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Implants  and  prosthesis    

Example  of  man-­‐made  biomaterials:  •  UHMWPE  =  Ultra-­‐High-­‐Molecular-­‐Weight  polyethylene      •  Metals:  e.g.  stainless  steel  and  <tanium      •  PMMA  =  polyethylene  methacrylate  (bone  cement)  

•  Polydimethylene  silixane  =  silicon  rubber    •  Dacron  (blood  vessels)    •  Polytetrafluoreten  =  Teflon  or  Gor-­‐Tex  (heart  valves,  ligaments,  ossicles  

for  the  ear)    •  Ceramics  and  glasses    

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Problems  to  overcome:  

•  Anatomic  compa<bility  •  Corrosion  •  Toxity  and  infec<on  •  Strength  •  Fixa<on  •  Long-­‐term  physiological  compa<bility  

Cemented  hip  prosthesis    

!

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Un-­‐cemented  hip  prosthesis    

!

Beware  of  wear!!    

!

Polyethylene  cup    

!

Metal  cup  

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No  wear:  Ceramics!    

!

Knee  prosthesis  

!

(Uni-­‐knee  –  one  condyle)  note!  Meniscus  

!

Total  knee  

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Shoulder  prosthesis    

!

with  stem  

!

without  stem  

Total  Hip  Replacement    

•  hAp://www.youtube.com/watch?v=WJ1E12xcaTs  

Abductor  mechanism  

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Total  Hip  Replacement    

Stress  shielding  

Results  from  finite  element  simulaMons,  change  in  energy  density  (σ�ε)  

Note:  Biomechanics  of  Arthroplasty,  chapter  16  in  the  book!  

•  Table  16.1-­‐16.2  Hip  and  knee  forces,  measured  and  esMmated      

Varus  deformity  

Normal  alignment  

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Note:  Biomechanics  of  Fracture  fixaMon,  chapter  15  in  the  book!  

Sa]y  factor  for  a  hip  prosthesis