Surface vs. Implanted Emg for Multifunctional Prosthesis Control: Pilot Results

It has been hypothesized that, due to the potential to both provide a larger number of independent control sites and selectively record from forearm muscles (in particular the deep muscles), intramuscular EMG should be advantageous for multifunctional prosthesis control [1]. The use of surface electromyograms (EMG) to control a multiple degree-of-freedom prosthesis has been investigated for several decades. A variety of approaches have been employed with groups using different numbers of input channels [2-3], feature extraction methods [3-6] and pattern recognition algorithms [3,7-8]. While much work has been done, all of these efforts have used surface EMG as the control signal. Only a single preliminary study was found that acquired intramuscular EMG for prosthesis control [9]. Admittedly, the technology has not existed for chronic intramuscular recordings to be clinically feasible for prosthetic use. The Implantable Myoelectric Sensor (IMES) that is being developed at the Northwestern University Prosthetic Research Laboratory will make chronic intramuscular recordings clinically feasible [10]. We hypothesize and hope to demonstrate that by utilizing intramuscular EMG it will be possible to substantially increase classification accuracies of multifunctional prosthesis controllers (i.e., increase the percentage of the time that the controller can correctly predict the intended movement of the user). If a substantial increase in classification accuracy is demonstrated, this will justify the invasiveness of using these devices. However, if similar accuracies can be obtained from surface recordings then there will be little justification for pursuing these devices for transradial prosthesis control purposes.