Effect of Center Keel Design ADRs on Vertebral Structural Integrity

[runagain]

Wait,

Bob,
You have bigger keels than me??
I thought I had big keels?
I do know I think it hurts after surgery with insertion of those big keels.
Oh my.


R (Always willing to inject a little humor into the situation).

[Carson]

Early version of the Maverick keel was ridiculously tall to the point I was surprised it was allowed on market. After cases of cracked vertebra the keel was revised. Can tell the difference in early version and later version easily by space between holes.



early version Mav



later version Mav (a-mav)

[trkdoc714]

I think the biggest factor of fractures is the method the surgeon uses to prepare the vertabrae for the disc. From my research before surgery, either a chisel or drill is used to create the pathway for the disc. In my opinion, the chisel would be more likely to be a cause of fractures.

I have the A Mav with the smaller keels (but they're still bigger than Runagain's ).

[Metalneck07]

WOW those are mighty big keels !!! I would think despite the potentional to fracture once they were in you wouldn't have to worry as much about the keel shifting since it looks like they are very well into the Vertebrae.
Run - Humor helps !! I like your humor.
Caitlin aka Metalneck07

[KanRunMo]

Whoa! This info is scary. I am petite and if I have an ADR I would have to be worried about the size of it. Somewhere I think I have read that they have different sizes. I might even need a "youth" size. My sister who is also petite, had a hip replaced when she was fairly young. The replacement was too big and she has had lots of trouble with it. They will not remove it for fear it would tear up her bone completely.

[Researcher]

Great feedback from everyone! Thanks. This appears to be a genuine issue of concern. I do not have a background in physiology or orthopedics, but have worked in engineering/manufacturing roles for a long time. The design challenge here is no different than for any application where two parts of differing composition are being joined together. I don't know enough about the strength of bone adhesion to non biological surfaces to know how much shear force and vertical tension that interface has to support and what can be expected with the materials being selected by ADR designers. If you have a large keel, then you don't have to rely as much on the bone to device main plate interface bonding. If you have a small keel or no keel, then the bone to device main plate interface bonding is more critical. If the keel is narrow, like the M6, then the device material needs to be tough enough to prevent cracks in the device itself where the keel joins the main plate. At least the differences in the CTE (coefficient of thermal expansion) of the vertebrae and artificial disc plate don't play a major role since the internal body temperate does not vary much. I still like the M6 best of all ADR designs. I think their engineers did their homework.

Phil