Powered Exoskeletons for Walking Assistance in Persons with Central Nervous System Injuries: A Narrative Review

Individuals with central nervous system injuries are a large and apparently rapidly expanding population as suggested by 2013 statistics from the American Heart Association. Increasing survival rates and lifespans emphasize the need to improve the quality of life for this population. In persons with central nervous system injuries, mobility limitations are among the most important factors contributing to reduced life satisfaction. Decreased mobility and subsequently reduced overall activity levels also contribute to lower levels of physical health. Braces to assist walking are options for greater-functioning individuals but still limit overall mobility as the result of increased energy expenditure and difficulty of use. For individuals with greater levels of mobility impairment, wheelchairs remain the preferred mobility aid yet still fall considerably short compared with upright bipedal walking. Furthermore, the promise of functional electrical stimulation as a means to achieve walking has yet to materialize. None of these options allow individuals to achieve walking at speeds or levels comparable with those seen in individuals with unimpaired gait. Medical exoskeletons hold much promise to fulfill this unmet need and have advanced as a viable option in both therapeutic and personal mobility state, particularly during the past decade. The present review highlights the major developments in this technology, with a focus on exoskeletons for lower limb that may encompass the spine and that aim to allow independent upright walking for those who otherwise do not have this option. Specifically reviewed are powered exoskeletons that are either commercially available or have the potential to restore upright walking function. This paper includes a basic description of how each exoskeleton device works, a summation of key features, their known limitations, and a discussion of current and future clinical applicability.