Reviews in Clinical Gerontology 1998 8; 155–161 Introduction A person who has a dropped foot is unable to lift the toes clear of the ground during the swing phase of walking. Such a problem is seen in peo- ple who have either a peripheral nerve lesion, as a result of trauma or disease, or an upper motor neuron lesion. It is the latter that responds to neu- romuscular stimulation; lesions of the lower motor neurons result in destruction of the neural pathway so that muscle contraction can be achieved only through direct stimulation of the muscle fibres. The first reference to functional electrical stim- ulation (FES) is in the classic work by Liberson et al., published in 1960. 1 At this time electrother- apy was commonplace, but functional elec- trotherapy was a new concept. Liberson defined it as follows: ‘. . to provide the muscles with elec- trical stimulation so that at the very time of the stimulation the muscle contraction has a func- tional purpose, either in locomotion or in pre- hension or in other muscle activity. In other words, functional electrotherapy is a form of replacement therapy in cases where the impulses coming from the central nervous system are lack- ing.’ Liberson et al. used a portable stimulator to correct drop-foot during walking. A train of pulses of 20–250 microseconds’ duration with a frequency of 30–100Hz and maximum peak cur- rent of 90mA was applied through conductive rubber electrodes. The negative (active) electrode was placed over the common peroneal nerve below the knee, and a large indifferent electrode either on the thigh or the lower leg. The stimula- tor was worn in the pocket and a heel switch was used to trigger the stimulus during the swing phase of the gait cycle. The switch was worn in the shoe on the affected side so that the electrical circuit was interrupted during the stance phase, when weight was on the heel, and allowed to flow when the heel was lifted during the swing phase. Liberson and colleagues study, though small and not analytical, is important, not only because it was the first. Despite technological advances such as multichannel and programmable stimulators with improved reliability and finer control, stim- ulation parameters and the basic idea have remained unchanged. Liberson was enthusiastic about the results, reporting that all subjects expe- rienced considerable improvement in gait. It is interesting to note that he also observed that ‘on several occasions, after training with the brace, patients acquired the ability of dorsiflexing the foot by themselves, although the periods of spon- taneous activity reported were only transitory’. Since Liberson developments have included the use of multichannel stimulation, percutaneous and implanted systems for walking and hand control, and closed loop stimulation to enable people with complete paraplegia to stand and take a few steps. This review, however, is confined to work with surface electrodes using single or dual channels of stimulation to correct dropped foot in subjects suffering from upper motor neuron lesions. Method Sixteen papers published between 1960 and 1997 were reviewed. A literature search using Medline traced nine publications, from which five more were found. Two further papers were reviewed, one published in Physiotherapy and one in Artificial O rgans (Table 1). Papers on the effects of neuromuscular stimu- lation fall into two categories: studies concerned mainly with the ‘orthotic effect’, that is the mea- Functional electrical stimulation: a review of the literature published on common peroneal nerve stimulation for the correction of dropped foot JH Burridge, ID Swain and PN Taylor Salisbury District Hospital, Salisbury, UK Address for correspondence: JH Burridge, Department of Medical Physics and Biomedical Engineering, Salisbury District Hospital, Salisbury SP2 8BJ, UK.