Hope this doesn't sound a daft question??

[dalhousie]

As I'm having a long recovery 7 months post ADR I've got plenty of time to mull things over & read posts on different forums . I was wondering as ADR's can put significant strain on facet joints leading to facet joint disease why do surgeons go ahead with ADR (as opposed to fusion) on patients who are known to have significant problems with their facets pre op.

I have activ L @ L4/5 & if you read the glossy brochure it advertises that it's kinder to the facet joints - how true that is in practice I don't know??

Can anybody enlighten me ?

[sportsnut3007]

Sorry Ruth, I do not have an answer. I do have a question for you though and other members on this board. Why do the ADR's put more stress on the facets? Is it bc of the lack of shock absorbing? Do they think the new ones such as the Freedom Lumbar and the M6 will put less stress on the facets?

[Justin]

As I'm having a long recovery 7 months post ADR I've got plenty of time to mull things over & read posts on different forums . I was wondering as ADR's can put significant strain on facet joints leading to facet joint disease why do surgeons go ahead with ADR (as opposed to fusion) on patients who are known to have significant problems with their facets pre op.

I have activ L @ L4/5 & if you read the glossy brochure it advertises that it's kinder to the facet joints - how true that is in practice I don't know??

Can anybody enlighten me ?

Hi Ruth. In regard to your comments above, I believe that inclusion / exclusion criteria for artificial disc replacement surgery is continually being refined. While it is contraindicated to place an artificial disc replacement device at a level(s) demonstrating advanced degeneration of the facet joints, grading facets is still somewhat an imperfect science (remember this is just my opinion here) that is based not only on diagnostics but also the "subjective" opinion of the operating surgeon. However, I think you would be hard pressed to find a surgeon place an artificial disc replacement device at a level with "significant facet problems." This is not to say that it doesn't happen.

The Activ-L artificial disc replacement device is a unique device. Essentially, it is a mix between the Charite, an "unconstrained" device, and the ProDisc, a "constrained" device. There was a recent publication on constraint and the increased "loading" on surrounding bones and ligaments: Biomechanical Effect of Constraint in Lumbar Total Disc Replacement.

Here's an excerpt from the publication:

Below, UAD = unconstrained device (Charite) and CAD = constrained device (ProDisc)

By the result of this study it is obvious that implanted segment with AD (artificial disc) has large range of motion and suffers from increased loading to surrounding bone and ligaments. The UAD, Charite, has larger range of motion but exert less loading to the implanted segment than the CAD, ProDisc. It seems that the mobile center of rotation of the UAD, Charite, has the ability to lessen the facet contact force and stress on the vertebral body.

Here's a couple interesting threads here at the Spine Patient Society on this:

• Different design concepts in lumbar total disc arthroplasty on ROM, facet joint forces & center of rotation L4-L5.
  
• Comparison of Biomechanical Function: Mobile-Core Versus Fixed-Core ADR

I hope this helps.

[KBear]

Ruth,
Both my surgeon and the surgeon who is seeing me post op told me that they think the Active L is the best disc on the market currently. They said it was easier on the facets and since it is somewhat a hybrid (between totally unconstrained and constrained), that it is better. I'm sure that is just their opinion and not sure if that is based on any scientific data whatsoever.

I was very concerned with ADR as my MRI report said moderate facet degeneration. All 3 surgeons I saw though, said that it was mild and that I was a perfect ADR canidate. My post-op surgeon, who I did not see pre-op, also said my facets were fine for surgery.

[dalhousie]

Both my surgeon and the surgeon who is seeing me post op told me that they think the Active L is the best disc on the market currently. They said it was easier on the facets and since it is somewhat a hybrid (between totally unconstrained and constrained), that it is better. I'm sure that is just their opinion and not sure if that is based on any scientific data whatsoever.

Kathy - I remember you saying that before but as they were involved in its design I thought they maybe a little bit biased. My surgeon also says the same about the activ though - he used to use Prodisc before that. BTW have you got the spike or keel activ? I've got the spiked one. I don't have facet problems at my ADR level but I don't want to develop them either.

Generally speaking I've heard of people who didn't have facet probs pre op go on to develop them post ADR. I think possibly they may be more in relation to the Charite - I can't quite recall. I need to look up some research stuff I have somewhere but I can't remember why the charite has started to fail. The Charite is unconstrained. In UHMWPE (page 179) the activ is classed as an unconstrained device but in some research articles it's classed as a semi-constrained one. Does anybody know which it actually is? I think having an engineer's brain would be very useful in getting your head around it all.

UHMWPE site:

UHMWPE Biomaterials Handbook: Ultra ... - Google Books

Activ research article:

Biomechanical Study of Lumbar Spinal Arthroplasty with a Semi-Constrained Artificial Disc (Activ L) in the Human Cadaveric Spine

On another tack the M6 lumbar ADR seems to look promising but it's early days for that. Watch this space I guess.

When I've got my fitness back to a greater degree I probably won't give this a 2nd thought but as I read posts during my resting time it does make you think.

[KBear]

The surgeon who did my surgery was co-inventor of the Activ L, so he is obviously probably biased. However, The surgeon who sees me now (I had surgery in Miami, FL and do my follow up in Dallas, TX), post-op, was not involved in the making of it, so I think he would be more un-biased.

As far as the design, I was told that the totally unconstrained, the core is not connected to either endplate and it is 3 loose pieces. The constrained is one piece, where the endplates and core are all connected. The Activ L, is in between, where the core is conneced to one endpiece; but not the other. So instead of 1 piece or 3 pieces, it is 2 pieces. I think they call it semi-constrained (I could be totally wrong on this.)

I have the spikes too, not the keel.