[mmglobal]

Wow Sharman... nice post. It's tough to find the time to respond to so much at once. Sorry for the delay.

But a disc, of course, is a unique ligament, in that it has at its core the jelly-like nucleus. I envision the nucleus as a swollen water balloon, its turgidity giving support and cushion to the adjoining vertebrae.

The analogy works, but think of the nucleus as more like crab meat instead of jelly. The last surgery I observed included putting an ADR in where there was a relatively tall and well hydrated disc. (There were structural issues and pathology at this level, but the nuclueus was nearly normal.... very unusual.) When the surgeon removed this big 'puck' of nuclues examined it very closely. I'm used to seeing nucleus tissue as crab meat, but this was so moist and the structure of the tissue seemed so much better. More degenerated discs are very tough and stringy. Discs that have been IDET'ed may have been turned brown by the barbeque that's been done on it. The worse the degeneration, the tougher and stringier the meat. The healthier the tissue, the whiter, moister, more tender, etc.... I swear you could put it in a crab salad and nobody would know the difference, although I don't know what it tastes like.

The discussion about the sources of discogenic pain needs some comment. I honestly don't believe that the pain mechanism is fully understood. All of the items mentioned are completely asymptomatic in some people, while highly symptomatic in others. Left out is the discussion of granulation tissue. With the annular tears, acidic toxins secreted by the disc, etc... an inflammatory response is generated. This may cause inflammatory tissue, normally on the dorsal disc wall that can be highly innervated. This is why careful discectomy is required for ADR. Lack of complete discectomy for ADR or fusion may result in ongoing pain.

ADCT

the recruited cells are (I believe should be) harvested from healthy discs

I'd have a very tough time allowing any procedure that would potentially damage a healthy disc. I've not heard this, but that doesn't mean it's not done. The only presentations I've seen regarding ADCT involve harvesting cells from the disc that requires the discectomy, not from a healthy disc. Again... the scope of my experience is limited... just because I haven't seen it, doesn't mean it's not true.

Injectable nucleus replacements

only inject enough to replace the material removed for the herniation, they don't replace the entire nucleus.

I've seen several presentations about many of the injectables. As I understand it, the slug of polymer that will become the nucleus replacement must be large enough and well shaped to have structural integrity. While it's true that they are not striving to do a complete discectomy, a large amount of nucleus is removed from the disc to provide a decent cavity for the injectant.

ADRs, there is no friction or hard surface that could result in particulate wear over time.

This is an interesting statement. I'm curious how the polymer will hold together over time... what will slough off? will there be wear? I'm reminded of other famous quotes:

• "It worked in the lab!"
  
• In theory, there is not difference between theory and practice. In practice, there is!

I don't buy the assumption that the current crop of nucleus replacements, whether injectible, endoscopically implanted, or more traditional implants like PDN will be easily revisable. What will the state of the endplate be after the failed device is explanted? Will it accomodate and ADR?

There are still a ton of questions and much of this technology is very new. However, this is what people warned me against when I went to Germany for my ADR 4.5 years ago. If I was early enough in the degenerative cascade to consider such treatments, I'd be taking a very good look at them. But, with what I've seen about new technologies, surgeons experience, failed deployments of what seemed to be the best thing since sliced bread (IDET, original PDN and many others), my look will be very skeptical. That doesn't mean don't do it.... it just means don't buy the markenting spin... do more homework... maybe wait for the exprience with the new technology develops.

Just my layperson... I'm not a doctor, yada, yada, yada, opinions based on my limited view of the spine world...

Mark