Patient controlled electrical stimulation via EMG signature discrimination for providing certain paraplegics with primitive walking functions

Abstract

In this paper we present the first patient-based results for a micro computer-based EMG signature-controlled functional electrical stimulation (FES) system, for restoring walker-supported and brace-free primitive walking to complete paraplegics, at the patients own command. Stimulation is thus controlled directly by the patient's own EMG signatures, generated by him at will, and which are produced by him at his erector spinae back muscles (while activating these muscles more or less as he would during normal walking, had the person not been a paraplegic). In this manner a switch-free simplistic but reliable information-gap is produced across the paraplegic's lesion, such that the above lesion's relatively normal EMG provides the control command to electrical stimulation of paralyzed peripheral (lower limb) nerves, to provide the basic functions of standing up, sitting-down and walking. The FES signals are at pulse rates close to the average ones occurring naturally at the corresponding nerves. The paper reports actual patient results for 3 paraplegics, two at T-9 (one complete, one with only residual sensation) and one T-6 complete paraplegic, who all subsequently achieved walking between parallel bars and two even with a walker (no braces in all cases), using the FES system, this walking being, to our knowledge the first hand-switch-free patient-controlled FES walking reported ever. The EMG signature-discrimination for control is as previously developed by D. Graupe for artificial-limb control, and it depends only on the EMG signature temporal parameters, while completely ignoring EMG power (amplitude) level. Whereas all 3 patients produced EMG parameters in the range reported below, adequate for controlling all functions involved, only one, a T-6 complete paraplegic, has so far (due to time limitations) achieved EMG controlled walking between parallel bars and by now also a few steps with a walker. One T-9 complete paraplegic, injured 5 years before coming to our program, was however able, within 4 weeks, to walk via FES with a walker, though with manual control. Note that the present approach is valid only for upper motor neuron paralysis situations (intact peripheral nerves and muscles). We are thus also attempting to apply this approach to certain hemiplegics and quadraplegics, for restoring some upper limb functions, using EMG signals from the trapezius (shoulder) level.