Spondy increase chances of ProDisc keel breaking?

ans · #1 (**permalink**) 12-17-2006, 07:09 AM

I wonder about this as I have spondy-whatever (actually retrosthilesis about 3-4 mm. lateral displacement). Two ADR docs who recommend fusion and ADR at L4-L5 say this shouldn't be a serious concern. But I wonder how strong the keel really is. I haven't researched this enough, admittedly.

http://www.spineuniverse.com/display...rticle114.html

Any input would be greatly appreciated.

Allan

chasswen · #2 (**permalink**) 12-17-2006, 11:07 AM

it would take a very great force to break the keel lenght wise.
and ans did you view the keel post from a few months ago?
chuck

mmglobal · #3 (**permalink**) 12-17-2006, 05:18 PM

ProDisc is cobalt chrome (with titanium spray coating). I've never heard of it breaking. The instability you describe would be in a plane that would not be adding stress to the keel. I can put you in touch with patients who have ProDisc done in spite of substantial instability.

Mark

ans · #4 (**permalink**) 12-17-2006, 09:20 PM

Thanks for your help.

Also Mark, I'd like to be in touch with spondy pts. who've had ProDisc. I do not know the cut-off margin e.g. 4mm displacement and Regan and Lauryssen seem unconcerned about it. Yet, the literature shows some concern re: fusion.

Hmm, so if the keel is nicely attached to the bone, I wonder to what degree instability/torsion can break it from the bone. This sounds like a question worth pursuing - maybe Drs. Delamarter, Dr. B., etc.

Best ~ Allan

Jim M2 · #5 (**permalink**) 12-18-2006, 12:32 AM

Allan,

Mark's stress analysis is right on. The stresses aren't in the direction to be of concern to the keel. Beyond that the strength of this type of alloy known as a "super alloy" in the world of jet and rocket engines is so strong your bones will give way long before the prodisc.

Here's some dicey info on retro vs spondo (I'll let Mark comment or delete if it's too off the mark). I always thought a mild spondo condition could often be associated with par defect. A more severe spondolis... could be associated with fractures as seen in the figures and x-rays in the spineuniverse article. Slight retro is good in that (i would think) it means you don't have notable bone defects. As a disc collapses the facets will guide a healthy upper vertebral body slightly backward relative to the lower body. I've tried to explain this observation to a few people but Laura (annapurna) is the only person who ever understood immediately what I was talking about.

changing the subject now, We're in our 4th night with no electricity and 20 deg temps here in the northwest. I'm at work just to stay warm and have internet. It's mostly dark if you drive at night. Gas stations with power to pump are out of gas. It's turning into a mad max movie.

see ya,
Jim

ans · #6 (**permalink**) 12-18-2006, 01:56 AM

Hi Jim,

Sorry you're freezing in WA (couldn't find this on Google's News). I know what that's like and brrr...

Not all spondy is associated with a pars defect and this I lack. With 3-4 mm. retro I wonder how strong my bone will be to absorb the torsion stresses.

One way to find out.

Be well ~ ans