title: Definition of coordinate system for three-dimensional data analysis in the foot and ankle.
abstract: BACKGROUND
  Three-dimensional data is required to have advanced knowledge of foot and ankle kinematics and morphology. However, studies have been difficult to compare due to a lack of a common coordinate system. Therefore, we present a means to define a coordinate frame in the foot and ankle and its clinical application.
  
  
  METHODS
  We carried out ten CT scans in anatomically normal feet and segmented them in a general purpose segmentation program for grey value images. 3D binary formatted stereolithography files were then create and imported to a shape analysis program for biomechanics which was used to define a coordinate frame and carry out morphological analysis of the forefoot.
  
  
  RESULTS
  The coordinate frame had axes standard deviations of 2.36 which are comparable to axes variability of other joint coordinate systems. We showed a strong correlation between the lengths of the metatarsals within and between the columns of the foot and also among the lesser metatarsal lengths.
  
  
  CONCLUSIONS
  We present a reproducible method for construction of a coordinate system for the foot and ankle with low axes variability.
  
  
  CONCLUSIONS
  To conduct meaningful comparison between multiple subjects the coordinate system must be constant. This system enables such comparison and therefore will aid morphological data collection and improve preoperative planning accuracy.
authors.affiliation: Department of Trauma and Orthopaedics, St. Vincent's University Hospital, Donnybrook, Dublin 4, Ireland. connorjgreen@gmail.com
authors.forename: Connor
authors.initials: C
authors.lastname: Green
authors.forename: Clare
authors.initials: C
authors.lastname: Fitzpatrick
authors.forename: David
authors.initials: D
authors.lastname: FitzPatrick
authors.forename: Michael
authors.initials: M
authors.lastname: Stephens
authors.forename: William
authors.initials: W
authors.lastname: Quinlan
authors.forename: Robert
authors.initials: R
authors.lastname: Flavin
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D016022:Case-Control Studies; D003198:Computer Simulation; D005260:Female; D005529:Foot Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D011300:Preoperative Care; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed