SAS6 and Prodisc Device Wear Analysis

[WayDownInCoCrMo]

Dear Friends,

My wife will undergo a Prodisc ADR in 2 weeks (Oct 9, 2006) ... but we still havent answered the basic questions of risk vs. reward. In particular, we dont know how long it will likely survive for a 50kg, 32yo woman. Some say 10 years. Others say 30. Evidence points towards 40. My guess is that it will not wear out for her ... unless it self-destructs.

If you have knowledge regarding the longevity of the Prodisc, please post it here. In particular, we are interested in the papers from SAS6 Montreal.

Kinematic results after ProDisc-C total disc replacement
Retrieval and wear analyses of ProDisc(r) lumbar disc implants
Rim fracture risk of highly crosslinked polyethylene total disc replacements

Some stuff I've found or heard:

http://www.worldspine.org/wsIII/ws3_193.pdf loss: 1.4mg/10M cycles. "linear
wear rate of 0.10-0.12 mm/million cycles"

Also, I have heard from Prospine: I talked with Dr. Bertagnoli about it yesterday and he told me that the expected life-time of a ProDisc implant is thirty years.

My Prodisc collection:
http://www.geocities.com/javanoginn/Prodisc/Prodisc.htm

Other Spine Conferences:
http://www.spine.org/calendar/nass_future_events.cfm

Thanks,
Matt

[mmglobal]

Matt,

I'll forward a copy of the proceedings of SAS6 to you as soon as I get your address. That contains copies of all of the abstracts for all of the presentations (if the abstract was submitted by the deadline.)

I have an additional copy for the iSpine lending library (that will be online soon.) Anyone who wants it can send an email to the info address on the contact page.

I'm going to post something that I'd already written.. it's going to answer some different questions than the ones you asked, but it will get me started answering some of your new and past questions.

The general session of SAS6 opened with "Total Lumbar Disc Replacement - Basic Science". I was surprised to see that four of the first six papers, plus another later in the day, were presentations by the same research group. Like many of the presenters, this group presents regularly at all the congresses I attend related to spine arthroplasty. Sadly, most of what they present seems to me, to be research intended to further marketing goals. this research is intended to create the impression of a technical advantage of one style of prostheses over the others.

1 Correlation of in vivo wear patterns and fracture patterns with in vitro TDR motion response

2 Rim fracture risk of highly crosslinked polyethylene total disc replacements

3 Analysis of textured endplates and bone on growth in retrieved Charite' total disc replacements

4 Characterization of the first explanted Maverick and comparison with implants tested using a spine wear simulator.

5 Impact of polyethylene oxidation on the long-term clinical performance of total disc replacements

I'll start with # 4 above, since that was interesting and informative. This is an example of how research will advance the science that future devices will be built upon. An explanted Maverick was analyzed for wear. This was compared to the wear that was observed in the testing environment. This is an effort to prove the validity of their testing. This was very interesting and informative about testing techniques.

#3 above is an example of the worst of the worst. All of the current crop of total disc include textured metal endplates. From what I can tell and I may be wrong, this research group is funded by Medtronic and just about everything they present has the same slant. Medtronic devices good.... other devices bad. They have hung their hat on metal on metal prostheses for the spine with the Maverick and Prestige lines. The sad thing is that they not trying to highlight the advantages of the devices they offer, they are trying to stifle advancement in the industry because they are several years behind. Sadly, the dishonest research that they fund provides political cover for insurance companies that are emboldened to deny lifesaving treatments that are FDA approved; saying that it's still experimental. So why am I discussing this along with the discussion of #3 above? Unfortunately for them, the Charite' with the textured endplates was FDA approved about a week before SAS. There were presenting a paper about demonstrating the inferiority of a device that was already obsolete. However, even if the textured coating wasn't FDA approved... this is still sham research. Everyone in the industry knows that the coated endplates are superior. It is sad that it took 17 months from approval of the Charite' to approval of the textured endplates. The 2-level Charite' that I had done in Munich 4 years ago (TODAY!) is with textured endplates.

So, if everyone in the industry knows this... what are they studying it for? It's another "Charite' bad" paper funded by competitors. This research is about markets and money, not about medicine and science. If insurance companies won't pay for ADR, more people will get fusions. Guess who is a major player in the fusion hardware ballpark?

The other papers are largely analyzing analyzing old devices with known problems. It's just rehashing the same old cases that have been presented over and over. It makes for sensational press. It makes for more fusions. It makes for more denial of payment for current ADR technology.

Let me tell you... I could not find a single surgeon who thought that this group was credible. Some argued that the research is useful and we will learn from it and I agree 100%. They are developing techniques for testing, analyzing, modeling, etc.... that will be very useful and they are advancing science. That is a byproduct of what they are doing. But, their research is not research to further technology.... it's a conclusion looking for a way to prove it. Sadly what they are doing is hurting countless spine patients who are being denied access to treatment options because of this sham research.

Sorry to stop here... I'm beat... gotta go.

More later,

Mark