title: Vector-field statistics for the analysis of time varying clinical gait data.
abstract: BACKGROUND
  In clinical settings, the time varying analysis of gait data relies heavily on the experience of the individual(s) assessing these biological signals. Though three dimensional kinematics are recognised as time varying waveforms (1D), exploratory statistical analysis of these data are commonly carried out with multiple discrete or 0D dependent variables. In the absence of an a priori 0D hypothesis, clinicians are at risk of making type I and II errors in their analyis of time varying gait signatures in the event statistics are used in concert with prefered subjective clinical assesment methods. The aim of this communication was to determine if vector field waveform statistics were capable of providing quantitative corroboration to practically significant differences in time varying gait signatures as determined by two clinically trained gait experts.
  
  
  METHODS
  The case study was a left hemiplegic Cerebral Palsy (GMFCS I) gait patient following a botulinum toxin (BoNT-A) injection to their left gastrocnemius muscle.
  
  
  RESULTS
  When comparing subjective clinical gait assessments between two testers, they were in agreement with each other for 61% of the joint degrees of freedom and phases of motion analysed. For tester 1 and tester 2, they were in agreement with the vector-field analysis for 78% and 53% of the kinematic variables analysed. When the subjective analyses of tester 1 and tester 2 were pooled together and then compared to the vector-field analysis, they were in agreement for 83% of the time varying kinematic variables analysed.
  
  
  CONCLUSIONS
  These outcomes demonstrate that in principle, vector-field statistics corroborates with what a team of clinical gait experts would classify as practically meaningful pre- versus post time varying kinematic differences. The potential for vector-field statistics to be used as a useful clinical tool for the objective analysis of time varying clinical gait data is established. Future research is recommended to assess the usefulness of vector-field analyses during the clinical decision making process.
authors.affiliation: School of Sport Science, Exercise and Health, The University of Western Australia, Perth, WA, Australia. Electronic address: cyril.donnelly@uwa.edu.au.
authors.forename: C J
authors.initials: CJ
authors.lastname: Donnelly
authors.affiliation: School of Sport Science, Exercise and Health, The University of Western Australia, Perth, WA, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Alexander
authors.affiliation: Department of Bioengineering, Shinshu University, Japan.
authors.forename: T C
authors.initials: TC
authors.lastname: Pataky
authors.affiliation: Department of Orthopaedics, Princess Margaret Hospital for Children, Perth, WA, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Stannage
authors.affiliation: School of Sport Science, Exercise and Health, The University of Western Australia, Perth, WA, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Reid
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Robinson
mesh_terms: D001696:Biomechanical Phenomena; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use; D002547:Cerebral Palsy / Q000188:drug therapy / Q000503:physiopathology*; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D005684:Gait / Q000502:physiology*; D006801:Humans; D015233:Models, Statistical; D018482:Muscle, Skeletal / Q000503:physiopathology*
chemical_list: D019274:Botulinum Toxins, Type A
keywords: Biomechanics; Kinematics; Lower-limb; SPM; Statistical parametric mapping