Poststroke Upper-Limb Rehabilitation Using 5 to 7 Inserted Microstimulators: Implant Procedure, Safety, and Efficacy for Restoration of Function

(A) A radiofrequency (RF) microstimulator (RFM) with an eyelet. (B) An intraoperative insertion tool. (C) A pulse shape showing the stimulation (Stim) phases. (D) The clinician fitting unit. The 2 attached coil cuffs for the arm and forearm were connected to the control unit. Note that the scale is 5cm. Abbreviation: Ampl, amplitude.

The microstimulator insertion and ejection tools are shown. (A) The ejection tool is withdrawn from the sheath. (B) The microstimulator has a suture threaded and tied to its eyelet. (C) The microstimulator is inserted into the sheath. (D) The ejector tool (plus syringe with antibiotic-saline solution) is inserted into the sheath pushing the microstimulator down the sheath. (E) The ejector tool approaches the mark line on its proximal part (arrow). (F) The ejection tool, having reached this line, has exposed the tip of the radiofrequency microstimulator to the tissue, which is ready for stimulation after the saline-antibiotic mixture is instilled.

Radiographs of the (A) upper arm and (B) forearm of subject 2 showing the distributions of radiofrequency microstimulators at their target sites. Note the 2 microstimulators for the posterior interosseous nerve and branches. (C) The upper limb in subject 2 with external cuff coils attached to the control unit (C2, C5). (C1) Resting. (C2-C6) Five evoked limb movements from different specific nerve motor point stimulation (as indicated). Abbreviations: ECU, extensor carpi ulnaris; ECR, extensor carpi radialis; PIN, posterior interosseous.

(A) The threshold of each of the 41 radiofrequency microstimulators was measured at 6 time events: immediate postimplantation (day 0), postimplant check (day 4), and phase 1 (days 15−90). The mean and SD values were plotted. The left hand values are the microstimulator thresholds converted to their charge density. (B) Five sheep were implanted with 13 microstimulators near the hypoglossal nerves. At postmortem, the distance (in millimeters) from each microstimulator's cathode to the nerve was measured and plotted against their final threshold stimulation values.