Page 31 - Maximizing the efficacy of ankle foot orthoses in children with cerebral palsy

IntrodUctIon
With an incidence of 2-3 per 1000 living births, cerebral palsy (CP) is the most frequent cause of motor disorders in childhood in Western countries[1]. Spastic motor disorders are most common in children with CP, with symptoms of spasticity, muscle weakness and decreased selective motor control[2], often causing limitations in mobility[3], which may lead to a restricted participation in everyday life[4].
Although more than half of all children with bilateral spastic CP walk independently with or without an assistive device[5], most experience mobility-related problems such as reduced walking speed and/or an increased walking energy cost[6-12]. These problems are often caused by gait deviations[13-16], which can be corrected by prescribing ankle foot orthoses (AFOs). An AFO imposes a mechanical constraint on the ankle, either to com- pensate for loss of function[17-19] or to counteract an excess of function[20,21]. An AFO there- fore acts by applying control to the ankle and foot and, dependent on its design, it can indirectly stabilise the knee and hip joints[22]. As such, AFOs aim to improve, i.e. normalise joint kinetics, joint kinematics and spatio-temporal parameters[17,23-26]. Improvements in joint kinetics and kinematics have been shown to be closely coupled to an improved walking energy cost, which leads to benefits in walking ability; an effect also noted in the context of orthotic interventions[23,25-27]. This applies especially to children who walk with excessive knee flexion in midstance, since this walking pattern is particularly energy consuming[9,10] and these children are liable to show deterioration in walking ability in (pre-) puberty[28,29].
A variety of AFO types are available, depending on the specific gait deviations of the child. For children who walk with excessive knee flexion, orthoses with a ventral shell, also known as floor reaction orthoses (FROs), are commonly prescribed[20]. Although FROs are widely used in spastic CP, evidence supporting their effectiveness is so far lack- ing. The decision-making process leading to FRO prescription is still based on expert opinion and experience (i.e. a trial-and-error approach), resulting in differences in treat- ment paradigms with respect to both the indication and the mechanical construction of FROs[30,31]. This is reflected in current literature, as studies have shown that wearing an FRO can be effective in decreasing walking energy cost, but may also have no effect[32] or even be adverse in some children in terms of walking energy cost or walking speed[26,32].
This variation in FRO effectiveness might be partly explained by the match of the
mechanical properties of the orthosis to a patient’s specific gait deviations. Research
in adults with neurological disorders has shown that walking energy cost with a typi-
cal spring-like AFO could be optimised by choosing the correct AFO ankle stiffness[33],
II
The AFO-CP protocol
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