Locally Delivered Minocycline Microspheres do not Impair Osseointegration of Titanium Implants in a Sprague-Dawley Rat Femur Model

Abstract Background The purpose of this study was to determine whether intramedullary administration of extended-release minocycline microspheres would affect osseointegration. Methods Twenty-two rats were randomized to minocycline or saline femoral intramedullary injection followed by implantation of titanium alloy rods. Following euthanasia at four-weeks, pushout testing was performed and bone-volume-fraction assessed. Results Pushout strength was marginally greater in minocycline-treated implants (122.5±39.1N) compared to saline (96.9±26.1N)(P=0.098). No difference was observed in energy to maximum load, mean stiffness, or peri-implant bone-volume-fraction(P>0.05). Conclusions Peri-implant minocycline administration did not impair implant fixation strength or peri-implant bone-volume, supporting its potential utility as an adjunct to intramedullary implants.