Constrained vs unconstrained, lumbar vs. cervical

[Fortitudine]

Is there any difference in wear issues other than debris that arise from cervical discs, constrained or unconstrained, compared to lumbar ADR?

[tmont]

Fortitudine,

I'm not an expert by any means, but I can tell you what I've been told in my travels. It's a place to start.

The biomechanics of the lumbar and the cervical spine are completely different :different loads to assume, different types of movement, different frequencies of movement,to simplify.

I have met people here--I THINK one might be Kanutta but not sure??--who have said that Norway and Sweden do not do cervical ADR because they don't believe in it, based on this difference in biomechanics.

Other doctors I've spoken to and dealt with personally believe that these differences don't compromise the validity of the technique, and there are those who feel that ADR is even MORE adapted to the cervical spine than the lumbar--for the same reasons! Also, I've been told several times that cervical ADR is far simpler to perform than lumbar, especially if the surgeon has experience in fusion techniques.

On the 'constrained vs unconstrained' (or 'semi-constrained, as in the Mobi-C--by the way, which disc possesses a truly 'unconstrained disc'? Does anyone know, or are the terms 'unconstrained and 'semi-constrained' the same here?):

Opinions differ. I can only talk about the ProDisc vs Mobi-C in this area, as theose are the two options in my case. It's been hard getting info (which you might know is one of my pet peeves--as patients we derserve the info they've got, no matter how little)

First, a little background:

The makers of the Mobi-C worked with Dr Thierry Marnay on the ProDisc, and then branched off to form their own company and their own products. The relationship between the former colleagues is 'tense', from what I was told by LDR Médical.

They created a prothesis with a more mobile core than the ProDisc. I was told that LDR Spine wanted to talk about their product and to reveal clinical data on the Mobi at the SAS6 conference, but that 3 of 4 papers were refused. Dr Marnay is a chief organizer of the conference. LDR Spine will be presenting one paper alone, on device centering (as of my last conversation with them over a month ago).

Now, to the technical aspects: ProDisc looks pretty promising so far, and they've got a jump start in time, and thus on clinical data. What's the difference between the ProDisc and the Mobi-C?

Although the spokesman told me the core of the mobi-C was 'semi-constrained' as well, he did say it moves more than the core of the ProDisc. You can see a video demonstration of this here:

http://www.ldrspine.com/secondgenerationdisc/index.html

I asked why so much mobility had been given to the core of the Mobi-C, and he replied that certain neck segments move more, and differently, than those in the lumbar spine. He used the image of an orange rolling across the floor: moving without constraint, the orange can roll a long time without damage to the skin. Add constraint or friction, and it will wear more quickly.

My next question was: well, on the other hand, can too much mobility be given to the cervical spine? He replied (and this is what caused Rich to pick up on a key point in another thread) that he'd probably opt for a fusion rather than ADR in a segment that was 'unstable', but would go for the ADR otherwise.

The discussion that came from that was interesting; I'll see if I can find it and re-post the link here.

http://adrsupport.org/eve/forums/a/t...1/m/2171068081

(found it-link to '(article (cervical)' started by rob_zzz. You posted there Laura but maybe others haven't seen it yet )

Last thing: an ADR next to a cervical fusion causes the prothesis to work a lot more. Wear has only been speculated and hasn't even been tested in vivo according to my source, and only a few cases exist (he said about 30) to date. However, the core of the Mobi-C supposedly can be replaced if necessary without removing the whole device.

That's all I've got so far--and I'm not intending by any means to be a spokesperson for LDR Spine--it took a lot of banging on doors and pulling of teeth to get even this info and I hate that--but as it is one of my two options I went digging and that's what I came up with.

Typing really fast, hope coherent!

Trace