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 cadaver specimens fixed with one of two different types of intramedullary locked nail systems; conventional antegrade nail fixation of the femur with the universal AO femoral nail or retrograde insertion in the femur with the universal tibial nail (a smaller diameter slotted nail) were utilized. Mechanical testing simulated one leg stance, and resultant deformation was measured in bending, torsion, and shortening. In stable fractures, fracture stability was similar to both devices, while in unstable fractures, the larger femoral nail was more stable. Furthermore, the simulation of single leg stance led to a coupled deformation of varus bending, axial shortening, and external rotation, which was dependent on bone geometry.