Page 32 - Maximizing the efficacy of ankle foot orthoses in children with cerebral palsy

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Chapter II
suggesting that there may be an optimal match between a patient’s characteristics and the mechanical properties of an AFO. A similar principal might also apply to FROs.
A conventional FRO is a rigid type of AFO, and includes a ventral shell and a rigid foot- plate. The biomechanical mechanism of an FRO is to create a knee extensor moment dur- ing midstance and terminal stance, by shifting of the ground reaction force forward[21]. Although an FRO might be effective in this respect, ankle push-off power is obstructed by an impeded plantar flexion in terminal stance and preswing. To enhance push-off power, a more spring-like FRO could potentially be beneficial, since it could store energy at the beginning of the stance phase that is released and returned in preswing. Achiev- ing a sufficiently high stiffness to counteract knee flexion while including the potential benefit of spring-like properties in terms of walking energy cost may result in an optimal FRO stiffness based on the least compromise between these two goals.
Designing and evaluating the efficacy of such an optimal FRO requires an evaluation of the effects of different degrees of FRO ankle stiffness on various aspects of gait, i.e. function, mobility and participation. This implies a need for a set of outcome measures that covers all domains of the International Classification of Functioning, Disability and Health (ICF)[34]. Evaluating the effects of an intervention on more than one of the ICF domains will provide insights into mutual relations, thereby aiming to identify possible working mechanisms[35] , which will contribute to improved FRO treatment.
FRO treatment could be further improved by identifying those children who could benefit from FROs[30]. Rogozinski et al.[21] explored clinical examination parameters that might explain the efficacy of FROs in CP children walking with excessive knee flexion. They found a strong, negative correlation between knee and hip flexion contractures and peak knee extension, achieved during walking with an FRO. Other studies have shown that child characteristics and environmental factors predict the response to re- habilitation interventions such as Botulinum toxin A injections[36-38] and surgery[39-41]. Spe- cific patient characteristics might also be relevant predictive factors for FRO efficacy.
In summary, evidence supporting the efficacy of FROs in children with spastic CP walking with excessive knee flexion remains inconclusive. Understanding of both the underlying working mechanisms and the factors predictive of treatment success is still lacking. Therefore, this project has two main goals: