The influence of polypropylene ankle-foot orthoses on the gait of cerebral palsied children
Clinical experience in Dundee in the use of polypropylene ankle-foot orthoses (AFOs) with cerebral palsied (CP) children had indicated that the use of the AFOs could affect markedly their gait. A research programme was established to investigate the influence of polypropylene AFOs on the gait of CP children. This included the use of a TV-computer gait analysis system. A 2-dimensional analysis was conducted which included the calculation of the external moments created by the ground-to-foot force vector in the sagittal plane at the hip, knee and ankle joints. A total of eight CP children were analysed walking barefoot and with a range of prescriptions of AFOs and associated footwear adaptations. Gait analysis was conducted on six normal children to obtain data for comparative purposes. In parallel to the gait analysis the influence of AFOs on the muscle activity of the ankle-foot complex was monitored using a force transducer and electromyography. Analysis of the data indicated that the kinetic aspects of the gait of CP children were different from normal children. The use of AFOs resulted in a modification of the nature of the ground-to-foot reaction force and the external moments generated, in the sagittal plane at the joints of the leg. Alteration of the characteristics of the associated footwear resulted in similar modifications to the gait patterns. An appropriate prescription resulted principally in the reduction of excessive external knee extension moments in mid stance and in the ability to generate improved push-off forces in late stance. The results of the research programme have confirmed the clinical impression, and attitude to management, that the AFO-footwear characteristics selected for a given child are critical. It is now apparent that further kinetic improvements, not necessarily observable clinically, may be possible by further fine-tuning of the characteristics.