This investigation intends to correlate titanium alloy plate strain and screw plate interface with titanium alloy metal ion release from posterior cervical spine implants in a dog model. It is believed that the magnitude of implant strain can influence the amount of metal released into the surrounding tissues and, in turn, that the concentration of material in the tissue will influence the implant's biological performance. Relative micromotion between various parts of the implant may accelerate the release of metal from the implant. As part of this investigation, a three-dimensional finite element model of the canine cervical spine segments(C3-C6), plates and screws will be developed. The model accuracy will be established through a convergence test, and it will be validated by modeling bench test loading schemes of ex-vivo specimens with strain gaged implants. The model will then be loaded as closely as possible to physiological conditions to depict the functional strain distributions. Contact stresses between the plate and bone and plate and screws will be examined. Finally, the results of the finite element model will be compared to the distributions of metal concentration found in the tissue.
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