A pilot study comparing the cognitive demand of walking for transfemoral amputees using the Intelligent Prosthesis with that using conventionally damped knees

Objective: To compare the cognitive demand of walking when using a conventional prosthesis with that using a microprocessor-controlled prosthesis. Design: Ten unilateral transfemoral amputees wearing conventional pneumatic swing phase control (conventional prosthesis) prostheses walked on a treadmill which enforced a pattern of constantly varying speeds. The subjects simultaneously performed a simple or a complex distracting task. Following a period of accustomization, the subjects performed the same test wearing a prosthesis with microprocessor control of swing phase damping (the Intelligent Prosthesis). Outcome measures: The three-dimensional trajectory (sway) of a retroreflective marker attached to the forehead was measured by a video-based motion analysis system, and used as a measure of gait quality. The ratio of the sway for the complex task over the simple task (the 'automation index') was used as a measure of the degree of automation of gait. Results: No significant differences were found in the automation index between the two devices. However, the total sway for the conventional prosthesis was significantly higher. Sway during the complex distracting task was significantly higher than during the simple task. Conclusions: The microprocessor-controlled prosthesis was not found to be less cognitively demanding than a conventional prosthesis.