Metabolic effects of using a variable impedance prosthetic knee.

A transfemoral amputation has a significant effect on walking. Though current prosthetic knee options serve to restore mobility, as do purely passive devices, they do not fully restore nondisabled gait. Persons with transfemoral amputation incur a higher metabolic cost during walking than persons without amputation and as a result walk slower and for a shorter distance before tiring. An original variable-impedance transmission prosthetic knee (VI Knee) was tested with five study participants with unilateral transfemoral amputation at two steady-state walking speeds, one below and one above their preferred walking speed. While walking with the VI Knee, participants with shorter limbs showed a reduction in metabolic cost compared with their conventional C-Leg prosthesis, while those with longer limbs exhibited an increase. Though differences were observed between speeds, overall, the difference in metabolic cost (reduction or increase) was found to correlate significantly with rise in the center of mass, with those with shorter residual limbs exhibiting less overall lifting of the body during gait.