Activation of lower back muscles via FES for pressure sores prevention in paraplegia: a case study

The aim of this paper is to show the feasibility of the use of functional electrical stimulation (FES) applied to the lower back muscles for pressure sores prevention in paraplegia. The hypothesis under study is that FES induces a change in the pressure distribution on the contact area during sitting. Tests were conducted on a paraplegic subject (T5), sitting on a standard wheelchair and cushion. Trunk extensors (mainly the erector spinae) were stimulated using surface electrodes placed on the skin. A pressure mapping system was used to measure the pressure on the sitting surface in four situations: (a) no stimulation; (b) stimulation on one side of the spine only; (c) stimulation on both sides, at different levels; and (d) stimulation at the same level on both sides, during pressure-relief manoeuvres. A session of prolonged stimulation was also conducted. The experimental results show that the stimulation of the erector spinae on one side of the spine can induce a trunk rotation on the sagittal plane, which causes a change in the pressure distribution. A decrease of pressure on the side opposite to the stimulation was recorded. The phenomenon is intensified when different levels of stimulation are applied to the two sides, and such change can be sustained for a considerable time (around 5 minutes). The stimulation did not induce changes during pressure-relief manoeuvres. Finally, from this research we can conclude that the stimulation of the trunk extensors can be a useful tool for pressure sores prevention, and can potentially be used in a routine for pressure sores prevention based on periodical weight shifts.