Implantable Myoelectric Sensors (IMES)

We are developing a multi-channel/multifunction prosthetic hand/arm controller system capable of receiving and processing signals from up to sixteen Implanted MyoElectric Sensors (IMES). The appeal of implanted sensors for myoelectric control is that EMG signals can be measured at their source providing relatively cross-talk free signals that can be treated as independent control sites. Therefore the number of degrees-of-freedom that can be simultaneously controlled and coordinated in an externally-powered prosthesis will be greater than with surface EMG or mechanical control sites. To explore the issue of intra-muscular signal independence and the ability to control them, human subject experiments have been performed in which intra-muscular EMGs were obtained. Choice of muscles was based on a desire to be able to independently control a two degree-of-freedom (DOF) wrist, and 3 DOF prosthetic hand. This paper provide our result so far. INTRODUCTION: The limitation of current prostheses is not the devices themselves but rather the lack of sufficient independent control sources. A system capable of reading intra muscular EMG signals would greatly increase the number control sources available for prosthesis control. We are developing a chronically implantable sensor system to create multiple control sites to detect commanded movements. We are developing myoelectric sensor capsules (Fig. 1) that can be chronically implanted into the residual muscles of an amputee’s arm. By localizing the points at which myoelectric activity is detected, these points can be treated as independent control sites with minimal cross-talk. Consequently, the number of degrees-of-freedom that can be simultaneously controlled and coordinated in an externally powered prosthesis will be greatly increased in comparison with surface EMG sites, while obviating the problems of tapping into cut motor control nerves. Our Implantable MyoElectric Sensor (IMES) system will be capable of reading EMG signals from up to 16 inductively coupled, implanted bipolar differential electromyographic (EMG) sensors. These sensors receive their power, digital addressing, and command signals from an external transmitter/receiver coil worn by the patient. The external coil required for the inductive link is laminated into the prosthetic socket such that this coil will encircle the implanted electrodes (Fig. 2). Each implanted sensor acts as an intramuscular electrode to detect the electrical activity generated as a by-product of normal muscle contraction. The implants transmit these muscle signals, or myoelectric (EMG) signals, over a shared transcutaneous magnetic link. Each sensor’s electronics and associated circuitry will be housed in a previously developed RFB BION® hermetically sealed package provided by the Alfred Mann Foundation Fig 1: Alfred E. Mann Foundation RFB BION® Package. The inter-electrode spacing is appropriate for whole muscle activity