Researchers with the U.S. Department of Veterans Affairs (VA) Minneapolis VA Health Care System have developed an ankle-foot prosthesis that can provide increased balance confidence while standing and swaying in people who use lower-limb prosthetic devices.
Because the natural foot uses a rocker shape for walking, but a flatter shape for standing and swaying, prosthesis users can have impaired balance and reduced balance confidence. This led researchers to test develop and test an ankle-foot prosthesis that has a flatter effective rocker shape with a larger radius for standing and swaying tasks. The prototype was a single-axis prosthetic foot with a lockable ankle for added stability during standing and swaying. The bimodal ankle-foot prosthesis prototype was tested on a “pseudo-prosthesis,” a walking boot with a prosthetic foot beneath it. It was then compared to a single-axis prosthetic foot, as well as to data from able-bodied individuals that was collected in a previous study.
According to the research, the results suggest that the bimodal ankle-foot prosthesis prototype provides a biomimetic effective rocker shape for walking and an inherently stable base for standing and swaying. The radius of the prototype’s rocker shape for standing or swaying suggests that it may provide inherent mechanical stability because the radius is larger than the distance from the body’s center of mass to the floor, which is typically 50-60 percent of height.
The study was published in the July 2013 issue of the Journal of Medical Devices.
