A team of researchers, noting that at the end of movement to sit down, users of passive prosthetic knees must overcompensate with their upper body, residual hip, and intact leg, and/or sit down with an uncontrolled movement, studied whether powered prostheses would provide more control in that situation. The researchers found that a powered knee-ankle prosthesis significantly improved weight bearing symmetry during sit-down compared to a passive prosthesis. The resulting study concluded that powered prosthetic devices have the potential to improve balance during sit-down and provide insight for future development.
Ten individuals with unilateral transfemoral amputations participated with their prescribed passive prosthesis and a knee-ankle prosthesis provided for the study. Subjects performed three sit-downs with each prosthesis while researchers recorded joint angles, forces, and muscle activity from the intact quadricep muscle. Outcome measures included weight bearing symmetry and muscle effort of the intact quadricep.
The results indicated that the average weight bearing symmetry improved by 42.1 percent when subjects sat down with the powered prosthesis compared to their passive prostheses, and every subject’s weight bearing symmetry improved when using the powered prosthesis. Although the intact quadricep muscle contraction differed in shape, neither the integral nor the peak of the signal was significantly different between conditions.
The open-access study, “Can a powered knee-ankle prosthesis improve weight-bearing symmetry during stand-to-sit transitions in individuals with above-knee amputations?” was published in the Journal of NeuroEngineering and Rehabilitation.
