Evaluation of conventional and dynamic ankle foot : orthosis in cerebral palsy subjects using gait analysis

Abstract

of thesis entitled Evaluation of Conventional and Dynamic Ankle Foot Orthosis in Cerebral Palsy Subjects Using Gait Analysis submitted by Gilbert W.K. Lam for the degree of Master of Philosophy at the University of Hong Kong in December 2003 Conventional ankle foot orthosis (AFO) is commonly prescribed for children with dynamic equinus and it creates a three-point pressure system to control this deformity. However, in the past 10 years, dynamic ankle foot orthosis (DAFO), which controls the equinus deformity by altering the sensory input of foot reflexes, has been increasingly used as an alternative to the AFO. These two orthoses control the equinus deformity by different mechanisms, but few kinematics, kinetics and electromyography (EMG) studies have been conducted to compare them. The aim of this study was to document alterations of gait and to evaluate the biomechanical and electromyographic effects of different orthotic treatments on walking in spastic cerebral palsy (CP) patients. Thirteen CP patients with dynamic equinus and eighteen normal subjects underwent motion analysis with Electromyography (EMG). The CP patients received three sessions of data collection on the same day: barefoot (group 1), using AFO (group 2) and using DAFO (group 3) while the normal participants served as control. The repeated measured ANOVA test was used for statistical calculation. The CP subjects had a significant shorter stride length, a slower walking speed and an abnormal ankle positioning when compared to the normal control. In addition, the muscle firing duration was longer and the muscle median frequency (MF) was higher for all muscle groups than those of the normal subjects. These findings were characteristics of spasticity in cerebral palsy patients. The longer muscle firing duration and higher muscle MF also indicated that these muscles would get tired much sooner than that of normal subjects. Both conventional ankle foot orthosis (AFO) and supramalleolar type of dynamic ankle foot orthosis (DAFO) allowed longer stride length; permitted better pre-positioning at initial contact; successfully controlled the excessive plantarflexion during the swing phase and reduced the muscle firing duration of the calf muscles. Moreover, DAFO allowed a significant larger total ankle range of motion. On the other hand, AFO significantly reduced the excessive MF while DAFO did not. In summary, DAFO has the advantages of controlling equinus, allowing longer stride length and imposing less restriction on ankle motion. Subjectively, DAFO was preferred by patients because they were lighter and less bulky.