title: Biomechanical response to ankle-foot orthosis stiffness during running.
abstract: BACKGROUND
  The Intrepid Dynamic Exoskeletal Orthosis (IDEO) is an ankle-foot orthosis developed to address the high rates of delayed amputation in the military. Its use has enabled many wounded Service Members to run again. During running, stiffness is thought to influence an orthosis' energy storage and return mechanical properties. This study examined the effect of orthosis stiffness on running biomechanics in patients with lower limb impairments who had undergone unilateral limb salvage.
  
  
  METHODS
  Ten patients with lower limb impairments underwent gait analysis at a self-selected running velocity. 1. Nominal (clinically-prescribed), 2. Stiff (20% stiffer than nominal), and 3. Compliant (20% less stiff than nominal) ankle-foot orthosis stiffnesses were tested.
  
  
  RESULTS
  Ankle joint stiffness was greatest in the stiffest strut and lowest in the compliant strut, however ankle mechanical work remained unchanged. Speed, stride length, cycle time, joint angles, moments, powers, and ground reaction forces were not significantly different among stiffness conditions. Ankle joint kinematics and ankle, knee and hip kinetics were different between limbs. Ankle power, in particular, was lower in the injured limb.
  
  
  CONCLUSIONS
  Ankle-foot orthosis stiffness affected ankle joint stiffness but did not influence other biomechanical parameters of running in individuals with unilateral limb salvage. Foot strike asymmetries may have influenced the kinetics of running. Therefore, a range of stiffness may be clinically appropriate when prescribing ankle-foot orthoses for active individuals with limb salvage.
authors.affiliation: Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, United States. Electronic address: erussell.kin@gmail.com.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Russell Esposito
authors.affiliation: Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, United States.
authors.forename: Harmony S
authors.initials: HS
authors.lastname: Choi
authors.affiliation: Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, United States.
authors.forename: Johnny G
authors.initials: JG
authors.lastname: Owens
authors.affiliation: Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, United States.
authors.forename: Ryan V
authors.initials: RV
authors.lastname: Blanck
authors.affiliation: Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, United States.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Wilken
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D001915:Braces; D004867:Equipment Design; D005528:Foot; D061826:Foot Orthoses; D005684:Gait / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012420:Running / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: IDEO; Joint stiffness; Kinematics; Kinetics; Limb salvage; Mechanical work; Military