Ring Removal Device

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Ring Removal Device

• Team
• Evan Rogers, Sujan Bhaheetharan, Tyler Allee,
  Steve Noel
• BME 301
• February 24, 2006

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ClientScott Springman, M.D.
AnesthesiologistUW - HospitalAdvisorWilliam
Murphy, Ph.D.ProfessorDept. of Biomedical
EngineeringUniversity of Wisconsin
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Overview

• Current Ring Removal Techniques
• Current Problems
• Background
• Product Specifications
• Proposed Designs
• Future Work
• Questions

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Problem Statement
An improved method is needed to remove rings from
a patients swollen finger. Currently, it is
necessary to push, prod, and hurt patients while
trying to remove rings. Removal is necessary
because some surgeries have a high risk of
inducing generalized body edema, including
fingers. If the finger swelling is too great, the
blood supply to fingers may stop and potentially
lead to gangrene. When is necessary to cut off
the ring, an instrument that severs one part of
the ring exists. We will create a mechanical
device that will allow the ring to spread open
easily without pinching the patients fingers.
Traditional "tricks" exist to try to reduce
tissue water in the finger to help remove an
un-cut ring. We will develop a process that may
include these, while creating a new device to aid
in ring removal.
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Background
Destructive Method
Removal Method

• String method
• Wrap string from distal end toward the ring to
  push excess fluid out of finger to reduce size
• String fed under the ring start unwrapping it.
• Unwrapping of string forces ring off
• Surgical Glove Method
• Feed glove under ring
• Over lap ring, and remove ring

• Ring Cutter
• Ring is cut at one end
• Pried open
• Ring can be later soldered back together
• Common Methods
• Reducing finger tissue temperature to reduce
  swelling
• Lubrication
• Elevation

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Problems with Current Methods

• String Method
• Requires high degree of skill
• Time-consuming
• Uncomfortable
• Limited by arthritis
• Surgical Glove Method
• Hard to feed glove under ring
• High probability of glove failure
• Limited by arthritis

• Destructive
• Difficulty removing ring after severed
• Prying Ring apart
• Ring destroyed
• Common Methods
• Low rate of success
• Limited by arthritis

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Finger Physiology

• Upper limit
• Shear Strength of bone
• 68 MPa
• Lower Limit
• Therapy treatment for patient with leg
• edema
• 6.67 kPa
• Finger Edema
• Also called dropsy
• Fluid accumulation in intercellular spaces

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Finger Physiology

• Finger Arthritis
• Nodules develop around knuckles
• Made up of bone spurs (osteophytes)
• Become swollen and inflamed
• Reasons for removal
• Prevent fluid buildup
• Prevent lack of circulation to distal end of
  finger
• MRI

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Product Specifications

• Device does not require high degree of skill
• Minimizes discomfort for patient
• Expedites current process
• Inexpensive
• Factors in permanent swelling (arthritis of the
  knuckle)
• Factors in removable swelling

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Design 1 Shape Memory Alloy

• Non-Destructive Method
• Nitinol - Mix of Nickel and Titanium of
• equal weights
• Mechanics
• Two Phases Superelastic and Rigid Memory
• Phase transform temp range 41º to 64º F
• Force generation during phase change,
• recovering elastic deformation
• Design
• -Cylindrical design
• Two design
• - Compression of finger
• - Expansion of ring

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Design 2 Polyurethane Compression Sheath
Plastic hook

• Non-destructive Method
• Material
• High Poissons Ratio
• Higher Ultimate and shear strength
• Elastic
• Varying thickness due to different stress
  concentrations
• Threading System
• Ads in threading sheath between ring and finger
• Tension in long axis of finger cause compression
  of swollen tissue
• Lubricated, Elevation, Cold compress

Finger sheath
Sheath overlaps ring
Pull overlapped sheath to remove ring
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Design 3 Ring Spreader

• Destructive Method
• Used in conjunction with ring cutter
• Adds in spreading ring after cutting
• Hand crank design
• Force output 6.5 times force input
• Ratchet safety system

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Design Matrix
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Future Work

• Finalize designs
• Build Prototype
• Test Destructive/Non-Destructive Prototypes and
  make necessary changes
• Develop step by step procedure to be use in
  conjunction with device

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Questions?