Development of an implantable myoelectric sensor for advanced prosthesis control

Abstract

Modern hand and wrist prostheses afford a high level of mechanical sophistication, but the ability to control them in an intuitive and repeatable manner lags. Commercially available systems using surface electromyographic (EMG) or myoelectric control can supply at best two degrees of freedom (DOF), most often sequentially controlled. This limitation is partially due to the nature of surface-recorded EMG, for which the signal contains components from multiple muscle sources. We report here on the development of an implantable myoelectric sensor using EMG sensors that can be chronically implanted into an amputee's residual muscles. Because sensing occurs at the source of muscle contraction, a single principal component of EMG is detected by each sensor, corresponding to intent to move a particular effector. This system can potentially provide independent signal sources for control of individual effectors within a limb prosthesis. The use of implanted devices supports inter-day signal repeatability. We report on efforts in preparation for human clinical trials, including animal testing, and a first-in-human proof of principle demonstration where the subject was able to intuitively and simultaneously control two DOF in a hand and wrist prosthesis.

FIG. 1

Schematic of the implantable myoelectric sensor system. Implant devices are 2.4 mm diameter × 16.7 mm length, and act as differential amplifiers. One or more devices can be implanted into gross muscle, and telemeter EMG data to an external coil connected to a telemetry controller (TC). The TC passes the EMG to the prosthesis controller to drive a prosthesis.

FIG. 2

System used in 2 DOF prosthesis control demonstration. Fine-wire intramuscular electrodes were attached to the IMES electrodes via springs. The coil is not shown so the IMES cuff can be seen.