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3D technology in the science of orthotics

Discussion in 'Biomechanics, Sports and Foot orthoses' started by annakostrikki, Jun 13, 2016.

  1. annakostrikki

    annakostrikki Welcome New Poster

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    I would appreciate your opinion based on your experience, if any, with 3d technology systems in customizing orthotics.

    Are 3D scanners accurate data collection apparatuses? It certainly looks like its the best way, but is it in real life?

    Is there any evidence that proves the possibility of 3D 'derived' insoles can be more beneficial than prescription orthoses or even pre-fabricated ones??

    What do your patients say??
  2. efuller

    efuller MVP

    Plaster of paris is a 3d technology. If you knew the exact shape of the orthotic that you wanted then you should be able to get that shape with CAD-CAM, or whatever they call it now, or plaster of paris. The hard part is knowing whether or not the shape you want is the best shape for the patient. For some people, the prefabricated shape is the best one. For other people the best shape for the orthotic will need some customization. The wrong customization can make things worse. The right customization can make things a lot better. A good example is the medial heel skive. Again the hard part is knowing what the patient needs. There are many theories on what the patient needs.

  3. Yep, the body doesn't care whether it has a device made via CAD/CAM, via plaster cast and vacuum forming, or via injection moulded pre-fab. If we can deliver the required changes in the external forces acting at the foot-orthosis interface which places the loading on the injured tissue back within it's ZOOS, the body will be happy. I was lecturing at a Biomechanics Summer School this last weekend and made the point: no-one knows what the optimal arch height is of a foot orthosis- basic knowledge that we just don't have.

    Back to the OP, we can have a system which is highly accurate at capturing an image of the foot- yet that is useless if we don't know what position we need to capture that image in, nor how to manufacture the best orthoses to that image.... And that, is the current state of play.
  4. Ian Drakard

    Ian Drakard Active Member

    At the risk of repetition:
    Yes 3D scanners are accurate- but foot positioning can be an issue depending on scanner design.

    No there isn't any evidence and there won't be. A badly designed CADCAM orthoses is just as bad as a bad cast orthoses.

    There is potential for design features possible with milling or printing to be of further benefit over what could be achieved through traditional methods. But to be honest I'm struggling to see these being implemented widely any time soon.
  5. Daniel Bagnall

    Daniel Bagnall Active Member


    The problem I currently see with 3D scanners is the way they are being used. My main issue is to do with the methodology. Depending on the clinical context a podiatrist should be able to achieve the same outcome with a scanner in the same way they would capture the foot morphology when performing a neutral suspension cast. The majority are either positioning the foot incorrectly or resorting to semi or full weight bearing scans for the convenience of taking a 3D scan.
  6. Ian Drakard

    Ian Drakard Active Member

    For clarity I'm not too concerned with a particular casting postion, or for a scanner to exactly capture morphology as in neutral suspension casting (however repeatable that is). I am concerned with the shape/design features of the final device.

    If you are currently happy with how you get from a neutral suspension cast to the end product that's fine. If you move to scanning it's how you achieve an end product that will still have the effect you're after.

    I will scan in various ways, or cast and scan that if it's easier to get the shape I want to start from. Why do I sometimes cast then scan it? Because I can't manipulate the foot the way I want and scan it at the same time. I also take quite a few measures of both foot and footwear to factor in as well. I can't remember when I last took a straight neutral suspension cast.
  7. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Ian,

    Just for clarification, irrespective of position, are you saying you're not concerned if a scanner isn't capturing the exact shape (morphology) of the foot? Shaping is also important to me whether I scan or cast. In terms of shape I believe a scan should capture exactly what I would achieve in a cast.

    The point I'm trying to make is that in principle a scan should be able replicate what you'd capture in a non-weight bearing cast otherwise it's pretty hard to determine a starting point in 3D space unless the scan is partial or full weight bearing. I don?t think resorting to weight bearing scans is the solution for determining a reference point. I was using neutral suspension more as an example. I probably should have said non-weight bearing cast. As you've pointed out, depending on what you're wanting to achieve in terms of prescription variables, not all scanners will allow you to position the foot correctly hence the need to revert back to casting.
    Last edited: Jun 15, 2016
  8. Phil Wells

    Phil Wells Active Member

    I would add that the ideal digital technology is not all about the capture of the foot contours and orthotic design. These are only components of how ground reaction forces, CoP modulation etc are applied.
    I am hoping that the technology will soon be able to tell us about the shoe dimensions - sole unit and inner sole geometry, upper material properties and function etc - dynamically and statically.
    Maybe traditional video capture with clever software interfaces coupled with motion tracking - wish list no 1!

  9. Ian Drakard

    Ian Drakard Active Member

    Hi Daniel

    The scanner should be able to capture whatever it's scanning with reasonable accuracy otherwise it's pretty pointless as a scanner!

    As to what shape is captured I'm more concerned with the final shape of the orthoses as that's what someone will wear for therapeutic effect. I try to capture the foot in whatever position is closest to that to minimise my workload at design stage (or give me the information i need to make design decisions). I'm not entirely clear why you think that can't sometimes be semi weight bearing or weightbearing.

    For arguments sake, if the final device I want bears little resemblance to the original foot (ie significant skive angles, arch fill etc), what information are you actually using from the scan/cast?

    By starting point in 3d space I'm not sure what you mean?
  10. Didn't I say that at Summer School 3 years ago? :cool: Scans nor casts actually treat patients; foot orthoses do. As long as you deliver the "right" design variables in your devices then everyone is happy.
  11. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Ian,

    Thanks for clarifying.

    I'm saying that scanners can be and are often used in a way which compromises the shape the clinician is trying to capture for optimal therapeutic effect (often for the sake of convenience) compared to NWB casting.

    Based on my own clinical experience and outcomes when considering a functional orthoses my preference has always been NWB casting. Depending on the type of scanner one is using I don't think it's always possible to capture the shaping you would otherwise be able to capture in a cast. In all the functional orthoses you've prescribed how many full weight bearing or semi weight bearing casts have you taken?

    Most scanners output STL file format. If you're capturing a NWB scan how do you determine how you've aligned the foot in free space in order to ascertain a starting point when it comes to modelling?

    Aside from treatment outcomes, for ethical reasons, I think a true custom bespoke device should resemble the shape of the foot as well as taking into consideration prescription variables. Casts or scans might not be treating the foot but they still currently form the basis for orthotic design which I believe still makes this process important.

    Last edited: Jun 16, 2016
  12. efuller

    efuller MVP

    Hi Daniel,

    In this discussion, you may have missed someones point because you have a different definition of functional orthotic. I've made many functional devices, out of plastizote, for insensate feet, off of semi weight bearing casts. Are you trying to make a distinction between functional and accommodative? I've added varus heel wedges to some of those EVA devices.

    Are you worrying about forefoot to rearfoot relationship when you ask how to align the cast in free space? You don't necessarily need to have a reference point of a scan. You can decide that you want a 4mm intrinsic forefoot valgus post and you can decide that you want to have your heel cup look like it has a 2mm medial heel skive. You can make the device, with those design features without having a reference point.

    I agree that finished orthotic should look somewhat like the foot when you are done. However, your design variables can make the device look different from how the foot looks. If you know what you want your piece of plastic to look like you can get that shape even if start with a block of polypropylene. As was mentioned earlier, if you get the shape of the "cast" closer to what you want the finished product to be there will probably be less work getting the shape that you want.

  13. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Eric,

    Thanks for your comments.

    Correct. I guess it does come down to how one views or defines functional. My interpretation might be different to yours but I'm of the opinion that semi or full weight bearing capture would be more appropriate for accommodative devices.
    I partially understand what you're saying but how do you ascertain where to start that measurement from if you were to ask for a 4mm intrinsic forefoot valgus post? You can't plot any reference points onto an STL file such as a heel bisection? This can be transferred across onto a cast but not necessarily in a 3D scan.

  14. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi again Eric,

    I thought I should clarify some of my answers.

    No not the cast. I?m referring to a NWB scan of a foot and how one ascertains a reference point from an STL file in CAD. If you do not have a reference point then a lab is simply guessing the starting point at their discretion.

    How do you derive that measurement? Are you referring to maximum eversion height test? I think we are talking about two different things here. A weight bearing measurement such as this would help me determine a prescription variable but would not necessarily correlate to calibrating NWB 3D scan. I guess this could work if you thought it was necessary to scan the foot in this position (as you assess it) which doesn?t seem logical to me.

  15. markjohconley

    markjohconley Well-Known Member

    goodaye Ian I haven't casted for ~20 years. Can't see the point. Just have the lab add (or delete) the desired design variables into an orthosis whose shape relative to the insole of the footwear is based on that insole (i send a template of the insole to the lab with a prescription for the modifications) so you actually get an orthosis which doesn't have to be radically modified (reduced) to fit the footwear; have never sent a pedgraph? tracing of a bare foot, pointless as the foot's shape alters when shod, mark
  16. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Mark,

    Is capturing the shape of a shoe innersole your standard methodology for fabricating a functional custom orthotic?

    Do you take into consideration foot geometry or do you prescribe an orthotic that's line of best fit?

  17. If I have a scan of a foot in my CAD I can simply insert a reference plane which contacts the centre of the first MTPJ and the centre of the 5th MTPJ, from here I can insert another reference plane angled at the desired number of degrees and "extrude" a forefoot balance of desired thickness and/ or angulation between the planes, very much like one would do with a plaster cast... No other references required. But, if someone were to say "balance to neutral" I wouldn't have clue... but then I'm not really sure why someone would ask to "balance to neutral" in the first place. Rather, I would specify a forefoot wedge angle which requires nothing more than the insertion of a couple of reference planes within the CAD software. Which CAD software are you using Daniel?

    For the record, "functional" versus "accommodative" orthoses, is outmoded, out-dated terminology that is meaningless and we are well past the time and beyond the knowledge base in which we should even be talking, nevermind thinking in these terms. Please avoid such ridiculous terminology- it's crap. if you don't understand why, please put your hand up and I should be happy to explain this to you.
  18. efuller

    efuller MVP

    When you place an orthotic with it's anterior edge on a flat surface and look at it from behind you can get an idea of what kind of wedge effect, if any, there is in the heel cup of the orthosis. So, that measurement is from the anterior edge of the orthosis.

    When you look at the sagittal view of the scan along the plantar surface of the lateral foot there is the shape of the lateral arch. If you add an intrinsic forefoot valgus post that shape is altered and the height of the orthotic's arch is higher than foot's lateral arch. The few times that I've ordered cad cam devices, asking for an intrinsic forefoot valgus post, I've been concerned that I have not been getting it. This is a software problem. If your cast manipulation software can't create this shape then you can't get an intrinsic forefoot valgus post. This is true even if you have a heel bisection and have a forefoot valgus scan. It all depends on how the software makes the heel bisection vertical. Do you know how your software does that?

    You will notice that I said a 4mm intrinsic forefoot valgus post and not a 4 degree intrinsic forefoot. If you use the degree measurement you need a heel bisection. If you use the height measurement, you do not need a heel bisection.

  19. Disagree. You simply put a reference plane in across the 1st and 5th met heads then another reference plane angled from this at the number of degrees you require. I think problems arise when people are using CAD systems specifically designed to make foot orthoses, versus CAD systems upon which you could design a space-ship if you wished. I'm currently working on a space-ship upon mine...

    The problem is that a lot of the CAD users don't have enough experience of plaster modification. Personaly, I follow the same old process that I did with a plaster cast. So, once I've "extruded" my forefoot balance in the scan, I then run splines from this, proximally along the cast. Manipulating the splines curvature then allows me to loft a surface onto these- hence I can create a shape of superior surface to the orthoses that one would expect with a plaster cast modification.

    I honestly believe that the CAD systems that people are using to make foot orthoses result in ease of knocking out foot orthoses; unfortunately these CAD systems were not developed by people who have experience in manufacturing foot orthoses. Therein lies the problem. Buy a proper CAD system, rather than an "orthoses" CAD system. Phil Wells will agree.
  20. Ian Drakard

    Ian Drakard Active Member

    Yep. I also remember having a conversation about it along similar lines circa 2011, which means you'd probably already got to that point way before that. Now 2016. Do you feel like you're :deadhorse: ;)
  21. efuller

    efuller MVP

    How familiar are you with the Root protocol for making orthotics? Do you understand how nails were placed in the cast and this changed the shape of the finished orthotic. I think we are talking about the same thing, but we approach it from a different perspective. The Root protocol would take a negative cast and put a heel bisection on it. If the cast had a forefoot valgus the nail would be placed in the fifth met head to move the heel bisection to vertical. That is how the decision is made to make the othotic have an intrinsic forefoot valgus post. I make that decision using the maximum eversion height measurement. So, this weight bearing measurement, for me, has great bearing on what I want the orthotic to look like.

    What does not seem logical to me is deciding to treat a forefoot to rearfoot relationship in a NWB neutral position cast. The vast majority of feet don't stand in neutral position. As the STJ changes position the forefoot to rearfoot changes position. So the stance forefoot to rearfoot relationship is not what is seen in the neutral position relationship. It does come down to what you believe about how an orthotic works. If you believe the "deformity" is supported then it doesn't make sense to use the neutral position forefoot to rearfoot relationship.
  22. efuller

    efuller MVP

    You are correct.
  23. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Simon,

    In your explanation I?m making the assumption you?re working with an STL file. Is that correct? Are you saying that your method above calibrates the scan based on the frontal plane position (whatever position you thought was appropriate to achieve optimal patient outcomes) before you start designing, thus aligning the foot to how you captured it in free space? Or is your measurement simply based on the amount of force you think is necessary based on an arbitrary starting point at your discretion?

    I am certainly by no means an expert when it comes to CAD but I certainly think there is knowledge gap amongst podiatrists when it comes to CAD. Through time I?ve observed that a lot of digital labs now days are promoting bad methodology (lab discretion being one of them) and are more profit driven. They are not doing the profession any good and in my opinion are deskilling podiatrists.

    As a result, I have reverted to modeling and manufacturing my own devices. It?s certainly been a steep learning curve but I?m enjoying learning a new skillset. The software suite I am using is called Lasercam. Obviously there is no software out there that is the ultimately the ?best? but I have found this system to be the most ethical and practical in terms of the methodology, being open architecture, and from a design perspective. I am definitely achieving better clinical outcomes with my patients now that I am in control.

    Agree. For ease of the discussion and to answer Eric I was trying to differentiate what I was specifically referring to. I understand the correct definition of an orthosis but I actually think the word custom orthotic is a very broad in itself. I think that as a profession we need to perhaps consider calling a true custom orthosis something that is more unique and specific to the podiatric profession.

  24. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Simon,

    In your explanation I?m making the assumption you?re working with an STL file. Is that correct? Are you saying that your method above calibrates the scan based on the frontal plane position (whatever position you thought was appropriate to achieve optimal patient outcomes) before you start designing, thus aligning the foot to how you captured it in free space? Or is your measurement simply based on the amount of force you think is necessary based on an arbitrary starting point at your discretion?

    I am certainly by no means an expert when it comes to CAD but I certainly think there is knowledge gap amongst podiatrists when it comes to CAD. Through time I?ve observed that a lot of digital labs now days are promoting bad methodology (lab discretion being one of them) and are more profit driven. They are not doing the profession any good and in my opinion are deskilling podiatrists.

    As a result, I have reverted to modeling and manufacturing my own devices. It?s certainly been a steep learning curve but I?m enjoying learning a new skillset. The software suite I am using is called Lasercam. Obviously there is no software out there that is the ultimately the ?best? but I have found this system to be the most ethical and practical in terms of the methodology, being open architecture, and from a design perspective. I am definitely achieving better clinical outcomes with my patients now that I am in control.

    Agree. For ease of the discussion and to answer Eric I was trying to differentiate what I was specifically referring to. I understand the correct definition of an orthosis but I actually think the word custom orthotic is a very broad in itself. I think that as a profession we need to perhaps consider calling a true custom orthosis something that is more unique and specific to the podiatric profession.

  25. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Eric,

    Yes I think we do agree somewhat. I understand Root protocol and understand your rationale for using maximum eversion height test. I wouldn?t say I design an orthotic strictly based on Root philosophy. I design an orthotic based on what I think will deliver the best treatment outcomes for my patients.

    For arguments sake I am specifically referring to NWB 3D scans. There needs to be an agreement between the clinician and lab as to the position you are scanning the foot in otherwise the lab is guessing (sadly a lot labs do that). In terms of methodology at least with Root protocol there were objective reference points used to align the cast not that I am saying those reference points were/are reliable or relate to outcomes but their was at least some sort of consensus between the clinician and lab. This simple concept seems to be overlooked or is deliberately dismissed by a lot of digital labs. There will never be an absolute or 100% reliable method, however, arbitrary alignment is not a sound methodology.

  26. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi again Simon,

    When it comes to the specific shape you want to capture (which can be anything you like) in terms of deriving a forefoot angle are you still using the perpendicular bisection in the heel as a reference plane? If you're capturing a NWB 3D scan I assume you are then scanning the foot with the heel bisection perpendicular to the actual scanner so that you have a reference plane in CAD if you aren't transferring any reference points or measurements from the foot across onto the 3D image? When I say forefoot angle I'm meaning purely in the context of the position you capturing the foot in at the time you take the scan. I'm not referring to this measurement or implying that this is used as a prescription variable to achieve an outcome. I am speaking in terms of calibrating the scan in CAD. I also don't necessarily favour neutral suspension casting as an absolute position the foot needs to be captured in but my preference would be NWB as I believe I am able to capture a better shape when it comes to orthotic design.

  27. markjohconley

    markjohconley Well-Known Member

    Goodaye Daniel, the shape and size of the sock lining / insole only determines the transverse plane shape and size of the of the orthosis; it is not a design variable as such; i use it to get a accurate size / shape to fit into the footwear (of the insole) as the foot within that insole's footwear is definitely different shape to that same foot unshod

    not really, I don't consider arch height as that important, far rather fit a orthosis with a lower height for a foot than attempt to replicate (which of course doesn't really happen); unfortunately the orthotic manufacturer i have used doesn't cater for all desirable design variables so I can add before fitting; still takes far less time, for me, to process; always remember an orthotic technician (from casts) telling me just how much fiddling to the cast occurs; i imagine 'photoshopping' the scans also occurs, pleased to be corrected

    What i've said re. casting and the longitudinal arches doesn't apply to total contact orthoses for pressure deflection of ulcerated feet; also can add to the inferior surface to alter the ORF.

    I have to repeat I think we're kidding ourselves if we think an unshod foot replica, whether cast or scan, is a replication of what happens to that foot in the footwear, all the best, mark
  28. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Mark,

    If a lab is balancing a cast/scan and is not requesting the podiatrist to draw heel bisections and/or provide frontal plane measurements they are guessing. So yeah there does seem to be quite a bit of fiddling. This seems to be very common these days particularly with digital labs.

    I?m not sure I understand you. Why wouldn't you consider arch height important when it is a prescription variable in it's own right?

    I totally agree and I think is complete nonsense. Casting or scan position does not correlate to foot position. I hope I haven't given you that impression.

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  30. markjohconley

    markjohconley Well-Known Member

    Daniel, I'm only a very minor player in this game .... can follow everyone's posts except Messrs S. Spooner, always have to re-read several times, and D. Smith, the same when any physics is involved.
    I haven't bisected or measured since I left the course, 28 years ago; was Root trained and couldn't fathom 'exact' measurements. I still eyeball, pt prone, and note, and consider.
    Medial Longitudinal Arch, again I note and consider but rarely, apart from the TCO's, attempt full contact (opposite extreme to whatshisname?); use a deep 1st ray cutout a lot.
    I am certainly open to change my ideas, have been wrong many a time in my life on all subjects.

    all the best, mark
  31. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Mark,

    Thanks for your response. I'm certainly not having a go at you either.

    I'm definitely not implying we should treat heel bisections or forefoot to rear foot relationship. The irony is that if you're not taking those measurements then the lab will be when aligning a scan or cast. Sure, you might be able knock out a decent orthotic and achieve outcomes but this isn't my argument. The issue I have is with the methodology and is opening the door for pre-fab systems to take over. IMO, this is not the way we should be going forward as a profession.

    I totally get that it's all about figuring out the right prescription variables. People seem to forget that when it comes to the design process, ultimately prescription variables must begin at a starting point whether that happens in CAD or in a traditional sense. If the scan of a foot or cast is aligned (balanced) based on lab discretion then this could adversely affect the outcome of your chosen prescription variables which can be the difference between a good or bad custom orthosis.

    The impression a lot of digital labs give off these days is that it's all plug and play. You basically take a scan of the foot and leave the rest up to the lab. To get around discretion labs will often ask the podiatrist to take a full weight bearing or semi weight bearing scan i.e. capturing a compensated foot - not for the sake of better outcomes but purely for their convenience so they have a reference. Good luck trying to figure out the shape of a heel, forefoot, skive angles and placement etc...?? Some labs even have the audacity to pre-populate prescriptions based on pathology or even say you can't have that prescription variable because their line of best fit software doesn't support that. This is dumbing down the profession.

  32. markjohconley

    markjohconley Well-Known Member

    thanks Daniel, a tad worrying, I'll have to stew on this a bit, Mark
  33. LeonW

    LeonW Active Member

    Advantages of using 3-D camera to capture shape of feet compared to using plaster.
    1. Clean (plaster makes a mess)
    2. Fast ( a few minutes rather than involved plaster process)
    3. Efficient ( Can email the images and prescription) With plaster you need to post which is expensive and moulds can warp in transit.

    There is some discussion as to the accuracy of the 3-D system however the above i find to be true.
  34. mr t

    mr t Member

    Hello everyone,

    Good posting so far it has been an interesting read... I just wanted to add my two cents.

    I am going to assume that most of us would agree that a suspension plaster cast is arguably the best way to capture foot data and that capturing a non-weight bearing scan with the right 3D scanner in the right environmental conditions can capture foot data with acceptable levels of accuracy.

    From what I can gather those of us involved on this thread have a clear understanding that if you design an orthotic from a weight bearing scan using a CAD program then the CAD program is doing a lot of work. It is relying heavily on prescription variables that even experienced clinicians can have trouble prescribing to a high degree of confidence. As an example, some of this high degree of work in CAD could be picking an arbitrary arch height from clinical observation and then correlating this to your CAD model. If a CAD model is based on reference from a foot scan in a non-weight bearing vs. weight bearing position, then the degree of topographic correlation would most certainly be lower with a weight bearing scan. What I am observing happening in the industry is that podiatrists are capturing 3D scans from weight bearing positions and not giving considered thought to prescription variables, but instead allowing for laboratories using CAD programs to use generic functions to make orthoses.

    In a lab environment if a podiatrist is sending a weight-bearing scan then there is more subjectivity in lab work in a CAD environment. I am not saying that orthotics produced this way can?t give good clinical results, I am more concerned about the lack of specificity to a patient?s foot and the merit in making a custom orthotic from a 3D scan to begin with. Perhaps you would be better off saving a patient money and prescribing a modified prefabricated orthotic.

    If you capture a 3D scan using a non-weight bearing scanner, then it is the responsibility of the clinician seeing the patient to inform the laboratory as to the specified alignment of the 3D scan in CAD. Without a measurement reference of forefoot to rearfoot relationship then the CAD will no longer be based around the topography of the 3D scan as the positioning of the 3D scan becomes more arbitrary.
    Using a reference plane across the 1st/heel (valgus relationship) or 5th/heel (varus relationship) is an example of a methodology of correlating clinical measurement to CAD. I am not saying that this should be to a ?neutral? position or anything of the sort, I am just trying to highlight the importance of clinic -> laboratory correlation in measurement.

    The reason that this is so important is that a very low percentage of podiatrists are doing their own CAD, and a much larger percentage of podiatrists are capturing 3D data within clinics. There is importance in correlating clinical measurement with initial starting position in a CAD environment. It may seem intuitive to some on this thread that use CAD programs often, but it is not intuitive to the profession at large. I strongly believe that the starting position of a non-weight bearing scan in CAD is of incredible importance to the orthotic manufacturing process as I believe a high degree of topographic correlation is important to the clinical outcomes of the orthoses.

    I believe that a point that Jeff Root raised on this forum is very valid as to how surface topography effects functionality of orthoses and how weight bearing techniques can lead to less than ideal outcomes.

    ?If we use a semi-weightbearing or full WB cast or scan which via compensatory action has allowed ground reaction force to dorsiflex the 1st ray or the medial column, then the resulting orthosis won?t support the forefoot with the medial column plantarflexed relative to the lateral column. So, an intrinsically corrected orthotic shell that is made to capture the medial column plantarflexed relative to the lateral column (ie captures the everted ff to rf relationship) will encourage the windlass mechanism. Conversely, if weight bearing forces are allowed to dorsiflex the medial forefoot during casting, then the shell shape will not act to promote relative plantarflexion of the 1st ray. Therefore, I believe intrinsically posting an everted forefoot angle will do much to improve the mechanical efficiency of the windlass mechanism.?

    It can be argued that orthotic models can be produced in CAD to compensate for the change in contours of weight bearing methodology, but it makes logical sense to begin a manufacturing process from a non-weight bearing scan so that subjectivity in CAD is limited.

    As Simon stated in this thread, ?no-one knows what the optimal arch height is of a foot orthosis- basic knowledge that we just don't have.? [/I]While this is true, would it not be reasonable to say that if we have captured data from a point that more closely resembles the final product, while simultaneously aligning the foot in a position that gives rise to an arch height that can easily be adjusted for in degrees, distance or percentage, then would it not be easier to quantify small changes required and come to a quicker understanding is what is needed for particular patients? If we are using variables based of an arbitrary 3D model created with less reference to the initial foot, then would it not be harder to quantify particular areas of the orthotic that require changes in order to achieve optimal clinical outcomes on a patient by patient basis. Would it not be in the best interest of practitioners to try and more accurately rationalize small changes to prescription variables in a more repeatable way?

    I would just like to highlight some of the ways that I attempt to increase repeatability and confidence in CADCAM technology as I think it is valid to the initial question.
    When we ask for 3D scans we ask for three measurements that help determine positioning in CAD. The first is rearfoot to forefoot relationship which helps us to align a scan in CAD. We use VRML2.0 format scans that allow the clinician to mark key areas on the foot for alignment as they have a photographic overlay. This alignment in the lab is therefore repeatable and well understood between the clinic and the lab. The second measurement is the distance between the posterior aspect of the heel and the lowest point of the heel. By measuring this distance, we can align the scan with the appropriate amount of translation in the sagittal plane. Foot scans can be flared slightly at the heel due to the limitation of 3D scanners, therefore ascertaining what is the most posterior point of the calcaneus on a scan is difficult. By taking a measurement we can eliminate this variable and achieve proper sagittal plane translation. The third measurement we ask for is simply a length measurement between the 1st MPJ and the heel centre. Because we use VRML2.0 file format this serves as a calibration tool while giving us a measure if we need to ascertain 1st MPJ centre during manufacture.

    I wanted to highlight the measurements that are taken to try and show how important I believe it is in manufacture to capture proper measurement data for repeatability. If an orthotic requires slight modification, it is easier to quantify changes if the initial alignment is well understood.

    If we start our orthotic design from a non-weight bearing position, then it is easier to deliver these design variables with a higher degree of confidence as the resultant foot orthotic will have a closer anatomical resemblance to the initial foot. Now, remember I am not saying in any way that a foot orthotic can?t be made from a solid square of polypropylene with good clinical outcomes, however making a foot orthotic from a solid block of polypropylene poses two main issues. The first issue is that the individual grinding the block of polypropylene needs a considerable amount of skill. The second issue is that the individual grinding the block of polypropylene will find it more difficult to achieve repeatability in the final product.

    So my apologies for the long winded response and back to the original question? is there benefit to using CADCAM technology? If done poorly then no it is dangerous and regressive for the industry. If done properly with proper control and consensus by the podiatry community, then it will benefit the industry and patients immensely. As a lab that?s been CNC for 20 years and some 220,000 pairs of orthotics we see so many different techniques, but without too much self-promoting the overwhelming consensus is that non-weight bearing scanning methodology produces better results and measurement is vitally important.
  35. daveeardley

    daveeardley Member

    Hi all,
    In this thread when people are referring to 3d scans, I am assuming they are referring to the flat bed type scanner that have been historically popular. I appreciate the difficulties in either manipulating the foot to the desired position in a NWB scan, or the shape flattening problems of full or partial weight bearing scans.
    I have been using for some years now two different types of hand held scanners.
    These are the cubify sense hand held scanner ( which can be had for less than ?400) and the Artec EVA 3D ( which is more like ?10,000). We have done some in house accuracy testing, including on the fuel 3d, which I don't propose to reproduce here, but we certainly found some models to give accurate, consistent results..
    The technique I use is to have the patient prone on the couch with their feet hanging over the end. I then loop resistance bands around their toes and onto the underside of the chairs foot rest. This way I can very the position of the foot by selecting which toes I loop over. I can also vary the force by tightening the resistance band. This is sometimes a little awkward as the band can slip off. But generally this way I can apply appropriate force to get the foot in the position I wish, then scan away with the hand held.

    The hand-helds do however, pick up quite a lot of extra information, such as the foot rest etc. This requires extra time to post process, but a technician does this. Time spent doing this myself would negate the time saving and mess saving of digital casting. Time best spent based considering the prescription,treatment plan, exercises and stretching.

    No solution is perfect, but this is working for me at this time. Hope this helps.

    Regards David
  36. scottma

    scottma Member

    CAD/CAM technology has been employed in dentistry for more than 3decades. At this moment, accuracy is clinically acceptable , however, limited to hard tissue. If soft tissue is involved , scanner image is not acceptable. Foot morphology has much dimensional variability, you need to determine one particular position , and foot orthosis is fabricated based on that particular foot shape. The important issue is soft ware, different company can make difference.
    Scott ma, dds
  37. efuller

    efuller MVP

    When I do a bio eval, I will have the patient stand and I will apply a mild upward pressure into the arch of the foot and then measure the distance from the top of my finger to the floor and ask for this height in the positive cast and expect that height in the finished orthotic. The problem of arbitrary arch height is the same for CAD as it is for plaster. You could call some of those plaster casts generic, or arbitrary, or non custom, if the prescription did not include a requested arch height. This is not a new problem.

    If the prefabricated device has the arch height that you would request, and the other variables that you plan on asking for, then yes the prefabricated device would be the same and a lot less expensive. However, if you can quantify the exact difference in shape that you want, you can make the argument that the custom one would be better. You can also make that arch height request regardless of "casting position".

    Simon correctly pointed out how you could incorporate an intrinsic forefoot valgus post into a CAD CAM orthosis without knowing forefoot to rearfoot. All he needed to know was the angle that he wanted the post to be different from plantar surface of the cast. The practitioner still needs to ask the lab to make the heel cup shape how the practitioner wants it in relation to the posted forefoot. The lab also needs to understand what is being asked. I agree the clinic to lab correlation is important.

    A weight bearing cast can give you many of the parameters that you need if you know what some others should be. If you know what heel cup shape you want, the amount of forefoot valgus intrinsic post you want, and the arch height you want, then you can apply those to the weight bearing shape of the foot.

    I learned to make my positive cast changes to neutral position casts. However, I could learn to make those changes to fully weight bearing casts, given a little time to experiment. It's just a matter of what your experience is. If you know what you want your orthotic to look like, you can make the orthotic from a weight bearing cast.

  38. mr t

    mr t Member

    Hello Eric,

    You raise some good points. Allow me to elaborate on some of my previous comments to clear some things up.

    Just a question, if you were to undertake a test where you apply pressure to the medial arch on a patient in a weight bearing position could you correlate this to the medial arch height of an orthosis created if a non-weight bearing 3D scan is aligned with a specified forefoot angle? If you think about the proposition of a defined frontal plane giving rise to an easily calculated arch height, then it isn?t too difficult. Essentially your clinical test is a way of ensuring repeatability between clinic and lab, and the methods that I utilize are similar. An example of alignment at a 9 degree forefoot position is seen below.


    I agree that arch height can be arbitrary in CAD, but if using good methodology this is not the case. If you align according to a well understood clinical measure in the frontal plane the arch height of a CAD model will be dependent on the anatomy of the 3D scan. This height can be quantified very easily and then reduced by a specified number of degrees/millimeters/percentage if needed. I am not saying that this arch height is necessarily going to be the 'perfect' height, however it is definitely now based on a patient?s 3D foot scan and changes can easily be made in CAD. It would also not only be the arch height specifically that is now based on the scan but all contours. This is where a weight bearing scan would be inadequate as there is a much higher degree of subjectivity in CAD.

    In the image below is a non-weight bearing scan of my foot superimposed onto what will be the machined orthotic negative. I have raised the scan by 2mm so that everyone can clearly see the topographic correlation at the foot ? orthotic interface.


    A podiatrist took this scan from a non-weight bearing position which would resemble a neutral suspension cast. The forefoot alignment measurement was a 9 degree varus/inverted forefoot position. By aligning the forefoot to this angle the entire orthotic geometry is then specific to the prescribed foot position. If I draw a line to the maximum arch height I can clearly see that the height can be measured based on the anatomy of the 3D scan of my foot. In this particular program I use percentage/millimeter/degree changes to modify the requested arch height of the orthotic. This is based on changes to the initial orthotic model that is based on the foot topography.

    Below is an image of a weight bearing scan of my foot. I am happy with the orthotic contours of the previously shown orthotic negative, therefore I have shown this side by side with the machined negative (lower image).


    Now, I am not saying that a podiatrist is not capable of using skill in a CAD package to make a clinically effective orthotic from this scan, but I am definitely saying it is more subjective. You can see by the relative difference in the anatomy of the two images how much subjectivity is required in a weight-bearing scan to achieve the same end product. I do understand that some individuals see prescription variables of a prefab CAD system to be able to have the same clinical efficacy as the custom example that I have shown and I don?t expect to be able to change this opinion, nor do I disagree with this entirely. Experience has simply shown me that the methodology of using NWB foot data with measurement produces orthotics with better clinical outcomes. I?ve had many, many podiatrists go from NWB -> WB scanners due to their relative ease of use and lack of required clinical measurement, but not one single podiatrist has continued with this methodology and among the 300 podiatrists that use my laboratory none of them utilize WB scanning methodology.

    From what I understand (and please correct me if I am wrong), Mr. Spooner uses a reference plane along the forefoot to create a platform in much the same way one would modify a traditional plaster cast. So in essence, using a clinical measure which is either measured using an instrument, or ascertained from his clinical experience to post his forefoot in CAD which would cause a relative change in the frontal plane positioning of his rearfoot. I have done similar things using generic CAD programs like PowerShape and this is a valid and repeatable way of achieving a frontal plane position that can be adjusted if needed. The frontal plane alignment would therefore alter the height and angulation of various regions of the foot orthotic if spline curves are drawn from this forefoot platform. The forefoot plane being angulated at say a 4-degree valgus would cause a relative eversion of the entire foot and hence cause a heel bisection (if drawn) to evert 4 degrees. This measurement is a good way to provide correlation between clinic -> CAD. I take issue when a non-weight bearing scan is taken with no reference or a weight bearing scan is taken in order to avoid the need for a reference measurement due to a lack of clinical understanding or laziness.

    I agree that you can technically get the intended clinical outcomes from a weight bearing scan, but I believe weight bearing scans should be reserved to other sectors such as the pedorthic market where weight bearing foot data is actually extremely vital in a CAD environment so that anthropometric data can be used to properly manufacture custom footwear. It?s simply not as well suited to custom foot orthoses than non-weight bearing.

    I believe the heel shape and arch shape should be a reflection of the foot anatomy taking into consideration areas of +/- expansion similar to the examples that have been shown in the images above. Much in the same way a traditional plaster modification technique applies minimal to no fill in the medial heel section, however this well-defined foot geometry is not present in weight bearing techniques leading to an increase in subjectivity in CAD.

    I don?t doubt that you could do this with a certain degree of experience, but I believe there is more subjectivity in the process which in my view is regressive methodology and simply doesn?t make sense if our ambition is to improve our industry and ensure that the services that we provide are to a higher level than a prefab machine in the shopping mall.

    The final image I wanted to show is something that I thought people here might find interesting. It might be a little messy to view but I think it?s something worth seeing.

    I?ve written a program that will output a 3D comparison file between two objects. It will allow you to add/subtract 3D meshes from one another to ascertain geometrical changes in 3D scans. If you look at the image below it shows the relative difference between a non-weight bearing and a weight bearing scan of the same foot. As you can clearly see there are wide ranging differences between the two files and not just in the arch, but across the entire surface of the orthotic. The amount of surface contact at the foot orthotic interface is sure to have impacts on tissue stress and resultant clinical outcomes. I will reiterate again that I believe starting from a point of manufacturing that more closely resembles foot anatomy is more repeatable and enables a clinician to more easily quantify prescription variables and necessary changes to the orthotic surface.

    Last edited: Jun 22, 2016
  39. Phil Wells

    Phil Wells Active Member


    I think we may be trying to fit a round peg to fit a square hole!
    What most CAD orthotic software has failed to do is to create a new methodology that links the end result - the orthotic - and the input method - the image of the foot - to gives us the ORF we need for the individual. Instead they have tried to make a software interface that mimics the traditional manufacturing methods -losing all of the potential benefits of CAD.
    Trying to apply Root style forefoot/rearfoot measures is not the way to go as we are trying to get the software to work to our way of thinking instead of trying something else.
    For example, scanning technology will allow us to scan the foot fully weight bearing, semi weight bearing and 'corrected' non-weight bearing. The 3 images can then be over laid to show the differences between the extremes and come up with a design that applies the forces we deem clinical appropriate. From a reference perspective the use of a couple of lines on the foot and the use of colour .obj or 2.0 VRML will suffice.
    The design process can use all of the current 'prescriptions' available from a Blakes to an intrinsic forefoot post with all of them effecting the surface contour, the ORF with the shoe and the material characteristics.

    The problem is that the learning curve is very steep but from personal experience well worth it.

  40. efuller

    efuller MVP

    The reason that I take the medial arch height measurement is that I find it does not correlate well with height of the arch of the neutral suspension cast. That is in some feet the standing arch height is close to the neutral position arch height and in others there is a large difference. This goes to the concept of arch fill. Different people different amounts of medial expansion "fill" or plaster added to the original positive cast to make an orthotic.

    I'm not sure what you are asking by alligned with a specific forefoot angle and arch height of the cast. An intrinsic forefoot valgus post will change the arch height on the lateral side of the cast, but not the medial side of the cast. I want to be able to control, independently, the medial and lateral arch height.

    As I control medial and lateral arch height, I also control heel cup shape relative to the anterior edge of the orthotic. I assume you are familiar with the medial heel skive and how it alters the shape of the heel cup.

    I rarely make an intrinsic forefoot varus post. An intrinsic forefoot varus post only raises the medial arch height. Then fill needs to be added to make the device comfortable. If there is a large amount of forefoot varus in my cast, I will get the heel cup of the orthosis to appear inverted by using a medial heel skive, or my version which is to add expansion plaster on the plantar lateral aspect of the heel.

    Why do you think there are better outcomes with NWB casting. NWB casts will tend to have higher arches. This is often negated by adding medial expansion plaster (arch fill)

    When you use medial, or lateral, heel skives a forefoot correction does not necessarily have to "change" the orientation of the heel cup. You can take a 5 degree forefoot varus cast, add an intrinsic forefoot valgus post and then add a medial heel skive and get a "vertical" heel cup. When I speak of knowing what you want your orthotic to look like is what I'm talking about. We are not confined to the forefoot to rearfoot relationship of the cast.

    I believe the shape of the arch of the orthotic should be such that it applies a small amount of force to the medial arch when there is no muscular activity. There is a too much, and a too little, arch pressure from the orthotic. In my experience, the shape of a cast from a semi weight bearing foam box is quite close to the neutral suspension cast when you look at the area around the medial calcaneal tubercle.

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