Artificial total hip_replacement[1] (1)
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Artificial Total Hip Replacement
Arthur Hernaez
Materials Engineering
Mission College - Spring 2011
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Overview• Biomedical Engineering
• The human body
• Understanding Artificial total hip replacement
• Choosing materials and causes of failure
• Conclusion
What is Biomedical engineering? Why learn about it?
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Biomedical Engineering
“Biomedical engineering blends traditional engineering techniques with biological sciences and medicine to improve the quality of human health and life” -UConn BME website
Fig 1. Fig 2.
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Hip Fracture
• High impact tackles
• Minimal protection of hip joint
• Common fracture location
• Replacement required
Fig 3.
Fig 4.
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The Human Body
• Constant body temperature
98.6°F or 37°C
• Bone and muscle anisotropic
Body fluids – corrosive to metals
1 wt% NaCla Other components
• Muscles transfer forces
Fig 5.
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The Human Body III
• Biocompatible to foreign objects
Location
chemistry
shape
• Apriori vs. priori testing
Fig 5.
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The Human Body II
• Bone and cartilage attatchmennt
• Composite of protein collagen and brittle hydroxyapatite
• Anisotropic composite
These are some typical values:Cortical Cancellous
Stiffness (E, GPa) 17 0.1-2Strength (UTS, MPa) 150 2-20Strength (Yield point, MPa) 100 -Strain to failure (%) 1.5 2.5
Fig 6.
Fig 7.
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The Human Body III
perpendicular
parallel
Fig 7.
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Hip joint replacement
Fig 8.
Fig 9
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Hip Joint replacement II
1.) Ball attached to stem
2.) Femoral Stem
3.) Acetabular cup
4.) Fixing agent
4
3
Callister
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Fixing agent• Poly(methyl methacrylate) acrylic
(PMMA)
• Thermoplastic
• Reaction: PMMA powder mixed with
Liquid methyl methacrylate (wik)
+
Callister
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Femoral stem
• Yield strength > 500 Mpa
• TS > 650 Mpa
• %EL > 8%
• Corrosion rate < .01 mil per year
• Fatigue Strength:
400 Mpa at 10^7 cycles
• Avg person per year: 10^6
Callister
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Ball attached to stem
• Ceramic: polycrystalline aluminum oxide or zirconium oxide
• Good hardness but brittle
• Attached to femoral stem
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Acetabular cup
Ultra high molecular weight polyethylene
-Excellent wear and tear resistance
-Low coefficient of friction
-Inert
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Hip joint replacement overview
1.) Density
2.) Properties
3.) Reproducibility
4.) Cost
Life span 15-25 years
Callister
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Choosing Materials
Callister
Femoral Stem
They all meet
Minimal
requirements
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Choosing Materials
Femoral Stem alloys:
316L stainless steel – best corrosive rate
Co-28Cr-6Mo – best Modulus
Ti-6Al-4V – best biocompatibility
Reasons for different materials – people vary
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Failure
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Failure II
Other causes
Sharp edges
Fatigue strength
Not biocompatible
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Conclusion
• Make use of all type of materials and their properties
• Ethical testing for biocompatibility with animals
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Citations• Bionic arm• http://www.impactlab.net/2006/12/03/new-bionic-arm-technology-offering-hope-to-amputees/
• http://www.physorg.com/news194246067.html -heart
• http://winmyfantasyleague.com/frank-gore-lost-for-the-season-fantasy-implications/
foorball player
http://www.healthdetails.org/general-information/hip-fracture-diagnosis-treatment-and-protection-methods-147.html
Pg 4 joint
http://www.wisdomwoman.com/nerve/?p=610 –muscles pg 7
http://health.allrefer.com/health/hip-joint-replacement-hip-joint-replacement-series.html pg 6 normal hip joint
http://www.reshealth.org/yourhealth/healthinfo/default.cfm?pageID=P08957 hip joint pg 6
Ball and cup pic pg8-12
http://healthguide.howstuffworks.com/hip-joint-replacement-picture.htm
Callister – materials engineering
http://healthguide.howstuffworks.com/hip-joint-replacement-picture.htm
The overview pg 7
http://www.cposm.com/index.php/orthopaedic-services/hip/ pg7
http://www.orthopaedia.com/download/attachments/23724188/Hip+fractures.jpg?version=1&modificationDate=1290971451000
fracture