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Background: We examined the ability of foot care professionals to consistently capture the forefoot-to-rearfoot angular relationship of a single-cast foot.
Methods: Eleven Canadian certified pedorthists each cast a single foot twice using the plaster of Paris and foam box techniques. Three independent raters subsequently measured the resultant casts. Statistical analysis of the data provided generalizability coefficient estimates (2) of the intracaster, intercaster, and rater reliabilities.
Results: Intracaster reliabilities were excellent when the plaster and foam box techniques were used (2 = 0.831 and 0.939, respectively). The casters were more intrareliable when foam was used (F = 2.755, P = .003). Intercaster reliabilities were poor for both techniques (2 = 0.410 and 0.425). Although, intrarater reliability was excellent (2 = 0.882), interrater reliability was poor (2 = 0.418).
Conclusion: Although plaster of Paris casting is widely perceived by the foot care community as the gold standard, other casting techniques may prove to be equally reliable.
Its now obvious that negative model production methods that have a reference plane (ie the floor) are more repeatable than negative model production methods that do not have a reference plane (ie the traditional NWB plaster casting).
HOWEVER, just because a method is repeatable, does not necessarily make it the correct method ... it could just be reliably repeating the wromg position of the foot with incredible accuracy.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Its now obvious that negative model production methods that have a reference plane (ie the floor) are more repeatable than negative model production methods that do not have a reference plane (ie the traditional NWB plaster casting).
HOWEVER, just because a method is repeatable, does not necessarily make it the correct method ... it could just be reliably repeating the wromg position of the foot with incredible accuracy.
So foam MIGHT be getting right all the time OR might be getting it wrong all the time.
And POP, at least in the subjects who showed less intra tester repeatibility are DEFINATELY getting it wrong SOME of the time.
And possibly the casts we take so lovingly and with such exquisite attention to detail and repeatibility get sent off to a lab where they get "cast corrected" to within an inch of their lives to make them virtually identical to all the others anyway.
A study i'd like to see would be a scan of the anterior surface of a bunch of different lab made shells of feet the same size but different ff/rf relationships, arch heights etc. THAT would be an interesting bit of data!
It appears, having looked at the full text, that all is not what it seems....
From methodology
Quote:
The gait-referenced casting technique, developed by Edward Glaser, DPM (Sole Supports Inc, Lyles, Tennessee), attempts to cast the foot at its uncompensated midstance posture, where the maximal natural arch height is captured with the subtalar joint in its most stable position.
The MASS position is studiously not mentioned however it looks much like if from the description.
Sneaky little ******
So it appears that this study shows only that the Ed glaser school of casting is more repeatible.
So foam MIGHT be getting right all the time OR might be getting it wrong all the time.
Exactly. It not just foam, its the negative model methods that have a reference plane (ie the floor) which could inculde semi-weightbearing plaster cast that are really good at repeatably getting the same position ...that does not mean it the correct position.
We have done a study on both:
Chuter V, Payne CB, Miller K: Variability of neutral position casting. Journal of the American Podiatric Medical Association 93:1-5 2003
Payne C, Chuter V, Oates M, Miller K: Evaluation of a weightbearing neutral position casting device. Australasian Journal of Podiatric Medicine 35(3)65-71 2001
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
It appears, having looked at the full text, that all is not what it seems....
From methodology
The MASS position is studiously not mentioned however it looks much like if from the description.
So it appears that this study shows only that the Ed glaser school of casting is more repeatible.
In fairness to the researchers and Ed, the declaration of this interest is at the end of the paper.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
I agree with Craig here. However, IF the uncompensated forefoot to rearfoot alignment is significant, it cannot be captured using weightbearing techniques.
A note regarding the methodology. For the intra-observer reliability I would have liked to have seen far more repeated trials than just two, better to have fewer "observers" and more repetitions for intra-observer. And for the inter-observer, I would have liked to have seen more observers.
If Figure 1 is at all accurate, I am concerned with the thumb and forearm positioning that was employed during the non-weightbearing plaster of paris casting. This hardly looks like proper neutral suspension technique!
If Figure 1 is at all accurate, I am concerned with the thumb and forearm positioning that was employed during the non-weightbearing plaster of paris casting. This hardly looks like proper neutral suspension technique!
Mac
Chris,
For those who don't get JAPMA can you attach the image please?
The other point here is that in a clinical situation these patients could have been cast by any of the individuals who performed the casting. The rubbish inter-rater performance, suggests that a wide variety of "prescriptions" could have resulted. But the million dollar question is.... would it have made any difference?
For those who don't get JAPMA can you attach the image please?
Ask and ye shall receive Matthew 21:22
Quote:
Figure 1. Plaster of Paris casting technique. The patient is in the prone position. The caster locates and holds the foot in subtalar neutral while lightly loading the fourth and fifth metatarsal heads
"But the million dollar question is.... would it have made any difference?"
In my opinion, it depends on the magnitude of the differences, the method of manufacture and prescribed materials. Certainly when using thermoplastics and composite materials, you have less room for error. The devices will probably not be tolerable and comfort will be compromised.
It appears, having looked at the full text, that all is not what it seems....
From methodology
The MASS position is studiously not mentioned however it looks much like if from the description.
Sneaky little ******
So it appears that this study shows only that the Ed glaser school of casting is more repeatible.
Hmmmmmm.
Regards
Robert
How do papers like this get published in JAPMA where there is a clear conflict of interest with the researchers being consultants for the lab where the technique is used and promoted as the "only correct casting technique". Lucky for these authors that I wasn't the reviewer for this paper.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
The bit which frightens me about this is that there is no mention whatsoever in the abstract that they are comparing casting repeatibility in two different positions. The implication is that we are comparing like with like, that the study shows foam may prove equally reliable as POP.
My bike travels as fast as my car... when my car is in first gear!
If they said they were comparing fully WB in foam and STN in POP we would not consider it a fair comparison. MASS is a position based on finding the end range of joints rather than a point somewhere in the middle. I'm not surprised it was more repeatible.
I know we should not draw conclusions from abstracts but the truth is that there are a large number of podiatrists who don't have access to full texts, or lack the time to read every article they see in full. As such i think a misleading abstract is a very serious issue.
It does'nt exactly shout about the different positions in the full text either.
Which begs the question, even with good casting repeatability/ reliablity using any preferred method, how does it statistically relate to the reliability of achieving a predicted outcome for any individual prescribed orthotic therapy? Particularly without any orthotic modification upon review...
How do papers like this get published in JAPMA where there is a clear conflict of interest with the researchers being consultants for the lab where the technique is used and promoted as the "only correct casting technique". Lucky for these authors that I wasn't the reviewer for this paper.
We see this all the time in drug trials. I do not necessarily have a problem with it, provided that:
1. The conflict is explictly acknowledged (which in this case it was)
2. It is explicit in the methods what was put in place to eliminate the potential for bias (which in this case, not enough information was given for us to make a judgement; eg were the 3 raters who measured the casts 4 times aware of the source of funding and the purpose of the study? Was the employee of the sponsor one of the raters?)
It would be wrong to exclude company supported research by company employees from the literature. it would be worse to disguise it and not be explicit about what was done to eliminate potential biases because of the potential conflict.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The other point here is that in a clinical situation these patients could have been cast by any of the individuals who performed the casting. The rubbish inter-rater performance, suggests that a wide variety of "prescriptions" could have resulted. But the million dollar question is.... would it have made any difference?
Quote:
Originally Posted by Mac
Simon:
To address your previous question, "But the million dollar question is.... would it have made any difference?"
In my opinion, it depends on the magnitude of the differences, the method of manufacture and prescribed materials. Certainly when using thermoplastics and composite materials, you have less room for error. The devices will probably not be tolerable and comfort will be compromised.
Quote:
Originally Posted by PodAus
Which begs the question, even with good casting repeatability/ reliablity using any preferred method, how does it statistically relate to the reliability of achieving a predicted outcome for any individual prescribed orthotic therapy? Particularly without any orthotic modification upon review...
This is worthy of a whole new thread. There is no doubt casting is variable. There is also no doubt that rigid custom made foot orthotic work.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
This is worthy of a whole new thread. There is no doubt casting is variable. There is also no doubt that rigid custom made foot orthotic work.
Simple:
1. Patient would have got better anyway.
2. Placebo/ Hawthorn effects.
3. The orthosis reduced the stresses to within the zone of optimal stress.
4. Foot orthoses aren't precision objects and don't need to be precision objects to achieve 1, 2 or 3.
Reliability of casting techniques
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