SummaryA long oblique osteotomy model of canine femoral fractures was created to compare six methods of internal fixation. The following methods were tested: three cerclage wires, three lag screws, eight-hole dynamic compression plate attached with six cerclage wires, eight-hole dynamic compression plate attached with six cortical screws, eight-hole dynamic compression plate attached with six cortical screws superimposed over three cerclage wires, and an eight-hole dynamic compression plate attached with six cortical screws superimposed over three lag screws. The repaired femurs were mounted in a mechanical testing machine in an orientation designed to mimic physiological loading. Axial compression was applied which resulted in the test specimens experiencing simultaneous compressive and bending forces. The effects of the method of osteotomy repair, bone temperature, and bone diameter were analyzed. The maximum load and the stiffness of the composite fixation and bones were determined. There were not any statistically significant differences in stiffness among the groups. All fixation methods, in which plates were attached with screws, resulted in significantly greater maximum load values than treatment techniques where plates were not used. None of the fixation methods attained a mean maximum load greater than 58% of the mean maximum load of the control femurs.Six methods of commonly used internal fixation methods are compared. A method of in vitro positioning of test femurs to mimic in vivo orientation is presented. Maximum load capabilities of fixation do not significantly increase with the addition of interfragmentary compression to plate fixation.
