Heterotopic ossification in ProDisc-C????

[rob_zzz]

reading through the pubmed abstracts and came across this article again (about heterotopic ossification with prodisc-C - see first post in this thread).

I'd definitely be interested to know if anyone has gotten any further information from surgeons that do these procedures on whether there are any measures to counter this problem. Also its fair to say that without knowing the background of the study its hard to know how useful the results are, however its also true that similar studies in relation to other cervical prosthesis (e.g. bryan) have also showed results of this nature, so it sounds like HO is real in that it is something that occurs - but what level of impact it has is another question.

One surgeon I spoke to said that they prescribe NSAIDS after the surgery to help reduce early bone growth. I'd be interested to know if there are chemicals (almost the 'opposite' of bmp I suppose) that could be used during surgery to prevent HO in certain areas.

Also for those that have had a cervical prodisc-C - have you had x-rays at 1 or 2 year followup and what did they show?

Finally - it seems that even if there is a high incidence of HO, the patients are still doing ok - i.e. there are other studies that show patient satisfaction scores etc. one or two years on that still show good results. So this possibly comes back to the most important thing about a surgery being succesful decompression of the nerves causing the problems (spinal cord or peripheral nerves) without damaging them during the surgical process. And if this is acheived then the likelihood of a good outcome is high regardless of the implant used. Similarly quality of placement of the implant by the surgeon etc. selection of appropriate heights etc. etc. would all be factors - possibly more so than the actual 'thing' put in place.

i.e. on that basis it might be that the surgeon rather than the implant is the key determiner of the result. If this were the case it would also arguably still be a reason for travelling/expense to visit a surgeon with consistently good results.

[mmglobal]

This study really shows the problem trying to mine the data. I have spoken to several of the most experienced cervical ADR surgeons in the world and int he US about the study. None of them are experiencing rampant HO numbers as this study would suggest. None of them is experiencing HO numbers at a level that would even give them pause.

HO with the Bryan disc is a completely different topic. The Bryan procedure involves milling a negative into the endplate to accomodate the implant. It's a difficult procedure that is error prone. Excessive milling of the bone and potential positioning issues greatly increases the risk of HO. I believe that is why we have not seen Bryan approval and I never hear any buzz about it. Medtronic believes so strongly in the Bryan that they purchased the Bristol disc (now the prestige). IMHO, they knew that the Bryan was a non-starter.

I believe that what we see in this study is a prime example of why we must do everything we can to make sure that we are dealing with surgeons that are highly experienced with the technology they are using. I don't care if I'm dealing with the most experienced ADR guy in the world... I don't want to be his first, fifth, or tenth procedure with new devices or new instrumentation. This study lists nine surgeons and 54 patients? What was their training like? What other cervical ADR experience do they have? Is there an axe to grind?

There is one tidbit of incredibly valuable information that I take from that study. If you need ProDisc-C, don't go to those guys!

Mark

[rob_zzz]

Mark,

Thanks for the detailed reply and first hand feedback. I'd still be interested to know if there is anything in particular that these more experienced surgeons do that helps to prevent HO.

It must also have been/be a problem with other joint replacements (hips, knees) so you'd think there'd be already be a fair bit of information about the nature of the process that occurs, and the types of measures that can be done to prevent it.

I guess the more conservative fusion surgeons would be liking seeing this sort of research to justify holding off on ADR which is unfortunate. On the other hand I'm hoping the developers of the prosthetics will be open about the realities of these problems if they do in fact exist, and put active research into ways of preventing it.


Rob

[sahuaro]

Thank you, rob, for always asking important questions.
Mark: Since I am considering the Prestige LP cervica disk, I'd like to clarify your comments about the Bryan: is the increased risk of HO theoretical or have there been actual data reported? Since my understanding of the Prestige LP is that it also requires milling, then would the same concerns apply?

[rob_zzz]

thanks - I should probably add that I'm not trying to be deliberately difficult by raising the topic - I want this technology to work as much as anyone and think that we're all lucky to have the options available today that we do.
(and wish they were available a little closer to home from my own perspective but thats another story).

There are also known problems with fusion so even if there are some problems with ADR they still need to be compared contextually to the problems with fusion. (e.g. with fusions there are problems with the anterior plates that don't occur with ADR because there's no plating, problems with hip graft site for autograft fusions that don't occur with ADR etc.).

Sahuaro my laymans understanding is that the milling for the bryan is much more extensive than for the other discs (prestige and prodisc). As I understand it, with the other discs they use a tool to cut a relatively small slot(s) for the disc to lock into, while with the bryan they gouge/drill out a fairly large hollow that the ends of the disc fit into.



Rob

[mmglobal]

I don't think you are being difficult, Rob. These are tough questions and unfortunately, when you decide what to do, you still won't have all the answers as they don't exist yet.

Yes, with the Bryan disc, there is much more milling and the process is complicated and difficult. They must mill a negative in the bone that provides a 'cup' that the prosthesis fits into. Imagine the jig that is used to mill into both the superior and inferior endplates. Too many steps... to easy to get it wrong. I don't have the Bryan data at my fingertips and am relying on memory and impressions made when I attended the sessions where Bryan experience was presented.

For me, this really highlights the problem with the data and with this whole process. There is no question in my mind that there is a huge disconnect between the data and the experience. Especially with an extra-difficult surgery, there will be a greater disparity between the more skilled and experienced surgeons and the ones that are less so. I know several top surgeons that have done many Bryan procedures, but all of them stopped using Bryan when newer designs became available. They all talk about HO rates and the difficulty of the surgery. However, when I see Bryan data presented at the conferences, it looks much the same as for the other cervical discs. (And for the lumbar discs, and for fusion, and for.....) Maybe they all use the same computer program and it's stuck... only outputting 85% success rate, regardless of the input.

Regarding avoiding HO... I believe that it comes along with doing excellent carpentry. It comes with experience. There is a trade-off at many places in the surgery. Unless you have totally regular shaped end plates, some remodeling will be in order. How much? Too much or inappropriate remodeling and you increase the risk of HO, subsidence, migration. Too little remodeling and you don't have a good platform for the prosthesis, increasing the risk of migration, toggling (motion of the prosthesis), or ??? Use of bone wax may reduce the risk of HO, but inappropriate use of bone wax will come along with an entirely new set of risks. Again... experience, care, skilled surgeon are paramount.

Regarding Sahauro's question about theoretical vs. numbers... I don't know. My impression is that they abandoned Bryan because there was something that was much better... not because of HO rates. If there was only a choice between Bryan and fusion, I suspect that they would still be doing Bryan procedures where ADR is indicated and that, as with other surgeries, better surgeons will have better success.

Mark

[rob_zzz]

good comments - thanks again Mark.