Lower Extremity Review have a recent article from Larry Huppin on Technology: Choosing a digital foot scanner. We have had a number of previous threads on digital scanners, but two comments did jump out at me:
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I think rules are made to be broken. -
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Casting Rule #1: Non-weightbearing casting is the best method to ensure that the first ray will be plantarflexed.
There has not been a study done to see whether this is actually the case. Before I started utilizing a flat bed scanner I changed my technique using plaster. I found a way to plantarflex adn invert the lateral column, instead of DFing or "maximally pronating" it - this had an effect on the medial column where it was usually already sitting maximally plantarflexed.
If that is the case, and I think it is, then there is rarely a need to PF the 1st ray regardless of how we cast.
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Casting Rule #5: The negative cast must capture a perfect representation of the plantar aspect of the foot while the foot is held non-weightbearing in subtalar neutral position.
Says who? This is another one of those things that are passed down with no research to ratify it or not. There are different ways to cast. I am a proponent of capturing a true representation of the plantar aspect of the foot, but STJ neutral is a vague term and non-wt bearing neutral has it's problems as well.
In one of more of the studies I've read, partial weight bearing neutral was the most repeatable of all casts. Non-wt bearing neutral does not mandate that the AJ be at 90 degrees or the need flexed or extended, or say anything about rotation of the hip etc.
I appreciate Larry's take and respect him greatly. I just think it is time for us to explore other opinions and to finally start studying this in more detail.
Bruce -
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And here I am, arguing that the article is right... -cough- I'll shut up now.Last edited: Oct 7, 2009 -
thank you for pointing out the real issue in this discussion, that being, can you emulate a non-weight bearing cast technique in partial WBing or full WBing.
I think you can adn I do so regularly in Partial WBing.
I find it funny that people continuously say that the natural position of the foot is when it is non-wbing. Isn't the "natural position" of the foot when it is in use... from heel contact to toe off?
I see people eliminate the lateral arch in all types of casting in an effort to "lock or maximally pronate" the lateral column. I think this truly throws the baby out with the bathwater. There is more than one way to "lock" the MTJ in casting, and still allow the foot to pronate on the device. The question is does a partial wbing cast allow for a truer position of the foot in midstance than a foot casted nwbing?
I think it does.
Bruce -
I think we're in agreement. Wait 5 minutes and this rat brain may suddenly find a reason to disagree. ;-) With partial weight bearing, dependent on force, I'm assuming the lateral column isn't completely compressed, therefore it is still possible to see the midtarsal joints, at least as a shape. At least then, we have a choice whether or not to flatten it out. A recent development I'm completing now, actually does flatten out the lateral column for valgus post, but it's a choice and a software function, rather than what could be considered a kludge around a weakness in a system. The number 1 complaint labs I work with are bad casts. The chief culprit in terms of casts is UPS/FEDEX, and in particular, biofoam casts. They're cheap, easy and fragile. I've yet to see a consistant casting method that most practitioners use, but there's will be considerably more data to work with soon. -
There are a number of issues here.
Regarding semi-weightbearing versus non-weightbearing scans- the foot can be put into many positions semi-weightbearing and many positions non-weightbearing. The trick is to manipulate the foot into a position that requires a minimal amount of positive model correction to create an efficacious device.
As Bruce points out, the natural position of the foot is dependent upon a multitude of factors, not least: time. Subtalar neutral is only one potential position for the foot to possibly adopt during a given gait cycle. The successful clinician designs an orthosis that will minimise pathological stress on the target tissue without adding pathological stresses to the others.
I don't buy the MTJ locking myth and I don't believe that feet don't pronate and supinate on top of foot orthoses, if that be their will. Unless the device wraps up above the subtalar joint and directly limits the joint motion, I think it highly unlikely that no STJ motion will occur.
Why the interest in midstance? Do foot orthoses only work at this point? Personally, I try to identify the target tissue, i.e. the tissue under-stress and then work-out when during the gait cycle the pathological level of stress is being applied to the tissue and then design a foot orthosis that will reduce this stress at this time.
Foot orthoses are 4-dimensional devices. -
The interest in midstance, as always, is that is when the GRF's, ORF's, body weight, accelerations and gravity will have the most impact on the foot, and vice versa.
I don't disagree with you on any of your other points, but do you ever design an orthotic primarily for any other phase of gait but midstance? I am discounting AFO's functional or fixed for drop foot here as I think you will understand.
Bruce -
As for casting methods, at least in my application, it would be significantly easier to cast neutral than say, MASS post, but I don't spend my days casting patients and haven't been exposed to many casting techniques. I was taught how to use my own scanner by a podiatrist who visited me recently, and his preference seemed to be a gentle touch on the window, semi-weight bearing, neutral, feeling for neutral through the navicular while monitoring the foot for motion during the scan.
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Dazzle us with examples of the orthotics you make for other gait phases please!
Bruce -
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Bruce, it is not my intention here to make anyone out to be dense, it is a shame that you feel that way. Personally, I read and write on this forum in an attempt to learn more and to share my knowledge. In answer to your question, I give as an example any device with a functional forefoot extension. You can also manipulate the morphological characteristics of the rearfoot post or the orthosis shell. My point (that I thought you would understand) was that if, for example, we want to manipulate the Centre of Pressure pathway (you have suggested in one of your papers that changing centre of pressure pathway is a desirable and measurable effect of an efficacious foot orthosis), then this variable is time dependent and as such variations in the orthosis morphology along its length (from heel to toe) is potentially capable of changing the centre of pressure pathway from heel strike to toe-off. -
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I think what you are trying to say above is that in essence a scan or a cast captures an instant in time and that by taking multiple scans in multiple positions we get a better picture of the foot during gait (provided the scans are weightbearing and during gait-right?) Ultimately, technology will allow a 4D model of the foot and lower limb to be captured. In the mean-time...
Consider this:
Lets say we can identify the tissue under stress and the very moment that the stress in that tissue reaches pathological levels with a given activity. Should we capture the foot in this position or in some other position? -
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[Check4SPAM] RE: URL Attempt
non-weight bearing, and or Semi weight Bearing casts have been widely taken in from most legitimate laboratories in North America.
In my opinion we chose the Sharp Shape scanner for use in our laboratory.
The more you discuss WEIGHT BARING casts, the more you legitimize pressure scanners as a means to making custom orthotics.
David
COLLast edited by a moderator: Sep 22, 2016 -
HI everyone , just want to know if anyone has any details on what labs use the sharp shape foot scanner. I have been using this very happily for about 5 years but the lab I used has gone out of business and I am left with a scanner which is standing idle catching dust in the corner of my surgery. or does anyone want to buy my scanner?!!
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That is the problem I have with closed source scanners. What happens if you no longer like the product from the lab or (as in this case), the lab goes out of business?
Would it not make more sense for there to be open source scanners that you can buy from the traditional medical or podiatry supply houses. You scan the foot, then go to a drop down menu and choose which lab to send it to. Does that not make more sense not to be tied to one particular lab with what could be a white elephant? -
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http://meshlab.sourceforge.net/
Joe can probably tell you more as I think he runs a pay per scan type system. -
For reference, there are more client/server sites than listed and until they're ready to go public I'm content to forward leads to them privately. My kiwi client/server site will be publicly listed shortly, and my Aussie Client/Server customer will be visiting first week of November.
The only fees I charge for my product are what they've been for the past 9 years, which are royalties, effectively translating to $0.50/surface. Routing of client data is free, and of key importance, respecting the agreements between both parties, paramount. When a potential customer comes to me for my product, I consider them open to all labs until they settle on a provider. When a lab buys a scanner for one of their customers, I start with the assumption that the new client site has an agreement with that lab and the new client understands that my product is for OreTek only, and that I will not interfere with any agreement between them and their supplier until both parties are amicable to the change.
One point to clarify. My charges do NOT increase because someone has purchased a scanner, and there are NO routing click charges. The royalties I refer to are the same as they've always been, and relate to the number of units sold using OreTek. It costs no more to route data from client to Client/Server, and no charges are assessed for such automation. In rare occasions, clients have preferred to pay their own royalties (Savings for paying early), but most clients never see an invoice from me, other than for hardware.Last edited: Oct 14, 2009 -
Last week, I removed support for anything .raw, simply because it was an unnecessary and troublesome distraction. Piedmont Orthotics is looking for a buyer for his $6500.00 cast scanner and $8000.00 wand digitizer, if anyone is interested. :rolleyes: -
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[Check4SPAM] RE: URL Attempt
We take all Sharp Shape scan files. We are located in Canada; but have the cheapest rates around. We are hopefully not going out of business as we have been established for over 30 years. Our American rates are only about $70.00 US.. and with already having a scanner we could probably do it for less. Check us out at www.canadianorthotics.com
thanks,
David -
Re: [Check4SPAM] RE: URL Attempt
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[Check4SPAM] RE: URL Attempt
Well, There are several sharpe shape systems out there.And we chose the Sharp Shape scanner for use in our laboratory. In my opinion the more you discuss WEIGHT BARING casts, the more you legitimize pressure scanners as a means to making custom orthotics. Anyway nice post.
Thanks a for the information.....keep posting..............
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Re: [Check4SPAM] RE: URL Attempt
Other examples here after I blank out actual patient data.
Loss of usable data.In the last example, it's still possible to intuitively find the cuboid, but much more difficult than in a non-weight bearing scan and much of the "natural" shape of the foot is lost. In discussions with 2 labs, having both types of scans combined is useful in determining fat pad expansion, and will be available in coming versions, but I myself prefer non-weight bearing scans. In non-weight bearing scans, one of my codes has no difficulty in finding the arch from medial to lateral, and plotting a nonlinear curve through the mid-tarsal joints. This method becomes considerably less reliable in semi or full weight bearing scans, but I still have one person doing standing full weight bearing scans. God only knows why. :deadhorse: -
Recently, a customer who insists on using my scanner for weight bearing casting sent me an example of a full weight bearing scan of his foot. As I've written earlier, it's like the inverse of pressure mapped system, providing only usable data in the arch and perimeter regions, everywhere but where contact is made. Personally, I have little confidence in weight bearing scans, and perhaps that is simply because it no longer has much resemblance to a foot. Quantifiably, the greater majority of the input data is actually a solid representation of the window, and not the foot.
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