Comparison of energy efficiency between Wearable Power-Assist Locomotor (WPAL) and two types of knee-ankle-foot orthoses with a medial single hip joint (MSH-KAFO)

Abstract

Objective: To compare the energy efficiency of Wearable Power-Assist Locomotor (WPAL) with conventional knee-ankle-foot orthoses (MSH-KAFO) such as Hip and Ankle Linked Orthosis (HALO) or Primewalk.

Study design: Cross over case-series.

Setting: Chubu Rosai Hospital, Aichi, Japan, which is affiliated with the Japan Organization of Occupational Health and Safety.

Methods: Six patients were trained with MSH-KAFO (either HALO or Primewalk) and WPAL. They underwent 6-minute walk tests with each orthosis. Energy efficiency was estimated using physiological cost index (PCI) as well as heart rate (HR) and modified Borg score. Trial energy efficiency with MSH-KAFO was compared with WPAL to assess if differences in PCI became greater between MSH-KAFO and WPAL as time goes on during the 6-minute walk. Spearman correlation coefficient of time (range: 0.5–6.0 minutes) with the difference was calculated. The same statistical procedures were repeated for HR and modified Borg score.

Results: Greater energy efficiency, representing a lower gait demand, was observed in trials with WPAL compared with MSH-KAFO (Spearman correlation coefficients for PCI, HR and modified Borg were 0.93, 0.90 and 0.97, respectively, all P < 0.0001).

Conclusions: WPAL is a practical and energy efficient type of robotics that may be used by patients with paraplegia.

Keywords:

• Wearable power-assist locomotor
• Orthosis
• Energy efficiency
• Physiological cost index
• Spinal cord injury
• Rehabilitation

Acknowledgements

We gratefully acknowledge Mr. Hagemu Higuchi and Mr. Hiroshi Deguchi of ASKA Corporation for their technical assistance. We also thank all participants for joining our study.

Disclaimer statements

Contributors None.

Funding None.

Conflict of interest WPAL used for the present study was lent free of charge from the Tomei Brace Company. AU is a salaried employee of the Tomei Brace Company. The remaining authors declare no conflict of interest.

Ethics approval None.