Walking down slopes and over uneven terrain is problematic for people with unilateral transtibial amputations. Accordingly, prosthetic ankle devices have been added to some dynamic response feet. To this extent, a pair of researchers from the Division of Medical Engineering, School of Engineering, University of Bradford, England, conducted a study to determine whether use of a microprocessor-controlled (MPC) passive-articulating hydraulic ankle-foot device improved the gait biomechanics of ramp descent in comparison to conventional ankle-foot mechanisms.
The study cohort included nine active people with a unilateral transtibial amputation. They repeatedly walked down a 5 degree ramp using a hydraulic ankle-foot with the microprocessor active or inactive or using a comparable foot with a rubber ball-joint (elastic) ankle device. When inactive, the hydraulic unit’s resistances were those deemed to be optimum for level-ground walking, and when active, the plantarflexion and dorsiflexion resistances switched to a ramp-descent mode. Residual limb kinematics, joints moments/powers, and prosthetic foot power absorption/return were compared across ankle types.
Foot-flat was attained fastest with the elastic foot and second fastest with the active hydraulic foot. Prosthetic shank single-support mean rotation velocity and the flexion and negative work done at the residual knee were reduced, and negative work done by the ankle-foot increased when using the active hydraulic compared to the other two ankle types. The study findings suggest that use of an MPC hydraulic ankle-foot will reduce the biomechanical compensations used to walk down slopes.
This study was published December 5 in the journal Clinical Biomechanics (Bristol, Avon, England).