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The Effect of 6 Weeks of Custom-molded Foot Orthosis Intervention on Postural Stability in Participants With >/=7 Degrees of Forefoot Varus. Clin J Sport Med. 2006 Jul;16(4):316-322
Quote:
OBJECTIVE: Postural stability (PS) was assessed in a group of participants with >/=7 degrees of forefoot varus (FV) after 6 weeks of custom-molded functional foot orthosis (FO) intervention to investigate the effect of FO intervention in a population that may have decreased PS due to their foot structure.
DESIGN: A force platform was used to assess right and left single-limb stance position and eyes open and eyes closed condition PS.
SETTING: PS was assessed in a biomechanics research laboratory.
PARTICIPANTS: Twelve participants with >/=7 degrees of FV (MFV) and 5 participants with <7 degrees of FV (LFV) participated in the study.
INTERVENTIONS: PS of the MFV group was assessed initially when FOs were received and after 6 weeks of FO intervention. The LFV group PS was assessed during initial and 6-week testing sessions.
MAIN OUTCOME MEASURES: The root mean square of the center of pressure velocity was used to quantify single-limb stance PS during no FO and FO conditions.
RESULTS: LFV group PS did not change significantly (P=0.829) over the 6-week time period. Significant improvement was, however, reported in the MFV group anteroposterior (P=0.003) and mediolateral (P=0.032) PS at the 6-week assessment versus the initial assessment during both the noFO and FO conditions.
CONCLUSIONS: Six weeks of FO intervention may significantly improve PS in participants with >/=7 degrees of FV both when wearing FOs and when not wearing FOs.
I wonder how many years it took them to find that many subjects with forefoot varus? - given how rare it is....
Good point Craig, the incidence of forefoot varus varies widely depending on how you are looking at it and who's doing the looking:
- 8% of 116 female subjects (McPoil et al, 1987)
- 86% of 120 male and female subjects (Garbalosa et al, 1994)
From the full text of this article:
"FV was assessed according to the method established
by Root and modified by Elveru. The measurements
were taken with the participant in a prone position
with the foot held in STJ neutral position by the
examiner."
It looks like they were basing their work in part on two studies that have recently investigated the effect of foot structure on Postural stability:
Cobb SC, Tis LL, Johnson BF, et al. The effect of forefoot varus on
postural stability. J Orthop Sports Phys Ther. 2004;34:79–85.
Hertel J, Gay MR, Denegar CR. Differences in postural control
during single-leg stance among healthy individuals with different
foot types. J Athletic Training. 2002;37:129–132.
Cobb reported significantly decreased anteroposterior
postural stability in participants with >7 degrees of FV
compared with participants with <7 degrees of FV.
Hertel however, did not reveal significant postural stability
between participants classified with pes planus foot
structures compared with those with pes rectus foot
structures.
Regardless of the varus issue, I think there are some interesting findings in this article with regards to FO's and postural stability.
Has anyone else noticed that the FOs used in this study were Sole Supports? :)
Good point Craig, the incidence of forefoot varus varies widely depending on how you are looking at it and who's doing the looking:
- 8% of 116 female subjects (McPoil et al, 1987)
- 86% of 120 male and female subjects (Garbalosa et al, 1994)
Forefoot varus is rare regardless of who is looking. Garbalosa did not load the forefoot in his study ...duh? and McPoil did not exclude forefoot supinatus from theirs.
Its obvious that the above study was not looking at forefoot varus, but the mostly the soft tissue contracture of forefoot supinatus .... very different beasts.... very different orthotic designs needed..., yet the authors chose to make a conclusion about forefoot varus.
Anyone else noticed how the beta error of studies using such low sample sizes is in all probability so high that the probability that the authors came to the wrong conclusion is greater than the probability that they came to the right conclusion?
Anyone else noticed how Ed Glaser has a new salesman on his team?
Perhaps Stu, you could tell us a littel about yourself?
Anyone else feel the need to swear?
Think of me as the Gordon Ramsey of Podiatry, or the big brother of UK Big Brother 2006 winner Pete: "w@nkers" 'nuff said.
Simon, I will let you know when Ed has new Sales People on his team. Right now that is myself and one other. Stu keeps to the research, he is horrible with sales :)
Simon, I will let you know when Ed has new Sales People on his team. Right now that is myself and one other. Stu keeps to the research, he is horrible with sales :)
Thanks, seems he's horrible with academic questions too. Could you let me know when you have a "question answerer" on your team?
Or perhaps since you are posting here you can take that responsibility? Could you tell me the beta error of the study comparing orthoses?
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Right. Same patients, same products, just different objectives? Could you supply as per the snake oil request - reviewers and their comments please?
Mark,
As I was not involved with this study (or the plantar pressures study) as an author, the information you request may be a little bit difficult to come by. I do think the reviewer's comments would be good stuff for this forum though, so I've sent a request to one of the authors to see if this is something I can get my hands on.
I have many questions too. Why the forefoot varus emphasis?
Forefoot varus is rare regardless of who is looking. Garbalosa did not load the forefoot in his study ...duh? and McPoil did not exclude forefoot supinatus from theirs.
Its obvious that the above study was not looking at forefoot varus, but the mostly the soft tissue contracture of forefoot supinatus .... very different beasts.... very different orthotic designs needed..., yet the authors chose to make a conclusion about forefoot varus.
Craig,
I hope I didn't imply that I feel that forefoot varus is common. I would agree that the prevalence is much closer to 5% than 87%. Seems to me that forefoot varus can be grossly over-reported due to a few factors, one of which is the subtalar neutral off weightbearing measurement of the 2:1 inversion/eversion ratios. Garbalosa reported high interrater reliability with these ratio measurements, but from what I understand they didn't erase the bisection marks from measurement to measurement??? Kinda takes the punch out of interrater reliability.
You covered this topic well in the "posting for forefoot varus" thread.
I agree that this study did nothing to differentiate or account for forefoot varus vs. forefoot supinatus. Do you think that this renders all of the conclusions from this study invalid? Meaning, no matter what it's called (forefoot varus, supinatus, rigid or flexible deformity, compensated or uncompensated varus) it’s still a foot. My thoughts are that although the conclusions regarding forefoot varus and postural stability lose some of their luster, one can still conclude that FO intervention improved postural stability over time (albeit only in the study group with greater than 7 degrees of forefoot varus). Studies with more subjects are definitely needed.
I’d love to hear your thoughts on the mechanoreceptor function and adaptation period discussion in this article.
Randomized clinical trial into the impact of rigid foot orthoses on balance parameters in excessively pronated feet.
Rome K, Brown CL.
University of Teesside, School of Health and Social Care, Centre for Rehabilitation Sciences, Middlesbrough, UK. K.Rome@tees.ac.uk
OBJECTIVE: To evaluate the effect of rigid foot orthoses on balance parameters in participants with clinically diagnosed excessively pronated feet. DESIGN: Randomized clinical trial. SETTING: University biomechanics laboratory. PARTICIPANTS: Thirty female and 20 male healthy participants (mean 23.8+/-2.2 years old) with excessively pronated feet, according to a validated foot classification system were randomly assigned to either a control or intervention group. INTERVENTIONS: Balance testing was performed using the Balance Performance Monitor with an over-the-counter rigid foot orthoses. MAIN OUTCOME MEASURES: Standing balance in the form of mean balance (measures the participants ability to stand with an even load), medial-lateral sway and anterior-posterior sway. All participants were measured while standing bipedally. RESULTS: There was no significant mean difference in balance scores between the control and intervention group at baseline. After four weeks the results demonstrated no significant differences between mean% balance (p >0.05) and anterior-posterior sway (p >0.05). However, there was a reduction with the intervention group in medial-lateral sway (p=0.02). CONCLUSION: The use of foot orthoses in the current study may have improved postural control by stabilizing the rear foot and thus maintaining balance. By the same argument, the benefits of limiting excessive foot pronation may contribute to effective control of internal rotation of the tibia and thereby reduce counter-rotatory motion at the knee and lower leg and maintain balance.
I agree that this study did nothing to differentiate or account for forefoot varus vs. forefoot supinatus. Do you think that this renders all of the conclusions from this study invalid?
I think what really renders the conclusions from this study invalid is the lack of statistical power and flaws in the methodology.
I hope you will give me a chance to answer some of your questions before you pass judgment. I do hope to engage in some debate, but I’m not all that interested in bickering.
You had a lot of questions, and I’ll try to answer them as best I can.
Quote:
Forgive me, but it doesn't take years to collect data from 17 subjects- this is less than I would expect from an undergraduate dissertation. BTW, before you start with your: yeh, but, no, but... routine- I know a little bit about research in this field.
Simon, I have no doubt you know quite a bit about research in this field. What I was referring to was the years of data collection that has been done at Georgia State leading up to this article and many others that are to follow. I am hearing from the authors, they have a massive database of kinematic data that describes how the orthotics work in 3D, and it took one year just to set up the points and model the equations for the study.
Quote:
Could you tell me the beta error of the study comparing orthoses?
Hint: Try googling "statistical power"
So let’s talk about the stats a bit here. And if this turns into a “big picture debate”, then maybe it’s more appropriate for a new stat thread unrelated to specific articles. I notice that there may be a similar debate going on in the “plantar fasciitis treatment” thread.
First I should say that I don’t claim to be a superstar statistician, so maybe I’ll learn something along the way.
You ask about the beta error and statistical power. Stat power was over 0.6 for the study comparing orthoses. Not the best, but not the worst I’ve ever seen either. The stats were run by the biostats consultant for the university. There were no questions on power from the reviewers at CJSM.
I understand beta error or type II error to be the chances that you are not rejecting the null hypothesis when the alternative hypothesis is true (whew, that’s a lot of double negatives). The null hypothesis in these two studies being that there is no significant difference between the study groups or that there were no differences in the two orthotics groups.
In other words, this type of error is the chance that you’ll miss the true effect (i.e. declare that there is no significant effect) when it really is there. The rate of false negatives.
So then, if we are discussing the beta error for this study, I think we are saying that there is a 30 something percent chance that there actually was a statistically significant difference between the two groups being measured that may have been missed.
In summary, (when talking about beta error only) aren’t we just saying that with these two studies, there is a decent chance that the findings of statistical significance between the two groups were underestimated? Now I realize we are only talking about beta error here, but otherwise the confidence levels and p values look pretty good for most of the results.
Moving on,
Quote:
..And if they are published in such high quality journals...
Are you saying you do not approve of the Clinical Journal of Sports Medicine, and the Journal of Sports Rehabilitation? I know they’re not the NEJM, but I thought they were pretty rigorous with their peer review.
Which I guess brings up that bigger debate, one that is being covered in another thread. I thoroughly enjoy this forum and all of its threads, and the tendency when discussing issues in academia is to quote articles and research. What standards do we hold the journals to for discussion in this forum? I have read the CONSORT standards posted by Craig and I agree that sample sizes for trials need to be planned carefully, with a balance between clinical and statistical considerations.
I have copied a quote from Kevin Kirby in that thread:
Quote:
I feel that we should not blindly dismiss research just because it doesn't have the statistical power or methodological prowess that other research studies have and then rip to shreds the research that does not live up to "research perfection
"
Simon, please don’t get me wrong. I am not saying that these studies are beyond reproach, the best ever produced, and that they prove beyond all reasonable doubt that postural stability is changed by a foot orthotic. What I am saying is that I think they are decent studies, done in decent journals, by ethical authors in university departments with good reputations and something worth discussing in this forum. I think we all agree that with a bigger study, the power would go up and the type II error would go down and we would have a better study.
Nope that's not me, but I bet that guy is wondering why his website is getting so many hits lately. I'm a DC (chiro) by education with a background and continuing interest in lower extremity biomechanics and a practice in Denver. No formal podiatric training, but I hope that won't preclude me from posting here. :)
Randomized clinical trial into the impact of rigid foot orthoses on balance parameters in excessively pronated feet.
Rome K, Brown CL.
This study is discussed in the Cobb article. I've copied some of the discussion for those that haven't sifted through the full text:
The improvement over time in AP PS in the current study but not in the Rome31 study may be related toseveral factors in addition to the differing statistical designs. First, the length of time between the initial test
and retest differed between the studies. Perhaps improvements in AP PS secondary to FO intervention do not FIGURE 5. Representative scatter plot of ML RMSCOPV versus AP RMSCOPV for the initial PS assessment [subject 2 left foot eyes closed position ()FO condition]. Further study with multiple retest periods would be required to definitively answer this question.
Another factor may be differences in the construction of the FOs used in the 2 studies. The custom-molded FO used in the current study provided all of its support through the MLA. The prefabricated FO used by Rome31 incorporated rear-foot and forefoot posting to control foot function. The support directly under the MLA provided by the custom-molded FO used in the current study, as opposed to indirect control through rear-foot
and forefoot posting, may have provided additional support to the MLA through increased arch structure stiffness. As the center of gravity line traveled anteriorly and posteriorly during single-limb stance, the custommolded FO may have provided greater foot stability. In addition to differences in FO construction, the FOs used in the current study may have provided greater stability because they were custom-molded and fabricated to each participant’s foot. The FOs used by Rome31 were prefabricated and each participant received the same degree of forefoot and rear-foot posting. The unexpected result from the current study was the significant AP and
ML PS improvement over the 6-week period during the ()FO and (+)FO conditions. Unless the FO intervention also resulted in permanent, or at least
transient, change in foot structure over the 6-week time interval, neither of the above mechanisms account for the improvement reported during the ()FO condition.
Right. Same patients, same products, just different objectives? Could you supply as per the snake oil request - reviewers and their comments please?
Hi Mark,
Sorry, I don't think we're going to be able to discuss these. The author doesn't keep these comments on file, and feels it is a breach of reviewer ethics to discuss them, especially when they are addressed in the revisions. I can understand her point of view, considering she is a reviewer herself.
You ask about the beta error and statistical power. Stat power was over 0.6 for the study comparing orthoses. Not the best, but not the worst I’ve ever seen either. The stats were run by the biostats consultant for the university. There were no questions on power from the reviewers at CJSM.
>60% power with 17 subjects now that is impressive, could you show me the calculation, with specific reference to the effect size calculation and the probability of detecting a clinically relevant difference please? Then we can discuss it more.
We seem to be talking about two papers here. From the paper on plantar pressures:
"The results of this study suggest that the effect of custom-molded orthotics on plantar pressure might not be evident until after a period of accommodation and that forefoot- and rear-foot-posted orthotics (PAL) might affect plantar pressures differently than mediolongitudinal-arch-supported orthotics (SOLE). The SOLE orthotic appeared to be more effective in achieving the goals of custom-molded orthotic intervention, which include decreased pressure on the lateral metatarsal heads and increased pressure under the first metatarsal head at toe-off."
Anybody else have problems with this conclusion or is it just me?
If I have a patient with an ulcer sub 1st MTPJ the "SOLE orthotic would be more effective in achieving the goals of custom-molded orthotic intervention" apparently.
Here's an alternative conclusion that could have been drawn:
Patients with pathologies related to excessive pressure beneath the 1st MTPJ should not use SOLE orthotics.
You ask about the beta error and statistical power. Stat power was over 0.6 for the study comparing orthoses. Not the best, but not the worst I’ve ever seen either. The stats were run by the biostats consultant for the university. There were no questions on power from the reviewers at CJSM.
I understand beta error or type II error to be the chances that you are not rejecting the null hypothesis when the alternative hypothesis is true (whew, that’s a lot of double negatives). The null hypothesis in these two studies being that there is no significant difference between the study groups or that there were no differences in the two orthotics groups.
In other words, this type of error is the chance that you’ll miss the true effect (i.e. declare that there is no significant effect) when it really is there. The rate of false negatives.
So then, if we are discussing the beta error for this study, I think we are saying that there is a 30 something percent chance that there actually was a statistically significant difference between the two groups being measured that may have been missed.
In summary, (when talking about beta error only) aren’t we just saying that with these two studies, there is a decent chance that the findings of statistical significance between the two groups were underestimated? Now I realize we are only talking about beta error here, but otherwise the confidence levels and p values look pretty good for most of the results.
Stu, what this really means is that assuming the beta error you report is correct, there is a >30% probability that the conclusion drawn by the authors was wrong. It doesn't take a genius to work out that as we approach 50%, we might as well flip a coin.
Quote:
Originally Posted by StuCurrie
Are you saying you do not approve of the Clinical Journal of Sports Medicine, and the Journal of Sports Rehabilitation? I know they’re not the NEJM, but I thought they were pretty rigorous with their peer review.
As you know, I didn't comment on the Clinical Journal of Sports Medicine, which is index medicus linked. My comment was made with regard to the Journal of Sports Rehabilitation which is not, hence in the schem of things is a weak journal. In my experience peer review can be somewhat of a lottery; depends who is sent the manuscript for review.
The study we conducted in 2004 used a pre-fabricated FO. The reason for the design was based just simple on the most common type of FO manufactured by the UK s company at that time. We were surprised by the results so we have conducted further trials. A paper that is soon to be published in Gait & Posture demonstrates that in 40 older female patients with standardised footwear that flat insoles (control, grid, dimple and plain, n = 10 for each condition). The results demonstrated no significant difference in postural stability and comfort after 4 weeks. We are currently conducting two other studies relating to foot orthoses and postural stability:
1. Evaluating pre-fabricated rigid orthoses with a textured insole in older adults with standardised footwear.
2. Evaluating the muscle activity of different insole materials on postural stability in older adults
please tell me why I can not accept this new research as evidence of the benefit of foot orthoses. Are you saying that what these researchers did was in error or that the researchers were biased or possibly had a hidden agenda? I feel that we should not blindly dismiss research just because it doesn't have the statistical power or methodological prowess that other research studies have and then rip to shreds the research that does not live up to "research perfection".
Nope that's not me, but I bet that guy is wondering why his website is getting so many hits lately. I'm a DC (chiro) by education with a background and continuing interest in lower extremity biomechanics and a practice in Denver. No formal podiatric training, but I hope that won't preclude me from posting here. :)
Stu
Stu:
Welcome to Podiatry Arena, Stu. I have enjoyed your postings so far as you seem to not need to be constantly marketing Sole Supports orthoses as Ed Glaser has done in many of his previous postings to Podiatry Arena. It would be interesting to get more chiropractors in this forum.
Even though I'm sure there are good chiropractors in my area, chiropractors in Northern California don't seem to know much about foot orthoses since all the ones in my area make this device called a "Foot Leveler" which looks like a patchwork of pads and wedges all glued between two pieces of leather to make what they call an orthosis. They are really pretty useless as far as I can see since they don't match the contours of the foot and my patients have told me that they were quite expensive but not helpful.
Why do chiropractors use these "Foot Leveler" devices for foot orthoses? Are you all not trained in proper negative casting technique for foot orthoses in chiropractic college?? What is the theory behind all the bumps and pads on the "Foot Leveler" orthoses?? Are they meant to directly mechanically support the foot or provide CNS stimulation to the sole of the foot???
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
One of the things about this study that I found interesting was the improvement in postural stability after 6 weeks with an orthotic, even when the test was done without the orthotic in the shoe. There was an inmprovement in postural stability after 6 weeks of orthotic wear in BOTH the +FO and -FO test conditions. In the discussion section the authors theorize on the mechanisms of this finding:
Perhaps then, the primary benefit of FO intervention
on PS (postural stability) was related to improved mechanoreceptor
function secondary to the increased contact area between
the FO and the plantar surface of the foot.4,31 If improved
mechanoreceptor function was the mechanism, the results
of the current study would suggest that there is an
adaptation period during which the improvement in
mechanoreceptor function occurs.
I was interested in hearing thoughts on this mechanoreceptor function theory. Maybe KROME could comment on whether he found any similar adaptation period in any of his postural stability studies.
Foot orthotics and postural stability
Linear Mode
