older patients and less active younger patients. The only disadvantages they mentioned were an inability to change liner thickness after final component cementing and inability to use constrained inserts. Also poly exchange is not possible.
Another study in JBJS Am published in 2010 also supports the use of all poly tibial components.
As always there is another side of the coin. So check for yourself and decide. Happy replacing!!
yes this is a good option. One has to be careful if you are using bone grafting in medial defects in which case i would prefer metal tray so that i could use an extension rod for the added protection of the graft in the initial period.
ReplyDeleteif both give equal results then , the advantage of using all poly is the cost whereas there are several other advantages as mentioned for metal back.
ReplyDeleteMetal backed components do not offer any significant advantage except if you need a stemmed implant like Dr Joshi mentioned. Theoretical advantages of better longevity have not been proven conclusively. Whereas the All-Polyethylene tibia is not only cheap but also monoblock. I feel that is a huge advantage as it eliminates the problem of backside wear.
ReplyDeleteAll poly is really cost effective and durability is also proved in western papers, in India i think we have to wait and see for long tern results with large number volumes. Some cases who is having osteoporotic bone i think ll polly tibial tray is not a good choice.
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