Evaluation of FES systems: methodological considerations

The application of functional electrical stimulation (FES) systems can be broadly divided into those in which the application is thought to principally have a therapeutic effect (such as prevention of shoulder subluxation) and those in which the principal effect is of a functional nature (such as gait systems). However, the boundaries for this division are not clear, for example the use of the peroneal brace may result in some carry over effects in addition to the functional use of the device. To examine the methodological considerations of evaluating an FES system one needs to consider development of such systems. The evolution of an FES system for clinical use can be broadly broken down into the following stages: initial concept; initial design; trial on a few subjects (in many cases just one subject); refinement of system; clinical trial on larger population and multi-centre trials; exploitation (involving manufacturers, service providers and education of professional users). At present there are many FES systems which have gone through stages one to three having been shown to work on one or two selected subjects, but for the majority of these there has been no follow up work to demonstrate benefits for a population