ADR and future osteoporosis?

[mmglobal]

Someone just posted a great question on the *** guestbook:

Posted by Yvonne:

If a pateint gets and ADR like Pro disc or Charite, will developing osteoporosis a few year later ruin what the ADR accomplished? Yes or no?

How and why? How can it be prevented?

I know this has been discussed and I'll try to answer based on my understanding. I'll also ask some of the doctors and post the best reply that I get.

The risk of osteoporosis or osteopenia is subsidence, where the prosthesis sinks or subsides into the vertebral body. The risk of subsidence is greatly increased by undersized or poorly positioned prostheses. Undersizing the prosthesis provides a smaller footprint that will not as much support as a larger prosthesis. Anterior positioning places the rear portion of the prosthesis, over soft cancellous bone towards the center of the vertebral body, instead of over the hard cortical bone around the outer portion of the vertebral body. Anterior positioning also concentrates the center of force exerted on the prosthesis on the back portion of the prosthesis, which is located over the softer portion of the vertebral body. This is because 70% of the weight is supported by the back 1/2 of the column. That is why most of the damage done to, and pain generators in our discs are in the posterior portion. That is also why it is important to locate the center of the prosthesis behind the midline of the vertebral body.

Look at films for both Willie/MrBee and Tony/ADR2002 for classic examples of subsidence. Both are poorly located, undersized prostheses.

With bone density issues, they can push the limit and still do ADR with vertebroplasty; injecting bone cement into the vertebral body to strengthen it, reducing the chance of subsidence. (Vertebroplasty options are much more advanced in Europe where they can use newer bioactive bone cement.)

The original question was about future osteoporosis. Again, the risk has to do with subsidence. From all the presentations I have seen during the last 3 years worth of congresses, such as SAS; and from all the discussions I've had with the surgeons... I believe that subsidence is something that happens in the first few months post-op. If subsidence hasn't occurred at 6 months, then it will not occur. At the places I've been where long term outcomes and complications are discussed with the surgeons who's expereince is measured in decades... late subsidence is not included in the complications discussed.

I believe that this is for several reasons. first, when osteointegration is complete, the load is distributed across the plate. Second, Wolff's law states: "Remodeling of bone ... occurs in response to physical stresses - or to the lack of them - in that bone is deposited in sites subjected to stress and is resorbed from sites where there is little stress" So, under the prosthesis where greater stresses would result in subsidence, Wolff's law results in increased bone growth/strength. Before 6 months, the natural response from Wolff's law has not had enough time to add enough strength... especially in the face of undersized or misplaced prostheses.

So, would early detection and treatment be important for ADR post-op's.... absolutely... just like it is important for people without ADR. I would think that the risk of fracture of a long fusion would be greater too, for someone who has developed osteoporosis. It will be interesting to hear the doctors compare the risks.

What has anyone heard from their doctors about this issue?

Mark

[spotty14]

What I was told about ADR and osteoporosis was the need for a T score under -2.5. I still wonder about the quality of the bone even if the safe T scores are reached through treatment. Would new bone support an ADR? some say that even after the new bone has grown in that it takes additional time for it to become harder/denser bone. My doctor also mentioned that age is a factor in determining bone quality & fracture risk because a younger persons bones are less fragile than an older persons bones. I would think also that the reasons identified for developing osteoporosis in the first place would be significant in long term treatment and bone growth with ot without ADR.

[Rein]

Mark

Thank you very much for addressing this issue. It was something I had been thinking about recently. Short of actual prosthesis materials failure, this seemed to me to be the only other concern for longterm viability.

If I understand your post correctly, the conclusion is: If the prosthesis is sized and placed correctly, the body will eventually compensate with adequate bone growth and density in the area supporting the prosthesis, which should prevent it from subsiding. In those patients who may have inadequate bone quality at time of placement, there is (or will be, eventually, in this country) adequate measures that can be taken to ensure stability.

Reading your statement of Wolf's law leads me to wonder if some of our more athletic ADR's haven't helped (rather than increased potential failure risk) their placements by doing the very things they did prior to surgery, such as skiing, tennis, etc.. (Activities whose impact action causes bone to grow harder around the prostheses.)

Hmmm. Day one, walk down the corridor to the nurses station and flirt in German. Day two, take the stairs, two at a time, rather than the elevator. Day three, skip rope 15 minutes. Continue skipping rope an hour a day for the next six months...

[biffnoble]

Day 4, don't bother to call the elevator just step directly into the shaft.

Day 5, make return Stateside trip via circus canon.....................

[Mariaa]

Mark,
Will be seeing Dr.Spencer Thurs w/new MRI films and get his opinion re new films plus risk of subsidence re my level of osteopenia (last t score was -2.2 which was considered fine w/2 surgeons doing ADR in CA.). I'm due for another BMD exam this summer.

Like Spotty, I also wonder about findings on DEXA scores here and then reality of bone once going in to do surgery. It seems that it would be best to air on the side of caution and have the cement available to utilize should it be needed...

I think in my case these are the things that will have to be reviewed in terms of am I still a US candidate for ADR surgery

1)MRI films
2)CT scan re endplates
3)Discogram re pain generators (L3 concordant or not this time)
4)BMD re t score

Then the general med stuff that hopefully won't yield any weird findings now that I'm officially over 50!!!

[ans]

Maria,

Good luck w/your consultation.

I too am interested in osteopenia and arthroplasty.

You mention that you had a CT scan of your endplates. I never heard of this one. Is this test necessary in your opinion and revealing in ways that an MRI is not?

Thanks a lot - Allan

[Anita]

Hello,

My husband's osteopeania was discovered in a bone density scan pre-operatively in Straubing with Dr. Bertagnoli. Jim's T-score was -2.1 at that time. Bio-active bone cement was used after pro-disc placement. We are very fortunate to have had the surgery in Germany because the USA limitations for ADR AND bone cement are -1.5 T-score.(Even if a triple ADR was possible in the US)

Dr. Bertagnoli was very serious about Jim being EXTRA careful the first 6 weeks and the first 3 months. He was very clear, "Don't be stupid"..!He suggested that if the pro-discs were to shift in that period of time it would related to my husband over exerting in ANY direction that would alter the micro-architechture of the bone.

As an aside, a "Don't be stupid", from Dr. Bertagnoli is a VERY effective motivator! He was also very concerned as to why a man of 43 would be osteopenic and strongly urged him to see his internist and bone specialist. We both strongly feel it would be in his best interest to take very good care of himself for the first year and just let his body heal around the pro-discs, in fact it would be rather foolish to do otherwise.

I do believe more men should be screened for this, it is not "just a woman's disease", just as heart disease is not just a male disease.

In the meantime he is seeing his internist and we are doing our own research as well. He is a young man with a lot of life to live.

Anita Peludat

[Mariaa]

Allan,
My OSS said a CT scan would show endplate status~I've not heard this before, in fact upon asking other surgeon was told that they wouldn't know until going in...(or maybe wouldn't completely know?)~

Anita,
I agree re the BMD testing being done for males also. I think the screening should start earlier than it does for women and also be done for males. I don't think DEXA exams are very expensive regarding routine health care screening and especially regarding what such testing might reveal.

[ans]

Thanks Maria. I'm surprised CT's have such good resolution.

I think bone scans are impt. for anyone who smoked in their life too. (Yes, I was that stupid).

[Mariaa]

Allan,
I smoked in the past ~ tho the last time was after my L4 discectomy failure and only for one year... previous to that it had been 17 years since I last smoked... (teenager on cigarrettes from 14 to age 20 ~ now that's STUPID!) ...probably would have jumped off a bridge w/all my stupid smoking friends also~