Artificial total hip_replacement[1] (1)
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Artificial Total Hip Replacement
Arthur Hernaez
Materials Engineering
Mission College - Spring 2011
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?
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.
Hip Fracture
• High impact tackles
• Minimal protection of hip joint
• Common fracture location
• Replacement required
Fig 3.
Fig 4.
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.
The Human Body III
• Biocompatible to foreign objects
Location
chemistry
shape
• Apriori vs. priori testing
Fig 5.
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.
The Human Body III
perpendicular
parallel
Fig 7.
Hip joint replacement
Fig 8.
Fig 9
Hip Joint replacement II
1.) Ball attached to stem
2.) Femoral Stem
3.) Acetabular cup
4.) Fixing agent
4
3
Callister
Fixing agent• Poly(methyl methacrylate) acrylic
(PMMA)
• Thermoplastic
• Reaction: PMMA powder mixed with
Liquid methyl methacrylate (wik)
+
Callister
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
Ball attached to stem
• Ceramic: polycrystalline aluminum oxide or zirconium oxide
• Good hardness but brittle
• Attached to femoral stem
Acetabular cup
Ultra high molecular weight polyethylene
-Excellent wear and tear resistance
-Low coefficient of friction
-Inert
Hip joint replacement overview
1.) Density
2.) Properties
3.) Reproducibility
4.) Cost
Life span 15-25 years
Callister
Choosing Materials
Callister
Femoral Stem
They all meet
Minimal
requirements
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
Failure
Failure II
Other causes
Sharp edges
Fatigue strength
Not biocompatible
Conclusion
• Make use of all type of materials and their properties
• Ethical testing for biocompatibility with animals
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