Metabolic effects of using a variable impedance prosthetic knee

Area of Science:

• Biomechanics
• Prosthetics
• Gait Analysis

Background:

• Transfemoral amputation significantly alters walking mechanics and increases metabolic cost.
• Current prosthetic knees do not fully replicate natural gait, leading to reduced endurance.

Purpose of the Study:

• To evaluate the metabolic cost and gait characteristics of a novel variable-impedance prosthetic knee (VI Knee) in individuals with transfemoral amputation.
• To compare the VI Knee's performance against a conventional prosthetic knee (C-Leg).

Main Methods:

• Five participants with unilateral transfemoral amputation walked at two speeds (below and above preferred) using the VI Knee and a C-Leg prosthesis.
• Metabolic cost and changes in the center of mass were measured.

Main Results:

• Participants with shorter residual limbs experienced reduced metabolic cost with the VI Knee compared to the C-Leg.
• Participants with longer residual limbs showed increased metabolic cost with the VI Knee.
• Metabolic cost differences correlated significantly with the rise in the center of mass, with shorter limbs exhibiting less vertical body movement.

Conclusions:

• The VI Knee's effect on metabolic cost is limb-length dependent in transfemoral amputees.
• Optimizing prosthetic knee impedance may reduce metabolic demand and improve walking for specific amputee populations.
• Further research is needed to understand the relationship between residual limb length, prosthetic design, and gait efficiency.