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. 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.

Preparing positive cast to cater for shank of footwear

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Nov 24, 2009.

  1. markjohconley

    markjohconley Well-Known Member


    Members do not see these Ads. Sign Up.
    One of the "elephant(s) in (my) room" is we cast plantigrade foot and yet most footwear (with an elevated 'flat' heel region) is not designed for same.
    And, i know i've asked this one before, but is it ankle plantarflexion or forefoot plantarflexion that occurs?
    Lots of ways to go with this, but how 'bout does the ankle joint position affect the ROM or position of other joints, is it obvious or has there been any research? And if it's forefoot plantarflexion isn't that needed to be considered?

    A simple one, it's been a long time since i made alterations to a positive cast, is how do they nowadays prepare the positive to get that accommodation of the shank shape in?

    Obviously this isn't an "elephant inthe room" in many if any other pod's so I'd appreciate advice to rid me of same, thanks, mark c

    (someone said I'm just keeping my CPD points up, bastard!)
     
  2. markjohconley

    markjohconley Well-Known Member

    I meant ...
    axis position...
     
  3. Hey Mark.

    Nice question!

    Generally speaking I do cast plantergrade. However If I'm going to put the orthotic In a shoe with a substantial heel I will sometimes cast the foot slightly planterflexed. Easy in foam, you just don't push the heel all the way to the bottom of the box.

    Regards
    Robert
     
  4. Boots n all

    Boots n all Well-Known Member

    If you look at a men's or children's shoe last, you will see it is forefoot plantar grade until you get into heel pitch (not heel height)greater than 2cm (for memory).

    Women's shoe last are sometimes given more ankle plantar flextion to accentuate the calf making the ankle look smaller
     
  5. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    The FAS system can cast the foot in a plantar flexed position. Northwest Lab also have an in-shoe casting system that can cast the foot plantarflexed..
     
  6. efuller

    efuller MVP


    Very interesting question. I haven't thought about it for a while either. To rephrase the question: What happens when the foot stands on a surface with a greater curvature than the lateral arch of the foot?

    Yes, the range of motion of the midfoot allows the forefoot to assume a more plantar flexed position relative to the rearfoot, but how does the foot maintain this position? What changes are there in location of forces and muscle activity? These situations arise whenever someone wears high heeled shoes, so this is not a trivial question. Some women patients that I've had prefer this to low heeled shoes.

    Thinking about the forces involved. When the body is standing the force of body weight through the tibia and ground reaction force on the metatarsal heads will dorsiflex the forefoot on the rearfoot until something stops the dorsiflexion. It is usually stopped when the plantar ligaments become tight. When the forefoot is plantar flexed on the reafoot the plantar ligaments wont be tight. So, when on shoes with a high degree of curvature, what keeps the forefoot plantar flexed on the rearfoot? I don't know and it is an interesting research question.

    At one point, when we first got the EMED at CCPM some women students wanted to see the effects of high heels. Of course, most podiatry students don't wear high heels especially to class so most of them were "novice" to using high heeled shoes. Of the 5 students who could bring in high heels, one was a waitress who worked in high heels. The four novice wearers all stood with their weight mostly on the forefoot. The experienced wearer balanced her weight more evenly between forefoot and rearfoot. (I was a little nervous about the high point pressure (From the pointy heel of the shoe) damaging the EMED platform. Seemed to work ok.) Just thought I'd throw that observation out there for those who want to pursue the research project.

    Cheers,
    Eric
     
  7. Laurie Foley

    Laurie Foley Member

    Hi Mark,
    "A simple one, it's been a long time since i made alterations to a positive cast, is how do they nowadays prepare the positive to get that accommodation of the shank shape in?"
    I would look at the OTC orthotic range, Plastosan. These are designed to fit along the shank of a women's shoe. In the past I have used a pair of the appropriate length/width, and pressed them up-side-down into wet plaster to make a negative. This then reflects the shank angle you require (and you have a cast you can reuse !)
    Laurie Foley
     
  8. Petcu Daniel

    Petcu Daniel Well-Known Member

    Hi,

    I think that a negative mold of the plantar surface of the lasts with different heel heights could be useful. With these molds will be possible to check the fit between the orthosis and a general pattern of the plantar surface of a shoe last with a given heel height. I've attached a lateral view and the longitudinal profile [section] of a last.As you can see, there is an "heel angle" formed by horizontal and longitudinal profile which, I suppose, could influence the design of the rearfoot post. This angle differs depending on the heel height !

    Daniel
     

    Attached Files:

Loading...

Share This Page