GRASPING IN HIGH LESIONED TETRAPLEGIC SUBJECTS USING THE EMG CONTROLLED NEUROPROSTHESIS

A four channel functional electrical stimulation system with surface e lectrodes was developed and tested to give individuals with complete C 4 and C5 tetraplegia a possibility to perform a grasping function. The proposed neuroprosthesis is EMG controlled, and it is voluntarily act ivated using the deltoid muscle of the contralateral arm. The duration of the processed above the threshold EMG signal was used to control t he duration of the grasp, and the amplitude of the EMG signal was used to control the grasp strength. The following are the benefits of the proposed system: (1) restoration of the lost grasping function; (2) na tural and easy to train control of hand opening and closing; (3) smoot h adjustment of the grasping force; (4) a subject can use natural cont rol strategies to control the prosthesis; and (5) the control algorith m is easy to integrate into a micro-controller device. Functional test s with a subject with C4 to C5 complete tetraplegia showed that the sy stem significantly increased the subject's independence in performing everyday tasks. The limiting factor for using the proposed neuroprosth esis was the fatigue of the proximal arm muscles. Surprisingly, the fa tigue of the finger flexors, finger extensors and the contralateral ar m deltoid muscles were not the limiting factor. Note that the deltoid muscle of the contalateral arm was used to control the prosthesis. (C) 1998 Elsevier Science Ireland Ltd.