Hybrid Assistive Limb Intervention in a Patient with Late Neurological Deterioration after Thoracic Myelopathy Surgery due to Ossification of the Ligamentum Flavum

Abstract

Purpose: We evaluated improvements in gait after using the Hybrid Assistive Limb (HAL®) exoskeleton robot in a patient with late-onset neurological deterioration of lower extremity function after undergoing thoracic spine surgery for a myelopathy due to ossification of the ligamentum flavum.

Case presentation: A 70-year-old man participated in ten 20 min sessions of HAL intervention, twice weekly for five weeks. The effects of each HAL session were evaluated based on changes in performance on the 10 m walk test (10 MWT), lower limb kinematics quantified from motion capture, and the activation ratio of the gastrocnemius, measured before and after the intervention. Muscle activity was recorded using surface electromyography and synchronized to measured kinematics. The HAL intervention improved gait speed and step length, with an increase in the hip flexion angle during the swing phase and a decrease in the activation ratio of the gastrocnemius. The modified Ashworth scale improved from 1+ to 1 and International Standards for Neurological and Functional Classification of Spinal Cord Injury motor scores from 34 to 49.

Conclusion: Intervention using the HAL exoskeleton robot may be an effective method to improve functional ambulation in patients with chronic spinal disorders.

Figure 1

The exoskeleton Hybrid Assistive Limb (HAL), showing the power units of the hip and knee joints, bilaterally, which contain angular sensors, and the force-pressure sensors in the shoes.

Figure 2

A summary of the progression of symptoms of the patient.

Figure 3

(a) Midsagittal T2-weighted magnetic resonance image of the thoracic spine, 2 years before the HAL intervention and 15 years after the T9–T12 laminectomy. (b) A high-power magnification view of (a), showing a high-intensity change persisting in the decompressed spinal cord at the T11-T12 level (arrow).

Figure 4

A photograph of the HAL exoskeleton, including the All-in-One Walking Trainer with the harness which was used during gait session to prevent a fall. The trainer provided consent for use of his image in this report.

Figure 5

Graphs of the measured variables of the 10 MWT: (a) walking speed, (b) cadence, and (c) step length, measured without HAL, before each HAL session, and (d) walking speed, (e) cadence, (f) step length, and (g) walking distance, measured with the HAL, during each HAL session.

Figure 6

(a) Temporal profile of the angular position of the hip joint over the gait cycle, measured without the HAL, before and after the HAL intervention. (b) Range of motion of the hip over the gait cycle, measured without the HAL, before and after the HAL intervention. Error bars indicate the standard errors of the mean. Flex, flexion; Ext, extension; ROM, range of motion.

Figure 7

(a) Temporal profile of the angular position of the knee joint over the gait cycle, measured without the HAL, before and after the HAL intervention. (b) Range of motion of the knee over the gait cycle, measured without the HAL, before and after the HAL intervention. ROM, range of motion.

Figure 8

(a) Temporal profile of the angular position of the ankle joint over the gait cycle, measured without the HAL, before and after the HAL intervention. (b) Surface electromyography of the gastrocnemius muscles. (c) The muscle activation ratio of the gastrocnemius (swing phase to the total step cycle), before and after the HAL intervention. (d) Toe clearance, before and after the HAL intervention.

Figure 9

Step length before and after the HAL intervention.