Study of power prosthesis failures reveals differing effects on gait stability

A study of the effects of locomotion mode recognition errors on the volitional control of powered lower limb prostheses showed differing effects on gait stability, leading to the identification of “critical errors,” according to results published in Institute of Electrical and Electronics Engineers.

Researchers led by Helen Huang, MD, senior author of the study and associate professor in the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill studied five able-bodied people and two transfemoral amputees who were tested while wearing a powered prosthesis. The researchers simulated four types of locomotion mode recognition errors with different duration and at different gait phases to the prosthetic control.

The results showed that the effect of the errors on gait stability depended on the phases in which the errors happened and the amount of mechanical work change applied to the knee caused by the errors.

“We not only want to improve the decoding accuracy, but determine which errors are important and which have little or no impact on users,” Huang stated in a press release. “Understanding the problem is an important step in finding ways to make these prostheses more reliable.”

The researchers created a new index to evaluate the potential locomotion mode recognition systems for volitional control of powered artificial legs which identifies “critical errors,” errors which caused the subjective feeling of unstable balance in any of the subjects.

The researchers hope the results “might shift the paradigm for evaluating and optimizing the performance of locomotion mode recognition system[s] and aid the future design of volitionally-controlled powered artificial legs,” the authors stated in the published results.

“Any system that involves a human interface will have occasional errors,” Huang stated. “But we think we can find ways to make those errors effectively insignificant.”

For more information:

Zhang F. IEEE. 2014;doi:10.1109/TNSRE.2014.2327230.

Disclosure: The authors have no relevant financial disclosures.

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