The efficacy of a motorized lower-limb prosthetic device: a pilot study

BACKGROUND Performing daily activities is challenging for individuals with a transfemoral amputation. Technological advancements in prosthetic prototypes aim at improving functional independence. A state-of-the-art active device, the CYBERLEGs-gamma (CLs-ɣ) prosthesis, consisting of powered ankle and knee joints, has been designed and constructed. The control system combines pressure-sensitive insoles and inertial motor units to synchronize both joints to work together. To date, the novel device has not een clinically evaluated. Therefore, the objective of this study was to investigate the efficacy of the CLs-ɣ prosthesis during daily activities compared to current passive and quasi-passive devices . METHODS Participants performed a familiarization trial, an experimental trial with the current prosthesis, three adaptation trials and an experimental trial with the CLs-ɣ prosthesis. Participants completed a stair climbing test, a timed-up & go test, a sit to stand test, a two-minute dual task (i.e. the psychomotor vigilance task during treadmill walking) and a six-minute treadmill walk test at normal speed. Nonparametric Wilcoxon-signed rank tests were conducted with critical alpha set at 0.05. RESULTS Eight individuals with a transfemoral amputation (age: 55 ± 15 years, K-level 3) were included. Stride length significantly increased during walking with the CLs-ɣ prosthesis (p=0.012) because of a greater step length of the amputated leg (p=0.035). Normal walking speed was significantly slower (p=0.018), the net metabolic cost of transport was significantly higher (p=0.028) and reaction time significantly worsened (p=0.012) when walking with the CLs-ɣ compared to the current prosthesis. When participants took stairs, they adopted a step-over-step strategy with the CLs-ɣ prosthesis in contrast to step-by-step wearing the current prosthesis. CONCLUSION S A higher physical effort and cognitive demand were required during activities wearing the novel motorized prosthesis. Although performance outcome measures did not improve, participants had a greater stride length and better simulated able-bodied stair ambulation.