Tuesday, April 5, 2011

Now What? If you remove the Depuy implant and replace it, what goes in its place? What are the alternatives and risks associated with them? (1 of 4)

Hip Replacement Implants
Your surgeon will select the design of the hip replacement and size of femoral ball to give you the range of motion and stability that you need to function. There are several different choices of hip implants to consider, each using varying materials and having different pros and cons:
  • Metal Ball and Polyethylene Liners
  • Ceramic Ball and Polyethylene Liner
  • Metal Ball and Metal Liner
  • Ceramic Ball and Ceramic Liner
Nice videos of each type can be found on this site:  http://bonesmart.org/hip/total-hip-replacement-implants/  summaries below taken fromt he same site.
Metal Ball and Poly Liner

The standard metal ball and polyethylene cup have been in use since the early 1960s. Scientific studies indicate the use of improved polyethylene liners, called ‘highly crosslinked’ bearings, result in overall decreased wear of the implant.

Because of its durability and performance, Metal-on-Polyethylene has been the leading artificial hip component material chosen by surgeons since hip replacement surgeries have first been performed. The metal ball is cobalt chrome alloy and the liner is polyethylene. Polyethylene is the most understood and used of all the liner materials, offering the surgeon a range of options to obtain stability in the body while the operation is underway.

This ability to adapt and customize during the surgical procedure is an important attribute of polyethylene. It is also the least expensive bearing.

All implants shed wear debris. Your body has to cope with any wear debris that is released when you use your hip implant, unlike your car engine that has special filters to remove the wear products. Currently, wear resistant polyethylene liners, called “highly crosslinked polyethylene” are in use which, during the manufacturing process, have been treated with a short burst of radiation to help the cup resist wear.

Over time, the body may see polyethylene wear particles as invaders or a source of infection. As the body starts to attack them, this leads to osteolysis, a “dissolving of the bone”, which may result in having to replace the implant (known as revision).

Metal-on-Polyethylene implants wear at a rate of about 0.1 millimeters each year.

In the next three days, I will post the other options and then will look at the studies surrounding the wear debris associated with the metal on poly since is seems to be the option of choice  over the others.

4 comments:

  1. Dear Connie-great information from your site.

    My wife had a DePuy Pinnacle Implant. Used a metal head and poly(Altrx) liner within the acetabular cup-held in with one screw. Everything fine for six months, then terrible pain inside thigh and hip. Trouble walking. The crosslinked poly with the porocoat Pinnacle Summit stem is supposed to be the ultimate solution. The surgeon went from a #4 to a #3 to a #2 femoral head (metal ball) and impacted the ball into the poly liner. Pain is requiring many tests. Waiting on metal blood test and bone scan. It appears that there is a gap at the top of the cup and this is causing some of the problem. Final answers not in yet. BUT, wanted your readers to know that it is possible for the metal on poly to fail. The poly liner even utilized a lip and the cup was screwed to the bone. The surgeon told me that Zimmer also was a big problem for him as the cups were not marked correctly as to their size. This could be a possible DePuy problem also. It irritates me that no lawyer will speak to me as the DePuy unit has a poly liner and not subject to any of the MoM recalls. Remember, there are reasons such as cup shifting, loosening, poly particles shedding if cup is not aligned properly. I insisted the surgeon NOT use a DePuy of any sort-surgery done May 3, 2010. He did anyway. His "excuse" was he used a non-recalled DePuy unit. I have talked to surgeons that feel DePuy's big problem(other than metal on metal) is the acetabular cup is not engineered properly. It is not deep enough. You already know this anyway-just throwing my two-cents into the ring.

    Thanks for your time,

    Jim S.

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  2. Hi Jim,

    Yes, I had similar concerns. My surgeon told me that he "had personally placed over 1000 Pinnacle cups and have revised a very small number due to infection, but none due to loosening, excessive wear, liner issues, metal debris etc. I am comfortable using that implant, although I do not use the MoM version."

    I really think many of these issues are a result of varing lev els of surgical skills.

    I can't beleive if you had directed that the surgeon not use Depuy, he disregarded your directive.

    I stronly suggest that you contact one of the lawyers on the MDL committee which I published earlier this year. They will talk to you. These Attornies are quite versed on this litigation. You can find that list here on my blog.:
    http://www.mydepuyhiprecall.com/2011/04/list-of-14-lawyers-appointed-to-serve.html

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  3. I am allergic to the metal on metal as they had to remove my first hip and replace it ....i now need another hip onthe other side and they are putting in duprey poly on ceramic....is there any problems with this?

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  4. HI,

    I hate to tell you there are no problems when combining metal with poly. What I can say is that there are a lot less problems when combining metal with poly. I have a metal with poly revision. there are problems with all of these implants. There are just different problems with different materials.

    Most of the recalls are associated with metal on metal. If your question is has this particular one been recalled, the answer is no. From a sloughing perspective. The least problems will occur from Ceramic on Ceramic, then Poly then anything involving metals then metal on metal will have the highest problems. All hips shed something as is noted above in the article. That article above has 3 other parts to it. might want to read those as well.

    LMK if you need anything else.

    Regards,

    Connie

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