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Fatigue testing of arthrodeses plates

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Julien D, Jun 17, 2009.

  1. Julien D

    Julien D Welcome New Poster

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    Hello All,

    I need to detemine the physiological loads occuring in the foot during gait to make sure that arthodeses plates will mechanically resist.

    I am trying to determine the moments about the 1st cuneiform/1st met joint and navicular/1st cuneiform during the most loaded phase of gait (push off..?)

    Maybe this info is already somewhere but I cannot find it. I have studied articles (Jacob, Gefen) but cannot deduce coherent forces from them.

    Even tricker, I need to determine what load to apply on a bone plate for fixing cuboid fractures.

    Any help is greatly appreciated.

  2. Try contacting Prof. Chris Nester: C.J.Nester@salford.ac.uk

    Or Erin Ward, who may have this data, and moreover can test the plates for you using his cadaver walking apparatus- Erin D Ward DPM
    1302 Warford St
    Perry, IA 50220-1622
    (515) 465-4821

    Sorry I don't have an e-mail address for him- someone will add it.
  3. Julien:

    I would be interested in why you want this information. Are you designing a new plate, or are you doing a research project or are you a student writing a paper?

    Bone plates normally don't fail or suffer from fatigue fractures. Typically, the screws will loosen at the bone-screw interface before the plate fails. This is an engineering issue and if you don't have an engineering background, then this may be a difficult task for you to determine without testing your surgical construct on fresh-frozen cadaver specimens.

    In addition, I don't think that testing in the dynamic gait simulator as Dr. Spooner mentioned will work since none of them, to my knowledge, test the cadaver specimens at full physiologic loading conditions. Free body diagram analysis will allow you to estimate moments at the joints of interest fairly accurately, but won't help you with expected motion at the screw-bone, and screw-plate inteface.

    Hope this helps.
  4. Julien D

    Julien D Welcome New Poster

    Simon, Kevin,

    Thank you for your answers.

    I am designing new plates. I agree with you Kevin, plates usually don't fail from fatigue failures but it is a manner for us to characterize their mechanical behaviour. I am trying to determine a meaningful testing protocole using biological loads and not a protocole driven by 3 point bending standards. My goal is to determine what load to apply on the 1st metatarsal head to create a realistic bending moment at the 1st CM joint (then I will have to do the same work for a the nav/1st cuneiform and for the cuboid)

    I do not have any problems working with free body diagrams but I lack entry inputs for my calculations i.e active muscle forces, GRF on met heads, etc).

    Also I have been looking at all your posts concerning the windlass mechanism and I am starting to wonder if a 1st cuneiform/metatarsal plate should be tested in dorsiflexion or plantarflexion...



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