Two subjects were selected for participation in this study, subject 1 with high tetraplegia and subject 2 with midlevel tetraplegia. Subject 1 had a Brown–Séquard injury at the C1 level. The subject had motor paralysis below C1 with normal to hypersensitive sensation on the implant side. The only voluntary function on the implant side was shoulder shrug (upper trapezius). Subject 2 had an injury at the C5 level. The subject had some voluntary shoulder movement and elbow flexion (including brachioradialis) with a limited range of motion. The triceps and wrist extensors of subject 2 were partially denervated.
A summary of implanted electrodes is shown in Table I. Multicontact selective electrodes [Fig. 2(c)] were used on the radial nerves of both subjects and the musculocutaneous nerve of subject 1. Multicontact nonselective electrodes [Fig. 2(d)] were used on the suprascapular nerves of both subjects and the axillary nerve of subject 1. Single-contact electrodes [Fig. 2(e)] were used on the thoracodorsal and long thoracic nerves of both subjects. Target muscles and consequent nerve cuff locations and type were chosen based on prior musculoskeletal modeling studies [1 (link)], [2 (link)]. The MetroHealth Medical Center Institutional Review Board approved the study and subjects gave informed consent prior to participation. An investigational device exemption was obtained from the FDA prior to initiation of the study.