Device for acute rehabilitation of the paretic arm after stroke Team: Carly Brown, Sasha Cai Lesher-Perez, Lee Linstroth and Nathan Kleinhans Advisor: Professor Mitch Tyler, UW-Madison and Michelle Johnson, Ph. D, Marquette University Department of Biomedical Engineering University of Wisconsin - Madison 7 December 2007
Abstract Stroke affects 700, 000 people each year 4 with two-thirds of those people sustaining a long-term physical disability 3. The number of longterm disabilities can be reduced with improved methods of rehabilitation in the acute phase, which is up to three months poststroke. We have designed a device that mechanically moves the hand in the supination/pronation movements of the wrist and flexion/extension of the hand. We constructed a prototype that manually moves the arm in the specified motions, which are controlled by a microprocessor. We are meeting with product designers to make our prototype aesthetically pleasing. We are also waiting on IRB approval to begin testing on patients.
Background Stroke is the top cause of long-term disabilities in the US. To reduce the number of people that are left with a disability, rehabilitation is a necessity. There are several types of rehabilitation methods that are used throughout rehabilitation centers in the US. Some current rehabilitation methods are: • Physical/Occupational Therapy – works on compensation methods for loss of functioning • Constraint Induced Motor Therapy – restricts movement of good arm and forces patient to use affect arm to regain motion • Electrical Stimulation – uses electrical impulses to stimulate muscles or nerves to do certain motions 5 • Robot-Aided Therapy – uses mechanical means and biofeedback to facilitate motion that was lost 1 Our device utilizes the aspects of robot-aided therapy to focus on the rehabilitation of two specific motions of the arm: supination/pronation of the wrist and flexion/extension of the hand.
Current robot-aided devices Most devices differ in many ways such as the motion that is focused on and the sophistication of the device. MIT has developed many devices that works on various parts of the body: arm, wrist, hand, and leg 6. Figure 1 shows a MIT-Manus robot-aided device. The patient is attached to the device, has a visual stimulus and the device measures the movements that the patient is able to do. Figure 1. MIT-Manus planar robot 6. Device works on planar movements with patients
Results This design allows for a mechanical means to facilitate movement in the impaired hand. Supination and pronation of the wrist can be done simultaneously with the flexion/extension of the hand or the motions can be done independently. This system allows for repetitive motion with varying degrees for speed and frequency that can be adjusted while the patient regains motion.
System The system is composed of a wrist rotating cylinder, which focuses on rehabilitating the supination/pronation of the wrist. Embedded within the wrist rotator, there is a finger flexion/extension attachment so the patient can work on gross grasping motion. This device is controlled by a microprocessor. The wrist rotator is powered by a 12 V high-torque low-rpm motor. The finger flexion/extension device is automated by a 12 V 3˚ stepper motor.
Hand grasping device, has elastic wound through slots to hold hand Wrist sits here, supported by vertical plates Stepper motor 12 V motor Roller bearings
Microprocessor The microprocessor is powered by a 9 V battery, which controls the speed and amount of rotation of the wrist rotator. The Hbridge switches the polarity of the motor to switch directions and limits the power that the motor receives to keep it rotating at desired speeds. The potentiometer is an external switch that can be set by therapist to varying speeds depending on the patient’s functional level. The limiting switches are the safety mechanism to stop the motor from over rotation. The microprocessor will control the motion of the hand grasper in the same ways as it does for the wrist rotator.
Clinical Trials Phase 1: System testing • Ensure technical specifications are met • Ensure programming meets system criteria Phase 2: Clinician testing • Test time it takes to set up the system after a demonstration • Survey them about their opinion of the system efficacy Phase 3: Pilot study • Do a comparative study with 6 patients • System is used for 10 sessions • Patients tested for active and passive range of motion and grip strength • Results compared between the groups at the end of the session to determine effectiveness of the system
Future Work Before clinical trials begin, the system will be connected to a visual display system that will run a game for the patients to do throughout therapy session. The game will have spots appear on the screen that will prompt the patient to move the cursor to that spot. Rotating the wrist or opening/closing the hand will correlate with different motions on the screen, such as vertical and horizontal movement. We are also going to be incorporating a Servo motor with an encoder which will allow the microprocessor to get readings on torque, velocity, and position. This will improve the quality of our program and allow the system to allow for active motion of the user. The prototype will also be redesigned to be more attractive for the user. This will entail scaling down the device, adding padding, rounding edges and hiding screws.
References 1 Burgar, et al. Development of robots for rehabilitation therapy: the Palo Alto VA/Stanford Experience. Journal of Rehabilitation Research and Development. Vol. 37: 663 -673. 2 Diffrient, N. , Tilley, A. , & Bardagjy, J. (1981). Humanscale. No. 1 -3. 3 National Stroke Association. (2007). www. stroke. org. (Dec 1, 2007). 4 The American Heart Association (2007) www. americanheart. org (Oct. 17, 2007). 5 Yozbatiran, N. Electrical stimulation of wrist and fingers for sensory and functional recovery in acute hemiplegia. Clinic Rehabilitation. Volume: 20: 4 -11. 6 Krebs, H, et al. (26 October 2004). Rehabilitation robotics: pilot trial of the spatial extension for MIT-Manus. Journal of Neuroengineering and Rehabilitation. Volume: 1: 5.
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