Monitoring Functional Arm Movement for Home-Based Therapy after Stroke R.Sanchez 1, D.Reinkensmeyer 1, P.Shah 1, J.Liu 1, S. Rao 1, R. Smith 1, S. Cramer 2, T. Rahman 3, J. Bobrow 1 1 Department of Mechanical and Aerospace Engineering, University of California, Irvine, USA 2 Department of Neurology, University of California, Irvine, USA 3 A. I. DuPont Hospital for Children, Delaware, USA

OUTLINE Background Methodology –T-WREX Design –Java Therapy Software Enhancements –Device Testing Results

Background 50% of Stroke survivors have chronic arm/hand motor impairment. In 1999, more than 1.1 million American adults reported functional limitations (difficulties with activities of daily living) resulting from stroke. Stroke costs the United States $30 to $40 billion per year (American Stroke Assoc.).

The Stroke Rehabilitation Paradox There is increasing evidence that intensive sensory motor training can improve functional recovery. However, stroke patients are getting less therapy and going home sooner due to economic pressures. There is little technology available to continue therapy at home in order to maintain, improve, or monitor recovery.

T-WREX Mechanical Design Training- Wilmington Robotic Exoskeleton (modified from WREX, T. Rahman) designed for use in arm movement training by weakened Stroke Survivors at home. T-WREX is a 5-DOF, backdriveable, passive anti- gravity position tracking system. Utilizes elastic bands, wrapped around two four bar mechanisms, to counterbalance the arm.

T-WREX Sensorized 5 potentiometers encased in protective housings measure arm movement. Measurement accuracy is measured within ±0.50cm. Potentiometers do not require homing, only an initial calibration. Arm position is calculated from the matrix exponentials formation.

Java Therapy 2.0 Java Therapy 2.0 allows the user to: –perform organized and monitored rehabilitative video game prompted exercises from the home. –keep track of usage and progress.

Java therapy 2.0 cont… Uploads subject data to a main server on the web. Communicates with T-WREX through a custom dll (dynamic link library). The doctor / therapist can: –monitor patient progress and activity. –assign games / exercises based on performance.

Device Testing Five volunteers with a history of chronic stroke ( > 3 months prior) and persistent motor deficits, but absence of cognitive deficits, neglect, and shoulder pain participated in the study. Three types of movement tests were performed with and without gravity balance, with the order of presentation of the two conditions randomized.

Movement Tests 1.Functional Test: A sub section of the arm motor Fugl-Meyer Motor Score consisting of 14 tasks that could be performed while in the orthosis (Score range 0-28). 2.Reaching Movements: The subject reached to soft targets located at the boundary of the arm’s passive workspace eight times. –One target was placed in the workspace contralateral to the impaired arm and one ipsilateral. –The subjects also reached upwards from the lap to the highest point possible eight times. 3.Drawing movement test: The subject traced circle patterns (Ø18cm) presented on a transparent plastic disc in the vertical plane, centered in front of them, 4-5 fist lengths from the front of the shoulder.

Functional Test Results The score on the subset of arm motor Fugl- Meyer testing without gravity-balance was 9.0 (+/- 6.2 SD) and with gravity-balance was 10.4 (+/- 6.5 SD), out of a possible score of 28. The change in Fugl-Meyer was marginally significant (p =.054) for a one-sided, paired t- test comparing the change to zero.

Reaching Results Effect of gravity balance on reaching movements. (A)Average reaching range of motion across subjects to targets with and with out gravity balance (distance traveled to target / total distance to target). –Gravity balance significantly improved reaching to the contralateral target. (B)Average height reached above lap, with and without gravity balance. No short-term learning was observed across eight movement attempts. –Gravity balance significantly improves vertical reach.  p <.05, paired t-test.

Tracing Movement Results Effect of gravity balance on tracing movement for one subject. –The subject attempted to trace a circle 30 times, without gravity balance (top four panels) and with gravity balance (bottom four panels). –The panels show example trials throughout the 30 trials. –Tracing circles with gravity balance improved over time and shows an obvious masked motor function capability.

Discussion T-WREX’s gravity balance function improved: – a clinical measure for arm movement. –range of motion for reaching. –accuracy of drawing movements. These results highlight the “threshold” nature of gravity: –a threshold amount of strength is required to move against gravity. –gravity balance appeared to unmask a latent motor learning capability that was not apparent with gravitational loading. All subjects were pleased with their experience and asked to participate in future studies.

Conclusion Our initial test with T-WREX showed that the device will provide a means to measure and safely assist in naturalistic arm movement. We envision using T-WREX to provide: –gradable levels of assistance by adding or removing rubber bands. –the ability to perform software guided home based therapy (telerehabilitation). –quantitative feedback of progress at home and at the clinic. We hope to increase access to and improve functional outcomes of arm therapy after stroke.

Acknowledgements Supported by the Department of Education National Institute on Disability and Rehabilitation Research (NIDRR), H133E020732, as part of the Machines Assisting Recovery from Stroke (MARS) Rehabilitation Engineering Research Center (RERC) on Rehabilitation Robotics and Telemanipulation and NIH N01-HD University of California Irvine, Biomechatronics Laboratory.