The effect of limited sensory information on exoskeleton performance in people with complete spinal cord injury.

Despite the absence of somatosensory information from the lower extremities, people with complete spinal cord injury (SCI) can maintain postural stability in an exoskeleton. This is partly because humans are able to reweigh the relative dependence on each of the senses. However, when the sensory environment is changed, people with complete SCI are limited in their ability to reweigh their sensory organization towards more dependence on somatosensory information. The aim of this study was to investigate the effect of limited visual and/or auditory information on exoskeleton performance in people with complete SCI. Three experienced exoskeleton users performed twelve walking trials in the ReWalk exoskeleton. In each trial, the presence or absence of visual and/or auditory information was varied. Exoskeleton performance was operationalized as the walking distance covered and the amount of crutch loading. In one participant, the distance covered decreased when visual information was limited. The other two participants did not show substantial differences in distance covered between sensory conditions. Two participants decreased crutch loading when visual information was restricted, and one participant decreased crutch loading when auditory information was limited. The current study suggests a limited influence of the presence or absence of visual and auditory information on the distance covered in people with complete SCI walking in an exoskeleton. Interestingly, crutch loading seemed to decrease rather than increase when visual or auditory information was limited.

Case Report: Description of two fractures during the use of a powered exoskeleton.

Introduction: Powered robotic exoskeletons are a promising solution to enable standing and walking in patients with spinal cord injury (SCI). Although training and walking with an exoskeleton in motor complete SCI patients is considered safe, the risks of unexpected (technical) adverse events and the risk of fractures are not fully understood. This article reports the occurrence of two different cases of bone fracture during exoskeleton usage. Furthermore, advice is given for extra safety training and instructions. Case presentation: The first case concerns a 47-year-old woman with T12 AIS A SCI. Her exoskeleton shut down unexpectedly probably causing a misalignment of the joints of her lower extremities relative to the joints of the exoskeleton, which resulted in a fracture of her left tibia. The second case involves a 39-year-old man with L1 AIS B SCI. An unexpected fracture of the right distal tibia occurred without a specific prior (traumatic) incident. Discussion: Exoskeleton training instructors, SCI patients and their buddies should be instructed how to handle emergency situations. Furthermore, they should be aware of the risk of stress fractures of the lower extremities. Proper alignment of the exoskeleton relative to the body is of utmost importance to reduce fracture risk. In the case of swelling and discoloring of the skin, radiographic examination should be performed in order to exclude any fracture.