Myoelectric control sites in the high-level quadriplegic patient.

The purpose of this investigation was to determine optimal myoelectric control sites in the C4 level quadriplegic patient. The criteria used for selecting sites as usable by the patient for myoelectric control were as follows: (1) The remaining repertoire of movement could be performed by the subject without producing interfering myoelectric activity at the control site. (2) Adequate myoelectric output could be produced from the underlying musculature. (3) Electrical silence at rest could be demonstrated at the site. Eight muscle groups of the head, neck and scapula were studied on six high-level quadriplegic patients using surface electromyography. The subjects were asked to perform 12 tasks, including active movements of the head and neck, swallowing and speaking. Following this, the subjects performed a series of maximal and submaximal voluntary contractions. Using the above criteria, sites feasible for functional myoelectric control were found over portions of the frontalis, upper and middle trapezius, and temporalis muscles. Other sites found acceptable for subjects individually were located over areas of the platysma, lower trapezius, and masseter muscles. Thus, myoelectric control sites for the operation of externally powered devices are present in the high-level quadriplegic patient. Sites have been demonstrated from which the user is able to generate adequate myoelectric output for the operation of such devices, but do not limit the remaining movements of the individual.