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View Full Version : Re: Dynamics ond kinematics of plantar foot structures



Brian Davis
04-21-1998, 11:48 PM
Regarding Harald Bvhm's posting, one article to look at is "Dynamic function
of medial foot arch" (J. Kayano, 1986, J. Japanese Orthopedic Association,
60, 1147-1156).

This study utilized an "electro arch gage" which basically consisted of two
thin rods connected by a leaf spring. As the rods move towards aeach other,
they increase the curvature of the leaf spring. This defromation is then measured
using a strain gage that is mounted on the leaf spring. In practice, one end of
the distal rod is attached to the skin on the medial side of the first metatarsal head,
and the proximal end of the proximal rod is attached to the skin on the medial
aspect of the calcaneus. (The article gives pictures of the device.)

The author reports that the medial arch stretched rapidly just after heel strike and
became longest at the early period of the foot-flat phase. The degree of change
in the length of the arch ranged from 3.7 mm to 9.5 mm, with the mean value being
6.3 mm.

As a footnote (excuse the pun), some work done in my lab suggests that the
amount of stretch in the plantar aponeurosis profoundly affects the stress distribution
in the plantar fat pad. The reason is that as the aponeurosis is stretched, it becomes
increasingly stiff (in a non-linear manner) and as a consequence the fatty tissue gets
"sandwiched" between the ground and the stiffened plantar aponeurosis. If anyone
has looked into this issue, I would appreciate their comments/insight.

Regards, Brian

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