The Effects Of Robotic Assisted Locomotor Training On Functional Recovery

Mehdi M Mirbagheri, Rehabilitation Institute Of Chicago/Northwestern University; Krista Settle; Cheng-Chi Tsao; Elisa Pelosin; Willam Z Rymer

Description: A novel system identification technique was used to characterize the effects robotic assisted locomotor training (LOKOMAT) on neuromuscular properties, gait and muscle strength in the chronic stages of rehabilitation following motor incomplete SCI. The results demonstrate the significant therapeutic effects of the LOKOMAT on the neuromuscular mechanical abnormalities, impairments in voluntary movement, gait speed and endurance and muscle strength, indicating that LOKOMAT can be considered as effective physical intervention for improving function and daily activity.

Background Spinal cord injury (SCI) typically results in spasticity, weakness and impaired coordination. Spasticity, including exaggerated stretch reflexes and involuntary muscle spasms, disrupt daily activity, cause shorter life span, and has physical, emotional and social costs. An effective treatment of spasticity could therefore have many benefits. The major aim of this study was to quantify the effects of Robotic-Assisted Locomotor training (LOKOMAT) on neuromuscular abnormalities associated with spasticity and locomotor function in SCI persons with incomplete injury.

Methods A novel system identification technique was used to characterize the effects of LOKOMAT on reflex dysfunction, muscle and passive mechanical properties, strength and ambulation in the chronic stages of rehabilitation following motor incomplete SCI. We also determined the effects of LOKOMAT on repeated voluntary movements of the ankle from full plantarflexion (PF) to dorsiflexion (DF) at maximum speed, quantified by measuring their kinematics parameters. To quantify neuromuscular mechanical properties of the ankle, Pseudorandom Binary Sequence (PRBS) perturbations were applied to the ankle at different ankle positions. Passive, intrinsic and reflex contributions to the ankle stiffness dynamics were separated using a parallel-cascade identification method. The effects of LOKOMAT on these mechanical properties were evaluated by monitoring the changes in these properties over the intervention time period. LOKOMAT was performed 3 days for 4 weeks during a 1-hr period including set-up time with up to 30 minutes of training during a single session. The experimental trials were performed at baseline and 1-, 2- and 4-weeks.

Results Following LOKOMAT training, (1) passive and reflex stiffness, abnormally increased in SCI, were significantly reduced, (2) kinematics parameters quantifying the ankle voluntary movement (i.e. Active Range of Motion, Peak-Velocity and Peak-Acceleration of the movement) improved substantially, (3) gait speed and endurance measured by 10-m and 6-min walk test respectively increased, and (4) muscle strength measured in terms of isometric Maximum Voluntary Contraction (MVC) enhanced significantly.

Conclusions The parallel cascade identification technique has been successfully used to characterize the effects of LOKOMAT on ankle stiffness and its reflex and intrinsic components. The results demonstrate the significant therapeutic effects of the LOKOMAT on the neuromuscular mechanical abnormalities, impairments in voluntary movement, gait speed and endurance and muscle strength.

These findings demonstrate that LOKOMAT has a potential to alter the responses of various spinal pathways, which can alter neuromuscular function and behavior and their recovery. Thus, LOKOMAT can be considered as effective physical intervention for improving function and daily activity in SCI.