Page 59 - Maximizing the efficacy of ankle foot orthoses in children with cerebral palsy

The shank-to-vertical angle
Ankle and hip joint
Increasing heel height resulted in a significant increase in ankle dorsal flexion angle, hip flexion angle and internal plantar flexion moment at midstance. The internal ankle plantar flexion moment further increased as a result of the stiff footplate, whereas ankle angle, hip angle, and internal hip moment were not affected by footplate stiffness (see Table 3.1). No interaction effects of heel height and footplate stiffness were found for ankle angle (F=1.66, p=0.218), hip angle (F=0.24, p=0.790), ankle moment (F=0.32, p=0.732), and hip moment (F=0.05, p=0.953).
Shank-to-AFO angle
Mean (SE) Shank-to-AFO angle at midstance significantly decreased with increasing heel height (F=46.9, p<0.001), with a mean (SE) angle of 18.3° (1.23) for the low, 15.3° (0.92) for the medium, and 13.0° (0.64) for the high heel height condition. Mean (SE) Shank-to-AFO angle was 15.4° (0.91) while walking with the flexible footplate, and 15.6° (0.92) with the stiff footplate (F=0.945, p=0.356). No interaction effect of heel height and footplate stiffness was found (F=1.14, p=0.341).
dIScUSSIon
The present study demonstrates that the SVA is responsive to changes in the AFO- FC heel height, which resulted in an increase in lower limb joint flexion angles and net internal extension moments. In line with our hypothesis, the stiff footplate did not affect the SVA, although it did alter the net internal ankle and knee joint moments. The stiff footplate also affected the knee flexion angle, which is in contrast with our hypothesis.
A recent study of Jagadamma and collegues[12] showed the effects of tuning rigid AFOs on joint kinematics and kinetics in children with spastic cerebral palsy. In that study, tuning was based on inclining the SVA, starting from 12°, until the ground reaction force alignment during stance was closest to normal. They found that increasing the SVA resulted in an increased knee angle and a non-significant increase in peak hip flexion in stance. Another study of Jagadamma et al[11] also showed that when the SVA was increased from 5.6° to 10.8° after tuning, the peak knee flexion angle in stance increased. This is comparable to our study, as the SVA increased with increasing heel height, resulting in an increase in knee and hip flexion angles. Our results also show an increase in ankle dorsiflexion angle with increasing heel height, while the rigid AFOs aimed to
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