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e1
QUESTIONS
1. Briefly define the following, using examples where
applicable:
a. angiogenesis
b. osteointegration
c. stress shielding
d. enucleation
2. Name two medical device applications in which
textured or porous materials/coatings are used.
Describe how the surfaces were rendered textured/
porous.
3. For each of the medical device applications listed above,
why are these porous/textured materials/coatings used
4. Do a calculation of stress transfer between a metal
of high stiffness and a bone of low stiffness. For sim-
plicity, assume two independent cylindrical elements
of equal volume acting in parallel (you may have to
5. Speculate how the calculation in Question 4 would
change if the two cylindrical elements are bonded
together. Why is osteointegration important?
6. Design a tissue integration surface for an electrode
ANSWERS TO QUESTIONS
1. a. Angiogenesis: the growth of new blood vessels
from pre-existing vessels.
b. Osteointegration: growth of host-bone into an
more load than the bone, the bone becomes weak-
ened and susceptible to fracture and implant
loosening.
d. Enucleation: removal of the eye (i.e., due to severe
trauma, disease); surrounding eye muscles typi-
cally remain intact.
sular contracture around breast implants).
h. Micromotion: repeated mechanical agitation, often
leading to loosening of implant fixation with host
tissue, increased inflammation, increased fibrous
encapsulation.
i. Percutaneous: penetrating the body through a
j. Marsupialization: epithelial down growth that
forms a pocket around the implant.
2. a. Femoral stem of hip implant – sintering, grit blast-
ing Ti
orbital implants)
b. Promote angiogenesis (i.e., glucose sensors)
c. Disrupt fibrosis (i.e., breast implants)
4.
∗Screen ( ) = Young's Modulus of Elasticity (E) strain ( )
σ ε
0.5[E(bone) (bone)+E(metal) (metal)]
For simplicity, assume no-slip iso-strain condition:
= =
+
= +
(bone) (metal) (total)
(total) = 0.5[E(bone) E(metal)] (total)
E(total) 0.5[E(bone) E(metal)]
ε ε ε
σ ε
CHAPTER I.2.15
Textured and Porous Materials
e2
5. The calculation would not change because it assumes
a no-slip condition, but would be more realis-
6. The porous metal surface would have to be effi-
ciently conducting, so one would have to incorporate
