Effect of the helical orthosis on biomechanical gait variables
peripheral neuropathy, weakness of the evertor muscles, AFOs, AFO
PERIPHERAL NEUROPATHY
This is one of the first studies to evaluate the impact of AFOs on biomechanical gait variables in patients with peripheral neuropathy or NMD. The purpose of this analysis was to explain the results of the functional gait tests, however fewer significant effects of the condition were found on kinematic and kinetic variables than expected. This could result from several factors. First, we controlled the gait velocity: participants were constrained to walk at the same speed as the noAFO condition in both AFO conditions. Gait speed was therefore sub-maximal in the AFO conditions since participants were able to walk faster with the AFOs, as demonstrated by the 6MWT results. We chose this design to differentiate the specific effects of the AFO on ankle biomechanics from the more general effect, which is typically an increase in gait velocity. Second, as can be seen in Table The primary aim of an AFO is to prevent foot drop during swing phase. Median peak plantarflexion during swing was above − 5 deg with both the plsAFO and hAFO, showing that the support provided under the forefoot reduced plantarflexion. Our next aim in the design of the hAFO was that it should not interfere with ankle mobility. The results showed that this was achieved with the hAFO whereas the plsAFO limited plantarflexion during the loading response. However, although the median difference in this plantarflexion angle was significant between the hAFO and the plsAFO, it was only of 1.1° and therefore could result from measurement error. Furthermore, although quasi-stiffness during stance was higher with the hAFO than in the noAFO condition, the value was lower than with the plsAFO. Quasi-stiffness provides an indication of overall joint stiffness, including muscles and ligaments combined with the stiffness of the AFO [The hAFO was designed with a heel cup to provide ankle stability in the frontal plane since people with peripheral neuropathy or NMD often have weakness of the evertor muscles. The inversion/eversion moment has rarely been studied in the literature in comparison with the plantar/dorsiflexion moment [Although the hAFO was also designed to increase propulsion thanks to its spring like behaviour (carbon material and helical shape), we did not demonstrate this effect. However, this could not be fully analysed due to the design of the study which involved a controlled gait speed. However, in contrast with some other orthoses [