Exploring the energy efficaciousness of reciprocating gait orthoses and powered exoskeletons for adults with traumatic paraplegia

Background – Although there are numerous physiological, psychological and social benefits associated with the use of reciprocating gait orthoses (RGOs) and powered exoskeletons for ambulation in adults with paraplegia as a result of spinal cord injury (SCI), a major factor contributing to non-adherence is the high energy expenditure associated with their use.(1) A greater understanding of the energy consumption and activity intensity associated with ambulation in these orthotic devices might facilitate further design improvements and augment rehabilitation training.
Aim – This literature review will produce a synthesis of evidence pertaining to energy expenditure while walking with RGOs and powered exoskeletons as prescribed for adults with traumatic paraplegia and explore whether advanced orthotic solutions positively impact energy cost and improve adherence.
Method: Search Strategy - Population Intervention Comparison Outcome method and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to search for and report pertinent literature. Search terms including parapleg*, orthos*, RGOs, exoskeletons, energy* connected with Boolean operators AND/OR were used within search engines including SUPrimo Library, PubMed, Web of Science, Embase, IEEE Xplore, ProQuest and clinicaltrials.gov website. Inclusion criteria comprised studies reporting energy outcomes with commercially available RGOs and FDA approved exoskeletons involving adults with traumatic paraplegia. Eleven and seven studies pertaining to RGOs and exoskeletons respectively were graded using Scottish Intercollegiate Guidelines Network grading system which was also used to collate levels of evidence and provide grades of recommendations.
Results- Energy outcomes for RGOs and exoskeletons did not differ significantly, despite weight difference between devices. Compared to RGOs, ReWalk and Indego, EksoGT showed the most energy efficient scoring as demonstrated by heartrate response (HR), O2 consumption and O2 cost even with higher levels of SCI. Isocentric RGO (IRGO) showed improved scores with energy parameters including HR and Physiological Cost Index with the introduction of articulated AFOs with dorsiflexion assists lowering metabolic cost with improved velocity. The Louisiana State University RGO showed improved scores with VO2 rate, O2 cost, energy expense and energy cost, with the addition of functional electrical stimulation demonstrating improved cardiac output, although impact on energy remained inconclusive. Respiratory exchange ratio values indicated that RGO walking is a strenuous activity, while metabolic equivalent of task scores demonstrated that walking with exoskeletons is classified as light to moderate activity.
Discussion and Conclusion- Although the level of evidence is low, with insignificant energy score differences between exoskeletons and RGOs, there is an indication that EksoGT is more efficient than other exoskeletons and RGOs. Evidence regarding which RGO is more energy efficient remains inconclusive. Longitudinal studies with larger sample sizes, exploring energy outcomes out with gait laboratories, evaluating the impact of training to increase aerobic capacity, muscle strength and endurance and subgroup analysis based on participant demographics would contribute to evidence-based practice.

1. D'Ambrosia R, Solomonow, M., & Baratta, R. V. . Current status of walking orthoses for thoracic paraplegics. Iowa Orthop J. 1995;15,: 174–81.