| Summary: | 碩士 === 國立成功大學 === 醫學工程學系 === 81 === In this study, we adopted hydroxyapatite(HA) to provide
fixation of implant and bone, that HA have advantage in
offering reproducible skeletal attachment in total joint
replacement by bone ingrowth and bone ongrowth. The purposes
are to analyze the effect of HA-coated implant on strain
distribution of long bone and to compare interfacial shear
strength of different HA coating thickness. A plasma-sprayed HA
coatings (about 50 micro,50μ) was applied to the Ti-6Al-4V and
Co-Cr-Mo rods, and were implanted intramedullarly in the distal
femur of mongrel dog. The implants were harvested after twelve
weeks and prepared to evaluate distribution of strain and shear
strength. Another test was to investigate the biological
reaction and shear strength of the long bone with
intramedullary nail of without or with different HA coatings at
twelve and twenty-four weeks. As bone ongrowth on implant
surface after 12 weeks, femoral bending rigidity increases, the
mechanical axis strain reduces, and the top of rod increase
especially for Co-Cr-Mo stem. Shear strength and shear
stiffness indicated by push-out test that Co-Cr-Mo stem have
well-fixed rigidity than Ti-6Al-4V. According to this
phenomenon, there would sereously have stress shielding with
time on Co-Cr-Mo stem than Ti-6Al-4V. Histologically, after
period of 12 and 24 weeks implantation, there are no extensive
direct apposition or lining of the ongrowth to the uncoated Ti-6
Al-4V surface, but the HA coating support mineralization
directly onto its surface. The HA/bone interface
osteointegration increase with time for HA coating, and the
bone ongrowth of 200μ HA coating have well apposition than
that of 50μ. Direct comparison of shear strength values reveal
that the 200μ have good strength than 50μ at 12 weeks
postimplantation. The specimen of 200μ significantly failure
at HA/implant interface by push-out test.
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