The effect of surface treatments on the interface mechanics of LTI pyrolytic carbon implants

A mechanical and histological evaluation of LTI pyrolytic carbon implants was undertaken to determine the effect of various surface treatments on the retention characteristics of the implants. Five types of surfaces were evaluated, including as-deposited, fine grit-blasted, coarse grit-blasted, ground, and plasma oxygenated. The four surface treatments were chosen in an attempt to emulate the morphology of the as-deposited implants. The implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for periods of 12 to 24 weeks. Although the as-deposited implants exhibited the greatest interface strength at 12 weeks the results of mechanical testing after 24 weeks implantation indicated no statistically significant difference among the interface strength values or among the interface stiffness values of the implants. The histologic response of the implants was similar; while all implants exhibited areas of direct implant-bone apposition, the as-deposited implants exhibited this behavior to the greatest extent. Thus the ability to duplicate the biological response to the as-deposited LTI carbon surface appears possible by one or more of the treatments evaluated.