Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

POP casting vs Impression box casting

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Robertisaacs, Aug 29, 2006.

  1. Members do not see these Ads. Sign Up.
    I'm curious

    What are peoples' views on impression box casting? Do people find it to be less accurate than POP neutral suspension casting or does the ability to easily modify the negative make up for the weight bearing complication. Is it a lazy shortcut for people who have a nice carpet in their clinics and don't want it ruined or is it a valid and easy way to do the same job?

    Any thoughts?

    Robert Isaacs
  2. Admin2

    Admin2 Administrator Staff Member

  3. Craig Payne

    Craig Payne Moderator

    I use both...

    The crucial question I ask about any method of negative model production is "can you manipulate the foot segments into the position you want them to be in?". Different methods of negative model production allow you to do different things.

    Some points:
    1. There is NO evidence of any different outcomes of one method being better than another.
    2. There is some evidence (ie McLay et al) on slight differences in shapes between 3 methods of negative model production (plaster cast, foam box and optical scan), but that did not show one method to be "better" than another
    3. We have published two studies and I am aware of a couple of others on casting variability/repeatability. The methods that are weightbearing are more repeatable/ less variable than the non-weightbearing methods (but we have no evidence if that variability is important or not, but could assume it should be).

    There is a lot of passion in the discussion with some being very aggressive in arguing what they do is better, but we simply have no evidence. I have seen people argue that the semi-weight bearing methods (ie foam impression; semi-weightbearing plaster cast; FAS system; Amfit) are better because they compress the soft tissues somewhat. I have seen people argue that the non-weightbearing (ie plaster cast; optical scan) are better because they do not compress the soft tissues :confused: .... I actually have no idea if that is important or not, but love provoking the proponents to see what arguments they use when I ask things like "how do you know its important?"

    It all comes down to personal preference of what position you want the different foot segments to be in and the method that you use allows you to do it.
  4. casting methods


    Thanks for that. I tend to agree that its all about whether you can get the foot in the position YOU want it (rather than the position it falls into or that gravity forces it into) when you cast. I use both techniques but i tend to get better results using the boxes in most cases. Taking a cast with the patient sitting generally allows me to hold the ST / MT joints where i want them and applying downward force on the knee rather than asking the patient to weight bear means there is not so much force that i lose control of the foot.

    My personal and very unscientific view is that when casting some GRF to put the soft tissues somewhat nearer to their weight bearing conformation would allow closer control of the skeletal tissues beneath. Anyone else got a view on this?
  5. Phil Wells

    Phil Wells Active Member

    I have found that using foam box's with flexible feet is usually very difficult to get good results. I think this may be due to different levels of stiffness within the segements of the foot reacting differently to the GRF. i.e. a flexible 1st ray may dorsiflex more than the lesser rays resulting in a inaccurate 'image' of the foot being captured. This may not be a problem if it is then well corrected when making the positive model.

    I am playing with a non-contact digital image capture system at the moment that allows semi to full weight bearing images to be taken. I will hopefully then compare these to foam impressions (I am going to scan the box's and compare both files in a piece of CAD software) done in the same manner to try and ascertain if the GRF from the foam is influential. I have a gut instinct that the cutaneous feedback from the foam causes the foot to react - either positively or negatively.

    I don't tend to use foam in kids as the above factors and many others make it too difficult.

  6. efuller

    efuller MVP

    Hi Robert,

    You can screw both methods up. I like to compare my cast to the shape of the foot in the position that it is casted in. You cannot do that with the foam box. Although, if you don't check your plaster cast versus the foot, then this is not at advantage for plaster. I've seen foam box impressions where the patient stepped down with their heel and then pushed down with their forefoot and created an abnormally high arched cast. You cannot compare this mistake to the foot, but it can be obiously visable upon inspection. The redo sure takes much less time. However, this mistake can be avoided by paying attention as you put the foot into the foam.

    I did a study on fat pad expansion upon weight bearing and found that it was not predictable for individual patients. Therefore I measure the heel width, weightbearing and make sure the orthotic is that wide before dispensing. This means that the lab has to add varying amounts of expansion plaster around the heel to match the width of heel that is asked for. This is a degree of complexity that some may shy from.

    You can add a medial or lateral heel skive and intrinsic or extrinsic wedging to devices made from both casts. I believe this a lot of what makes the orthosis work. So, you don't have to cast in neutral position to get a device that works. I decide what my forefoot to rearfoot relationship in the orhotic should be based on the maximum eversion heigt test. (Standing, ask the patient to evert and estimate the height of the lateral column off of the ground.) No wedge if they cannot lift of the ground 0-5mm the height of the wedge at the 5th met head is the same as in the test. Above 5mm consider shoe internal height. Again this can be done in either type of casting method.


  7. Josh Burns

    Josh Burns Active Member


    Dear All,
    There is some evidence on outcomes between different impression techniques:

    Guldemond NA, Leffers P, Sanders AP, Emmen H, Schaper NC, Walenkamp GHIM. Casting methods and plantar pressure: effects of custom-made foot orthoses on dynamic plantar pressure distribution. Journal of the American Podiatric Medical Association 2006; 96: 9-18.

    Foot orthoses are widely used to treat various foot problems. A literature search revealed no publications on differences in plantar pressure distribution resulting from casting methods for foot orthoses. Four casting methods were used for construction of orthoses. Two foam box techniques were used: accommodative full weightbearing method (A) and functional semiweightbearing method (B). Also, two suspension plaster casting techniques were used: accommodative casting (C) and functional subtalar joint neutral position (Root) method (D). Their effects on contact area, plantar pressure, and walking convenience were evaluated. All orthoses increased the total contact area (mean, 17.4%) compared with shoes without orthoses. Differences in contact areas between orthoses for total plantar surface were statistically significant. Peak pressures for the total plantar surface were lower with orthoses than without orthoses (mean, 22.8%). Among orthoses, only the difference between orthoses A and B was statistically significant. Differences between orthoses for the forefoot were small and not statistically significant. The gait lines of the shoe without an insole and of the accommodative orthoses are more medially located than those of functional orthoses. Walking convenience in the shoe was better rated than that with orthoses. There were no differences in perception of walking convenience between orthoses A, B, and C. Orthosis D had the lowest convenience rating. The four casting methods resulted in differences between orthoses with respect to contact areas and walking convenience but only slight differences in peak pressures.

    There is of course a need to look at health-related, quality of life outcomes between impression techniques.

    Joshua Burns PhD, B App Sc (Pod) Hons
    NHMRC Australian Clinical Research Fellow
    Institute for Neuromuscular Research
    The Children's Hospital at Westmead
  8. Craig Payne

    Craig Payne Moderator

    Josh - you right on that evidence, that there are some differences in the plantar pressure pattern between different methods of negative model production, but which is the the most appropriate change for better clinical outcomes? We just don't know ....(....but we getting closer to getting an understanding of which changes are predictive or better clinical outcomes) ie
  9. Robert:

    I have tinkered with foam box casting many years ago but, like Eric Fuller, have not been impressed with my ability to compare the resulting imprint within the foam box to the plantar foot when using a foam box. For this reason, I have always gone back to what I know best, supine negative casting technique with plaster splints (of which I use many variations).

    I am sure that as long one understands the principles of negative casting, orthosis manufacture, and foot and lower extremity biomechanics, nearly any technique which captures a three-dimensional impression of the plantar foot can be used to make effective and therapeutic custom foot orthoses. I would imagine that one would likely need to modify the positive cast preparation technique and possibly the orthosis materials and construction technique when changing from one casting method to another due to the changes in foot shape that may occur with each impression casting method.

    One must remember that the negative casting technique is only "one of the links of the chain" that allow optimum orthosis manufacture. Here are the other links of the chain that allows optimum orthosis manufacture. It is must be remembered that the chain that produces optimum custom foot orthoses, as a whole, is only as strong as its weakest link.

  10. Thanks all. It seems as always there is a spectrum of opinions with some very sound reasoning on all sides. I think the esteemed Mr Kirby summed it up best with
    "Perform accurate negative casting specific to the intended optimum orthosis design."

    So long as the cast is accurate and specific to the intended orthosis design the rest is probably moot.


  11. PodAus

    PodAus Active Member

    Measure outcomes with each method you employ; consider time & $ involved with each method; add to your preference of practise and patient wow factor = best method for you to use in clinic

  12. EdGlaser

    EdGlaser Active Member

    I like foam for now

    :) I recommend foam casting at this time. Similar to Phil we are researching new mediums both analog and digital.

    When choosing a medium or technology of casting I would ask:
    (for each question, I will give you my reasoning, why I do what I do)

    What position do you want to put the foot in?
    I personally recommend MASS position over neutral. MASS position is simply the maximum amount of arch possible at midstance when the heel and forefoot are in full contact with the supporting surface.
    Is there a frame of reference in the casting technique making repeatability possible?
    There is relatively little for plaster. A difficult proposition to control 26 bones out in space as the plaster is drying. I like Craig’s article Jan. 2003 JAPMA, Variability of Neutral Position Casting of the Foot. Most techniques of using foam also lack frame of reference. This can be achieved in foam however by bottoming out every step of the technique…you will always push them to the floor….never through the floor.

    How meaningful us the final shape of the cast to the final shape of the orthotic?
    Cast correction or modification on a gradient scale divorces the shape of the orthotic from the shape of the foot held in the desired position. A full contact device must be shaped like the bottom of the foot when it is held in the desired position. Shape becomes critical as does repeatability.

    Will manufacturing match casting?
    If the casting technique places the forefoot on the ground while the rearfoot is in some degree of supination, it would make sense to then “read” the rearfoot off of the forefoot.
    Will the lab be able to reliably interpret the data you send them and translate that into a meaningful device? Or Will the lab be able to “trust” your cast?
    How does the lab assure itself that casts it is receiving are cast using the same technique or level of aptitude? We attempt (not always successfully) to train every new provider that is allowed to use our technology.

    Can the cast be QC’d as Eric points out?
    We use the pen test: since a pen us usually a cone shaped object (what we call in the US a BIC Pen), the deeper it is impressed in the foam, the wider the hole. At the end of casting we recommend every cast is stuck with the cone shaped point of the pen in the center of the first, fifth mets and heel. Three equal size holes indicates that these three points are on the same plane.

    Is soft tissue compression desirable?
    I think yes. The shape of the final orthoses, when full contact is desired should be the shape that the foot will assume when plantar pressures are applied evenly over the plantar surface which will necessitate a compression force during casting. Foam applies an even force and is rated often between 1.75 and 2.5 psi.

    Most important however is not medium but technique. I will submit to you our technique here for consideration: right foot
    1. Patient keeps socks on and pulled up to avoid wrinkles. (Socks are not excessively thick unless that is what the patient regularly wears or has a specific use for this orthosis involving these socks). This mimics actual use, smoothes skin lines and reduces the moisture “fissuring the foam”.
    2. Patient is seated on the edge of the chair…knees free to move up and down.
    3. Foot centered in the foam front to back with slightly more room on the lateral side.
    4. Box is positioned so that the knee is comfortably directly over the ankle. Mimics midstance and takes care of sagittal and frontal plane leg position.
    5. A finger is placed on the second metatarsal and the box is rotated in the transverse plane until the finger is visually in line with a “knife hand” bisecting the thigh.
    6. The right hand is placed across the right knee using the fingers on the lateral side of the knee to prevent knee abduction.
    7. The left thumb is then placed under the neck of the first metatarsal and the forefoot is maximally inverted.
    a. This places the rearfoot in supination
    b. Levels the anterior facet and moves the head of the talus onto this facet, preventing sagittal plane rotation around the posterior facet.
    c. Externally rotates the tibia
    8. A vertical shoulder thrust is then applied to the hand on the knee with the right shoulder in contact with the knee. The heel is thus bottomed out.
    9. The tips of all eight fingers are then placed along the lateral side of the foot between the fourth and fifth metatarsal shafts and a vertical pressure is applied to lower the lateral column. For some patients there is still a considerable lateral arch but most patients, the styloid process barely touches bottom.
    10. The tips of the toes are then lowered with the thumbs to release the windlass effect.
    11. The metatarsal heads are then bottomed out completely.
    12. Recheck the lateral and met heads for vertical compression.
    13. Slight trust is applied along the STJ axis to “seat” the heel with the right hand while the left hand applies a vertical force on the head of the first met to prevent rocking back. When pressing on the forefoot there was some rocking so that final thrust seats the heel. Applying force along an axis will usually minimize rotation around that axis because there is no perpendicular distance between force and axis…torque is zero.

    We find that this technique is accurate, repeatable, closed chain, full contact and give us the shape of the foot with soft tissues compressed in the MASS position. This process has gone through an evolution as thousands of practitioners have tried it and shown us new and creative ways to screw it up and although it is still not fully fool-proof we have found the repeatability to be adequate for our purposes. Can it get better…always and I appreciate any recommendations.
    If you like, this technique can also incorporate plaster by placing plaster splints over the foam while performing the steps above and allowing the plaster to dry with the foot in the foam before removing either.
    Casting of the foot is only relevent to the degree that the data gathered in the cast translates into influencing the final shape of the device.

    Ed Glaser, DPM
  13. podstudent

    podstudent Member

    hey everyone

    i like to compare the actual orthotic to the patients foot rather than comparing the negative cast. why? because doesn't really matter what the negative cast looks like, its what the orthotic technician does with it. Remember, what you ask for is not always what you get. The tissue expansion after a inversion of the negative cast is estimated by the technicians eye (most of the time).

    i personally tend to like the foam box, i haven't any problems so far and when checking the orthotics to the patients foot, i do always find it holds the patient in neutral, the shape of the arch is good and the sizing is good. and that is what is important. and if a podiatrist believe he way of casting does the same, the good for them and the patient.

  14. Thats the attraction of the foam for me. You get 75% of the expansion on loading the foot by 25% of the patients mass.

    And if you want to you can press out whatever expansion you need directly into the foam at time of casting. Moves the "cast correction" stage of manufacture back under your control.

  15. Griff

    Griff Moderator

    Does it???
  16. Interesting. Where do these numbers come from, Robert?
  17. Hey Simon

    Vern L. Houston, Gangming Luo, Carl P. Mason, Martin Mussman, Maryanne Garbarini, and Aaron C. Beattie
    Changes in Male Foot Shape and Size with Weightbearing
    J Am Podiatr Med Assoc 2006 96: 330-343.

    Ok, it was 71%. The memory comes and goes. If you want a copy of the full paper i can email it to you.

  18. Thanks Robert. Yes please.
  19. Mark_M

    Mark_M Active Member

    Im not a fan of foam boxes. Mainly due to the lab I use.

    When the lab make a positive mould ,I found the weight of the plaster expanded the impression...resulting in a wider, less conforming orthotic.

    I have used a lab that scans the foam impressions and this gave a good result.
  20. Boots n all

    Boots n all Well-Known Member

    l have never seen or heard that before, by how much are you saying the foam casting expands?

    .........must be heavy plaster:confused:
  21. Mark_M

    Mark_M Active Member

    Sorry, I didnt have my calipers with me at the time to give you an accurate measurement.
  22. Gibby

    Gibby Active Member

    Those foam boxes are not as good as true plaster casts. I have used those boxes, digital scanners (images sent through the internet to a lab), and the traditional plaster casts. The plaster is simply the best. It is messy, labor-intensive, and old-fashioned, but it is the best.
    We had a digital system for a while, and it was a neat toy, and we could make copies of the scans, but the actual orthotics were not as good as doing it the old-fashioned way, with plaster---
  23. Well thats settled then [​IMG]

    In the spirit of the style

    Those old plaster casts are not as good as Foam boxes. I've used both and foam boxes gave much better results. Foam boxes are simply the best.


  24. Gibby

    Gibby Active Member

    It is impossible to capture true neutral position when the person is weight-bearing.
  25. No it isn't.

    Sorry. I'll behave. Lets quit with the staccato non sequiters and get down to the nitty gritty.

    1. Do you beleive that the foot can be repeatably captured in the "true neutral" (cos there is abundant research which shows it can't)

    2. Do you beleive that once captured in the "true neutral" the calc can be accurately bisected to get this position onto an insole? (ditto)

    3. Do you beleive that a foot need be casted in "true neutral" to make effective orthotics?

    4. Why do you not beleive that a position (lets suspend disbelief and call it true neutral) cannot be acheived in a foam box?

    That'll do for starters.

  26. Gibby

    Gibby Active Member

    I think the foam box is fine for accomodative orthoses.
    I assumed we were talking about corrective devices.
    No, true neutral is not possible. Precision is better with an experienced person, but never perfect.
    Bisection is an estimate.
    True neutral is not needed in an accomodative device.
    Foam boxes are good. Plaster casts are better. Since the boxes are cheaper and cleaner, lots of podiatrists use them here. They get good results- better than over-the-counter devices. But for treating the hundreds of diagnoses we see, where STJ neutral and MTJ pronation is sought, plaster is better.
    How much better? Who knows? I get plaster in bulk, very cheap, so I can use it. I suppose it depends on the practitioner's circumstances and training---

    The differences in efficacy may not justify the difference in time and price---

    If you want to discuss further, I'll be back in touch when things are less busy. I am always open to discussion. Maybe there are techniques for casting that are better than the ones I learned in school (Miami) or residency, fellowship (Yale). I will certainly look into it. I also have a bias against those foam boxes they send me. They are made in China. The plaster is from the US and/or Germany...

    Here's an article from ACFAOM (American College of Foot and Ankle Orthopedics and Medicine), THANKS -John


    The following articles report on research completed, in whole or in part, under a grant from ACFAOM. Thanks to all those whose voluntary contributions to ACFAOM's Research Fund make such grants possible.

    Comparing Negative Casting Techniques: Foam versus Plaster of Paris
    Richard Berenter, DPM, FACFAOM

    This study was undertaken to determine whether there was any difference in the clinical outcomes related to the type of negative casting technique utilized in the manufacture of functional foot orthoses. Those practitioners who favor foam casting blocks argue that the technique is cleaner, faster, more cost effective and just as reliable a method to produce functional foot orthoses versus the plaster of Paris technique. On the other hand, a number of practitioners have argued that the foam block technique is inferior because the foam is incapable of capturing the shape of the foot with the subtalar joint in neutral position and the midtarsal joint maximally pronated thereby leading to an inferior foot orthosis, which will be less effective at reducing patient symptoms.

    Materials and Methods:

    A total of 38 patients were enrolled in the study. All of the patients presented with lower extremity symptoms associated with abnormal lower extremity function as determined by gait evaluation. At the time of the initial visit, each patient signed a consent form and completed the top portion of the data sheet which included both personal information and the amount of pain in each extremity (patients were asked to circle the amount of pain on a scale from 0-10 with 0 being no pain and 10 being the worse pain ever felt).

    Upon completion of all paper work, both feet of each patient were casted via the semi-weight bearing foam block technique and by the non-weight bearing supine plaster of Paris method. Both sets of casts were sent to a professional orthotic laboratory with a prescription filled out for an orthotic shell with a medium amount of arch fill, average heel cup depth, normal orthotic width (to the lateral border of the 5th metatarsal and bisection of the 1st metatarsal shaft) and a thickness of polypropylene which would behave in a semi-rigid behavior for the patient's stated weight. A laboratory technician was instructed to randomly select one of the two pairs of negative casts and keep track of which casts were used without the knowledge of the principal investigator. In this way, a double blind study was established since neither the principal investigator nor the patient knew which casts were used to construct the foot orthotics.

    Approximately 2-3 weeks following casting, the patient was dispensed a pair of functional foot orthoses and asked to walk around for a minimum of 10 minutes to gauge the comfort level of the orthotics. Each participant was asked to use one of 4 descriptive terms (very comfortable, comfortable, slightly uncomfortable or very uncomfortable) to describe the comfort level of 5 different regions on each foot orthosis corresponding to the heel region, medial arch, lateral arch, middle of the orthosis and distal edge. Patients were then sent home with standardized break-in instructions for the functional foot orthoses and returned to the clinic at intervals of 2 weeks and 4 weeks post-orthotic dispensal.

    At each follow-up visit, patients were asked to fill out a data sheet gauging the level of symptoms and comfort level of the orthoses. The data was then compiled and saved in a spread sheet format and upon completion of the study, the laboratory technician was contacted in order to identify which patients belonged to which study group, the foam box or plaster of Paris casting technique.

    The data was compiled and the two study groups separated by casting technique. An independent investigator (non-podiatrist) was contacted and asked to analyze the data to answer the following questions:

    1. Does the negative casting technique (foam vs. plaster) make a difference in the ability of the orthotic device to reduce symptoms?

    2. Does the negative casting technique (foam vs. plaster) make a difference in how comfortable the orthotic device feels to the patient?

    The data was analyzed in a variety of methods such as the mean reduction of pain, Fischer exact test and Chi-square with T-tests. A simple comparison of the average reduction of pain after four weeks of orthotic therapy indicates that the plaster of Paris orthoses achieved a mean decrease of 82.43% of pain versus 61.14% reduction in pain with foam box cast orthoses, with a level of significance p< 0.01. However, further analysis of the data demonstrated that casting technique had no statistical difference in the reduction of pain in patients presenting with high levels of pain, but a significant advantage for plaster of Paris orthotics in reducing moderate amounts of pain.

    The difference between the comfort levels of the orthoses from different casting techniques was also extremely interesting. No statistical difference was noted in the comfort level of any of the five regions studied (the heel, medial arch, lateral arch, middle of orthosis and distal edge) at the time the orthotic was dispensed. However, after one month of orthotic wear, the orthoses manufactured from plaster of Paris casts were statistically more comfortable in the medial longitudinal arch and the distal edge regions.

    Another analysis performed on comfort level of the orthotic devices compared improvement of comfort level between the orthoses from the two casting techniques. In this analysis, only the medial longitudinal arch was statistically more improved in the plaster of Paris technique versus the foam box method.

    Final Thoughts:
    The analysis of the data was fascinating in that both casting techniques were able to show some marked reduction in symptoms and reasonably comfortable orthoses. However, there were some statistical advantages of the plaster of Paris orthoses over the foam box devices.
  27. Craig Payne

    Craig Payne Moderator

    I teach and demonstrate all types of negative model production. ...its is easy to get the foot into STJ neutral in weightbearing or foam box casting .
    Neutral is not needed for any type of orthotic. Achieving neutral with a negative model method or getting the foot to neutral with a foot orthotioc has nothing to do with clinical outcomes.
  28. PodAus

    PodAus Active Member

    Couldn't agree more.

    As Kevin's written, it all comes down to ;
    Chain for Optimum Custom Foot Orthosis Production

    1. Properly evaluate patient's structure, functional capacity and gait function.

    2. Perform accurate negative casting specific to the intended optimum orthosis design.

    3. Write specific orthosis prescription in order to design optimum orthoses for patient's symptoms and/or gait pathology.

    4. Make certain that the orthosis lab manufactures the orthosis accurately to prescription.

    5. Fit orthoses to patient's foot to ensure intended conformity of device to plantar foot.

    6. Fit orthoses to patient's shoes to ensure proper orthosis-shoe fit and function.

    7. Examine patient's gait with orthoses in shoes and gather initial subjective information of orthosis comfort from patient.

    8. Perform followup of patient within one month to ensure optimum orthosis fit, function and therapeutic effect.

    9. Perform any orthosis and/or shoe adjustments as necessary to improve orthosis fit, function and therapeutic effect
  29. Boots n all

    Boots n all Well-Known Member

    Gibby said "It is impossible to capture true neutral position when the person is weight-bearing"

    Why cast weight bearing then if it is of concern to you?

    Sorry a little behind l realise
  30. david3679

    david3679 Active Member

    I think this comes down to how the clinician is able to understand the reason behind an orthotic prescription so the chain of events that lead though patient assessment and orthotic prescription and and then production. The medium in which this is captured has little to do with the success of your prescribed device it still comes back to why do you recommend an orthotic for the patient. As long as you have that understanding then your orthotic will work. However Personnel preference is not a matter of better or worse just thats what works for you.

    I have to say that the local NHS department does a lot of foam impression casts and I make a good living from their mistakes but think it still comes down to understanding. Using a foam box and controling the patient is important.

  31. The last does not surprise me dave! Foam box casts need less "cast correction" than pop but less is not the same as none which is what many people try to get away with.

    Since it bears on this debate, what problems do you see? I'm betting lots of excessive lateral arches and over bulky devices?

    Are the devices made in house? Perhaps the problem is that the technician did not know about how to prepare / treat foam positives differently to pop positives.

    Of course if there is a pod there who has been trained in BOTH BIOMECHANICS AND LAB PRODUCTION and who understands both properly that should not happen as he should be able to harmonise both sides of the process. :deadhorse: . If the tech and the pod are not in accord or if the pod is making them with inadequate lab training there will always be problems!

  32. I'm a patient and I want to be "controlled". :dizzy:
  33. david3679

    david3679 Active Member


    I read your reply and almost wet myself laughing:D
    Now if you want to be controlled I think that comes as a lifestyle choice:D
    I have seen numerous practitioners who have produced very poor orthotics from a poor foam box impression and think I comes down to control. How does the practitioner control the leg the foot and the postion during casting

  34. A better question is how does the position you cast the foot in relate to the "control" the orthosis exerts over the foot, if at all? What do we mean by control?
  35. david3679

    david3679 Active Member


    I suppose by controling the foot we are looking at the relavant contours of the foot. if you cast a foot and is not representive to what the patient has at the end of their leg is that going to produce a good orthotic and do we expect that to be successful?
    I have seen numerous insoles poorly designed from allsorts of casting methods and still stand by the thinking the cast must be reprentative of the foot we are trying to help, more than the medium the foot is captured in.

  36. Foot orthoses work by altering the kinetics beneath the foot, thus the only thing we could possibly control are the ground reaction forces at the foot-orthosis interface. However, we do not really know how to "control" these. For example, we think that the addition of rearfoot post will stiffen the medial longitudinal arch section of an orthosis and potentially shift the centre of pressure more medially, but we don't know how to control the amount that this shifts, nor do we have any knowledge of the effects that this or any other of the orthoses prescription variables have of the resultant GRF vectors. In my opinion, "control" is a word used too frequently within podiatric biomechanics when in fact, we have very little "control". In other words, we might be able to give the forces a nudge in the right direction, but we have no real mastery over them.

    So the question you need to answer is how do the contours of an orthosis relate to the GRF they exert? Does this need to "match" the shape of the foot? I doubt it.
  37. david3679

    david3679 Active Member

    Hi Simon
    If we are looking at does the orthotic need to match the contours of the foot to acheive the changes that we require to help the patient I would say No it doesn't.
    Would we acheive the same results using an orthotic that doesn't have the congruence of the foot. then yes we could.
    Would we be able to acheive the same level of comfort for the end user if the device was none representative of the foot.
    From the previous statements the element of "control" was based around casting precedure with different casting mediums and not the patient spiel of having to "control what the foot does" so how best could we describe these precedures without utilising the excessively used control word?

  38. daisyboi

    daisyboi Active Member

    I find both methods equally useful although POP seems to upset my cleaner and since she is a formidable woman, I tend to use foam boxes for most casts. I cant say that I have had better results from either system. Just anecdotal I know but I personally find very little difference. I think Kevin makes a very valid point in that there are so many links in this chain that contribute to the final outcome. I guess its better to make a half decent foam impression cast than a shody POP one (and visa versa obviously), so using what you are personally more comfortable with should result in the best outcome you can achieve for your patient.
  39. mokgatle

    mokgatle Member

    I personally prefer foam impression box. I use semi-weightbearing technique and it usually gives my patient good results, so if your patients are happy it means the technique is useful and clinically plausible. Why not use foam then? since it also doesn't require too-much of tissue expansion/build-up.

    With POP casting: Feet on the air, do we walk off-ground?...No! Plaster bandage can change shape as it takes time to dry-out, soft tissue expansion inadequate as there is no skin tension along the foot. I had several orthotic comebacks due to minor mistakes when technichians try to adjust the positive casts. Remember the costs involved when posting one orthotic three 3-4 times for minor re-adjustment.

    at the end of the day, the foot is not all about the neutral sub-talar joint. Bio-mechanics involves the moments and amount of forces occuring in a limb during gait, the upper body must be considered as well, 1st ray function, especially the 1st MPJ dorsiflexion

    The best technique is you, How well do you do the technique.
    You be the judge
  40. PodAus

    PodAus Active Member

    Considering the cost benefit of foam over pop, particularly with the time saving, then the preference may become clearer for busy practitioners.

Share This Page