title: Transmissions within the tarsal gearbox.
abstract: BACKGROUND
  The dependence of the movements of the calcaneus, cuboid, navicular, and talus on each other have been described as the tarsal gearbox. To provide a basis of its modeling, data on transmissions between tarsal joint rotations within this gearbox are required. The feasibility of tibiocalcaneal rotations to predict tarsal joint rotations is of interest because a meaningful relation would allow the use of common motion analysis with skin markers to investigate rearfoot kinematics.
  
  
  METHODS
  We performed linear regression analyses between tarsal joint and tibiocalcaneal rotations on the basis of magnetic resonance imaging of tibia and tarsal bone positions during quasi-static foot pronation and supination.
  
  
  RESULTS
  In the frontal plane and transverse planes, linear models were found to predict tarsal joint rotations quite well (r(2) = 0.83-0.97 for the frontal plane and r(2) = 0.73-0.95 for the transverse plane). For each degree of talocalcaneal rotation, there was 1.8 degrees of talonavicular rotation in the frontal plane and 1.6 degrees in the transverse plane; each degree of talocalcaneal rotation resulted in 0.6 degrees of calcanealcuboid rotation in the frontal plane and 0.7 degrees in the transverse plane; each degree of calcaneocuboid rotation resulted in 3 degrees of talonavicular rotation in the frontal plane and 2.8 degrees in the transverse; each degree of tibiocalcaneal rotation resulted in 0.9 degrees of talocalcaneal rotation in the frontal plane and 0.9 degrees in the transverse plane; and each degree of tibiocalcaneal rotation resulted in 1.6 degrees of talonavicular rotation in the frontal plane and 1.3 degrees in the transverse plane.
  
  
  CONCLUSIONS
  The present study provides a basis on which the tarsal gearbox in the frontal and the transverse planes under quasi-static conditions can be modeled. Furthermore, it is concluded that tibiocalcaneal rotations are practical for predicting tarsal joint rotations during quasi-static motions.
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland. pwolf@ethz.ch
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
authors.forename: Alex
authors.initials: A
authors.lastname: Stacoff
authors.forename: Roger
authors.initials: R
authors.lastname: Luechinger
authors.forename: Peter
authors.initials: P
authors.lastname: Boesiger
authors.forename: Edgar
authors.initials: E
authors.lastname: Stuessi
mesh_terms: D000328:Adult; D002111:Calcaneus / Q000502:physiology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D011403:Pronation / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D013484:Supination / Q000502:physiology*; D013640:Tarsal Joints / Q000502:physiology*; D013977:Tibia / Q000502:physiology*