The effects of prosthetic ankle stiffness on stability of gait in people with trans-tibial amputation

Abstract

The ability to control balance during walking is a critical precondition for minimizing fall risk, but is compromised in persons with lower-limb loss due to reduced sensory feedback mechanisms and inability to actively modulate prosthesis mechanical function. Consequently, these individuals are at increased fall risk as compared to their able-bodied counterparts. A number of gait parameters, including symmetry and temporal variability in step/stride characteristics have been used as estimates of gait stability and fall risk. This study performed an investigation into prosthetic ankle rotational stiffness effects on gait parameters related to walking stability of trans-tibial prosthesis users. Five men walked with an experimental prosthesis that allowed for independent modulation of plantarflexion and dorsiflexion stiffness. Two levels of plantarflexion and dorsiflexion stiffness were tested during level, uphill, and downhill walking. The results demonstrate that low plantarflexion stiffness reduced time to foot-flat, and this was associated with increased perceived stability, while low dorsiflexion stiffness demonstrated trends in temporal-spatial parameters that are associated with improved gait stability (reduced variability and asymmetry). Prosthesis design and prescription for low rotational stiffness may enhance gait safety for trans-tibial prosthesis users at risk of unsteadiness and falls