Restoration of motor function of the paralyzed patient by means of multichannel Functional Electrical Stimulation (FES) is effective as a medical treatment. In the clinical application of FES, many electrodes which we developed are implanted for selective control of individual muscles. Because of the low percentage of electrode failure in the body, stable FES control has been achieved for a long time. However, expanding the FES application causes the increase in the number of electrode failure even if the percentage of the failure is low. Therefore, a quantitative evaluation of implanted percutaneous electrodes for FES is required in clinical site. We developed a new measuring system of the electrode impedance over the frequency range of 20Hz to 10kHz. This measurement made it possible to estimate whether the implanted electrode is broken or moved. In addition, it could also provide information of disconnection status between the electrodes and the stimulator. The characteristics of the electrode impedance can easily discriminate the electrode condition, i. e., breakage, movement, etc., without surgical operation. This new evaluation method is quite useful in clinical site.
