Shorter ADRs Less Facet Joint Stress????

[KenG]

Hi Michelle,

I feel it makes sense to regain the disc height by surgery rather than leaving the
reduced disc height with DDD as it is. of course if you don't have symptom or pain with it, surgery is not needed, I think. I haven't had ADR yet, but I just got
reply from doctor telling me that by regaining the disc height, it helps realign the spine and get less load to the facets and also good effect to the ligament laxity.
that is what I heard.

the thing is (sorry for my english), the present artificial disc is a little bit higher than the normal human disc, so it gets a little bit more of the height with artificial disc, but I personally feel a little higher is better than shortage of the natural height I guess. I think the minimum height of the discs now are 8.5mm
to something like 10 mm as I read somewhere.

[Michelle Maree]

I do not want to FUSE!!..........I may need Marks advice on this one, but does anyone know much about facet replacement? Is it now a viable option if you have facet problems after ADR surgery? Does it seem to work successfully together? And is it an option now instead of revision surgery.
I saw on Dr.B's website that there is now Total Motion System or TMS but it is very early days yet and is not available for L5/S1.

There is just such an acceleration in motion preserving technology at the moment that it would be a shame to fuse just yet. I will leave no stone unturned before I do!

[mmglobal]

Over the years, there has been a lot of focus on the height of the prosthesis and amount of disc height restored. Some discs are shorter than others. Some discs requre less 'over disctraction' to install.

As I began to focus on this more and more, I noticed something very significant. While we were all talking about the need for shorter prostheses, I kept watching surgery after surgery, in which the shortest height cores were not selected. The size and location of the prosthesis should match the best fit achieved with the most appropriated sized trial implant and very careful attention paid to getting it right. For devices with selectable core heights, like Charite', Activ-L, ProDisc... the height of the core selected will be determined by the tension on the system. The doctor will apply the appropriate amount of force to the distraction too and the disc space will be distracted to a distance that will be determined by the patients' anatomy.

If the surgeon would be focused on selecting the shortest core possible instead of selecting the most appropriate sized core for your anatomy, the result would be decreased stability and increased risk of migration, increased risk of facet degeneration and probably other complications as well. (I'd like to research and write more... but can't now.)

I've seen the TSMS surgery a few times... very interesting. This is not to be thought of as an opportunity to do a posterior implantation of an ADR. This is for people who's posterior elements are too far gone to be a candidate for ADR. (Maybe future systems will provide posterior ADR implantation as a first choice... but I don't think this is it.) From what I've heard, the facet replacements are going well because facet pain can be so pronounced and straightforward to confirm. Longevity of the implants and the entire system is something I look forward to seeing good results for, but remains to be seen. (Unfortunately, we are not typically in a position to wait a decade or two before we choose our poison.)

All the best,

Mark

[Michelle Maree]

Hi Mark nice to hear from you,
What is a trial implant? Is it something the surgeon fits into the space before the real one to test the size?
How much distraction can you get away with without damage to nerves, ligaments facet joints etc? I know this is probably individual, but at what point does the surgeon go, "o.k, well, this is looking a bit riskier than I thought. I might have to fuse? "
How often does this actually happen? Is it more a wait untill after and see?
How long IYHO before facet replacement is routinely used in the case of facet related problems after ADR instead of revision surgery?
Thanks,
Michelle.

[mmglobal]

How much distraction is too much? Please remember all the 'I'm not a doctor" qualifiers here... I'm just sharing my layperson's experience... I can be completely wrong.

I don't think they know during the surgery. They can't ainticipate how much damage is being caused in the posterior elements. When will they abort ADR and convert to fusion. There will be a different answer depending on the doc. I've seen completely collapsed disc spaces that most surgeons would say is too severely collapsed for ADR, still be completely mobile and have a VERY easy implantation. I've also seen much less severely collapsed segments that are VERY immobile and are VERY difficult to remobilize and might have had ADR procedure aborted by less experienced surgeons.

I think we might wish for more "OK this is too tough" kind of assessment. More accurately would be wishing for surgeons to know BEFORE scheduling the surgery when they would be getting in over their heads. Much of the trouble I see comes from surgeons without a great deal of experience getting involved in very difficult cases.

I already see facet replacements or other posterior stabilization technologies being applied behind ADR. It's still very new. Even when common place, each case will still be completely unique. IMHO, it will be many years before this can be done in the US because the new technologies will not be applied to these types of cases until long after approval.

Mark