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Objectives: World War II veterans constitute the largest proportion of persons eligible for health care in VA facilities, and most of these veterans are at increased risk for stroke. With the dramatic reduction of inpatient rehabilitation length of stay following stroke, efficient and effective interventions have become critical. The objectives of this project are to establish the therapeutic efficacy of robot-assisted movement in subjects with chronic stroke, and to understand the mechanisms by which this therapy promotes motor recovery.
Methods: A clinical trial is underway to evaluate the therapeutic efficacy of robot-assisted movement for recovery of shoulder and elbow motor function. Chronic stroke subjects (> 6 months post-stroke) are randomly assigned to a robot or control group. Both groups receive 24 one-hour sessions over two months. A typical robot group session includes tabletop tracing of circles and polygons, and a series of 3- dimensional targeted reaching movements, all assisted by a Puma 560 robot arm. Four modes of assistance are used. In passive mode, the subject relaxes as the robot moves the limb in a predetermined pattern. In active-assisted mode, the subject triggers initiation of the movement with force toward the target and then "works with the robot" as it moves the limb. In active-constrained mode, the robot provides a viscous resistance in the direction of movement and spring-like restoring forces in all other directions. In bimanual mode, the subject attempts bimanual mirror-image movements while a 6- DOF digitizer measures movement of the contralateral limb and the robot moves the paretic limb to the mirror-image position with minimal delay. A typical control group session includes NeuroDevelopmental Therapy (NDT) targeting upper limb function, and 5 minutes of exposure to the robot with target tracking tasks. All subjects are evaluated pre- and post-treatment with clinical and biomechanical measures.
Results: Data from the 10 robot group subjects and 9 control subjects who have completed the study indicate robot-assisted movement may have advantages over conventional NDT-based therapy. In terms of the upper limb portion of the Fugl-Meyer examination (FM) of motor function, there is a trend towards greater improvements in the robot group compared to controls, but this trend is not yet significant. However, when considering only the shoulder and elbow portions of the FM, robot group improvements are significantly greater than control group improvements (p<0.05). There is evidence that the improvements in robot trained subjects are due to increased activation of paretic muscles and decreased antagonist co- contraction.
Conclusions: If it can be shown that robot-assisted movement has significant therapeutic value, robotic systems can be integrated into clinical practice, potentially improving outcomes and increasing the efficiency of the clinical staff. Therapists could supervise setup of patients in the robotic system and instruct on the movements and modes to be practiced. An extended period of unsupervised exercise would proceed, with automatic feedback of data to motivate performance. Patients could thereby increase the amount of therapy received in the clinic, with the robotic system facilitating many of the exercises that require labor-intensive manual manipulation.
Acknowledgments: This work was supported by VA Merit Review Grant #B2056RA.