Prosthetic Leg

Development of a Powered Transfemoral Prosthesis

Despite significant technological advances over the past decade (such as the introduction of microcomputer-modulated damping during swing), commercial transfemoral prostheses remain limited to energetically passive devices. That is, the joints of the prostheses can either store or dissipate energy, but cannot provide any net power over a gait cycle. During level walking, transfemoral amputees expend up to 60% more metabolic energy relative to healthy subjects, and exert as much as three times the affected-side hip power and torque relative to healthy subjects (which also results in significantly increased socket interface forces), presumably due to the lack of power generation at the knee and ankle joints. The inability to deliver joint power also impairs or precludes other locomotive functions, such as walking upstairs and up slopes or ramps.

It is our hypothesis that a prosthesis with actively powered knee and ankle joints will significantly enhance the mobility of these transfemoral amputees, both by diminishing the biomechanical disparity between transfemoral amputees and healthy persons during level walking, and by enabling forms of locomotion, such as ramp and stair climbing, not presently afforded by passive prostheses.

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