title: Kinematic angular parameters in PD: reliability of joint angle curves and comparison with healthy subjects.
abstract: BACKGROUND
  Most previous biomechanical studies of Parkinson's disease (PD) have been restricted to the description of spatiotemporal parameters and certain peak values for angular parameters. The reliability of joint angle curves and comparisons with control data are of major interest in PD, since variability in gait cycle timing is a feature of this pathology.
  
  
  METHODS
  We used a video motion analysis system to record kinematic, spatiotemporal and angular parameters in 32 'off-drug' PD patients. The reliability of the patients' lower limb joint angle curves in the sagittal plane were analysed using the intra-class correlation coefficient (ICC), together with fast Fourier transform (FFT) analysis and hierarchical classification for discarding deviant curves. Lastly, we compared average curves (using a mixed model and the bootstrap method) for the less-affected and more-affected sides of PD patients and then compared the patient data with the results from 30 age-matched controls.
  
  
  RESULTS
  The ICC-based procedure was easily applicable. Only 9.4% and 12.5% of the patients' hip and knee curves (respectively) were deemed to be unreliable. However, the PD patients' very high cycle-to-cycle variability in the sagittal plane ankle curves prevented us from applying to this joint. For the knee joint, the curves for the most disabled patients (who walked at below 0.5 m/s) were not reliable. We did not find any differences between the less and more disabled sides. The differences between patient and control curves concerned the double-support time during the stance phase and the time point for maximum knee flexion during the swing phase. Patients and controls differed in terms of the hip extension phase, with lower values in PD.
  
  
  CONCLUSIONS
  We have developed the use of validated statistic tools for unambiguously comparing PD patients and controls in terms of joint angle curve differences.
authors.affiliation: Department of Neurology, Lille University Medical Centre, Lille, France. A-Delval@chru-lille.fr
authors.forename: Arnaud
authors.initials: A
authors.lastname: Delval
authors.forename: Julia
authors.initials: J
authors.lastname: Salleron
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bourriez
authors.forename: Séverine
authors.initials: S
authors.lastname: Bleuse
authors.forename: Caroline
authors.initials: C
authors.lastname: Moreau
authors.forename: Pierre
authors.initials: P
authors.lastname: Krystkowiak
authors.forename: Luc
authors.initials: L
authors.lastname: Defebvre
authors.forename: Patrick
authors.initials: P
authors.lastname: Devos
authors.forename: Alain
authors.initials: A
authors.lastname: Duhamel
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000503:physiopathology; D001696:Biomechanical Phenomena; D005260:Female; D005583:Fourier Analysis; D005684:Gait / Q000502:physiology*; D006621:Hip Joint; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D015203:Reproducibility of Results