Rehabilitative Finger Mount to assist Finger Movement in Chronic Stroke Patients

 

Sindu Divakaran*, Bethanney Janney J, G Umashankar, Leena Nangai V

Department of Biomedical Engineering, School of Bio and Chemical Engineering, Sathyabama University, Chennai

 

ABSTRACT:

More than 10% of deaths worldwide have occurred due to stroke. In India the incidence of the disease is to be around 130 per 100,000 populations. The concept of assistive movement stroke therapy is new but widely known. The goal is to develop an assistive device for the individual movement of fingers of stroke patient. The device consists of a strain gauge sensor that will sense the amount of input/effort from the user. The sensed analog signals are converted to digital and then send it to a micro controller that determines the output of stepper motor. The stepper motor moves the individual fingers of the stroke patient.

 

 

 

INTRODUCTION:

Stroke is the third largest killer in India after heart attack and cancer and second largest in world, according to the World Health Organization (WHO). Though stroke causes many neurological disorders, the most commonly affected is the motor system. ¹

 

After stroke some patients regain no movement of the affected body part, but some regain movement but not full strength. Stroke survivors remain vocationally impaired and more than 30 percent of the survivors requiring assistance with activities of daily living. Stroke survivors may require a very high level of hand motor control before they actually use the limb in activities of daily living.²

 

The amount of damage done to brain varies among stroke victims and the physical disabilities vary as well. Commonly, stroke patients incur damage to one hemisphere of their brain. This damage leaves them physically impaired on the opposite of their body.

 

The brain is capable of many ways in which it tries to recuperate from its injury. Patient therapy during this post - stroke time could be extremely valuable. Physical therapy has been shown to restore functionality of the paretic limbs, especially when done early and often ³. However, the effectiveness of therapy is limited by the availability of therapists and the amount of practice that patients do on their own.

 

Some of the physical disabilities that can result from stroke include paralysis, numbness, apraxia (inability to perform learned movements), difficulties carrying out daily activities, pain, stiffness, etc. Emotional problems resulting from stroke can result from direct damage to emotional centers in the brain or from frustration and difficulty adapting to new limitations.

 

The goal of the design is to strengthen the movement of the patient's fingers (thereby able to regain his / her strength) so that it helps in the brain repair process as well.

 

Stroke rehabilitation is a multidisciplinary field that utilizes medical, social, educational, and vocational measures to help a person who has suffered a stroke to his/her maximal physical and vocational potential, considering the limitations they face.⁴

MATERIALS AND METHODS:

The device is designed considering the following features:

1.        It should sense the pressure developed during opening and closing of the fingers.

2.        It should be light and user friendly.

3.        It should not fracture the bones during movement.

4.        It should fit all stroke patients.

 

The device consists of a sensor (strain gauge) that senses the amount of input from the user. The input analog signal is sensed by an operational amplifier and the data obtained is converted into digital value by an analog to digital converter and sent to a micro controller that determines the output for the stepper motor that moves the fingers of the patient’s hand.

 

The mechanical part of the device works based upon cam lever mechanism. The model consists of mechanical system, electrical system etc. Mechanical system consists of gears, levers, springs and electrical system consist of resistors, sources, inductors etc. The device is also provided with a battery.

 

Sensor
Op-amp
A to D Converter		microcontroller		Stepper motor
				Stepper motor moves the individual finger

Figure 1: Block Diagram of the augmentive device design

 

Sensor:

In the prototype, a noninvasive sensor gives output analog signals that are processed by the micro controller. A strain gauge sensor is hence selected

 

The majority of strain gauges are foil types, available in a wide variety of shapes and sizes to suit a variety of applications. They consist of a pattern of resistive foil, which is mounted on backing materials. They operate on the principle that as the foil is subjected to stress, the resistance of the foil changes in a defined way.

 

The strain gauge is connected into a Wheat stone’s Bridge circuit with a combination of four active gauges (full bridge), two gauges (half bridge), or less commonly, a single gauges (quarter bridge). In the half and quarter circuits, the bridge is completed with precision resistors.

 

 

The complete Wheat stone bridge is excited with a stabilized DC supply and with additional conditioning electronics, can be zeroed at the null point of measurement. As stress is applied to the bonded strain gauge, a resistive change takes place and unbalances the wheat stone Bridge.

 

The result is a signal output, related to the stress value. As the signal value is small (typically a few millivolts.) the signal conditioning electronics provides amplification to increase the signal level to 5 to volts, a suitable level for application to external data collection systems such as recorders or PC Data Acquisition and

 

Analysis Systems:

It is found that ⁵ the maximum force exerted by a human finger can be in the order of 45N.

 

The input from the patient is sensed by the sensor and the sensed signal is converted into a digital signal and sent to the micro controller.

 

Microcontroller:

The PIC 16F877 micro controller board consists of circuits necessary to operate a micro controller with PC interface. It is a high performance RISC CPU. The board contains provisions for interfacing 8 analog inputs , has an enhanced memory, etc.

 

Stepper motor:

The stepper motor model used in the prototype operates with a 10V supply and draws .85 amperes per phase of current. Since the stepper motor was the major consumer of energy in this design, its energy data were used to approximate the energy usage of the prototype. Assuming use for 8 consecutive hours in a day, the device would consume 68 watt-hours.

 

A lithium-ion battery is the more viable option for the design, given its high specific energy density (128 Wh/kg) and relatively high volumetric energy density (230 Wh/L).

 

Mechanical system:

The mechanical system consists of elements like levers, gears, springs, and other elements, which allows us to see the flow of energy. Here the mechanical part of the kit works on cam lever mechanism.

 

Software description:

Embedded c:

The embedded system can be programmed through Assembly language C, C++, Java.

 

Ccs c compiler:

A CCS C compiler is software, which compiles a source code of one environment as an object file to be executed in different environment.

 

 

Micro vision:

Micro Vision for windows is an integrated software development platform that supports the ccs c compiler software development tools for the PIC MICROCONTROLLER.

 

Dscope:

Dscope is a software debugger, which simulates the hardware of the pic 16 and pic 18 series of the micro controller family and executes all machine instructions.

 

Finger mount:

The device consists of two small metal pieces which will look like the spine bone of the spinal cord. It has a pointed end in front and a broader end at the back. The pointed end of one metal piece is placed above the pointed end of another metal piece. Each metal piece has a narrow horizontal hole in the middle through which a metal rod is inserted. The metal rod should be in a compact size so that it can be moved freely (grease can be applied for free and smooth movement). After the metal rods, the first one (metal rod) is joined to the adjacent metal rod by means of some joint, without the other settings getting disturbed. Now the pointed ends, which is placed one over the other is placed above the middle joint of the finger. They are attached to the finger using Velcro straps. A motor is placed near the base joint of finger provides power supply for the movement of the fingers.

 

Figure 2: The finger mount prototype

 

METHODOLOGY:

The straps of the strain gauge sensor is attached to the upper arm of the patient’s hand and can sense the amount of pressure the person applies to it. When the pressure is sensed, this signal is sent to an operational amplifier for amplification and the amplified analog signal is converted and sent to the micro controller. The micro controller is programmed to process the signal and sends a new signal to the stepper motor instructing it to move in an appropriate way. The motor can be programmed for different speeds and different angles depending on how much input/pressure the user applies. Since the mechanical part of the device works based on the cam lever mechanism, it will restrict the movement of fingers to certain extent for safeness. Stepper motors are also more complicated than a typical DC motors because they need the precise amount of electricity to the exact place and time and usually have many wires integrated in the circuit. 

 

RESULTS AND DISCUSSION:

The prototype developed will be able to augment finger movement in stroke patients. The design has achieved the main goals i.e.) it senses when the patient tries to open his or her fingers and augment the movement based on pressure. It has many safety features.

 

By using the device the patient will be able to gain sensation and strength in his hand. It can also be easily removed from fingers and works only when the patient wishes. Overall it will be affordable and convenient for all stroke patients.

 

The device helps in augmenting the movement and also performs exercises.

 

Figure 3: Final prototype of the device

 

Another concern for the patient is that the device may be too heavy. Many stroke patients are already in a weakened state and may not be able to lift heavier objects. The goal of this design is to make the device as lightweight as possible so that the patient will not become fatigued throughout the duration of use.

 

REFERENCES

1.        C. D. Takahashi, L. Der-Yeghiaian, V. H. Le, and S. C. Cramer, “A robotic device for hand motor therapy after stroke,” in Proc. IEEE Int. Conf. Rehabil. Robot. (ICORR), 2005, pp. 17–20.

2.        Peter S. Lum, PhD Sasha B. Godfrey, PhD Elizabeth B. Brokaw, PhD Rahsaan J. Holley, OTR Diane Nichols,  American Journal of Physical Medicine and Rehabilitation Am. J. Phys. Robotic Approaches for Rehabilitation of Hand Function After Stroke, Med. Rehabil. and Vol. 91, No. 11 (Suppl), November 2012, 242-251.

3.        Cifu, D. X., and Stewart, D. G., “Factors Affecting Functional Outcome After Stroke: A Critical Review of Rehabilitation Interventions,” Arch. Phys. Med. Rehabil., 80(5), pp. S35–S39

4.        Pamela W. Duncan, et.al, Management of Adult Stroke Rehabilitation Care- A Clinical Practice Guideline, Stroke. 2005; 36:e100-e143.

5.        Jamshed Iqbal and Khelifa Baizid, Stroke rehabilitation using exoskeleton-based robotic exercisers: Mini Review. Biomedical Research 2015; 26 (1): 197-201

 

 

 

Accepted on 17.03.2017           © RJPT All right reserved