Neuroscience Poster Session

Re^2: Effect Of Hinged Ankle Foot Orthoses On The Oxygen Cost Of Walking

Michel Ladouceur

Hi again Dr Maltais,

Thank you for your reply to my question.

>To the best of my knowledge, most studies have looked at the effect of the orthoses after the child has been habituated to the brace, the rationale being that the effects are likely to be stable only after the child is familiar with the brace. In our study, for example, all children had been wearing hinged AFO for at least 2 years (avg. 5 years)and children wore their braces for about 8 hrs per day during the week. I agree with you that it would be interesting to see the effects of habituation to the AFO. Given that many children are under 5 yrs old when they receive their first pair of hinged AFO, I think much would need to worked out in terms of a feasible protocol. Younger chldren as you may know, are more of a challenge to test.

I do agree with you it would be a very challenging study to do in light of these constraints.

>First, I am hesistant to use the word minimal. The reduction in oxygen uptake we found due to the brace was the same as that found with orthopedic surgery, which is the only other effect that we could find in the literature (with a protocol that was sufficiently well defined) that used oxygen uptake during treadmill walking as an outcome measure.  So, while we know that the oxygen cost of walking is up to 2.5 times higher in these children compared to healthy peers, we do not know enough about the extent it can be affected by any intervention; therefore we really do not have sufficient data to quanitfy any change as minimal or maximal. Moreover, we do not know enough yet about how such changes translate into changes in daily function.

I apologise for not being clear enough on that point but my use of the word minimal was not to be used in a sense of comparaison with other manamgement modalities but more in the sense of a small change in the energy efficiency. Furthermore, as you state it is not known how such changes can translate into an increase in mobility. I would make the hypothesis that since mobility is not a linear continuum a small number of participants would have an improvement in their daily function.

>Now I have a question for you.
>What do you mean by an orthotic effect? Are you comparing the effect of using FES to a brace? What did you measure?  Was this with children with cerebral palsy?
>> in a greater period of time this orthotic effect is modulated and is >also present concurently with a therapeutic effect.
>Now I am interested in what you term a therapeutic effect and how this is different from an orthotic effect.

The orthotic effect is the difference between with and without the orthosis at one point in time whereas the therapeutic effects are the changes occurring over a certain time in the without orthosis condition. We investigated spinal cord injured participants with an incomplete motor function loss that were classified as chronic cases (>1 year post-injury). We measured their maximal overground walking speed, spatial-temporal and kinematics during overground walking, the walking efficiency using the Physiological cost index, a mobility scale as well as other locomotor tasks and reflex assessment using ramp and hold imposed perturbations. The objective of the study was not to compare the FES-assisted walking with any other interventions but to see what were the effect of using it. Suprisingly, all the participants had an improvement during the first year of using the FES-assisted walking  but all of the improvement was due to the therapeutic effect. Eventhough the orthotic effect changed during the intervention period on average it was equivalent to zero. But by further analysing the data it was shown that the orthotic effect was inversely correlated to the initial walking speed with the slowest walker benefiting more from the FES orthosis then faster walker, eventhough the therapeutic effect in absolute terms was higher for the fastest walker.  

Hence, the question I would like to see answered would be: Does Hinged AFO have a therapeutic effect that could be added to the orthotic effect that you report?

Thank you for your time and good luck also.


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