Trey DeLong
Lacey Gorochow
Brian Rappa
Adam Vandergriff
Sandra Wadeer
Advisor: Dave Martinez
VP of Sales at Zimmer, Inc.
Surgical Consult:
Dr. Michael Christie, M.D.
Southern Joint Replacement Institute
Problem Statement

Current tissue retractors are narrow, multiple
retractors are required especially in obese
patients
 NY times reports 34% adults are obese
 +Surgical Techs($20.00/hr*2-4hr/surgery*200k
surgeries/year)
 Time of surgery increases as well

Previous team designed an adjustable
retractor
 Complex and impractical for industrial
production
 Prototype could not be used in
surgery
Mechanism & Consequences

Mechanism causing the problem
Physical properties of adipose tissue allow it to wrap around
narrow retractors

Consequences of unresolved problem
Poor surgical field of vision
Increase cost for additional materials and personnel
Surgery Experience
4-5 in (6 in in bigger patient)
3 in
wide
Depth can range from
1-6 inches depending
(Patient Size)
Fat tissue getting in the way
Dr. Christie’s Perspective

Functions of retractor:
 Orient the incision
 Keep tissue from falling into
surgical window

Disposabile vs. Non
 Not “green”
 Strength concerns

Ideal Device:
 Robust
 Simple
 Movable window
Design Requirements &
Objectives
Keep back adipose tissue
 Fit multiple patient sizes and provide a clear view
of the surgical site
 Must be cost efficient

 Simple manufacturing
 cheap material

Ready for use in surgery
 Easily attached
 Easily sterilized

Strong enough to hold back fat tissue
Design
• Lofted feature-rounded to keep back tissue
• Curvature based on angle of known
measurements in surgery video
Material of Attachment Piece

17-4 Precipitation Hardening Stainless
Steel
 Composition: 15.5% Chromium, 4.5%




Nickel, 3.5%Copper
Ultimate Tensile Strength: 1000-1340 Mpa
High strength maintained up to 600°F
Corrosion resistance superior
Readily welded-preheating not usually
required
Stainless Steel Model

Weld rods onto existing retractor
to provide rails

Attachment made in machine
shop using CAD design
Goals

Reduce total hip replacement surgery
cost
 Less personnel in the operating room
 Less retractors needed for surgery

Increase vision and work room for the
surgeon
 Increase efficiency of the surgery
 Reduce surgery time
Performance Metrics

Retractor system work on 95% of
patients
 Different size attachments for non-
disposable.

Costs
 Keep production costs minimal
○ Mass production
○ Readily machined
 Predicted to be ~$300 for retractor and
attachments (non-disposable)
System and Environment

Role in surgery
 Increase view of region and allows access

Why its beneficial to the surgeon
 Reduce people near patient
 Reduce number of retractors
 Make surgery easier
Testing Methods

Verification and Validation

Hardware Testing

Stress Testing

Sterilization Testing
Verification and Validation

Verification: ensuring that all of the
parts of the device work together
 Obtained a model made of ABS plastic
made from an FDM process

Validation: making sure that the device
satisfies specified requirement
 Taking the actual prototype into surgery for
Dr. Christie to use
Hardware Testing Protocol

Use of mechanical equipment to test strength
of device
 Take retractor with similar properties to testing labs
 Apply a load using a compression/ tensile machine
to the device
 Hold the load over the device for several minutes
 Observe the deformation of the device over time

Mechanically test ability of steel to get the
properties
Stress Testing Protocol

Computer Modeling
 Use PDE Toolbox
(MATLAB) to analyze
tissue
 Obtain force load on
the retractor from
tissue data
 Model stress on the
retractor using force
loads
 Analyze model during
normal use
Sterilization Testing
Use in surgery
 Run through Autoclave to test resilience
and observe any remaining tissue
 Run through multiple cycles and
observe the number of cycles until
completely clean.

Next Steps…
Obtain a completed prototype to be
shown in the final presentation
 Conduct testing methods

 Verification
 Validation
 Hardware Testing
 Stress Testing
 Sterilization Testing

Present our final project
References





http://www.bls.gov/bls/blswage.htm
http://www.innomed.net/hip_rets_mis.htm#
Anchor-APC-49575
http://www.nytimes.com/2010/01/14/health/
14obese.html
http://www.orthosupersite.com/view.aspx?ri
d=1889
http://www.zimmer.com/z/ctl/op/global/actio
n/1/id/8140/template/PC/navid/10427