A biomechanical comparison of the antegrade inserted universal femoral nail with the retrograde inserted universal tibial nail for use in femoral shaft fractures

Femoral shaft fractures with and without bony contact were simulated in cad aver specimens fixed with one of two different types of intramedullary lock ed nail systems; conventional antegrade nail fixation of the femur with the universal AO femoral nail or retrograde insertion in the femur with the un iversal tibial nail (a smaller diameter slotted nail) were utilized. Mechan ical testing simulated one leg stance, and resultant deformation was measur ed in bending, torsion, and shortening. In stable fractures, fracture stabi lity was similar to both devices, while in unstable fractures, the larger f emoral nail was more stable. Furthermore, the simulation of single leg stan ce led to a coupled deformation of varus bending, axial shortening, and ext ernal rotation, which was dependent on bone geometry.