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Straight last, for whom?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Sep 21, 2012.

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  1. markjohconley

    markjohconley Well-Known Member


    Members do not see these Ads. Sign Up.
    Another class i missed. Had a 60 y/o male patient yesterday whose private podiatrist had prescribed straight lasted footwear (Brooks Beast?). This gent has a unilateral mid-foot collapse from a Tibialis Posterior muscle partial rupture? The midfoot is mobile, I can place it passively into a 'cavoid' shape. I was unable to ascertain the STJ transverse plane 'position' but the patient has no known history of ankle sprains. My query is why should the abducted forefoot be accommodated in a straight lasted shoe rather than an attempt to provide an external supinatory force with a curved lasted shoe?


    Also for the pedorthotists, the difference between a toe box and a toe puff?
    Thankyou, mark
     
  2. David Wedemeyer

    David Wedemeyer Well-Known Member

    Mark,

    When I was providing shoes, I would match the shape of the patients foot to the last. As described above I would not place your patient in a straight lasted shoe. The fit of the shoe is paramount, from there you can work your variables.

    Outsoling and wedges can be placed on the sole outer to achieve the effects you desire. If supination is your goal why not a custom orthosis or both? Just my thoughts.

    The toe box is merely the front area of the shoe that encloses and protects the toes. The puff is a stiffener placed between the sole and the lining.
     
  3. toomoon

    toomoon Well-Known Member

    If you are discussing running shoes, there is no such thing as a straight lasted shoe. Does not exist!
     
  4. David Wedemeyer

    David Wedemeyer Well-Known Member

    "Semi-curved" is the new "straight"!
     
  5. markjohconley

    markjohconley Well-Known Member

    Goodaye Simon, what term should i use for those footwear made on lasts like Brooks Beast were made on, thanks, not going you, am interested in the correct terminology, mark
     
  6. toomoon

    toomoon Well-Known Member

    Not really any such thing as semi curved either!
     
  7. efuller

    efuller MVP

    The last of the shoe will tend to apply forces in the transverse plane, specifically a medial to lateral force on the talar head and lateral to medial force on the fifth metatarsal head. I'm not sure that you can get enough moment from just that location. I could be wrong. I guess any little bit helps.

    Eric
     
  8. toomoon

    toomoon Well-Known Member

    I think we might be getting "last" confused with "lasting".. they are very different. in athletic footwear at least, it is almost inconceivable the "lasting" of the shoe will influence moments...
     
  9. Admin2

    Admin2 Administrator Staff Member

  10. I agree with Bartold. Looking at the plantar aspect of a running shoe and seeing a "straight shape" to the sole because there is more sole under the medial arch and thinking this makes the shoe a "straight last" (e.g. Brooks Beast) and then looking at the plantar aspect of a racing flat and seeing a "curved shape" to the sole because there is less sole material under the medial arch and thinking this makes a "curved last" is simply wrong.

    In shoe making, the "last" is the three-dimensional model around which the upper of the shoe is made. The last is not the three-dimensional shape of the shoe sole. For years, many within the running shoe community have equated shoe sole geometry with "straight", "semi-curved" or "curved" last, which really can be quite independent of the shape of the model around which the upper of the shoe is formed (i.e. the last). The terms should be "straight medial sole geometry", "semi-curved medial sole geometry" and "curved medial sole geometry", not "straight last, "semi-curved last" and "curved last", since the latter terminology is ambiguous, imprecise and confusing.

    In addition, shoe length and shoe width are two dimensional measures of a complex three-dimensional shoe last that has multiple design variables that gives each shoe its three-dimensional internal shape and volume. Therefore, if you think that you will get a proper fit for a three dimensional foot from just measuring the length and width of the foot, without considering the depth of the foot from dorsal to plantar, then you are sorely mistaken.
     
  11. toomoon

    toomoon Well-Known Member

     

  12. Enjoy it while it lasts, mate.;)
     
  13. For those who want to catch up on shoe terminology, here is a nice starter list for you:

     
  14. markjohconley

    markjohconley Well-Known Member

    Thanks Eric and Kevin.
    My question should've been,
    Should this foot be 'accommodated' in footwear with straight medial sole geometry, or should an attempt to impose an external supinatory force on it be used using footwear with semi-curved medial sole geometry (at least); or should i have asked, do uppers have any kinetic effects on feet?, mark
     
  15. markjohconley

    markjohconley Well-Known Member

    Just read Prof Kirby's post in that "Straight/curved last myth or fact?" thread, excellent. So I'm wrong, which i don't mind as long as someone sets me straight. Footwear with a straight medial sole geometry would be indicated for feet that need extra external supinatory forces as then an orthosis with more 'arch' could be accommodated, yes?
     
  16. markjohconley

    markjohconley Well-Known Member

    Would it then be true to say that an upper can't contribute positively to changing forces/moments but it can negatively eg too tight across instep increasing forefoot dorsiflexory moments?
     
  17. markjohconley

    markjohconley Well-Known Member

    In that comprehensive glossary "lasting" was not mentioned. Would lasting be defined as the process by which an upper is attached to the sole?
     
  18. Mark:

    In general, shoes that have the extra sole material under the medial longitudinal arch (e.g. Brooks Beast, see below) will have a sole that resists eversion better than a shoe with a cut-out sole at the medial longitudinal arch (e.g. Brooks Mach 12 racing flat, see below). Unfortunately, having this extra sole material adds significant mass to the shoe but does reduce the tendency for the shoe sole to undergo eversion compression for those feet with pronation related symptoms, all other factors being equal. By the way, the two shoes illustrated below, could have very well have been made over the exact same last (i.e. three-dimensional foot model), but many runners would mistakenly call the Brooks Beast a "straight last" shoe and the Brooks Mach 12 a "curved last" shoe.

    This fact that more medial sole material is better at preventing foot pronation uses similar mechanical concepts as using a medial sole flare on a shoe to resist pronation of the foot. The more surface area of sole contact and the higher the durometer of medial midsole material that is medial to the subtalar joint axis, the better the shoe will be at adding external subtalar joint supination moments to the foot during weightbearing activities.
     
  19. markjohconley

    markjohconley Well-Known Member

    Thanks Kevin. I have been told many a time that I'm not the only one that learns from your (and others) replies to my 'simple' questions. All the best, mark
     
  20. Mark:

    In a shoe with a fairly stiff upper, such as would be present in a leather hiking/work boot, the shape of upper may, by itself, cause an external subtalar joint (STJ) supination moment, especially if the foot has an abnormally three-dimensional morphology such as in a foot with a significantly medially deviated STJ axis. This would be less likely to occur in a shoe/boot with relatively compliant upper material.

    I am attaching one of my illustrations that I use commonly as a slide for my lecture on posterior tibial tendon dysfunction that shows how a medial heel skived foot orthosis and a hiking boot may be used together to synergistically create increased STJ supination moment in the treatment of posterior tibial tendon dysfunction.
     
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