title: Fractal dimension approach in postural control of subjects with Prader-Willi Syndrome.
abstract: BACKGROUND
  Static posturography is user-friendly technique suitable for the study of the centre of pressure (CoP) trajectory. However, the utility of static posturography in clinical practice is somehow limited and there is a need for reliable approaches to extract physiologically meaningful information from stabilograms. The aim of this study was to quantify the postural strategy of Prader-Willi patients with the fractal dimension technique in addition to the CoP trajectory analysis in time and frequency domain.
  
  
  METHODS
  11 adult patients affected by Prader-Willi Syndrome (PWS) and 20 age-matched individuals (
  
  
  METHODS
  CG) were included in this study. Postural acquisitions were conducted by means of a force platform and the participants were required to stand barefoot on the platform with eyes open and heels at standardized distance and position for 30 seconds. Platform data were analysed in time and frequency domain. Fractal Dimension (FD) was also computed.
  
  
  RESULTS
  The analysis of CoP vs. time showed that in PWS participants all the parameters were statistically different from CG, with greater displacements along both the antero-posterior and medio-lateral direction and longer CoP tracks. As for frequency analysis, our data showed no significant differences between PWS and CG. FD evidenced that PWS individuals were characterized by greater value in comparison with CG.
  
  
  CONCLUSIONS
  Our data showed that while the analysis in the frequency domain did not seem to explain the postural deficit in PWS, the FD method appears to provide a more informative description of it and to complement and integrate the time domain analysis.
authors.affiliation: Bioengineering Department, Politecnico di Milano, p,zza Leonardo Da Vinci 32, 20133, Milano, Italy. veronica.cimolin@polimi.it
authors.forename: Veronica
authors.initials: V
authors.lastname: Cimolin
authors.forename: Manuela
authors.initials: M
authors.lastname: Galli
authors.forename: Chiara
authors.initials: C
authors.lastname: Rigoldi
authors.forename: Graziano
authors.initials: G
authors.lastname: Grugni
authors.forename: Luca
authors.initials: L
authors.lastname: Vismara
authors.forename: Luca
authors.initials: L
authors.lastname: Mainardi
authors.forename: Paolo
authors.initials: P
authors.lastname: Capodaglio
mesh_terms: D000328:Adult; D005260:Female; D017709:Fractals; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011218:Prader-Willi Syndrome / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted