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Old 02-02-2005, 02:35 PM
Alastair Alastair is offline
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regarding Charite vs. ProDisc and facet loads. Someone quoted a paper....

"Is this what we are hearing in some papers?"

Yes it is. There was a paper about facet loading on unconstrained vs. semi-constrainied devices that got a lot of attention that was presented at SAS-4. (Read this as Charite' vs. ProDisc)

Dr. Moumene made a very detailed presentation about the testing that he did. 2 cadaver spines, one with ProDisc, one with Charite. There was a very intricate sensor system designed to measure loads on facets as the test configurations were moved through range of motion testing. He went into great detail about sensor design... all very scientific stuff and his testing did show higher facet loads in certain ranges of motion for Charite, but higher facet loads for other ranges of motion with ProDisc. However, it was not equal... the testing was clearly showing higher facet loads for Charite'. During the panel discussion, the first and last question were the same. I don't know if the last questioner didn't hear the first one, or if he just wanted to rub it in. In any case, it seem that every Charite' surgeon in the audience noted something interesting when the pictures were shown. Both of the surgeons I was sitting with mentioned it as soon as the pictures were up. Here is the question:


quote:
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Dr. Moumene, do you think it had any impact on data generated by your testing, the fact that the Charite' was implanted, not only upside-down, but backwards?
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He was obviously very embarassed. Even if the Charite was not bass-ackwards, how reliable is testing done on one spine each with these custom sensors? If there were 15 spines each, maybe I'd listen more. What if the rumors are true that the Charite was implanted by a ProDisc surgeon? It certainly wasn't implanted by a Charite' surgeon. What does this tell you about the test set-up? What was it designed to show?

Many Charite patients I know are getting way anterior placements. Many ProDisc patients I know are also getting inappropriate placements that are equally problematic. Some of the patients are assuming facet problems because they've been lead into that line of thinking by the hype that's been generated... they really don't know what their pain generators are.

Surgeons are now pushing the envelope on how much facet degeneration is allowed with ADR. Neither disc is magic and many patients with either disc will continue to have facet problems. There are also reasons for the facets to degenerate in spite of the other spine elements being perfect... ADR is not magic.

The big difference related to facet loading between Charite and ProDisc is the fact that with Charite' the center of rotation of the joint changes in a manner similar to a normal disc. The ProDisc does not allow the center of rotation to change. In some cases the more natural movement of the Charite' will be an advantage. In some cases, the constant center of rotation of the ProDisc will be an advantage. I doubt it will be possible to predict which device may have an advantage for any given patient.

Fortunately, the bottom line is that both devices are excellent. Proper implantation and proper patient selection will be huge factors in success, whereas ProDisc vs Charite will matter very little. If you've got contra-indications going in, your odds of success are substantially reduced... even more so if your surgeon doesn't have much experience dealing with your type of special case. If the other elements of your spine are in trouble, you've got problems no matter which prosthesis you got.

PS... we won't know for years if there is a huge difference. There are some modes in which ProDisc is worse than Charite. We should not be talking about which device is harder on the facets... They will both relieve facet loads in an unhealthy system.
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