This study investigated the immediate effect of a 10° dorsiflexion inducing AFO on spatiotemporal gait parameters compared to barefoot and a hinged AFO in ten children with spastic diplegia. The results showed that a 10° dorsiflexion inducing AFO improved gait velocity, cadence, step length, stride length, single support time, and double support time significantly more than barefoot and on a hinged ankle-foot orthosis.
Abnormal gait patterns may be observed in children with cerebral palsy. Crenna11 argued that children with cerebral palsy had abnormal gait because of weakened muscle strength, spasticity, a contraction coordination problem of the agonist muscle and the antagonist muscle, and the occurrence of joint deformation. Lim27 reported that children with cerebral palsy had difficulty in conducting daily life independently because of the decrease in gait velocity and step, the instability in the posture while walking, and excessively used energy. According to the previous studies on the gait characteristics of children with cerebral palsy, Gage et al.17 found that the gait of children with spastic cerebral palsy prevented a normal interaction between foot and ankle at the support surface and reduced the plantarflexion moment and force generation during the swing phase because plantarflexion persisted throughout the standing phase. Skrotzky44 reported that there were asymmetrical body movements, and McCubbin and Shasby32 argued that excessive extension reflexes consequently constrained movements by limiting functional and normal body movements and delaying or restricting the use of the antagonistic muscle. Additionally, Liao et al.26 showed that the gait ability of children with cerebral palsy was closely related to stability when standing up. They also argued that the slowed gait velocity reflected the asymmetry caused by decreased balance ability, reduced muscle strength, and deformed, damaged, and altered biomechanics due to reducing motor control ability after investigating the effects of balance ability while standing on that gait ability.26 Mann31 considered the decrease in stride length as an important factor. Skrotzky44 showed that the decrease in stride length of children with cerebral palsy varied by the disability severity of children with cerebral palsy and the stride length became shorter when the effects of the neuromuscular system became larger. Pope et al.40 reported that the limit of step length in children with cerebral palsy was caused by the reduction of the hip flexor, the decrease of pelvis rotation, and the increase of trunk flexion angle. Sutherland et al.47 argued that cadence, step length, and stride length, spatiotemporal parameters, were the simplest and most perfect variables for analyzing gait and they were basic elements for examining mature gait.
The results of this study showed that walking with a 10° dorsiflexion inducing AFO significantly increased gait velocity, cadence, step length, single leg support, and double leg support that walking with barefoot or with a hinged ankle-foot orthosis. In previous studies applying a hinged ankle-foot orthosis, Mael et al.30 found that wearing a hinged AFO improved the gait velocity of children with spastic cerebral palsy and decreased the strength of ankle by increasing the dorsiflexion during the initial contact and the swing phase. Chon et al.9 investigated the effects of a plastic hinged AFO on the gait of hemiplegic patients. They reported that it inhibited the excessive and abnormal movements of the plantarflexor and induced the normal initial contact of the foot to reduce the excessively energy consumption while walking, increase gait velocity, and improve gait ability. Brehm4 also showed that wearing a hinged AFO took less energy for walking and increased gait velocity than barefoot walking so it made more efficient gait. Buckon et al.6 investigated the effects of a hinged ankle-foot orthosis, an ankle-foot orthosis, and a posterior leaf spring on the gait of children with spastic diplegia and revealed that a hinged AFO increased step length and stride length significantly more than other orthoses. Radtka et al.41 investigated the effects of wearing a hinged AFO and an AFO on the gait of children with spastic diplegia and reported that they significantly changed step length. Ferrari et al.16 and Park et al.38 showed that wearing an ankle orthosis prevented the deformity and contraction of the ankle joint and improved walking efficiency and walking ability. Romkers et al.42 found that a hinged AFO regulated excessive plantarflexion during the swing phase and corrected the preliminary positioning of the foot required for initial contact. Balaban et al.2 argued that it changed the equinovarus gait, an abnormal gait pattern of children with cerebral palsy, to a normal gait pattern that contacted the heel first. Jacobs20 reported that a hinged AFO had a positive effect on maintaining body balance to keeping up a normal standing posture by improving the function of the foot, maintaining the body balance and equal weight distribution, and supporting weakened and impaired parts. Therefore, it is believed that the results of this study also showed that wearing a hinged AFO and a 10° dorsiflexion inducing AFO increased gait velocity, cadence, step length, and stride length, concurring with the results of previous studies. Kim and Park22 investigated the effects of an AFO on balance depending on ankle degrees and reported that the forward and backward movements of the pressure center of the body significantly decreased when the dorsiflexion angle of the ankle joint of the AFO was 10 degree. Collins et al.10 indicated that all ankle movements including dorsiflexion regulated the interactions between the ground and the foot and they were essential elements for gait and balance. They argued that dorsiflexion angle while walking should be at least 10° for these functional activities and normal gait. Mecagni et al.33 showed that when the range of motion of ankle joint was reduced, balance ability and functional abilities decreased and it changed the movements of the whole body to reduce the posture control ability including the generation of compensatory movements in the hip joint and truck. Esquenazi et al,14 Fatone et al,15 Nolan et al.36 suggested that the stability of the ankle joint reduced the instability of the ankle joint and increased the balance ability. Wang et al.48 reported that AFO made it easier to induce body center movement while walking to reduce body asymmetry and positively affect the static and dynamic balance. The gait ability of children with cerebral palsy is significantly related to the stability of standing posture, while the standing balance and walking ability are highly correlated. Andersson et al,1 and Williams et al.50 reported that the more stable standing balance improved functional movements in gait including a faster gait velocity. Willerslev-Olsen et al.49 argued that increasing the stability of the lower extremity in the stance phase was an important factor, which allowed the opposite foot to perform an accurate and smooth swing phase movements. Gage & Novacheck18 also indicated that, for conducting efficient and accurate gait, the stance phase had to be stable, the feet had to be at the appropriate positions before stepping at the end of the swing phase, and it is important to maintain an accurate and appropriate stride length. Hassani et al,19 Smith et al,45 and Buckon et al.5 studied the effects of a hinged AFO on the gross motor function and showed that wearing a hinged AFO improved walking, running, and jumping evaluation areas the most. The results of this study showed that wearing a 10° dorsiflexion inducing AFO provided more stability for the ankle than a hinged AFO to increase the range of joint motion more concurring the results of previous studies. Therefore, the increase of the ankle joint movement was thought to have contributed to the improvement of the postural control ability and the balance ability to improve gait ability even more. Winter et al.51 investigated ankle and hip mechanisms in a standing posture using eight adult subjects and reported that an ankle strategy was completely dominant in the anteroposterior balance and a hip strategy was dominant in the mid-outward balance. Jian et al,21 and Zettel et al.53 showed that the anticipatory postural conrol that moved to the center of pressure to backward in the gait preparation phase and outward of legs in the swing phase, and the movement of the center of pressure helped the body maintain the trunk straight during single leg support and the base of support to forward with the legs in the stance phase. Kim22 found that wearing a 10°dorsiflexion inducing hinged AFO improved balance ability while standing. Therefore, it would increase the stability of supporting body weight with one leg while walking and generate sufficient propulsion for the opposite leg in the previous swing phase. Additionally, an increased dorsiflexion angle could further improve foot dragging in the swing phase, resulting in the improvement of other gait variables including step length and stride length. Balaban et al.2 found that wearing a hinged AFO decreased the single leg support and double leg support of children with spastic hemiplegic cerebral palsy. The results of this study also, as in the previous studies, showed that wearing a 10° dorsiflexion inducing hinged AFO significantly decreased single leg support and double leg support the most. These results suggested that wearing a 10° dorsiflexion inducing hinged AFO increased gait velocity and cadence greatly, which included a factor of reducing the relative support time. However, a 10° dorsiflexion inducing hinged AFO was believed to increase stable weight support by aligning the rear-foot and the mid-foot during the stance phase.35 Consequently, it is believed that stable weight support can secure the stability and mobility of the lower extremity to positively influence spatiotemporal gait indices. Moreover, it seems that securing the stability and mobility of the lower extremity can generate the cooperative movements of lower extremities and improve symmetrical body movements such as walking. Although the results of previous studies do not provide direct evidence that wearing a 10° dorsiflexion inducing AFO will improve gait ability more than wearing a common hinged ankle-foot orthosis, the results of this study confirm that wearing a 10° dorsiflexion inducing AFO increases the gait velocity, cadence, step length, and stride length of children with cerebral palsy and decreases single leg support and double leg support. Considering all these results, wearing a 10° dorsiflexion inducing AFO of children with cerebral palsy helped them adjust their ankle movements from abnormal to normal, which would increase gait velocity, cadence, step length, and stride length, and the whole gait cycle, resulting in the improvement of the gait function.
However, previous studies have shown somewhat contradictory findings regarding the effects of a hinged AFO on kinematic gait parameters.13 Moreover, it is difficult to derive a clear basis for the meaning of each variable’s effects. There is still no concrete evidence that applying ten-degree dorsiflexion to a hinged AFO would further enhance walking. This study has several limitations. First, this study analyzed the gait of a short distance due to the limitation of the length of the equipment. Therefore, it is difficult to generalize and interpret the entire gait of children with spastic diplegia. Second, this study used ten children with spastic palsy, a small sample size. As a consequence, it is difficult to generalize the results of this study for all children with spastic diplegia. Third, this study was conducted based on a cross-over design, so it was impossible to investigate or observe the durability of the effects of barefoot, a hinged ankle-foot orthosis, and a 10° dorsiflexion inducing AFO on gait. Therefore, future high-quality studies should complement these limitations and conduct long-term follow-up using a larger number of subjects.