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jcgonzalez88
10-09-2000, 09:35 PM
Here is a summary of all the answers I got concerning the ankle torque.
The values I made reference in the first message were for the
antero-posterior ankle stiffness when standing, that could be the
reason for the differences in the values of the messages I have
received.

The reference of the paper where I got this information is:
Ankle stiffness of standing humans in response to imperceptible
perturbation: reflex and task-dependent components.
By Richard C. Fitzpatrick et al.
Journal of Physiology (1992), 454, pp.533-547.

Thanks to all answerers


-----Original Message-----

I would like to get information about the torque that appears in
the ankle joint during an inversion / eversion rotation of about 30
degrees (ankle sprain). I just need an approximate value for a
general adult population.

I have found some information about ankle stiffness for the
antero-posterior movement of the ankle. The value of the stiffness is
between 400 and 800 (Nm/rad) for adult men, but I think I can not
extrapolate this data for inversion / eversion rotation of the ankle.


__________________________________________________ _________


J. Marcus Hollis:

We have found in our clinical studies of ankle laxity that you can
easily
get 30 of inversion with a 4 Nm moment without injury or discomfort.
(The device we use actually measures the tibia-calcaneous motion or the
motion of what we call the ANKLE JOINT COMPLEX. This will have greater
mobility in inversion than just the ankle joint)

Of course in all depends on the individual. The ankle stiffness varies
greatly among individuals.

J. Marcus Hollis, Ph.D.

__________________________________________________ _________

Ian Wright:

Regarding ankle joint mechanical properties, check out:

Chen, J., Siegler, S., and Schneck, C.D., 1988, "The three-dimensional
kinematics and flexibility characteristics of the human ankle and
subtalar
joints- Part II: flexibility characteristics, Journal of Biomechanical
Engineering, Vol. 110, pp. 374-385.

__________________________________________________ _________

Karol Galik:

Check the folloowing article:

"I. C. Wright, R.R. Neptune, A.J. van den Bogert, B. M. Nigg: The
influence of foot positioning on ankle sprains: Journal of Biomechanics
33
(2000) pp. 513-519".

Karol Galik
PhD student at ME department
University of Pittsburgh, PA
412 624 9776 Phone
kagst34@imap.pitt.edu


__________________________________________________ _________

Jim Funk:

The question you ask is actually quite complicated. Have you
investigated
the automobile safety literature? Several papers have addressed this
question in one form or another. However, many factors affect the
stiffness of the ankle joint. For one thing, human volunteers have
stiffer ankles than cadavers, even with relaxed muscles. Active muscle
contraction would tend to further stiffen the ankle joint. Also, ankle
stiffness increases when the joint is subjected to dynamic rotation
compared to quasistatic rotation. Axial loading of the leg also
stiffens
the ankle joint in inversion/eversion and may affect the mode of injury.

In addition, the precise definition of inversion-eversion must be
addressed. For example, is the angle defined by the rotation of the
calcaneus relative to the tibia or the forefoot relative to the tibia?
Forefoot rotation relative to the calcaneus can be substantial. Also,
ankle stiffness about the inversion/eversion axis increases when
rotation
about the other axes (dorsiflexion/plantarflexion and internal/external
rotation axes) are constrained.

Various papers have reported that injury (ligament tears or malleolar or

fibula fractures) occurs at greater than 60 degrees inversion/eversion
(Begeman et al., 1993), 30-35 degrees inversion/eversion (Parenteau et
al., 1998), or less than 10 degrees inversion/eversion if injurious
levels
of axial loading are present (Funk et al., 2000). The moment at which
injury occurs has been reported to be 34 Nm in inversion and 48 Nm in
eversion (Parenteau et al., 1998). The stiffness of the ankle joint is
non-linear, and increases at higher rotations. However, the value of
400-800 Nm/rad is quite a bit higher than what is reported in the
literature for untensed volunteers and cadavers subjected to quasistatic

rotation without axial loading (Crandall et al., 1996; Petit et al.,
1996;
Jaffredo et al., 2000). Of course, all of these numbers may vary
depending on the age, mass, and gender of the subject.

Here are the references I used:

Begeman, P., Balakrishnan, P., Levine, R., King, A., Dynamic Human Ankle

Response to Inversion and Eversion, Proc 37th Stapp Car Crash Conf, SAE
933115, pp. 83-93, 1993.

Crandall, J.R., Portier, L., Petit, P., Hall, G.W., Bass, C.R., Klopp,
G.S., Hurwitz, S.R., Pilkey, W.D., Trosseille, X., Tarriere, C., Lassau,

J.-P. Biomechanical Response and Physical Properties of the Leg, Foot,
and Ankle, Proc 40th Stapp Car Crash Conf, SAE paper 962424, pp.
173-192,
1996.

Petit, P., Portier, L., Foret-Bruno, J.-Y., Trosseille, X., Parenteau,
C.,
Coltat, J.-C., Tarriere, C., Lassau, J.-P., Quasistatic Characterization

of the Human Foot-Ankle Joints in a Simulated Tensed State and Updated
Accidentological Data, Proc. Internation Research Conference on the
Biomechanics of Impact (IRCOBI), pp. 363-376, 1996.

Parenteau, C.S., Viano, D.C., Petit, P., "Biomechanical Properties of
Human Cadaveric Ankle-Subtalar Joints in Quasi-static Loading," Journal
of
Biomechanical Engineering, Vol. 120, pp. 105-111, 1998.

Funk, J.R., Tourret, L.J., George, S.E., Crandall, J.R., The Role of
Axial Loading in Malleolar Fractures, Biomechanics Research, SP-1494,
pp.
9-21, Society of Automotive Engineers, SAE paper 2000-01-0155, 2000.

Jaffredo, A.S., Potier, P., Robin, S., Le Coz, J.-Y., Lassau, J.-P.
"Cadaver Lower Limb Dynamic Response in Inversion-Eversion," Proc.
Internation Research Conference on the Biomechanics of Impact (IRCOBI),
Montpelier, France, pp. 183-194, September 2000.

Jim Funk
Research Scientist
Automobile Safety Laboratory
University of Virginia
1011 Linden Ave.
Charlottesville, VA 22902
Phone: (804) 296-7288
Fax: (804) 296-3453

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