Monday, February 23, 2009

Prosthetic Foot-Ankle Mechanism

Prosthetic Ankle-Foot Mechanism Capable of Automatic Adaptation to the Walking Surface Journal of Biomechanical Engineering (03/09) Vol. 131, No. 3, Williams, Ryan J.; Hansen, Andrew H.; Gard, Steven A. From ACFAS.

A conceptual design for a prosthetic ankle-foot mechanism with the ability to automatically adapt to the slope of the walking surface has been produced, and a prototype mechanism was designed, developed and tested on three subjects with unilateral transtibial amputations walking on level and ramped surfaces as a proof of concept. The device can automatically adapt to the surface by switching impedance modes at key points of the gait cycle, and it mimics the behavior of the physiologic foot and ankle complex by boasting a low impedance in the early stance phase and then shifting to a higher impedance once foot-flat is reached. The "set-point" at which these impedance changes take place is reset on every step so that proper alignment for the surface can be achieved. The user's bodyweight is tapped by the mechanism to help change impedance modes, and no active control is necessary. It was theorized that the mechanism would cause a shift in the equilibrium point of the ankle moment and the ankle dorsiflexion angle in order to accommodate the walking surface, and this behavior was verified for two of the three test subjects.


Dr. Tina A. Boucher, DPM
Central Connecticut Foot Care, LLC
Podiatrist in Meriden CT
http://www.centralctfootcare.com/
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