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)

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.