Page 38 - Maximizing the efficacy of ankle foot orthoses in children with cerebral palsy

38
Chapter II
Optimal AFO selection procedure
Following a standard procedure, evaluation of FRO efficacy of the three configura- tions (T1K1, T1K2 and T1K3) will lead to selection of the subject’s optimal FRO configura- tion (see Figure 2.2). Since clinical assessment of FRO effectiveness in children walking with excessive knee flexion is mainly based on knee kinematics in stance, the minimum amount of knee flexion (i.e. peak knee extension) in the single support phase will be the main discriminating parameter. The configuration that results in smallest peak knee flexion will be selected as the subject’s optimal FRO. Differences of less than 5o will be considered equal, since this angle lies within the variability of 3D-gait analysis[45]. Should minimum knee flexion in single support be unable to discriminate between the remain- ing configurations, walking energy cost (expressed as net non-dimensional energy cost relative to speed-matched control cost (SMC-EC)[46,47] will be decisive. In this situation, the FRO that results in the lowest SMC-EC will be selected as the subject’s optimal FRO.
Outcome measures
Outcome measures for this study are categorised in accordance with the ICF[34] and cover the components ‘body functions and structures’ and ‘activities and participation’, as well as personal and environmental factors[34]. An overview of all outcome measures is presented in Table 2.2.
Primary outcome
Our primary outcome measure is walking energy cost, which will be measured dur- ing a 6-minute walking test on an indoor oval track. Subjects will be asked to walk at a self-preferred comfortable speed, during which oxygen uptake and carbon dioxide production will be measured using the accurate and reliable Metamax 3B portable gas analysis system (Cortex Biophysik, Leipzig, Germany). Calculations will be based on mea- surements during a steady state of walking, defined as a period of at least one minute in which fluctuations in walking speed, oxygen uptake and carbon dioxide production show the least change[47].