Influence of gait analysis on decision-marketing for lower extremity surgery

Responsiveness of outcome tools used to assess individuals with cerebral palsy

D OEFFINGER PHD A, A BAGLEY PHD B, G GORTON BS C, S ROGERS
MPH A, C TYLKOWSKI MD A, AND FUNCTIONAL ASSESSMENT
RESEARCH GROUP (FARG)

  1. 1. Shriners Hospitals for Children, Lexington, KY;
  2. 2. Sacramento, CA;
  3. 3. Springfield, MA, USA

Objectives: Responsiveness of outcome tools is difficult to assess in the absence of a criterion standard for change in function. Various statistical techniques have been used to determine tool responsiveness, including standardized response mean (SRM). The study objective was to establish the responsiveness of outcome tools used to assess physical function and quality of life for individuals with cerebral palsy (CP).

Design: Prospective, longitudinal, multicenter outcomes study.

Setting: Orthopedic clinics and motion laboratories. 

Participants: Convenience sample of 377 individuals with CP in Gross Motor Function Classification System (GMFCS) Levels I to III.

Method: Gross Motor Function Measure (GMFM) dimension D and E, the Pediatric Quality of Life Inventory (PedsQL), Pediatric Outcomes Data Collection Instrument (PODCI), Functional Activities Questionnaire (FAQ), the Functional Independence Meaure for Children (WeeFIM) scorces, 0 2 cost, temporal-spatial gait parameters, and GMFCS level were collected at baseline and at a 1-year follow-up visit. SRM values were calculated (change score/standard deviation of change score) for each tool for the subset of individuals who did not have surgery between assessments (n=290) and those who did (n=87). To allow for interpretation using Cohen’s effect sizes, SRM values were adjusted (SRM a) based on the correlation between baseline and follow-up scores (SRM/sqrt(2)/ sqrt(1-r); r=correlation).

Results: SRM a values for the non-surgical group were at the trivial level (<0.2) for 26 of 35 tools. Only Parent PODCI Upper Extremity & Physical Function (0.51) reached a medium effect size. For the surgical group, 20 of the 35 tools were above the small effect level (12, SRM a > 0.2 and 8, SRM a <-0.2). Only Parent PODCI Transfers & Basic Mobility (0.50) exceeded a medium effect size.

Conclusions: The small SRM values reported for the non-surgical group support the expectations of minimal changes in a 1-year period as the natural history of children with CP is characterized by a gradual deterioration  of gait function. More tools reached at least a small effect size in the surgical group, suggesting that orthopedic surgery results in small positive or negative changes in outcome scores. The lack of responsiveness noted could be attributed to the heterogeneity of the study population and large variability in surgical intervention, varying from isolated muscle release to multilevel bony and soft tissue procedures. In a more controlled intervention study larger SRM values might be expected. From the study design, it is difficult to know whether the tools were not responsive or if surgery does not change what the tools measured. Overall, SRM 2 values were small and did not demonstrate tool responsiveness at a moderate effect size.

Acknowledgements: Funded by Shriners Hospitals Clinical Outcomes Study Advisory Board, grant no. 9140.

 
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