ADAPTABLE RETRACTOR FOR

TOTAL HIP REPLACEMENT

SURGERYTrey DeLong

Lacey GorochowBrian Rappa

Adam VandergriffSandra Wadeer

Advisor: Dave MartinezVP 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 patientsNY 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 productionPrototype 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 visionIncrease cost for additional materials and personnel

Surgery Experience

Fat tissue getting in the way

4-5 in (6 in in bigger patient)

3 in wide

Depth can range from 1-6 inches depending (Patient Size)

Dr. Christie’s Perspective Functions of retractor:

Orient the incisionKeep 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 manufacturingcheap material

Ready for use in surgeryEasily attachedEasily 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

SteelComposition: 15.5% Chromium, 4.5%

Nickel, 3.5%CopperUltimate Tensile Strength: 1000-1340 MpaHigh strength maintained up to 600°FCorrosion 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

costLess personnel in the operating roomLess retractors needed for surgery

Increase vision and work room for the surgeonIncrease efficiency of the surgeryReduce surgery time

Performance Metrics Retractor system work on 95% of

patientsDifferent 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 patientReduce number of retractorsMake 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 togetherObtained a model made of ABS plastic

made from an FDM process

Validation: making sure that the device satisfies specified requirementTaking the actual prototype into surgery for

Dr. Christie to use

Hardware Testing Protocol Use of mechanical equipment to test strength of

deviceTake retractor with similar properties to testing labs Apply a load using a compression/ tensile machine to the

deviceHold the load over the device for several minutesObserve 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

VerificationValidationHardware TestingStress 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?rid=1889

http://www.zimmer.com/z/ctl/op/global/action/1/id/8140/template/PC/navid/10427