1. Continuous Passive Motion Hand Rehabilitation

2. Design Team Project Sponsors: Group Members:
Bert Lariscy, Vanderbilt University EE graduate
Crystal Bates, Occupational Therapist
Jim Lassiter, MCN Chief Occupational Therapist
Group Members:
Jonathan Webb ME
Matthew Byrne ME
Jennifer Hornberger BME
Aaron Hadley BME

3. CPM Devices
Continuous Passive Motion is a method of rehabilitation following injury or surgery.
Its main aim is to increase movement of the joints while preventing overextension or further damage and to prevent the buildup of scar tissue.

4. CPM Market Injuries
Typical surgeries where CPM is needed post operatively:
ankylosis of joints
dislocation of fingers and wrist
sprain and strain of wrist joints
tissue replacement at hand joints

5. Sales Market Primary Clients: 1) Physical Therapy Clinics
2) Post-Operative Individuals
155,000 physical therapy jobs in the United States
Approximately 75,000 patients per year in need of care
Ownership Costs: $3,000-$7,000
Rental Costs: $600/month
Product is used for six weeks or less after surgery, typically for 8-10 hours a day.

6. Design Problem Problems with current CPM device:
fingers not allowed independent motion
thumb not a part of the system
heavy and bulky
complex, difficult to set up and use

7. Design Goals Safety is of primary concern.
It is necessary to make a completely new design that will incorporate independent finger motion, so as to allow for greater customization of rehabilitation.
If possible, the thumb should be incorporated into the design in at least one dimension of movement.
It must also be lightweight and portable, so that a patient can treat themselves at home.

8. Design Goals
Following the evaluation of the comparison chart, the following ranking of design objectives was obtained.
The following parameters are not necessary, but desirable in the final design.
Clearly, the portability aspect of the device is the most important to meet patient needs, especially considering the heavy daily usage by patients.

9. Design Specifications
Starting Position – open palm
Range of Motion (ROM)
-15 degrees (Hyperextension) to 270 degrees (Flexion)
Speed of Motion
Minimum of 2 degrees/second to a maximum of 54 degrees/second
Speed to be set by physician based on rehabilitation plan

10. Previously Explored Techniques
Magnetic fields can control joints of individual fingers though adjusting the induced current of an electromagnet wrapped around individual finger joints.
Problems:
1.) A large current is needed to induce a strong magnetic field, hindering power source portability.
2.) The magnetic force varies with the square of the magnetic field, creating speed control issues.
Shape Memory Alloys maintain the ability to deform and reform their shape when exposed to certain temperatures, and this property could be used to move the finger joints.
1.) Precision uncertainty and fatigue
2.) Temperature dependence range is too high for human touch.
Magnetic Field
Memory Metals

11. Mechanical Tension
A series of small pulleys and strings will be used to move the fingers.
These strings would be placed on the palm and back of the hand.
Each finger and even each joint could be moved independently.
A computer would control the length of the strings to set the desired position and allow for tension response.

12. ME Department’s Artificial Hand
The ME Department’s artificial hand uses similar tendon-like cables.
Tension returns the finger to an extended position.
The “tendons” are inside the finger, but for our CPM model the strings would have to be outside the body.

13. Inflation
Initial inflation of the air/fluid-filled bladder adjustable to fit all hand sizes.
Each finger attached to one of five individual compartments to allow different ROM for each finger
Rate of inflation controlled through strain gauges and pressure sensors.
Problems
feedback so device will stop if there is too much resistance
ROM not as large as existing devices
Air supply source

14. Future Directions Order materials
Calculate forces necessary to move fingers.
Submit prototype design for outside production by March 1st.
Test prototype
Revise Prototype