title: A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop.
abstract: BACKGROUND
  A self-contained, self-controlled, pneumatic power harvesting ankle-foot orthosis (PhAFO) to manage foot-drop was developed and tested. Foot-drop is due to a disruption of the motor control pathway and may occur in numerous pathologies such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The objectives for the prototype PhAFO are to provide toe clearance during swing, permit free ankle motion during stance, and harvest the needed power with an underfoot bellow pump pressurized during the stance phase of walking.
  
  
  METHODS
  The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.
  
  
  RESULTS
  Toe clearance during swing was successfully achieved during all trials; average clearance 44 +/- 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.
  
  
  CONCLUSIONS
  This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA. rchin2@illinois.edu
authors.forename: Robin
authors.initials: R
authors.lastname: Chin
authors.forename: Elizabeth T
authors.initials: ET
authors.lastname: Hsiao-Wecksler
authors.forename: Eric
authors.initials: E
authors.lastname: Loth
authors.forename: Géza
authors.initials: G
authors.lastname: Kogler
authors.forename: Scott D
authors.initials: SD
authors.lastname: Manwaring
authors.forename: Serena N
authors.initials: SN
authors.lastname: Tyson
authors.forename: K Alex
authors.initials: KA
authors.lastname: Shorter
authors.forename: Joel N
authors.initials: JN
authors.lastname: Gilmer
mesh_terms: D000842:Ankle; D000843:Ankle Joint; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005528:Foot; D020233:Gait Disorders, Neurologic / Q000628:therapy*; D006621:Hip Joint; D006801:Humans; D007719:Knee Joint; D008297:Male; D009989:Orthotic Devices; D010865:Pilot Projects; D011312:Pressure; D016138:Walking; D055815:Young Adult