Restoration of Hand Function in Cervical SCI

Inclusion Criteria: * Male or female adults 18 years of age or older; * Cervical spinal cord injury as defined by: a) International Standard for Neurological Classification of Spinal Cord Injury motor level of C1 through C7; and b) American Spinal Injury Association Impairment Scale (AIS) grade A, B, or C; * Six months or more post-injury (neurostability); * Neurologically stable following any nerve transfers affecting the upper extremity (typically, one-year post-surgery); * Musculoskeletally and neurologically stable following any tendon transfers affecting the upper extremity (typically 6 months post-surgery). * Peripheral nerve innervation to upper extremity muscles, including Grade 3/5 or higher Stimulated Manual Muscle Testin at least two of the muscles in one arm: * Good proximal voluntary upper extremity strength as defined by biceps/ brachialis / brachioradialis strength of 2/5 or higher on Manual Muscle Testing the side intended for implantation; * Medically stable; and * Able to understand and provide informed consent; Exclusion Criteria: * Other neurological conditions (Multiple Sclerosis, diabetes with peripheral nerve involvement); * Associated peripheral nerve / brachial plexus injury; * Progressive Spinal Cord Injury; * Active implantable medical device (AIMD) such as a pacemaker or defibrillator; * Active untreated infection such as urinary tract infection or pneumonia; * Active pressure injury; * History of coagulopathy, HIV, cardiopulmonary disease, bradycardia, poorly controlled autonomic dysreflexia, or chronic obstructive pulmonary disease that would preclude safe participation in the trial as determined by the investigator; * Unhealed fractures that prevent functional use of arm; * Extensive upper extremity denervation (fewer than two excitable hand muscles); * Involvement in other ongoing clinical studies that exclude concurrent involvement in this study; * Currently pregnant (neuroprosthesis implantation delayed until no longer pregnant based on self-report); Urine or serum testing will happen during the pre-surgery evaluation. * Presence of disease that might interfere with participant safety, compliance, or evaluation of the condition under study; * Other significant medical findings that, in the opinion of the investigator, preclude safe participation in the trial