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Wolfs law our inbuilt force plate

Discussion in 'Biomechanics, Sports and Foot orthoses' started by mike weber, Oct 26, 2009.

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    Ive been reading bits and pieces over the last weeks about bending moments of the metatarsals.

    Over this time Ive come to think abouit Wolfs law. . Nice and simple increase load > bone growth. The more the load the thicker the bone.

    But since reading these 3 articles Ive come to the point that we maybe able to use wolf´s law a guide the level and direction of Bending moments over many years. This may make our orthotic prescription better customised. Of course it may only be theorical and have no bearing in the real world.

    Article 1 suggested read by Kevin about bending moments in the metatarsals

    Articel 2 Bending moments in the 2 met and then effect of heel lift and muscle balnce on these moments

    Article 3 Bending moments in long bone ( this is research in sheep and primates) but the maths show that bending moments are not linear.

    From these calculations we maybe able to work backwards and work out where the casue of the bending moment is comming from and design more specific custom orthotic or treatment plan in the case of muscle fatigue.

    thinking too much or something to consider ?
  2. Michael:

    You should also read this recent research article by Erin Ward, DPM, and coworkers where 2nd metatarsal strain was significantly more affected by custom orthoses than semi-custom orthoses during "walking" of cadaver feet in a dynamic gait replicator.
  3. Thanks Kevin. I´m off read that now, but 1st .

    What do you and or others think of the idea of using bone measurments to show what
    10 000´s of foot strikes have had on the foot to work out where the force has come from and using that as 1 of the guides to presription writing?
  4. Michael:

    Bone strain can be modeled using finite element analysis and can be estimated also using such techniques as free body diagrams.

    First, it is a given that all bones undergo deformation (i.e. strain) during weightbearing activities. The longer bones that are more narrow will bend more for a given load than will other bones. Engineering principles tells us that the first metatarsal will bend less with a given plantar metatarsal head load than the second metatarsal would bend with an equivalent plantar load added to the second metatarsal head. This is due to the greater cross-sectional area, or area moment of inertia, of the first metatarsal compared to the second metatarsal.

    Secondly, patients will complain of bone pain or bones will become tender some time before bone fracture occurs in repetitive microtrauma injuries. Cases of repetetive excessive bone strain such as metatarsal stress reactions or medial tibial stress syndrome will cause the bone to become painful or tender to palpation well before a fracture occurs. So, the intelligent clinician, when detecting tenderness along the long bones of the foot and lower extremity, will already know that excessive bone bending may be the cause of this long bone pain.

    One test that I have used over the last decade is that I will commonly palpate deeply on the dorsal aspects of the metatarsal necks in my patients that complain of diffuse forefoot pain to find which metatarsal shaft is most tender. The most tender one is likely the one that will show a stress reaction on the MRI, without needing to spend $1,000 or more on the MRI to start diagnosing and treating the injury, a "pre-stress fracture of the metatarsal".

    When I treat patients, I use my understanding of mechanical modelling techniques for the foot and lower extremity to allow me to be a better clinician so that, if I see pain in a certain location, I can more effectively determine the most likely mechanical cause of the pain. This is the basis of using tissue stress theory to more effectively treat patients with mechanically-related pathologies of the foot and lower extremity.
  5. This one of those ideas I keep coming back to.

    Just came across this ( Yes please IG)

    Three-dimensional micro-level computational study of Wolff's law via trabecular bone remodeling in the human proximal femur using design space topology optimization

    Journal of Biomechancis. Volume 44, Issue 5 , Pages 935-942, 15 March 2011

    Christopher Boyle, Il Yong Kim

    Which fits with this paper - Asymptomatic Tibial Stress Reactions: MRI Detection and Clinical Follow-Up in Distance Runners

    Previously posted Anatomy and injury pictorial essay thread

    Maybe the future will be measure bone work backwards to have the ability to understand where on average the GRF vector comes from design an more specific ORF ??
  6. efuller

    efuller MVP

    So, if you wanted to show, using bone measurements, where the areas of high stress was, I think it could work. You might have to make some assumptions about the starting thickness of the bone to compare with the thickness you see at the time of measurement. However, bone measurements may not be the most simple test. I used to joke that the force plate was $10,000 machine that would tell us where the calluses are. Another favorite place of mine to look is the sock liner of the shoe. If they have been using it regularly for about a month you can get some pretty good information for writing your prescription.

  7. Eric I guess it´s just one of the pie in the sky random ideas you get (I do anyway), the maths looks very complicated to me and as you say a sock liner probably give you similar information .
  8. Griff

    Griff Moderator

  9. Thank you Sir

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