A research team, noting that modular prosthetic ankle components improve walking in transtibial prosthesis users but can reduce standing stability, evaluated the effects of stiffness of prosthetic foot-ankle components for an ideal middle ground for both conditions. The researchers found that ankle dorsiflexion stiffness influenced balance and gait, and that, overall, firm dorsiflexion stiffness offered the most advantages.
Firm dorsiflexion provided a smaller body sway on standing balance, a roll-over shape radius close to the one of able-bodied individuals, and reduced step length asymmetry while walking. Walking speed also had an influence on roll-over shape, which could lead to study of the effect of walking speed on foot performance to improve prosthetic foot design to maintain the same gait characteristics under different walking speeds.
Ten people with unilateral transtibial amputations who were categorized as at least K3 function participated. Standing balance and gait analyses at three self-selected speeds were performed at three levels of ankle dorsiflexion stiffness (soft, medium, and firm) using the College Park Venture foot. Repeated-measures analyses of variance were performed on standing balance, gait spatiotemporal, and roll-over shape outcomes. Gait kinetic and kinematic data were analyzed using a one-dimension statistical parametric analysis.
“The radius of [roll-over shape] under the firm condition, close to the radius of able-bodied individuals, could have caused the improvement in step length symmetry by a greater progression of the center of pressure, resulting in further progression of the prosthetic side,” the study’s authors wrote.
The study, “The effect of prosthetic ankle dorsiflexion stiffness on standing balance and gait biomechanics in individuals with unilateral transtibial amputation,” was published in the Journal of Prosthetics and Orthotics.