Does anyone know if the Activ L is designed for two levels or just one level? For instance, does the Activ L trial include two levels or just one level?

Thanks,
Mike

Hi Mike,

I know a member her that needs a 2 level and is considering the activL study.

What I would find out is whether they are using the endplates with the prongs or a keel.

If it was me I would want the keel. This comes from a conversation I had with Dr Delamarter where he observed/moderated for a training of an activL surgery. Dr D said the prong endplate slipped (I will leave it at that). Dr D said it only has prongs in the front.

Something to look into and I hope there is more discussion about the activL here in this in the future.

Paulette - you've worried me. I have an Activ-L with prongs (Zeegers). Any positive info on this anyone? I've heard the keel is not so good as it's virtually impossible to remove if things don't work out.

Vicky

Some patients - and docs - are not proponents of the keel as it requires removal of (comparatively) more bone; which may have other implications.

We are in over our heads here...

Vicky,

My theory is that if it is easier to take out it is also easier to pop out or move. But for sure if it is put in properly then it won't pop out without a keel. The problem is that we have a whole bunch of new surgeons here that are learning on the Charite which is very much dependent on the surgeons skill (as with all ADR's but I feel more so with the Charite), I would expect that the Activ-L with spikes will have the same issues but would not worry if you had it put in by Zeegers.

Brad

Vicki

I don�t mean to scare you or anyone, the activL sounds like a great disc, (just ask Brad) and if I was on the other side I would consider this study for sure!

I don�t know why Dr D felt compelled to tell me this as he was in the main area of the office with the PA/staff and others around where everyone could hear, (he knows I am active on this board). I was trying to get info on the activL.

Dr Z is the best at putting these in and you have nothing to worry about.

Like Harrison said we are all promoters of one thing or another. Dr D is a keel fan and is just concerned with the other end plate.

Does anyone know what end plate they are using in the study?

My impressions based on what I've seen...

I do not believe that migration is an issue for any of the brands of prostheses - if implanted properly. Implanted improperly, they are all problematic. Instead of considering which is less likely to migrate if implanted improperly, we should be selecting our surgeon to increase the risk of quality implantation... regardless of the prosthesis used.

Subsidence has to do with size, placement, surgical experience (how much endplate remodeling; proper remodeling if needed, etc...), bone quality. I presume that a keel gives more surface area to resist migration or subsidence, but that may be offset by the violation of the endplate. I'll bet that we'll never know which is more important and many docs will continue to be proponents of keel or no-keel configurations with equally convincing arguments.

Objections to keel configurations I've heard from the docs are:

1. You can't consider lateral repositioning at all once the keel cut is made.

2. Endplate destruction precludes revision to another ADR except in very rare cases.

3. This is the biggie: explantation must be from the front... as much access is required to remove one as is required to put one in. With scarring down of the vessels, this is not always possible. A non-keeled device may be removed obliquely. (note that shorter keels may provide advantage of a keel without requiring that 'straight out the front' removal.

I'll try to find out more about the clinical trial.

Mark

I love these detailed posts.

Mark,
If everything is prefaced with the fact that it depends on the surgeon then your item 1. is not a factor just as non-keel pop outs of the charite are not a factor when the placement is correct.

I would think that the revision of a charite, after the bone has grown around the prosthesis, would also preclude another ADR in most cases. They will most definately have to carve out the plate and do a number on the bone (although for sure much less than a Pro-disc but both will probably result in a fusion).

I believe that even if the disc is taken out from the side the doctor will still have to take the vessels and separate them from the vertebrae and the outer fibers of the remaining disc structure. If the vessels have scarred to both the upper and lower vertebrae, above and below the ADR, then the doctor will have to separate them otherwise he will not be able to distract the vertebrae enough to get the Charite out without tearing and pulling on the vessels (again, though it is still less than the pro-disc or the Activ-L).

Since none of us are doctors I would love to find this out from Dr. B or Reegan who have done a number of revisions. But we can imagine that any revision is bad, very bad.

I think the best argument for the Charite is that the core is easier to replace, than the Pro-disc. To me, this is what may wear and may need to be replaced long term. With the Charite, and the Activ-L, I can see that this can be done completely from the side without much problem or disruption. For the Pro-disc I think it must be taken out from the front and will need the vessels to be moved aside just as much as the original surgery.

I dont know about the Charite but the Activ-l even has a special tool for revising the core. It grabs the inlay (core) from any direction so you can take it out and put a new one in. This is one of the improvements they have made in this design.


Mark, maybe sometime when you are with Dr. B you can ask him his opinion about the ease of replacing just the core of each type of disc and let us all know. I really do think that this should be more of a discussion than the ease of which the plates are revised.

Hopefully we will get 50 years out of the core of each type and not have to worry about it!

Brad

Brad,

Most ADR complications occur very early after surgery, so later revision is uncommon.

You are thinking of the prosthesis becoming part of the bone and needing to be 'carved out'. I believe that it's more stuck to the bone. Even after osteointegration, they can get a purchase under the plate and pry it up... it'll pop loose, even with a keel. The problem with the keeled prostheses is that they must be slid forward... straight out the front... requiring more access. (My comment about shorter keels eliminating this requirement may be in play here.)

I think that you are misunderstanding the issue of remobilizing the vessels. I don't believe it's an amount of distraction issue... it's how much can the be mobilized. Being able to mobilize them enough for an oblique removal, but not enough for a straight anterior removal would be the issue for a keeled prosthesis. I have discussed this extensively with many top ADR surgeons and this is my 'lay' understanding. Yes... any revision is bad... if you are considering revision, you are in trouble.

I think that the concept of replacing the core is an idea that is attractive to the patients, but I don't here the doctors discussing it much. Obviously, removing the Charite core would be easier than removing the ProDisc core, but if the ProDisc core can be removed and replaced... who cares if it takes a few minutes longer. I think that the issue is, will core replacement be something that will be considered. I believe that it will only be in cases with some sort of mechanical issue, like incongruent placements or way anterior placements. These issues may cause excessive wear (probably true in devices without poly cores too.) This is a crystal ball question that we won't know the answer to until we see it. These issues are the reason why we talk about the primary concern being the quality of the surgery performed... not speed... not customer service... not price... not location... not the package deal... not the cool website... it's all about the quality of the surgery first... I believe that the device issues are second. That is not to say that they are not important... just that the best device implanted improperly is a problem.

Also remember that this spiney row that we hoe really sucks... even with the perfect device and perfect implantation... we still see failures. Perfect implantation does not guarantee success, it just increases the chances of success. Imperfect implantation does not guarantee failure... it just increases the risk of failure. Give yourself every chance.

Mark

Also, I spoke to one of the principal investigators for the Activ-L:

1. Both keeled and non-keeled Activ-L's will be used in the trials. I don't know how this will be determined.

2. Yes, ProDisc approval must be received before the trial can start.

When ProDisc approval will be received is another crystal ball question. It may be tomorrow. There does not have to be a panel discussion.... maybe / maybe not... we don't know. It may not be for some time. If you have a reliable crystal ball... please ask it and let us know. I asked my 8-ball, but it just keeps spouting BS.

Mark