title: Using musculoskeletal modeling to evaluate the effect of ankle foot orthosis tuning on musculotendon dynamics: a case study.
abstract: This case study examines the influence of an ankle foot orthosis footwear combination (AFO-FC) on musculotendon lengths and gait kinematics and kinetics after right thrombotic stroke resulting in left hemiplegia.
  
  
  
  Gait analysis was performed over three visits where the subject walked with an AFO-FC with two shank-to-vertical angle (SVA) alignments, a posterior leaf spring AFO (PLS AFO), and shoes alone. Biomechanical and musculoskeletal modeling was used to evaluate musculotendon lengths, kinematics, and kinetics for each condition.
  
  
  
  The AFO-FC improved walking speed and non-paretic kinematics compared to the PLS AFO and shoes alone. The operating length of the paretic gastrocnemius decreased with the AFO-FC improving knee kinematics in swing, but not stance. As the SVA of the AFO-FC was reduced from 15° to 12°, internal ankle plantar flexor moment increased.
  
  
  
  Musculoskeletal modeling demonstrated that the AFO-FC altered gastrocnemius operating length during post-stroke hemiplegic gait. Using these tools to evaluate muscle operating lengths can provide insight into underlying mechanisms that may improve gait and guide future AFO-FC design. Implications for Rehabilitation Modeling musculotendon operating lengths during movement has the potential to inform how ankle foot orthoses (AFO) affect tight muscles and improve mobility after stroke. Adjusting shank-to-vertical angle (SVA) of the AFO-footwear combination (AFO-FC) has the potential to improve gait kinematics by controlling length of the pathologic gastrocnemius and maximizing internal ankle plantar flexor moment of individuals with neuromuscular disorders.
authors: a Department of Mechanical Engineering and.
authors: Hwan
authors: H
authors: Choi
authors: b Department of Pediatrics , University of Washington , Seattle , WA , USA .|c Seattle Children's Research Institute , Seattle , WA , USA , and.
authors: Kristie
authors: K
authors: Bjornson
authors: d Prosthetics-Orthotics Center , Northwestern University Feinberg School of Medicine , Chicago , IL , USA.
authors: Stefania
authors: S
authors: Fatone
authors: a Department of Mechanical Engineering and.
authors: Katherine M
authors: KM
authors: Steele
mesh_terms: D000842:Ankle; D001696:Biomechanical Phenomena; D061826:Foot Orthoses; D020233:Gait Disorders, Neurologic / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016059:Range of Motion, Articular; D000071939:Stroke Rehabilitation / Q000379:methods*; D013710:Tendons / Q000503:physiopathology*
keywords: Ankle foot orthoses; gait; muscle length; musculoskeletal modeling; tuning
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