Design of a programmable multi-pattern FES system for restoring foot drop in stroke rehabilitation

A programmable and portable multi-pattern transcutaneous neuromuscular stimulator was developed and evaluated for correction of foot drop in stroke subjects. The stimulator unit was designed to optimize functionality while keeping its size and power consumption to a minimum. It had two channels of biphasic stimulation (charge-balanced and constant current), and all parameters were programmable to accommodate a range of stimulation profiles. The 'natural' electromyographic (EMG) pattern of tibialis anterior (TA) muscle stimulation envelope algorithms and constant amplitude stimulation envelope was provided for foot drop corrections in stroke patients. A foot-switch sensor was used to trigger the device in the swing phase of gait cycle. Various tests on prototype units were performed, including output power characteristics with a skin model, and tested with a stroke subject to validate the results. This paper provides a detailed description of the hardware and block-level functional electrical stimulation (FES) system design for applications in stroke rehabilitation.