Effect of prosthetic ankle units on roll-over shape characteristics during walking in persons with bilateral transtibial amputations

Some important walking functions are adversely affected or eliminated in prosthesis users because of reduced or absent ankle motion. This retrospective data analysis determined the effect of prosthetic ankle units on the characteristics of the ankle-foot roll-over shape in persons with bilateral transtibial amputations. Seventeen subjects were fitted with Endolite Multiflex Ankles to provide ankle plantar-/dorsiflexion during the stance phase of gait. Quantitative gait analyses were performed as subjects walked with (1) Seattle Lightfoot II feet (baseline condition) and (2) the prosthetic ankle units added. Roll-over shape radii and effective foot length ratio were calculated and compared for the two prosthetic configurations. When subjects walked with the ankle units, ankle motion increased (p < 0.001), peak ankle plantarflexion moment during stance decreased slightly, and ankle-foot roll-over shape radii were significantly decreased (p < 0.001) compared with the baseline condition. The effective foot length ratio of the roll-over shape was found to increase with walking speed (p < 0.001), but it was not significantly affected by the prosthetic ankle units (p = 0.07). Prosthetists and manufacturers are encouraged to consider the effect of combining prosthetic components on the overall characteristics of the prosthesis and the functions they impart to the user.