title: Comparison of 3 different methods to analyze ankle plantarflexor stiffness in children with spastic diplegia cerebral palsy.
abstract: OBJECTIVE
  To compare 3 different methods of measuring plantarflexor stiffness in children with spastic diplegia cerebral palsy (CP) and children without disability.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Human performance laboratory.
  
  
  METHODS
  A retrospective analysis was conducted with children with spastic diplegia (n=121; mean age, 8.4y) and children with typical development (TD) (n=48; mean age, 9.7y).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  An isokinetic dynamometer was used to measure ankle plantarflexor stiffness at 10°/s using 3 methods: (1) end-range method, which applied a linear slope to the end of the torque-angle curve; (2) set-range method, which applied a linear slope from 30° to 10° plantarflexion; and (3) a linear method, which applied a slope only to the linear portion of the curve.
  
  
  RESULTS
  Two-way analysis of variance revealed significant main effects for group and stiffness method. The end-range method showed no significant difference between groups for plantarflexor stiffness (P=.62), the set-range method showed the CP group with 120% greater stiffness than the TD group (P<.046), and the linear method showed the CP group with 35% greater stiffness than the TD group (P<.001).
  
  
  CONCLUSIONS
  The linear method appeared to resolve the issues with the previous methods; applying a linear slope to a nonlinear curve or applying a linear slope to the same range of motion for each child regardless of their range limitations. It is clear that children with CP have limited range of motion; therefore, stiffness occurs earlier in the range than would be expected for a typically developing child. Using the linear method, children with CP were 35% stiffer in the ankle plantarflexors than typically developing peers.
authors: Washington University Human Performance Laboratory, St. Louis, MO, USA. sross@maryville.edu
authors: Sandy A
authors: SA
authors: Ross
authors: Matthew
authors: M
authors: Foreman
authors: Jack R
authors: JR
authors: Engsberg
mesh_terms: D000293:Adolescent; D000843:Ankle Joint / Q000503:physiopathology*; D002547:Cerebral Palsy / Q000503:physiopathology* / Q000534:rehabilitation*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D052580:Muscle Stretching Exercises; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies