'crash testing' artificial discs

[rob_zzz]

I asked this question before but it seems to have dissappeared when the site was down the other week.

Does anyone know if they 'crash test' artificial discs?

I know that they do tests to simulate repetitive motion (i.e. the equivalent of looking left, right and bending down to touch your toes a number of times a day for many years) and they go ok under those scenarios.

What I'm wondering is if they also investigate how they behave in the type of stress that might be undergone in a car accident or fall - the sorts of things that don't happen every day but are still not unlikely over the course of a lifetime.

[Alastair]

Hi Rob,
I think it would be impractical to try and test discs. How could you simulate these in peoples spines and have a "Human" type accident?

I think a lot of people who have had accidents could have given a lot of feedback to the technical people but I have seen no Evidence of this.

I think you are ahead of your time -- - lol
Best
Alastair

[mmglobal]

At the conferences, several of the surgeons show pictures of horrible accident photos that patients have been involved in... no damage to prosthesis. They are very dramatic, but I don't think they give us too much important info.

Yes, they do a lot of testing on how much forces are required to break the device, but all of those forces are so far outside of what will damage the surrounding tissues. They are an interesting exercise. What is interesting and impossible to test in a lab, is how much force is required to dislodge an intergrated prosthesis. I believe that you have increased risk of displacing the prostheses with a serious impact, up until the time that osteointegration is complete. After that initial period, with a properly sized, properly placed prosthesis, I believe that the forces required to damage the discs, will already have damaged a healthy spine.

I believe that people with substantial malplacements are at increased risk for complications related accelleration injuries. (I also believe that they are at risk for accellerated wear, not only of the prosthesis, but also of other spinal elements.) This is especially true in multi-level cases.

In short... regardless of the status of your spine, try to avoid serious accidents! This is a great question, but I don't think it impacts our decision making process. "Doc, I've got a demolition derby a week from Friday... is that OK?"

Mark

[rob_zzz]

Thanks for the reply Mark - even to know that people have gone through bad accidents (unfortunate for them of course) but the prosthesis hasn't failed is reassuring.

Alastair - I agree it would be difficult to test with any real accuracy - maybe if they measured the loads/forces/speeds that crash test dummies go through during simulated accidents and tried to apply them to prosthesis implanted into a donor spine - similar to the way they do the standard motion testing - I think for that they implant into a cadaver spine and built a machine around it to simulate normal motion - they could possibly do something similar but applying more rigorous forces as estimated from crash testing.

I guess it wouldn't be accurate but might still uncover some aspects of prosthesis behaviour under unusual loads/stresses.

Love the demolition darby comment Mark! - good point

[paulam310]

Rob, before I got my disks I asked Delamarter's adr in charge person the same question. She told me that there have been people in car accidents after adr getting whiplash, but that it didn't hurt the disks. That was reassuring to me.

[sahuaro]

Mark--
In the cases of ADR patients who have been in accidents, as reported in the conference, what happened to the discs above and below the prosthesis? Although this might not be a determining factor in decision-making, it is something I have been concerned about it. I did ask a NS what would happen if another idiot decided to T-bone my car, and his response was that if I had fusion, the discs above and below would take the brunt of the force and be damaged. Hence my question of whether ADR would protect these other discs to some degree.

[mmglobal]

In August 1997, I was as healthy as a horse... playing soccer 6 days a week, skydiving a couple days a month... rock climbing.... loving life. I got rear-ended on the way to work and have never been normal since.

Healthy discs are damaged in accidents. Already incompetent discs are damaged in accidents. I believe that damage in an accident would be lower in ADR patients than in fusion patients because the excessive loads would be shared over more levels rather than concentrated on the levels adjacent to fusion. This is just my lay opinion.

I believe that failure loads for the devices exceed the failure loads for the surrounding tissues. In my opinion, there isn't any information about the survivability in an accident of one technology over another that is relevant to your decision process. Do what is best for your spine. Avoid accidents.

Mark

PS. I don't know about the condition of adjacent discs for the accidents reported at the conferences. I assume that they were OK because the gist of the presentation was that the patients were OK.

[mmglobal]

Amy, I occasionally play soccer with my 2 Charite's. A client of mine plays hockey several days a week in competitive adult leagues.

Much of the scarey data that was presented to the FDA was regurgitation of 15 year-old cases. Much of it was anectodotal and was compiled by people who are working for the competition.

Yes, there is the possibility of dislodging the prosthesis in an accident... as there is the possibility of damaging fusion hardware or healthy discs. This risk is very tiny with a properly sized and properly placed prosthesis. Improperly sized or malplaced medical devices of any type are at risk. The risk are greatest in the days and weeks that follow implantation, before the device haa fully settled into position and before osteointegration is complete. I don't think that the non-coated Charite' is a show stopper, bit I'll feel better when we can start implanting the coated version in the US.

Make the best decision you can based on the best information you can get. Get the device that is most appropriate. Try not to crash... try not to slip and fall. It is unhealthy for children and other living things. ADR does not create some magic halo around the operated level that would make one immune to damage from accelleration injuries.

Mark

[tegilman]

Mark, I didn't know that Charites could play soccer! Hmmmm I know that was a bad joke, but my real purpose for the response here is that all the important stuff has been said. I have my own experience at almost a year post op. I fell directly on my bumm while cleaning my garage. The only impact was on my ego. I have neve had any repurcussions since the fall. I also fell a couple of times this past winter. Still going and my three Prodiscs have taken care of my getting around.

Thelma

[mmglobal]

Thelma, you fell on your bum? Did you hurt him?