title: A three-dimensional model to assess the effect of ankle joint axis misalignments in ankle-foot orthoses.
abstract: BACKGROUND
  Misalignment of an articulated ankle-foot orthosis joint axis with the anatomic joint axis may lead to discomfort, alterations in gait, and tissue damage. Theoretical, two-dimensional models describe the consequences of misalignments, but cannot capture the three-dimensional behavior of ankle-foot orthosis use.
  
  
  OBJECTIVE
  The purpose of this project was to develop a model to describe the effects of ankle-foot orthosis ankle joint misalignment in three dimensions.
  
  
  METHODS
  Computational simulation.
  
  
  METHODS
  Three-dimensional scans of a leg and ankle-foot orthosis were incorporated into a link segment model where the ankle-foot orthosis joint axis could be misaligned with the anatomic ankle joint axis. The leg/ankle-foot orthosis interface was modeled as a network of nodes connected by springs to estimate interface pressure. Motion between the leg and ankle-foot orthosis was calculated as the ankle joint moved through a gait cycle.
  
  
  RESULTS
  While the three-dimensional model corroborated predictions of the previously published two-dimensional model that misalignments in the anterior -posterior direction would result in greater relative motion compared to misalignments in the proximal -distal direction, it provided greater insight showing that misalignments have asymmetrical effects.
  
  
  CONCLUSIONS
  The three-dimensional model has been incorporated into a freely available computer program to assist others in understanding the consequences of joint misalignments.
  
  
  CONCLUSIONS
  Models and simulations can be used to gain insight into functioning of systems of interest. We have developed a three-dimensional model to assess the effect of ankle joint axis misalignments in ankle-foot orthoses. The model has been incorporated into a freely available computer program to assist understanding of trainees and others interested in orthotics.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Prosthetics-Orthotics Center, Northwestern University, Chicago, IL, USA s-fatone@northwestern.edu.
authors.forename: Stefania
authors.initials: S
authors.lastname: Fatone
authors.affiliation: Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Prosthetics-Orthotics Center, Northwestern University, Chicago, IL, USA.
authors.forename: William Brett
authors.initials: WB
authors.lastname: Johnson
authors.affiliation: Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Prosthetics-Orthotics Center, Northwestern University, Chicago, IL, USA.
authors.forename: Kerice
authors.initials: K
authors.lastname: Tucker
mesh_terms: D000843:Ankle Joint / Q000503:physiopathology*; D003198:Computer Simulation; D061826:Foot Orthoses; D006801:Humans; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
keywords: Ankle foot orthosis; model