title: Passive-dynamic ankle-foot orthosis replicates soleus but not gastrocnemius muscle function during stance in gait: Insights for orthosis prescription.
abstract: BACKGROUND
  Passive-dynamic ankle-foot orthosis characteristics, including bending stiffness, should be customized for individuals. However, while conventions for customizing passive-dynamic ankle-foot orthosis characteristics are often described and implemented in clinical practice, there is little evidence to explain their biomechanical rationale.
  
  
  OBJECTIVE
  To develop and combine a model of a customized passive-dynamic ankle-foot orthosis with a healthy musculoskeletal model and use simulation tools to explore the influence of passive-dynamic ankle-foot orthosis bending stiffness on plantar flexor function during gait.
  
  
  METHODS
  Dual case study.
  
  
  METHODS
  The customized passive-dynamic ankle-foot orthosis characteristics were integrated into a healthy musculoskeletal model available in OpenSim. Quasi-static forward dynamic simulations tracked experimental gait data under several passive-dynamic ankle-foot orthosis conditions. Predicted muscle activations were calculated through a computed muscle control optimization scheme.
  
  
  RESULTS
  Simulations predicted that the passive-dynamic ankle-foot orthoses substituted for soleus but not gastrocnemius function. Induced acceleration analyses revealed the passive-dynamic ankle-foot orthosis acts like a uniarticular plantar flexor by inducing knee extension accelerations, which are counterproductive to natural knee kinematics in early midstance.
  
  
  CONCLUSIONS
  These passive-dynamic ankle-foot orthoses can provide plantar flexion moments during mid and late stance to supplement insufficient plantar flexor strength. However, the passive-dynamic ankle-foot orthoses negatively influenced knee kinematics in early midstance.
  
  
  CONCLUSIONS
  Identifying the role of passive-dynamic ankle-foot orthosis stiffness during gait provides biomechanical rationale for how to customize passive-dynamic ankle-foot orthoses for patients. Furthermore, these findings can be used in the future as the basis for developing objective prescription models to help drive the customization of passive-dynamic ankle-foot orthosis characteristics.
authors.affiliation: University of Delaware, Newark, DE, USA schranke@udel.edu.
authors.forename: Elisa S
authors.initials: ES
authors.lastname: Arch
authors.affiliation: University of Delaware, Newark, DE, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Stanhope
authors.affiliation: University of Delaware, Newark, DE, USA.
authors.forename: Jill S
authors.initials: JS
authors.lastname: Higginson
mesh_terms: D000328:Adult; D004867:Equipment Design; D005260:Female; D061826:Foot Orthoses; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D018583:Pliability; D016059:Range of Motion, Articular / Q000502:physiology; D012016:Reference Values; D055815:Young Adult
keywords: Gastrocnemius; induced acceleration analysis; orthotic; plantar flexor; soleus; stiffness