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For those of you who have attended my workshops at the last few PFOLA meetings, I wanted to provide close-up photos of one of the wood and rope foot models I constructed (with my son's help) a few years ago to demonstrate the mechanical effects of arch height, of metatarsal ray dorsiflexion stiffness, of differential medial to lateral column stiffness, and of plantar ligament and plantar fascia integrity on longitudinal arch load-deformation patterns.
In this model, the pink nylon cords model the plantar arch ligaments to each metatarsal ray and the blue nylon cords model the digital slips of the central component of the plantar aponeurosis. Each plantar ligament and each slip of the plantar aponeurosis may be individually tensioned to different lengths (using sailboat cleats) to either load the plantar ligaments or plantar fascia more or less, depending on the demonstration desired.
This model very clearly demonstrates the mechanical effect that increased arch height has in increasing the forefoot dorsiflexion stiffness. This is much the same effect as is seen in a cavus foot that will have a increased forefoot dorsiflexion stiffness compared to the planus foot. This mechanical effect is caused by the increased distance between the plantar fascia and the bones at the apex of the longitudinal arch causing less plantar fascia tensile force for a given vertical load on the longitudinal arch of the foot.
This type of model can easily be constructed using similar materials by a student or podiatrist that has basic woodworking skills. Models similar to this should be used by every podiatry school to help teach podiatry students biomechanics and to let them "feel the forces" for themselves. This is a very powerful educational tool for those of you who do teach biomechanics concepts to students!
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Sincerely,
Kevin
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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Very nice Kevin. Where do you find the time to do all that you do??
Funny, I get that same question asked to me at most seminars I lecture at...................
__________________
Sincerely,
Kevin
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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Have you any information on the maximum pronation test - or can you direct me to a paper with this explained?
Regards
Rob
Rob:
I originally described both the maximum pronation test and the supination resistance test in the chapter (see below) I did with Dr. Don Green over 15 years ago for Dr. Steve DeValentine's book on Foot and Ankle Disorders in Children, which is now out of print (Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992).
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Foot Models for Teaching Biomechanics
Linear Mode
