title: Relative forefoot abduction and its relationship to foot length in vitro.
abstract: BACKGROUND
  The human foot is often modelled as a rigid body in gait analysis. A more realistic model separates this segment into a forefoot and rearfoot. However, no three-dimensional data has been published on dynamic relative ab-adduction between these segments, and how this impacts changes in foot shape.
  
  
  OBJECTIVE
  The purpose was to quantify three-dimensionally forefoot ab-adduction relative to the rearfoot in vitro, and to determine how forefoot ab-adduction affects foot length.
  
  
  METHODS
  Video data were collected from reflective marker triads affixed to the ends of Steinmann pins drilled into the tibia, calcaneus, cuboid, and the first and fifth metatarsal bones. Medial and lateral foot length and forefoot ab-adduction relative to the rearfoot were calculated under two axial tibial loads (200 N, 600 N) and two input motions (dorsi-plantarflexion, internal-external tibial rotation).
  
  
  RESULTS
  It was found that patterns of change for each variable were dependent on the degree of rigidity of the foot. Relative forefoot ab-adduction values ranged from 4.4 degrees of adduction to 1.7 degrees of abduction. Medial foot length values changed +/- 0.8 mm (+/- 0.5%) and lateral foot length values changed +/- 0.5 mm (+/- 0.3%). Medial foot length was correlated positively with relative forefoot abduction, and external tibial rotation was correlated positively with relative forefoot adduction.
authors.affiliation: Human Performance Laboratory, University of Calgary, Alberta, Canada. lees@hss.edu
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: C C
authors.initials: CC
authors.lastname: Muller
authors.forename: D
authors.initials: D
authors.lastname: Stefanyshyn
authors.forename: B M
authors.initials: BM
authors.lastname: Nigg
mesh_terms: D000886:Anthropometry; D001696:Biomechanical Phenomena; D002102:Cadaver; D005528:Foot / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D016059:Range of Motion, Articular / Q000502:physiology*; D012680:Sensitivity and Specificity; D013640:Tarsal Joints / Q000033:anatomy & histology / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology