1. Growth Plate Measurement Device
Group Members: Andrea Schnelle
Adam Graf
Rafael Connemara
Barry Bass
Clients: Norman Wilsman
Ellen Leiferman
Advisor: Paul Thompson
10/18/02

2. Presentation Overview
Problem Statement
Product Design Specifications
Prior Methods
Drawbacks
Alternative Designs
Future Work
Questions

3. Problem Statement
Develop a more accurate and physiologically compliant method to measure the longitudinal lengthening of tibia in a lamb

4. Project Design Specifications
The device must not impede the natural movements of the lamb
Capable of measuring up to 1cm
Accuracy of within 10-20µm per measurement
Ability to produce time intensive sampling rates (every 1-5 minutes)
No elements of the device should span the growth plate

5. Prior Method: Fluorescent Dying
Dye injected into lamb and picked up by cells in the growth plate
Dye left behind as bone grows
Later a second injection given leaving another line
Growth measured in between 1st and 2nd line of dye

7. Drawbacks with Fluorescent Dye
Lamb must be killed to get growth measurement
Only one measurement can be taken
Does not produce a rate measurement on a small scale

8. Current Method: Contact DVRT (Differential Variable Reluctance Transducer)
DVRT implanted over growth plate and as bone grows NiTi alloy core position changes
Changes detected by measuring coils differential reluctance
Gives feedback every 2.5 minutes about daytime, date, position and battery life

10. Drawbacks with Contact DVRT
Method only gives 3-6 days of accurate data
Scar tissue and immune cell build up disrupts measurements
Noise created when lamb is on its feet
Element spans the growth plate

12. Design Alternatives Non-Contact DVRT Modified Existing Contact DVRT
Engineered Non-Contact Measurement Device

13. Non - Contact DVRT Pros Has <10 µm resolution
Capable of measurement every 2.5 minutes
Has no element spanning
the growth plate
Cons
Not capable of
measuring 9 mm
displacement

14. Theory
Two coils within the housing form the DVRT’s transmitting and sensing capabilities
A change in displacement causes a change in the signal detected by the sensing coil (Output)

15. Engineered Non-Contact Measurement Device
Current Research
Applies theory of non-contact DVRT
Involves two inductors
Change in displacement results in a difference in voltage sensed

17. Future Work Test to minimize voltage and maximize resolution
Modify the engineered non-contact device to be implantable
Continue looking into modifying the current method for extended use

18. Questions?