The Effect of Prosthetic Foot Component Stiffness on Initiation and Termination of Transtibial Amputee Gait

Lower limb loss is an increasingly common clinical problem in our society. Along with the loss of limb, amputees must also learn to use their new prosthetic device for their daily activities. The ideal stiffness characteristics of prosthetic feet for different functional activities may vary depending on each activity. Therefore the prescribed foot must be a compromise of multiple ideals out of functional necessity. Quantification of gait and stability characteristics is necessary to provide vital information into the design and prescription of future prosthetics to align with prosthetic users' needs and activity profiles.;The purpose of this study was to determine the effects of varying component stiffness of the prosthetic foot on locomotion and stability measures during gait initiation and termination. It was hypothesized that the leading sound condition would display greater excursions than the leading prosthetic condition for both mediolateral and anteroposterior excursions of the center of mass and center of pressure. It was also hypothesized that there would be differences between compliant and stiff heel components in each excursion measure.;Six male unilateral transtibial amputees participated in this study (41 +/- 13.7 years, 1.82 +/- 0.06 m, and 85.8 +/- 15.5 kg). Subjects completed gait initiation and termination trials while force plates recorded ground reaction forces and motion capture was used to measure body kinematics. Center of mass (COM) and center of pressure (COP) measures were derived from the data gathered. The originally captured data were filtered to obtain a clear signal to noise ratio. Specific gait events from the analysis provided consistent intervals to measure center of mass and center of pressure excursions in the two gait activities studied.;Results indicated that leading with the sound limb during initiation and termination increased the COM excursion in the anteroposterior direction. A lack of significant results in the COP and all M/L directions between leading foot conditions indicates there are multiple strategies to achieve initiation and termination. A reliance on the sound limb agrees with previous studies, and appears to be functionally necessary to transtibial amputee gait. However, prosthetic foot stiffness levels have varied effects and should be taken into account for the design and prescription of future prosthetic feet.