The effect of vibrotactile feedback for complete spinal cord injury patients on exoskeleton performance

Rationale: Complete Spinal Cord Injury (SCI) patients lack motor function below the level of lesion and are wheelchair dependent. Exoskeletons give complete SCI patients the ability to walk individually. Although exoskeletons generate the basic motions for ambulation, postural stability has to be maintained by the user. However, the ability of complete SCI patients to maintain postural stability is affected. This is because complete SCI patients miss essential somatosensory information from below their level of lesion. Hence, walking in an exoskeleton is demanding and crutches are necessary to maintain balance.

When sensory information of a specific system is lost, the lack of sensory information can be substituted by providing feedback to another sensory system. As sensory feedback has shown to improve postural control in patients missing essential sensory information, such sensory substitution may also be effectively incorporated in complete SCI patients using an exoskeleton.

Objective: The aim of this study is to investigate the effect of discrete vibrotactile feedback of mediolateral weight shift and step initiation for complete SCI patients on the use of an exoskeleton.

Study design: The proposed study is an experimental pilot study.

Study population: Ten complete SCI patients (American Spinal Injury Association Impairment Scale (ASIA) A or B), who previously participated in the exoskeleton training program of the Sint Maartenskliniek and are able to walk individually, are included.

Main study parameters/endpoints: The primary outcome measures are the maximal weight transfer onto a single limb during a standing lateral weight-shifting exercise, the mean velocity of the centre of pressure during quiet stance and the walked distance during one minute of straight walking.

Based on promising results of studies on sensory substitution, it is hypothesised that vibrotactile feedback provided to a complete SCI patient improves the performance with an exoskeleton.

Two sessions of one and a half hour.

In this experimental pilot study complete SCI patients, who previously participated in the exoskeleton training program of the Sint Maartenskliniek, are included. In the first session, subjects will start with a training session of one hour to become familiar with the vibrotactile feedback system during standing and walking in an exoskeleton. Subsequently, an experimental session of half an hour will follow in which the subjects will perform stance exercises while vibrotactile feedback is alternately present or absent. Within a week, subjects complete another experimental session of one and a half hour in which they will perform gait exercises while sensory feedback of different modalities is alternately present or absent.