Preliminary study of a robotic foot-ankle prosthesis with active alignment

Robotic prosthetic foot-ankle prostheses typically aim to replace the lost joint with revolute joints aimed at replicating normal joint biomechanics. In this paper, a previously developed robotic ankle prosthesis with active alignment is evaluated. It uses a four-bar mechanism to inject positive power into the gait cycle while altering the kinematics of the ankle joint and pylon segment to reduce loading on the residual limb. In a single-subject biomechanics analysis, there was a 10% reduction in peak limb pressures and evidence of greater gait symmetry in ground reaction forces when active alignment was implemented compared to walking with the daily use prosthesis. These results provide preliminary evidence that an alternative lower limb prosthesis may be capable of improving gait characteristics over traditional revolute designs.