A research team, investigating to what extent a microprocessor-controlled prosthetic foot (MPF) facilitated walking on slopes, concluded that the MPF adapted instantaneously to inclinations and, thus, eased the forward rotation of the leg over the prosthetic foot compared to standard feet with a fixed ankle attachment.
Seven people with unilateral transtibial amputations, seven with unilateral transfemoral amputations, and ten able-bodied subjects participated. Participants with amputations were studied while using a MPF and their prescribed standard feet with fixed ankle attachments. The study investigated ascending and descending a 10 degree slope. Kinematic and kinetic data was recorded with a motion capture system. Biomechanical parameters, in particular leg joint angles, shank orientation, and external joint moments of the prosthetics side were calculated.
Prosthetic feet- and subject group-dependent joint angle and moment characteristics were observed for both situations. The MPF showed a larger and situation-dependent ankle range of motion compared to the standard feet. It remained in a dorsiflexed position during swing, according to the study. While ascending, the MPF adapted the dorsiflexion moment and reduced the knee extension moment. At vertical shank orientation, it reduced the knee extension moment by 26 percent for people with transfemoral amputations and 49 percent for those with transtibial amputations compared to the standard feet.
For descending, differences between feet in the biomechanical knee characteristics were found for the transtibial group, but not for the transfemoral group. At the vertical shank angle during slope descent, subjects with transtibial amputations demonstrated a behavior of the ankle moment similar to able-bodied controls when using the MPF.
The MPF assumed a dorsiflexed ankle angle during swing, enabled a larger ankle range of motion, and reduced the moments acting on the residual knee of individuals with transtibial amputations compared to the prescribed prosthetic standard feet. For individuals with transfemoral amputations, the prosthetic knee joint seems to play a more crucial role for walking on ramps than the foot, the authors concluded.
The open-access study, “Benefits of a microprocessor-controlled prosthetic foot for ascending and descending slopes,” was published in the Journal of NeuroEngineering and Rehabilitation.