Foot and Ankle Immobilization Increases Understanding of Amputee Gait

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The anatomical foot-ankle mechanism facilitates power generation during walking, but this mechanism is altered for people with bilateral transtibial amputations when they use passive prostheses. Researchers at Northwestern University Prosthetics-Orthotics Center (NUPOC) studied the effects of bilateral foot and ankle immobilization on the gait of able-bodied participants to serve as a model for understanding gait and associated compensatory mechanisms in people with bilateral transtibial amputations.

Nine able-bodied participants walked at self-selected slow, normal, and fast speeds. They performed trials unaltered and when fitted with bilateral foot-and-ankle-immobilizing casts. Data from ten people with bilateral transtibial amputations walking at self-selected fast speeds was used for qualitative comparison.

Trials indicated that the average fast speeds for the able-bodied participants with the casts on and the normal speed with no casts were similar. The data from the able-bodied participants when using the casts more closely matched the data for the participants with bilateral transtibial amputations than the no-cast data. Ankle range of motion (ROM) and power generation at pre-swing in the cast condition were decreased, while trunk lateral flexion and transverse rotation ROM and peak hip power generation increased.

Results suggest that the absence of active ankle ROM and power generation contributes to the development of characteristic compensatory gait mechanisms displayed by people with bilateral transtibial amputations, according to the study's authors. The research can improve understanding of compensatory mechanisms resulting from reduced foot and ankle joint motion to inform lower-limb prosthesis design and function for improving gait quality of individuals with bilateral transtibial amputations.