Comparison of three-dimensional, assist-as-needed robotic arm/hand movement training provided with Pneu-WREX to conventional tabletop therapy after chronic stroke

Abstract

Objectives: Robot-assisted movement training can help individuals with stroke reduce arm and hand impairment, but robot therapy is typically only about as effective as conventional therapy. Refining the way that robots assist during training may make them more effective than conventional therapy. Here, the authors measured the therapeutic effect of a robot that required individuals with a stroke to achieve virtual tasks in three dimensions against gravity.

Design: The robot continuously estimated how much assistance patients needed to perform the tasks and provided slightly less assistance than needed to reduce patient slacking. Individuals with a chronic stroke (n = 26; baseline upper limb Fugl-Meyer score, 23 ± 8) were randomized into two groups and underwent 24 one-hour training sessions over 2 mos. One group received the assist-as-needed robot training and the other received conventional tabletop therapy with the supervision of a physical therapist.

Results: Training helped both groups significantly reduce their motor impairment, as measured by the primary outcome measure, the Fugl-Meyer score, but the improvement was small (3.0 ± 4.9 points for robot therapy vs. 0.9 ± 1.7 for conventional therapy). There was a trend for greater reduction for the robot-trained group (P = 0.07). The robot group largely sustained this gain at the 3-mo follow-up. The robot-trained group also experienced significant improvements in Box and Blocks score and hand grip strength, whereas the control group did not, but these improvements were not sustained at follow-up. In addition, the robot-trained group showed a trend toward greater improvement in sensory function, as measured by the Nottingham Sensory Test (P = 0.06).

Conclusions: These results suggest that in patients with chronic stroke and moderate-severe deficits, assisting in three-dimensional virtual tasks with an assist-as-needed controller may make robotic training more effective than conventional tabletop training.

Figure 1

Pneu-WREX is a four degree-of-freedom pneumatically actuated upper extremity orthosis for robot-aided movement training. The user can move her hand in 3D space, and use the grip sensor to grasp and release virtual objects on the computer screen.

Figure 2

Changes in outcome measures from first baseline evaluation (B1) to second baseline evaluation (B2), to Post-treatment (Po, i.e. following 24 therapy sessions), to three month follow-up (3M). Bars show one standard deviation. Solid lines = robot group, dashed lines = control group. * denotes a comparisons with p < 0.05, and + denotes a comparison with p < 0.1. FM = Fugl-Meyer Upper Extremity Score, MAL = Motor Activity Log. AOU = Amount of Use. QOM = Quality of Movement.

Figure 3

Subjects were asked to choose “robot” or “control” therapy in several categories after completing 24 training sessions that involved some exposure to each training type. Left: responses from subjects enrolled in the robot group. Right: responses from subjects enrolled in the control group.