| Summary: | 碩士 === 國立成功大學 === 醫學工程學系 === 82 === Repeated impact forces cause bone and joint degeneration.
Changes of bony microstructure due to repeated loading is a
popular topic nowadays.How these cyclic stresses affect the
generation of microcracks remains unknown. It is know that
microdamages jeopardize mechanical properties of bone. However,
in-vivo and in-vitro fatigue tsts showed very much different
results. Thus, we design a mechanical apparatus to implement a
falling body test. From repeated impact forces on rabbits, the
variations of mechanical properties and the generation of
microcracks in their tibia of hind limb can be measured through
a ultrasound technique and histology examination,respectively .
By performing the above experiments, a thorough understanding
of the occurrence of joint degeneration is a ultimate goal.
Results showed that after experiment,the rabbits' tibia elastic
modulus increased. This means that rabbit's bone went though an
adaptation process. Meanwhile,the unchanged material properties
from ultrasound measurement would suggest that microdamages did
not accumulate until the forth week, then the bone's elastic
modulus decreased. Scanning electron microscoppy was used to
examine surface of articular cartilage , the surface became
rough.It is believed that the change of surface roughness is an
important indication of the initial of OA .Thus , the
quantitative relation between surface rought and impact
conditions would be very important in the future.
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