B13... sorry I just noticed that this post fell through the cracks.
The M6 has an interesting design and is so far from being just another knock-off of existing designs like we've seen over and over. (and over.)
The pseudo-annulus looks interesting... it provides some properties similar to the elastomer designs without the problems associated with the longevity of the elastomer and the elastomer/metal interface. (however, as you've mentioned, there are questions about the longevity of the fibers. If I remeber correctly (and I could remember wrong!), it was one single thread, so any compromise of the thread compromises the entire barrier. The M6 provides a compressable core, so there is some shock absorption capability. This is generating some hype because intuitively that seems like a good idea. However, I wonder if that feature is an example of fixing a problem that doesn't exist as your spine is an entire system of shock absorbers... missing one or two out of 23 is probably not an issue.
Unfortunately, with what I do for a living, I see the complications. I already have 3 clients with M6 problems... two have had revision surgeries already. Like many other mobile core device, there is the potential for the core to get pushed in one direction and stay there, generating undesirable loads on the system. I've seen subsidence and migration. All the problems with other devices accrue in poor configurations. To be fair, these issues are generally the result of poor implantation and not device related.
As I said, it's an interesting design and I look forward to see how it fares. As with all other devices, I believe that if you are a good candidate and you get a proper implantation, it's likely to be a success. If you are not a good candidate or your get improper implantation, you are in trouble. If you are considering an M6 implantation, please go to a surgeon who does excellent carpentry, every time. Whatever device you get... you do not want to face revision surgery.
All the best,
Mark
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