Hybrid gait training with an overground robot for people with incomplete spinal cord injury: a pilot study

Abstract

Locomotor training has proved to provide beneficial effect in terms of mobility in incomplete paraplegic patients. Neuroprosthetic technology can contribute to increase the efficacy of a training paradigm in the promotion of a locomotor pattern. Robotic exoskeletons can be used to manage the unavoidable loss of performance of artificially driven muscles. Hybrid exoskeletons blend complementary robotic and neuro-prosthetic technologies. The aim of this pilot study was to determine the effects of hybrid gait training in three case studies with persons with incomplete spinal cord injury (iSCI) in terms of locomotion performance during assisted gait, patient-robot adaptations, impact on ambulation and assessment of lower limb muscle strength and spasticity. Participants with iSCI received interventions with a hybrid bilateral exoskeleton for 4 days. Assessment of gait function revealed that patients improved the 6 min and 10 m walking tests after the intervention, and further improvements were observed 1 week after the intervention. Muscle examination revealed improvements in knee and hip sagittal muscle balance scores and decreased score in ankle extensor balance. It is concluded that improvements in biomechanical function of the knee joint after the tested overground hybrid gait trainer are coherent with improvements in gait performance.

Keywords: gait; hybrid exoskeleton; lower extremity; motor recovery; muscular electrical stimulation; spinal cord injury.

FIGURE 1

Protocol for evaluation of hybrid gait training with Kinesis overground robot in iSCI. Examination sessions and walking conditions are identified as follows. Walking function evaluation session: E; examination of response to EMS: S; training session: T; hybrid-cooperative condition: HC; cooperative-only condition: CO; hybrid-stiff condition: HP.

FIGURE 2

Experimental setup for data collection and testing hybrid gait training with Kinesis overground robot.

FIGURE 3

Reference (blue) and actual (cyan) knee joint sagittal angle, interaction forces (red, [N.m/deg]), and ILC stimulation output (black, [μs]) during HC walking condition. First steps of left leg (A), last steps of left leg (B), first steps of right leg (C), last steps of right leg (D).

FIGURE 4

Single-subject performance in the cycle domain during the HC condition. Controller stiffness (magenta line), NTTI (red), maximum angle achieved during flexion (blue line), normalized torque-time integral (red line), and NILC (black line) of left (A,C,E) and right (B,D,F) legs. Green boxes indicate when EMS learning state was active within the cycle. Controller stiffness, maximum angle and normalized stimulation curves are scaled for visualization purposes.

FIGURE 5

Single-subject performance of quadriceps EMS during the walking experiment. The data represents the averaged stimulation for the knee extensor muscles during the stance phases of walking. Cycle means number of step.

FIGURE 6

Pre and post condition measures of physiological effort and subjective perceptions. The reported data are average and standard deviation for systolic BP, diastolic BP, heart rate, pain, fatigue, and comfort.

FIGURE 7

Sagittal manual muscle testing (MMT) score for (A) hip, (B) knee, and (C) ankle joints. The reported data are average and standard deviation of the relative changes between the examination sessions I–II, II–III, and I–III.

FIGURE 8

Results for spasticity ASHWORTH and PENN scales. Score can range from 0 to 4. The reported data are median and range.