Kevin,

Please excuse me, as it was 35 years ago that I took physics. Could you
send me to an article, book, web page, or some other source that explains
finite element modelling of the foot and lower extremity. I hope I am the
only one on this list serve that is in the dark.

Also please excuse my lack of physics knowledge, as I worked hard to get my
C. But I remember RXF as torque and the moment as the rotational weight. I
am trying hard to put together what you are saying, and it doesn't seem to
make sense. You say that since there is a very small positional change with
orthotics on the frontal plane, the motion of the joints doesn't matter as
much as the moments that are changed with the orthotics. To change the
moment, you have to change either R, or F. Since the force is constant
(body weight), the only way to change R is by moving the part away from the
axis. Since little or no motion is occurring, then how do we change R?

Craig found there is "no correlation between changes in the pattern of
rearfoot motion and symptom reduction". This confirms that there is no
change in rearfoot motion, so therefore there is no change in R.

Can you explain this contradiction to me?


Respectfully,

Stanley




At 07:09 PM 12/14/04 -0800, you wrote:
>Bruce and Colleagues:
>
>Kevin wrote:
>
><<5.  Scientific studies that only measure the kinematics of gait are
>basically useless in showing the mechanical effects of foot orthoses since
>they do not measure the forces and moments acting across the STJ,
>midtarsal joint, ankle joint and other joints of the foot during
>gait.  Only kinetic studies of the foot and lower extremity and/or finite
>element modelling of the foot and lower extremity will be able to show the
>mechanical and therapeutic effects of foot orthoses.  Many of these
>kinetic studies and finite element modelling studies have already clearly
>shown the mechanical effects of foot orthoses on the human foot.>>
>
>Bruce replied:
>
><<I can't agree with this statement.  I think that it would be more
>correct that say that kinematic studies focusing on calcaneal motion, or
>lack therof, are basically useless.  I think it may be possible to glean
>much more useful information by focusing on other parts or joints in the
>foot and ankle.  Much like Drs. Nester, Cocheba and Ward have done.  I
>certainly don't feel that their research to date has been "basically
>useless".>>
>
>Kevin replies:
>
>Thanks for taking the time to disagree with me, Bruce.  My statement above
>would better reflect my current thoughts on the subject if it read as
>follows:  "Scientific studies that only measure the kinematics of gait in
>live human subjects show little promise in helping us determine the
>mechanical effects of foot orthoses since they only measure motion and do
>not measure the forces and moments acting across the STJ, midtarsal joint,
>ankle joint and other joints of the foot during gait."
>
>For you to suggest that I think the research of Drs. Ward, Nester, Cocheba
>and colleagues is useless is a little bit off base, Bruce.  For one thing,
>their research was on cadaver specimens without foot orthoses being used
>so that their research did not even address the question of foot
>orthoses.  In addition, their research is not a pure kinematics type of
>research since they do have control over the force input into each of the
>muscle tendons during the walking cycle which allows a force quantity to
>be modified.
>
>Because of their ability to control tendon tension input this makes their
>research not purely kinematic since it has a large potential to gather
>useful kinetic data by relating muscle tendon force input to observed
>kinematic patterns.  This type of research on their machine with cadaver
>specimens could certainly be used with cadavers "walking" both with and
>without foot orthoses to determine how foot orthoses may change the
>tensile loading forces in the extrinsic muscles of the foot since they
>would have access to the kinetic function of the muscle tendons in their
>experimental model.
>
>Kinetics and finite element modelling, this is where the "pay dirt" will
>be in understanding how foot orthoses truly do work.
>
>Cheers,
>
>Kevin
>
>****************************************************************************
>Kevin A. Kirby, DPM
>Adjunct Associate Professor
>Department of Applied Biomechanics
>California School of Podiatric Medicine at Samuel Merritt College
>
>Private Practice:
>107 Scripps Drive, Suite 200
>Sacramento, CA  95825  USA
>
>Voice:  (916) 925-8111     Fax:  (916) 925-8136
>****************************************************************************
>
>
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