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An Opening in the Abdomen An Opening in the Market: Hernia Tensiometer. GROUP 2: Martha Ingram Megan Johnston Chelsea Samson. What Is a Hernia?. Laparoscopic. Open. Device Must:. Measure tension resisting closure at the suture line after: - dissection of the injury area

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Presentation Transcript
slide1

An Opening in the Abdomen

An Opening in the Market:

Hernia Tensiometer

GROUP 2:

Martha Ingram

Megan Johnston

Chelsea Samson

slide6

Device Must:

  • Measure tension resisting closure at the suture line after:
  • - dissection of the injury area
  • - separating fascia from muscle
  • placing the mesh
  • Isolate abdominal tissue
  • Bring edges together
  • Read tension at center of hernia
timeline done
Timeline - Done
  • Met with advisors
  • Researched hernia surgery and device requirements
  • Innovation Workbench
  • Literature research on current technologies
timeline current
Timeline - Current
  • Finalize materials list
  • Determine force sensor type and design circuit
  • Finalize mechanical system
timeline future
Timeline – Future
  • Order materials – Next week
  • First prototype made with acrylic
  • Test on porcine model – 4th week of Feb
  • Modify design – early March
    • Rebuild with surgical steel
  • Test new design – Late March
  • Report and Poster – April
force sensors
Force Sensors
  • Flexible Stretch Sensor
    • Changes resistance when stretched
    • Both ends must be wired
    • Requires 30-40 cords for our estimated load
    • All cords must be insulated
force sensors1
Force Sensors
  • Flexiforce
    • 0-25lb (0-100N)
    • Conductance (1/R) linear with load
    • Both terminal at one end
    • Requires compression force
    • We have Starter Kit
modified mechanics
Modified Mechanics
  • Flexiforce measures compression
  • Convert tensile force to compression force
  • System pulls against itself
force sensors2
Force Sensors
  • Strain Gage
    • Interlocking links
    • Strain gage mounted to a small piece of metal
    • Defected when tension applied to links
    • Requires Wheatstone circuit
circuit design
Circuit Design
  • Design proposed by Flexiforce
    • Converts change in resistance to change in voltage
  • Voltage will be converted to Force
calibration
Calibration
  • Initial calibration
    • Known weights applied
    • Measure voltage output
    • Create calibration curve to convert to force
    • Simple in Labview, more difficult in self-contained circuit
  • Tare
    • Zero out capacitor to indicate zero force
  • Normal testing
    • Provide surgeons with weights to test every 5-10 uses to confirm accurate results
current issues
Current Issues

Federal Constraints

--having minimal contact points with the body allows for easier acceptance through IRB

current issues1
Current Issues

Physical Limitations

---with an 18cm hernia diameter, the device has to be small (~9cm, or 3.5 inches, long & 2-3 cm high)

--small volume for both a movable arm and required circuitry

current issues2
Current Issues

Mechanical Difficulties

-- Need for a small internal power supply

--Device for keeping tissue stationary: handles get in the way

--How do we hold the moving arm in desired position while taking desired tension reading?

--Lesser experience/courses in utilizing magnets or advanced techniques in electronics adds some limitations to feasible solutions for our time period.

slide21

Hernia-Tensiometer Interface

environment

environment

The system (tensiometer) needs to be self-contained, having minimal points of contact with the environment (patient)

System

potential solutions
Potential Solutions

Federal Considerations

  • Design the system so that the clamping arm may also support the console above the patient (not on the patient)
  • Use stainless steel and other surgical materials that can be sterilized

Experience/Time Limitations

  • Seek advice from Mechanical Engineering & Electrical Engineering departments on creative internal power supply sources that are currently available

Physical & Mechanical Limitations

  • Perhaps use test-tube holders or similar alternative holding devices in place of surgical clamps
  • Position circuit near top of the console, and arrange force sensors near the moving arms at the base of the console
references
References
  • http://multianvil.asu.edu/ASU%20Multianvil%20Page/TheCube.html
  • http://zone.ni.com/devzone/cda/tut/p/id/6534
  • http://www.tekscan.com/flexible-force-sensors
  • http://www.imagesco.com/sensors/stretch-sensor.html