Heterotopic ossification in ProDisc-C????

[fortitudine]

Do we know any more about this issue? As I'm a potential ProDisc-C candidate, this worries me.


Posted December 03, 2006 10:56 AM December 03, 2006 10:56 AM
Folks,

An informed member was kind enough to share some recent information on ProDisc cervical and heterotopic ossification (autofusion).

I am quite puzzled by this and would have liked to have had the “story behind the numbers” before posting. However, I urge you all to NOT jump to any conclusions about the efficacy of the ProDisc C (or any other cervical discs) until more contextual information can be found on this issue. As you seasoned folks know, ProDisc C patients on this forum have done quite well.

Related topics from this board on HO here.
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Heterotopic Ossification in Total Cervical Artificial Disc Replacement.

Spine. 31(24):2802-2806, November 15, 2006.
Mehren, Christoph MD *; Suchomel, Petr MD, PhD +; Grochulla, Frank MD *; Barsa, Pavel MD +; Sourkova, Petra MD +; Hradil, Jan MD +; Korge, Andreas MD *; Mayer, H Michael MD, PhD *

Abstract:
Study Design. Prospective clinical study enrolled in 2 centers (Munich and Liberec) as part of a prospective European multicenter study with ProDisc C (Synthes Inc., Paoli, PA).
Objectives. The first goal of the study was to evaluate the rate of heterotopic ossifications identified with plain radiograph following total cervical disc replacement (TCDR). The second goal was to show whether segmental motion can be preserved, and whether TCDR can provide improvement of the patient's ability to perform activities of daily living as well as a decrease of pain.

Summary of Background Data. Only a few reports about the radiologic outcome after TCDR are published so far. Heterotopic ossification is a well-known phenomenon after total hip arthroplasty. The rate of heterotopic ossification following TCDR is unclear.

Methods. The radiographs of 54 patients (in total, 77 implanted prostheses) were analyzed 1 year after TCDR with a ProDisc C prosthesis. We classified the heterotopic ossification in 5 grades according to a recently published classification system for lumbar total disc replacement. For clinical parameters, the visual analog scale and the Neck Disability Index were evaluated preoperatively and 1 year postoperatively. The Student t test and Wilcoxon test were used for statistical analysis.

Results. In 26 treated segments (33.8%), no heterotopic ossification was detectable. Grade 1 ossifications were present in 6 levels (7.8%). A total of 30 segments (39.0%) showed grade 2 ossifications. Heterotopic ossifications that led to restrictions of the range of motion were present in 8 cases (10.4%). One year postoperatively, 7 cases (9.1%) had a spontaneous fusion of the treated segment. The clinical parameters improved significantly and were similar to previous reports about TCDR.

Conclusions. Only 33.8% of the patients did not show any signs of heterotopic ossification, and the rate of spontaneous fusion after TCDR 1 year after surgery was unexpectedly high. There were 49.4% of the patients with grade 2-3 ossification, which lets us suspect an even higher rate of spontaneous fusion after long-term follow-ups. Motion preservation after TCDR is only guaranteed if spontaneous fusion can be prevented. Thus, mobility of the implanted segments needs to be further studied.

[Michelle]

Consider me highly uninformed here, but are these painful or something? Granted, it wouldn't be good to fuse when you're looking for motion preservation with ADR, but how are you any worse off than going straight for fusion??? I'm asking, not being a smart-alek. Anybody?

[KL Aguilar]

I met Dr. Zeegers at a luncheon sponsored by Global Patients Network. Dr. Z talked about applying a type of wax that acted as a deterent to new bone spur growth. Perhaps someone like Mark will come along and answer this in more detail.

[mmglobal]

Greetings from Munich (AlphaKlinik room 905). I'm still in running the marathon that I do on these trips, but the last surgery was yesterday... hopefully I'll get more time to spend here soon. (It's Saturday morning and I've been here since before the surgeries started yesterday.)

This study is interesting. I've been seeing Bertagnoli do ProDisc-C procedures for more than 3 years. I've been seeing presentations about many different systems, now for the last 4 SAS and NASS meetings. I will see if I can get some perspective on this result.

I found the classification system that was referenced in the study. An article that references the system is posted here: Advances in Disc Technology.

Note that this article is from 2002, but I believe that the system they are talking about. Here is an overview of the grading system:

• Class 0: no heterotopic ossification (HO)
• Class I: islands of bone in soft tissue, bone not present between planes formed by the endplates
• Class II: bone present between the planes of the endplates, but not blocking motion
• Class III: motion blocked by HO and/or postoperative osteophytes
• Class IV: inadvertent bony ankylosis

"A member of the audience raised the point that the presence of HO may not correlate with outcome."

I know dozens of patients with prodisc-C and know ZERO with HO problems. (I suppose it's possible that some have Class I or II HO but it's not been discussed as a relevant issue.) Also note that my experience is with patients who are all less than three years out.

Look here for much of the data that was presented regarding the Charite.
http://www.cms.hhs.gov/mcd/viewdecisionmemo.asp?id=170

Search for heterotopic and you'll find charite studies with fairly large numbers and enormous percentages of HO... > 50%, as high as 80%. Horrible results! However, in the hundreds of charite patients I know, HO has only been an issue in extreme cases and for the most part, it's in people that should be fusing and autofusing represents a good result. (The HO patients that I know can be counted on one hand, without using 1/2 of your fingers.) IMHO, what we are seeing here is that early in the process with new devices, there will be a huge difference in outcomes depending on surgeon and technique. Early in the process, the appropriate techniques are not fully developed. I remember when there was a ProDisc surgeon in the Bay Area who was telling patients that his lumbar ProDisc experience was, "1/3 got better, 1/3 stayed the same, and 1/3 got worse!" Again... horrible results... but that is not the experience with the device across the board and there are surgeons who's outcomes far exceed the mean... just as there are surgeons who's results come no where near the mean.

I wish I had time to write more. This is an important discussion. It really shows why I'm always skeptical about data and studies. Many patients go through the process of searching for the Holy Grail of data and studies and evidence based medicine... only to be discouraged (and sometimes kept for seeking treatment) by finding things like this. I'm not suggesting that we should ignore data and studies... just don't panic... take your time and find out... dig deeper than what the paper says... dig deeper than what your doctor says.

All the best,

Mark

[necknose]

Mark:

Excellent, steady response as always. As one can glean from your signature: when the questions of efficacy and outcome are raised in relation to ADR you literally "walk the walk". You have more than a dilettante's interest in these questions and so far, in your experience, ADR has represented the salvation of a life: yours! You and the other successful ADR/spineys are to be congratulated. It's your Christmas present for this year and many more to come.

Glad the pressure of your escort duties is over, I assume till after Christmas 2006.

In your next post I hope you touch on some of the points mentioned below.

It should be pointed out that the study referred to is of Cervical not Lumbar ADR outcomes.

It seems that the essence of your post is that the surgeon is THE pivotal variable. You've pointed this out before.

What needs clarifying, besides the surgeon variable, across the Cervical (not Lumbar) ADR patient population is are these results: prosthesis specific, due to poor patient selection, a function of the degree of disease progression, patient age, other pathology related, etc..


Clarification Please:
"HO has only been an issue in extreme cases and for the most part, it's in people that [[[[should be fusing and autofusing represents a good result]]]]."

I'm acquainted with your oft cited observation that a single level cervical fusion is the "gold standard" of care in treating cervical DDD (DDD = all spine disease appropriately treated w/fusion), etc..

However I'm unclear about your statement: "should be fusing and autofusing". Is this observation based on the idea that: auto-fusing is a desirable outcome in DDD and further that if it's the end state of an ADR implantation it's desirable because auto-fusion in the presence of an ADR is preferable to auto-fusion as the result of "natural" end state HO, or some other explanation?

As other's have observed: auto-fusion as an outcome, is counterintuitive to the premise of ADR: motion preservation. This is esp. the case for multi-level cervical spine disease where 3+ levels of fusion leaves the patient w/greatly reduced ROM and in all probability significant chronic pain requiring constant medication for "life" is it possibility. Might it be posited that in cases where central spinal cord stenosis is the main concern, if auto-fusion is highly probable regardless of the surgical treatment applied, that low impact posterior approaches, e.g. split laminectomy, could ultimately be just as effective as ADR: esp. reduced the financial impact on the patient as well as elimination of the additional trauma, for some patients, of going to a foreign land for treatment, assuming split lami for example is in fact available in the US.

What, if you will, is the cost benefit equation in cases of probable HO of: ADR versus the best "traditional" treatments?

If you have the opportunity, enlargement on these aspects and others of auto-fusion would be appreciated.

************************************************** *******
Happy Holidays to you and all my fellow spineys. May we all have at least a brief respite from from the pains, fears, and the angst that all to often is the spiney's lot.

Good luck to us all!

[mmglobal]

I hope that someone can do the research to discover the background for this study. There are 8 authors listed. Are there 8 surgeons involved in this series of 54 patients. It is my understanding that while in, where studies are allowed to exclude 'training cases', they are not allowed to exclude these cases in Europe.

I do not know the details of this series, but are there 40 training cases out of 56 patients? Why should their experience be so much worse than other reported data?

Studies and data are useful, but must always be examined with a very critical eye. Now, for years to come, we'll be reading about literature reviews that will say something like, "Incidence of HO between 0% and 66%".

Mark