title: Ankle and subtalar kinematics measured with intracortical pins during the stance phase of walking.
abstract: BACKGROUND
  The absence of external landmarks on the talus has rendered the description of ankle and subtalar joint kinematics difficult. Abnormal motion at these joints has, however, been implied in the etiology of an array of lower extremity overuse injuries.
  
  
  METHODS
  Intracortical pins were inserted under local anesthesia in the tibia, talus, and calcaneus with external marker clusters traced by a video motion analysis system. Kinematic data were collected during walking trials on a flat surface for three subjects. Gait pattern was monitored by comparison of ground reaction force curves during stance phase with and without the pins inserted.
  
  
  RESULTS
  Results were presented in terms of helical axis orientation for both joints and the component rotations about these axes. Large intersubject differences were seen in both ankle and subtalar joint helical axis orientation. Maximum rotations over the complete stance phase for the ankle and subtalar joints respectively were: eversion/inversion, 6.3 degrees and 8.3 degrees; dorsiflexion/plantarflexion, 18.7 degrees and 3.7 degrees; and abduction/adduction, 5.0 degrees and 6.1 degrees.
  
  
  CONCLUSIONS
  The majority of ankle eversion/inversion occurred at the subtalar joint; however, the ankle component cannot be ignored. Abduction/adduction range of motion at the subtalar joint was surprisingly high, indicating that this component motion during walking is not purely attributable to the ankle joint. Future research should include greater subject numbers in order to present more universally applicable results.
  
  
  CONCLUSIONS
  The in vivo kinematics of the talus during weightbearing activity are poorly understood. The description of this motion may assist in the structuring of clinical rehabilitation and in the design and insertion of ankle joint prostheses.
authors.affiliation: Karolinska Institute, Department of Orthopedic Surgery, Karolinska University Hospital/Huddinge, Stockholm, Sweden. toni.arndt@cfss.ki.se
authors.forename: Anton
authors.initials: A
authors.lastname: Arndt
authors.forename: Pär
authors.initials: P
authors.lastname: Westblad
authors.forename: Ian
authors.initials: I
authors.lastname: Winson
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Arne
authors.initials: A
authors.lastname: Lundberg
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D001858:Bone Nails; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013380:Subtalar Joint / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing