title: Prosthesis Control with an Implantable Multichannel Wireless Electromyography System for High-Level Amputees: A Large-Animal Study.
abstract: BACKGROUND
  Myoelectric prostheses lack a strong human-machine interface, leading to high abandonment rates in upper limb amputees. Implantable wireless electromyography systems improve control by recording signals directly from muscle, compared with surface electromyography. These devices do not exist for high amputation levels. In this article, the authors present an implantable wireless electromyography system for these scenarios tested in Merino sheep for 4 months.
  
  
  METHODS
  In a pilot trial, the electrodes were implanted in the hind limbs of 24 Sprague-Dawley rats. After 8 or 12 weeks, impedance and histocompatibility were assessed. In the main trial, the system was tested in four Merino sheep for 4 months. Impedance of the electrodes was analyzed in two animals. Electromyographic data were analyzed in two freely moving animals repeatedly during forward and backward gait.
  
  
  RESULTS
  Device implantation was successful in all 28 animals. Histologic evaluation showed a tight encapsulation after 8 weeks of 78.2 ± 26.5 µm subcutaneously and 92.9 ± 31.3 µm on the muscular side. Electromyographic recordings show a distinct activation pattern of the triceps, brachialis, and latissimus dorsi muscles, with a low signal-to-noise ratio, representing specific patterns of agonist and antagonist activation. Average electrode impedance decreased over the whole frequency range, indicating an improved electrode-tissue interface during the implantation. All measurements taken over the 4 months of observation used identical settings and showed similar recordings despite changing environmental factors.
  
  
  CONCLUSIONS
  This study shows the implantation of this electromyography device as a promising alternative to surface electromyography, providing a potentially powerful wireless interface for high-level amputees.
authors.affiliation: Vienna, Austria; and Newcastle, United Kingdom From the Christian Doppler Laboratory for the Restoration of Extremity Function, Departments of Surgery and Cognitive Biology, and Divisions of Plastic and Reconstructive Surgery and Biomedical Research, Medical University of Vienna; Otto Bock Healthcare Products GmbH; and Newcastle NHS Trust, Foundation Programme.
authors.forename: Konstantin D
authors.initials: KD
authors.lastname: Bergmeister
authors.forename: Marie
authors.initials: M
authors.lastname: Hader
authors.forename: Soeren
authors.initials: S
authors.lastname: Lewis
authors.forename: Michael-Friedrich
authors.initials: MF
authors.lastname: Russold
authors.forename: Martina
authors.initials: M
authors.lastname: Schiestl
authors.forename: Krisztina
authors.initials: K
authors.lastname: Manzano-Szalai
authors.forename: Aidan D
authors.initials: AD
authors.lastname: Roche
authors.forename: Stefan
authors.initials: S
authors.lastname: Salminger
authors.forename: Hans
authors.initials: H
authors.lastname: Dietl
authors.forename: Oskar C
authors.initials: OC
authors.lastname: Aszmann
mesh_terms: D000818:Animals; D008297:Male; D051381:Rats; D001186:Artificial Limbs; D001707:Biopsy, Needle; D004195:Disease Models, Animal; D004567:Electrodes, Implanted; D004576:Electromyography / Q000295:instrumentation; D006614:Hindlimb / Q000601:surgery; D007150:Immunohistochemistry; D018482:Muscle, Skeletal / Q000473:pathology; D010865:Pilot Projects; D011474:Prosthesis Design / Q000295:instrumentation; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D012756:Sheep; D059015:Wireless Technology / Q000295:instrumentation