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Thread: Interesting aspect of the SpineCor

  1. #1
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    Interesting aspect of the SpineCor

    I was at St Justine’s this week and had the chance to speak with Dr Rivard about some of the SpineCor data. On the wall of the clinic was a Table (similar to the one attached) which aggregates the results of SpineCor bracing.

    I had two main questions relative to this Table. One, if not both, of them we have discussed here (well, maybe not here in ‘research’, but on the bracing forum).

    I asked for clarification on weaning explaining that on some of the powerpoint presentations and technical papers the term is used to suggest the present tense, ie, weaning is ongoing or occurring for a long period of time. He said that the when they say 5 years weaning, they mean 5 years w/o any brace wear at all.

    The other question I had related to the population of patients reported in the attached table who reached 5 years post bracing (N=69). They report an average POST BRACE Cobb angle for this population but only an average initial Cobb angle of the whole population (N=298). I wanted to know what the initial Cobb angle was for this smaller population (the last column in the attached table). Had these early patients all had smaller initial curves (than the later patients), the aggregated data suggesting a continued decrease in curve size would be highly questionable.

    I guess I was pretty surprised at what he did next. He got on the phone and called another fellow (perhaps a student or assistant involved with the data processing). This other fellow came in and Dr. Rivard explained the question to him. He opened the main data base and extracted the data of initial Cobb angle and Risser of just those patients who are 5 years post bracing (now in the N=90’s). He calculated the average initial Cobb angle for those patients and, you know what, it was 26 degrees, the same as the average initial Cobb angle for the whole population. (For anyone not following along, in my mind at least, this increases the validity/significance of the Spinecor results.) I have to say I was impressed with the openness of the calculation. Had the calc shown a significantly lower avg initial Cobb angle, it would have really brought into question the results. His response wasn’t ‘let me look into it and get back to you” it was more along the lines of ‘lets see’.

    Now, I would have loved to sit down and play with them and the data for the rest of the afternoon. Not only was the brace clinic busy but my daughter started to look a bit agitated with me.

    But, I still wanted to talk about what these results imply because that is really why we are giving the SpineCor a try. These data (again, attached figure) show that, even after SpineCor bracing has stopped the curve continues to decrease. This is in stark contrast to the Daniellson data (posted on another thread) showing a gradual (or not too gradual – not enough data points there to define the shape of the curve) increase over time post TSLO bracing.

    I asked Dr. Rivard about the mechanism of continued improvement after bracing ceases. He said that they believe that because the brace is dynamic, it trains the muscles over time to apply the corrective movement necessary to reduce the curve. After enough time wearing the brace, the muscles are trained to do it w/o the brace and continued correction is often seen (not a direct quote, just the gist I took away from the chat). Now the next question for us was what is “enough time”? Dr. Rivard said that if you quit bracing too early you loose all correction and it is as though all the bracing you endured was a waste of time. He would like to see my daughter braced until Risser 4 (and I lean more towards sticking with it till her digital skeletal age indicates maturity - the whole hand xray thing as my daughter Riser and skeletal age are discordant).

    The last thing we talked about that may be of general interest is related to strap tension. I asked if we couldn’t just tighten the straps up a bit to shorten the treatment time. He said that would be a big mistake. There is a sweet spot in the necessary tension (my gist, not a quote). He said that a SpineCor clinic in Europe aggressively tightened the tension and the results were terrible.

  2. #2
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    just curious

    Hi Concerned Dad,

    Did you by any chance ask the doctor your earlier question on the other thread about the status of kids braced pre-growth spurt (10 or 11) who are now on the other side of the adolescent spurt (15 or 16)?

    Thanks,
    mamandcrm

    G diagnosed 6/08 at almost 7 with 25*
    Providence night brace, increased to 35*
    Rigo-Cheneau brace full-time 12/08-4/10
    14* at 10/09 OOB x-ray
    11* at 4/10 OOB x-ray
    Wearing R-C part-time since 4/10
    latest OOB xray 5/14 13*
    currently going on 13 yrs old

    I no longer participate in this forum though I will update signature from time to time with status

  3. #3
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    Quote Originally Posted by mamandcrm View Post
    Hi Concerned Dad,

    Did you by any chance ask the doctor your earlier question on the other thread about the status of kids braced pre-growth spurt (10 or 11) who are now on the other side of the adolescent spurt (15 or 16)?

    Thanks,
    No I didn’t ask. I wasn’t sure how much time I had and I wanted to keep it focused on our particular situation. Besides that, I sort of forgot. I know the answer would be important to many of the folks here with young kids using SpineCor.

    After glimpsing the database in action though I would guess it would be trivial for him to calculate the results. He would need to show data JUST for patients who were braced at Risser 0. Sanders said in a study looking at Maturity Assessment and curve progression that “The period and pattern of curve acceleration began during Risser stage 0 for all patients” (CD Note – "for all patients" in his study). SRS Criteria also allow inclusion of Risser 1 and 2 which seems to have the potential of biasing the results in favor of bracing by including girls already past their peak curve acceleration stage.

    Of course, Sanders went on to show that Risser was not the best correlate to curve progression (see attached table) – something I thought we could discuss too if any one is interested. But Risser is what most everyone is using because it is easy to measure from a scolio x ray. However, as an aside, Dr Dolan said (on the “other” scolio forum) that they are taking hand xrays as part of the info they are collecting for the BrAIST study.

  4. #4
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    Here is a graphical depiction of your table.

    I don't see any difference among these groups. Admittedly, your 5 year follow up is underrepresented. The spread of the data is so large that none of these groups is significantly different from the others. Confounding this table is the fact that any Cobb measurement can vary up to +/-5 degrees.

    Are there fewer people follow up group because they opted out of treatment, or did they not participate in follow up care? or did they opt for surgery? How many from each group opted out for surgery. I think that might be a good measure of efficacy.

    Also, my error bars are plus or minus 1 SD. No one falls into the greater than 45 degree surgery group (about 68% of all patients). To cover the entire group, you have to go out 3 SDs. Again, the spread of numbers is so large, its hard to tell who failed bracing.

    I have to say, I am not against bracing, per se. I'm just saying that based on your evidence here the facts are not very compelling. We also don't have a wait and see group to compare with. I would guess that they are similar.

    p

  5. #5
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    I think your error bars are showing something other than error.

    Since we are dealing with a population mean it is more meaningful to look at the standard error of the mean. (the standard deviation divided by the sq root of the sample size).

    You see, it is entirely likely that a population of post braced patients will have a large standard deviation in their measurements. However, as you sample more and more of these patients, you should converge on the true sample mean. At the same time however, the sample standard deviation could remain totally unchanged. If N= 1million, the standard deviation could still be 10, but our guess at the true sample mean would be pretty darn accurate.

    So, I guess I would submit my attached graph showing standard error for the error bars is a more meaningful rendition of the error involved. I do admit however that I am still uncertain how exactly we deal with BOTH the error in determining the sample mean and the error involved with determining the angle of an individual measurement (5 degrees).

    Of course, a test of significance is what is really required. But using SD as error bars for a sample like this is incorrect (IMO).

    Here is a link to an interesting discussion on error bars
    Most researchers don't understand error bars

  6. #6
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    Quote Originally Posted by mamandcrm View Post
    Hi Concerned Dad,

    Did you by any chance ask the doctor your earlier question on the other thread about the status of kids braced pre-growth spurt (10 or 11) who are now on the other side of the adolescent spurt (15 or 16)?

    Thanks,
    Mamandcrm, I did ask a similar question... about those with JIS (who therefore are clearly before their growth spurt) who had gone on to reach maturity. He said they haven't yet compiled results for the JIS folks (only the AIS which are presented in their studies), but that they would be working on putting results together for JIS next. I don't know the time frame (and didn't think to ask until I had left)

    Concerned Dad, Interesting, thanks for sharing. I haven't checked yet to see if you posted about your daughter's results, but i'll check for other posts now. I hope all went well.
    daughter, 12, diagnosed 8/07 with 19T/13L
    -Braced in spinecor 10/07 - 8/12 with excellent in brace correction and stable/slightly decreased out of brace curves.
    -Introduced Providence brace as adjunct at night in 11/2011 in anticipation of growth spurt. Curves still stable.
    -Currently in Boston Brace. Growth spurt is here and curves (and rotation) have increased to 23T/17L

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    A few thoughts on the Coillard data table...

    1. The most obvious issue is what Pnuttro said about the fate of the 136 folks who are not accounted for at 2 years and the 229 folks who are unaccounted for by five years. For all we know they all went on to surgery.

    2. There is something funny about how the original population had about half the Standard deviation as any other group in the table. I can't put my finger on it but that bothers me.

    3. I don't think it is incorrect to plot the error bars from the table onto the graph and interpret it in the manner Pnuttro did. CD, why is that wrong?

    4. I'd like to know how confident Coillard and Rivard are that the patients are not still wearing the braces at least some of the time.
    Last edited by Pooka1; 03-13-2009 at 07:19 AM.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

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    "We are all African."

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    Quote Originally Posted by concerned dad View Post
    Of course, a test of significance is what is really required. But using SD as error bars for a sample like this is incorrect (IMO).
    Your table doesn't say if the errors are standard deviation or standard error, so your interpretation of my graph is based on my assumption of the data--that the table had SDs.

    So do your data approach significance?

    If so, does it change the outcome for the patients?


    Did patients drop out of follow up because they opted for surgery or no treatment?
    Last edited by PNUTTRO; 03-13-2009 at 09:48 AM. Reason: added another question.

  9. #9
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    A few thoughts on the Coillard data table...

    1. The most obvious issue is what Pnuttro said about the fate of the 136 folks who are not accounted for at 2 years and the 229 folks who are unaccounted for by five years. For all we know they all went on to surgery.
    I think we had a similar discussion already. Isnt it intuitive that some of the folks haven’t hit the two year or five year mark? Also, is it reasonable to expect a 100% follow up at 5 years? (We’re not traveling back to Montreal 5 years after we’re done on my dime to provide a data point for a paper). Although it would be reasonable to ask what percentage of the 5 year patients were available for follow-up (a number I don’t see reported). From the text of the paper:

    This prospective interventional study was carried out on a group of 639 patients (92.3% females) having idiopathic scoliosis treated with the SpineCor brace. Some 583 patients respected the inclusion criteria, 234 (40.1%) did not complete the treatment by brace at the time of the analysis and 51 immature patients required surgical fusion while receiving treatment, leading up to 298 patients who had reached skeletal maturity at the end of bracing. Out of this cohort of patients, 162 patients had 2 years and 69 patients had 5 years follow-up post-bracing.

    But this is why I asked the question about what was the initial Cobb angle of the 5 year patient group. One is left to assume that it is a random sample of the total initial cohort. When they calculated it for me it indeed was the same average as the total initial cohort. Of course Risser could be different, curve type could be different etc. But lets just say that it increased my confidence in the results to see the Cobb was the same between the two groups.


    2. There is something funny about how the original population had about half the Standard deviation as any other group in the table. I can't put my finger on it but that bothers me.
    Good point, I pondered that (and still do). I go back to a result from Sanders study where he made the observation that
    At this stage, curves also separated into rapid, moderate, and low-acceleration patterns, with specific curve types in the rapid and moderate-acceleration groups.
    (The “Stage” he is referring to is a maturity indicator of TW3 Stage F to G – the hand xray derived thing). So, in answer to your question about what happened to increase the standard deviation (SD), the girls went through their growth spurt. Some advanced, some stabilized, some reduced. The advanced and the reduced groups would increase the SD. Back to the Coillard data,

    Some 137 patients (46.0%) out of 298 stabilized their Cobb angle ( ±5°) at skeletal maturity at the end of bracing, 122 patients (40.9%) corrected their initial Cobb angle and 39 patients (13.1%) had 6° or more
    progression of their initial Cobb angle.



    3. I don't think it is incorrect to plot the error bars from the table onto the graph and interpret it in the manner Pnuttro did. CD, why is that wrong?
    I explained why I think it is wrong in my post above. I thought you in particular would get a kick out of the blog article I linked to as it goes sort of along with your “Why most published research results are false” paper.

    I would ask you to rethink my argument. The number we are trying to determine is the mean of a group. The standard deviation (SD) is indeed related to the confidence interval. However, the more measurements you include in your sample (N) the closer you will be to determining the true mean of the group. (a group with a small SD would require fewer measurements than a group with a high SD to reach the same level of confidence that you indeed have a reasonable estimate of the mean). PNuttro completely excluded consideration of N in his presentation of error bars.

    To really determine the significance of the results requires an appropriate statistical test. Coillard did not do that. A possible test methodology might be what Daniellson used. They say:

    Statistical Methods. Distributions of variables are given as mean, SD, and range. For comparisons between 2 groups, the Mann-Whitney nonparametric U test was used. For comparisons of proportions between 2 groups, Fisher exact test was used.
    All significance tests were 2-tailed and conducted at the 5% significance level. Survival curves were produced according to the Kaplan-Meier method.



    4. I'd like to know how confident Coillard and Rivard are that the patients are not still wearing the braces at least some of the time.
    Well, I have to say that after talking with my daughter, this is a non issue. This brace isn’t a teddy bear to be cuddled at night. When folks are done, they’re done. Unlike the Boston brace, the Spinecor deteriorates with use. How many 16 year old girls are going to be wearing their tattered brace when they don’t need to?

  10. #10
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    Quote Originally Posted by PNUTTRO View Post
    Your table doesn't say if the errors are standard deviation or standard error, so your interpretation of my graph is based on my assumption of the data--that the table had SDs.
    Yes, the Coillard table presented SDs

    So do your data approach significance?
    Good question. I suspect it does but I dont know how to do the appropriate statistical tests. (BTW, It's not MY data.)

    If so, does it change the outcome for the patients?
    I guess it all depends on what you mean by "outcome".
    Did it reduce the need for surgery? I dont think we can say yes or no on that.
    Did it reduce final curve amplitude? Well, IF the results are significant, then we could say yes.


    Also, regarding the 5 degree error in measuring Cobb angle. It seems to me that as long as this error is constant between the two groups you are comparing it should not make a difference. (if the sample size is large enough). Also, I'd like to know more about this 5 degree number. Is it intrAobserver or interobserver? I have remeasured my daughters xrays and come out with the same number (well, within 1 degree plus minus). I suppose double curves would be more difficult to measure. But, I dont even know what I'm doing and I get the same number. (Perhaps I'm doing it wrong each time. )

    Did patients drop out of follow up because they opted for surgery or no treatment
    another good question. From their paper...

    Eight mature patients out of 298 (2.7%) require surgery after weaning of the brace.

    This is at the 2 year point. They didnt present data for the 5 year point.

  11. #11
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    I'm going to have to buttonhole a friend of mine to explain to me how to properly represent the average about the mean of observations that have a precision of +/-5.

    I don't work with large numbers of averaged observations too much but when I have, I ignore the measurement precision if/when it is very small in relation to the error about the mean. In doing this, I might be part of the problem rather than the solution to the high falaciousness(!) of the literature.

    Nevertheless, I don't know if that is technically correct but it's what I have done. But I would not take that approach with these Coillard et al. data because it seems like the measurement precision is not very small in comparison to the error about the mean.

    The other issue that I learned the hard way is somewhat rarefied... you will get a different answer depending if you:

    1. average the start points and then average the end points and compare those two averages and say the average changed x%

    vice

    2. calculating the change fo each pair of start and end points individually and then averaging those changes.

    I know for a fact that at least working with percentages, the former is incorrect and the latter is correct. I assume it applies to non-percentages also but I don't know that without crunching some test data. I'll try that in a minute.

    The last issue is that there is something NQR about simultaneously saying:

    1. all patients go thru at least one 6 month weaning period,

    and

    2. Showing data from "2 years" wherein supposedly the patients didn't wear a brace at all.

    So if it's 2 years after any brace wear then it is at least 2.5 years after the treatment stopped. The table should be much clearer it seems.

    I also want to see the stats of how many patients required one, two, three, etc. weaning periods.

    I'd also like to hear what Coillard says about whether patients continue to wear the brace if they fail at least one weaning. I suspect some do.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

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    Quote Originally Posted by concerned dad View Post
    I think we had a similar discussion already. Isnt it intuitive that some of the folks haven’t hit the two year or five year mark?
    No. I don't think it is clear that ONLY 298 completed the treatment to date based on the table. Some must have dropped out for various reasons.

    Essentially, working ONLY with the 298 who completed treatment and reached skeletal maturity is data selection. This group could have a much lower average Cobb angle to start with than the folks who dropped out. I'd like to see the distribution of angles in the folks who dropped out (for any reason) vice those in the 298.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

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    Quote Originally Posted by Pooka1 View Post
    The other issue that I learned the hard way is somewhat rarefied... you will get a different answer depending if you:

    1. average the start points and then average the end points and compare those two averages and say the average changed x%

    vice

    2. calculating the change fo each pair of start and end points individually and then averaging those changes.

    I know for a fact that at least working with percentages, the former is incorrect and the latter is correct. I assume it applies to non-percentages also but I don't know that without crunching some test data. I'll try that in a minute.
    Well it seems that doing it both ways returns the same number in my test data. Hmmm.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

  14. #14
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    Some questions.

    If you really want to look at this critically, I have more questions.

    Quote Originally Posted by concerned dad View Post
    Some 583 patients respected the inclusion criteria, 234 (40.1%) did not complete the treatment by brace at the time of the analysis and 51 immature patients required surgical fusion while receiving treatment, leading up to 298 patients who had reached skeletal maturity at the end of bracing. Out of this cohort of patients, 162 patients had 2 years and 69 patients had 5 years follow-up post-bracing.
    What was the inclusion criteria?

    Because you have a large SD. I will assume that most of the patients probably had a curve in the 12-24 degree range to start and a few outliers in the greater than 40 degree range. Are these the ones that opted out for surgery? Did any of them have improvement?

    Anmore interesting number to me is the curve degrees of those that didn't complete the treatment--2 years later or 5 years later. Those might be a pretty good control population--wait and see group.


    Quote Originally Posted by concerned dad View Post
    PNuttro completely excluded consideration of N in his presentation of error bars.
    Actually, the SD is a calculation based on the number of samples in the group. The standard error is based on the average of the distribution. It doesn't account for outliers.


    Finally, what is the take home message here? In your opinion.


    p

  15. #15
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    Quote Originally Posted by PNUTTRO View Post

    Finally, what is the take home message here? In your opinion.
    The Take home message to me is that it is really difficult to discuss a technical paper unless we're able to post the entire paper.

    All your questions and points are good.

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