Disc design question : keel or spikes ?

[KenG]

Hi I have a question about artificial disc design.

ProDisc has keel and Active-L has both keel and spikes designs.
I feel that design with keel, it may get more stabilization but I read spikes have more of it in Active-L brochure or somewhere.

I guess the fact Active-L has both design means keeled design has some solid advantage too ?
I also would like to know what constrained / semi-constrained mean.

I think both ProDisc and Active-L is greatly designed and, hearing from all
the ADR post-op patients in the messageboards, I believe who is going to do the surgery is most important,
but I would like to hear from you.

[Katie]

Hi Ken, I think that the options of keel vs no keel may be because some people may have a really small (shallow) vertebrae and would be at risk of fracture with any keel at all. The spikes may be all they have 'room' for, if I am explaining it correctly. I think every device has several different sizes of keels for this very reason.

The reason there are so many proponents of the ProDisc and Active L may be because those are the ones already approved in the States, that those are what are available, vs because they are the best here. Of course, I think that they are the ones most often used by Dr. B in Germany as well, but I think that Maverick is also very popular here in Canada where we can use any of them, and the same with Stenum hospital in Germany. I may be completely wrong on all of this, but that is my inpression from what I have read. I hope someone will correct me if I am wrong.

Good luck with whatever you decide.

[Justin]

Hey Ken,

The keel vs. no keel was something I had to consider when I had my 2-level ADR in 2003. Katie, brings up a very good point about vertebral body fracture.

I ultimately went with the ProDisc because I felt that a keeled device made more sense at multiple levels. However, keeled devices add another element of difficulty if revision is ever needed.

I have to run an errand, but here is a link to a great publication to get started on the constrained vs. unconstrained devices:

Biomechanical Effect of Constraint in Lumbar Total Disc Replacement


Ken, I'll be back to explain this in more depth later. The questions you asked are very good questions.

[KenG]

thanks, Katie, Justin,

have you ever felt some kind of pain or more load since your two level Prodiscs
to your lumbar, Justin ? ( I should erace this question, it doesn't make any sense does it, sorry )

I really don't know exact mechanism of unconstrained and constrained and semi?
constrained design of the discs, but is it like more the core allowed to move, less
load or pressure to the facets ?

I also wanted to know why you felt keeled version made more sense to two level
prosthesis ? it is also interesting that Prodisc C has changed bit of keel placement to me.

[Justin]

thanks, Katie, Justin,

have you ever felt some kind of pain or more load since your two level Prodiscs
to your lumbar, Justin ? ( I should erace this question, it doesn't make any sense does it, sorry )

Ken, your question makes perfect sense actually. I have not felt any pain or unnatural loading of my spine due to my ProDiscs. :thumpup:

I really don't know exact mechanism of unconstrained and constrained and semi? constrained design of the discs, but is it like more the core allowed to move, less load or pressure to the facets ?

Yes, the short of it is how the disc is able to "move" or translate and the subsequent load placed on surrounding structures of the spine like the facet joints.

I also wanted to know why you felt keeled version made more sense to two level prosthesis? it is also interesting that Prodisc C has changed bit of keel placement to me.

Honestly, the keeled version made more sense to me for reasons that probably don't hold any weight in regard to engineering / relative forces / stability, etc. It was a personal preference at the time with the limited data available.

I'm promise I'll be back on later today to answer your questions more in depth...I didn't want to leave you hanging Ken. Keep doing your research--it will truly pay off when you feel confident going into surgery. OK, I gotta get back to some other projects that need attention.

Have a great day and enjoy your coffee!

[KenG]

at the time of 2003, Active-L wasn't on market yet probably ?
I saw someone's x-ray of 2005 on internet and one line was written in a way like
`Charite modified Active-L Aesecup (?)

it is interesting to see how the disc design improve or change little by little to be
better, of course.
it might be beneficial if we all could see chart of history of design change or something like that.

I saw Prodisc Ⅱ was on 1990 if I'm correct, and third generation of Prodisc appeared in around 1999 ? I don't know exactly when Active-L came out but it
is a kind of improved version of Charite Ⅲ ?

I don't know much about cervical disc design but, it is interesting that Prodisc C Nova is modified to have keel at the center on superior endplate and two keels are placed at inferior endplate for efficient use for multi level prosthesis ? please correct it if i'm wrong.

[KBear]

Ken- To correct Katie, it is the Charite and ProDisc that are FDA approved in the US. I am not sure if you are familiar with the FDA, so I will give my 'best' explanation of it. The FDA is our goverment oversight program that is in place to protect us from potential side effects of drugs or surgeries. Doctors can only implant the Charite and ProDisc in the US and this is all that insurers will pay for (many insurers will not pay for ADR at all, as they don't feel the technology is proven). There are clinical trials going on in the US, where you can receive Active L, Freedom disc; if you are a canidate (these are oversaw by the FDA and these devices are in the process of getting FDA approval).

In Germany, they have access to devices that we do not have in the US, or they are in clinical trials here (where the criteria is very strict, as the manufacturer wants everyone to have the best possible outcome, as they want FDA approval). We also don't have multi level approval in the US; which is why so many go to Germany for surgery.

You are right that the Active L has both a design with a large center keel and one with smaller keels. My surgeon (who is the co-inventor, with Dr Yue, of the Active L) said that the surgeon chooses this based on your anatomy (like Katie said that you may not have large enough vertebrae). I am not sure of why else they may differ on this, though I do know that revision is way more complicated and risky if it is a large keel device.

There are pros and cons to both restrained and unrestrained. It is my understanding that with restrained it can be too rigid and not enough movement or leeway. With the unrestrained, there is greater risk of the core coming dislodged. With the semi constrained (the Active L), the core is attached to the bottom plate, so no risk of it coming un-lodged and it still has the movement of a un-constrained. I am sure there are more reasons than this; but I don't know what they are.

You are doing a great job of researching and will be glad that you did. Like you said, one of the most critical factors is the surgeons skill and experience. When you find a surgeon that you are happy with, then they can explain why or why not they prefer certain devices.

[KenG]

Hi KBear,

thanks a lot for telling me about FDA trial and Active-L. Is your surgeon Dr. R Garcia ? if so, they co invented the Active-L at Yale with Aesculap.

Japanese FDA is always following u.s. FDA so, it is always late. it takes probably
10 + years that ADR possible in my country.

for me, realistic choise of disc would be either Prodisc or Active-L if I go to Germany I think.

I am wondering which is going to be in my L5S1 since both seems to have advantages...

[KBear]

Hi KBear,

thanks a lot for telling me about FDA trial and Active-L. Is your surgeon Dr. R Garcia ? if so, they co invented the Active-L at Yale with Aesculap.

Japanese FDA is always following u.s. FDA so, it is always late. it takes probably
10 + years that ADR possible in my country.

for me, realistic choise of disc would be either Prodisc or Active-L if I go to Germany I think.

I am wondering which is going to be in my L5S1 since both seems to have advantages...

Yes, my surgeon was Dr. Rolando Garcia; really great guy

[cavalier]

I was told by TBI & Dr B semi constrained which is Prodisc, Active L & Marverick all are - there maybe more as newer brands keep coming out - but those are all semi - are supposed to put less load on the facets than unconstrained per them. Also for a spondylo which I was I also was told the keel (Active L was not even out back then) was better than just teeth alone & the manuf's spec's for Charite didnt' remommend for a spondylo but Prodisc back in 04 had it on their spec's to handle a grade 3 spondylo. I no longer see that in their literature on their home page today. Obviously Active L combiens both teeth & the keel - bone density matters your actual spine density no matter which device you opt for - & all of this is taken into account the condition of you facets if you have a instablity - what degree etc -Charite is a GREAT product just like these others i mention - however it depends on what you have going on - I believe you have the retro correct ? That will be a factor. As I said TBI here in the States at the time was doing P.D. & the charite but both Zigler & Blumenthal felt P.D. was the better product suited for my condition. Had I not have wear to the facets & the spondylo - the Charite would have been a good fit. Blumenthal was doing Charite but said no for me & when I looked at both manuf's spec's I also had to agree. Dr B also agreed with TBI.
Best - Jill