Heterotopic triggered HAL method for patients with complete quadriplegia or paraplegia due to chronic spinal cord injury

Abstract

Patients with complete paraplegia after spinal cord injury (SCI) are difficult to walk by themselves. Gait training with conventional orthoses requires excessive upper limb usage and is difficult to train knee extensor during ambulation. Robotic devices have recently been used in clinical settings for such patients. Hybrid Assistive Limb (HAL) is a wearable exoskeleton robot that assists the user in voluntary control of knee and hip joint motion by detecting even very weak muscle activities. However, the conventional method using HAL is not applicable in patients with complete paraplegia. The purpose of this study is to describe voluntary gait and voluntary knee extension using Heterotopic Triggered HAL (T-HAL) method in patients with complete quadri/paraplegia after chronic SCI. Seven patients, 20–67 years old, C6-T11, AIS A-B, were enrolled in this study. HAL session consisted of two parts: the first session was voluntary ambulation using upper limb muscle activation; hip flexion and extension triggered by contralateral muscle activities of anterior deltoid and posterior deltoid and knee flexion and extension triggered by contralateral biceps and triceps brachii, respectively. The second session, for cases who could contract hip flexor, was done for active knee extension using hip flexor activation. Surface electromyography (EMG) was used to evaluate muscle activity of hip flexor and quadriceps femoris (Quad) in synchronization with motion capture. The modified Ashworth scale (mAs) score was evaluated before and after each session. In cases 1, 2, mAs score significantly decreased after each session. In all cases, EMG before the intervention showed no activation in either Quad. However, periodic activation of the lower limb muscles was seen during HAL ambulation. In case 3, 4, active contraction in both Quads was observed after intervention. These findings suggest that T-HAL method is feasible option for complete quadri/paraplegia with chronic SCI.