The stiffness of 11 different device configurations of external fixation was investigated in an experimental model using human cadaveric tibia. After application of the different devices, a diaphyseal osteotomy allowing removal of a 35 mm bone segment was performed in the specimens. Displacements of the bone fragments at the osteotomy site induced by compresion loading, torsion, and both anteroposterior and mediolateral flexion were measured with dispositives designed for this experiment. Maximal load and that required for inducing 1 mm displacement were recorded. The higher stiffness corresponded to the Orthofix fixator in axial compression, the Kronner biplanar device in anteroposterior flexion, and the triangular configuration of the AO device in mediolateral flexion. A total stiffness index of each configuration as an average of the behavior against all loading modahties was obtained. The indications, advantages, complications and the biology of bone consolidation wien regards to external fixation are considered. As conclusion, progressive loading of the extremity with unstable fracture requires a close monitorization, since most of the device configurations analyzed allow more than 1 mm displacement of bone fragments at the fracture site, even with low axial loading.

The stiffness of 11 different device configurations of external fixation was investigated in an experimental model using human cadaveric tibia. After application of the different devices, a diaphyseal osteotomy allowing removal of a 35 mm bone segment was performed in the specimens. Displacements of the bone fragments at the osteotomy site induced by compresion loading, torsion, and both anteroposterior and mediolateral flexion were measured with dispositives designed for this experiment. Maximal load and that required for inducing 1 mm displacement were recorded. The higher stiffness corresponded to the Orthofix fixator in axial compression, the Kronner biplanar device in anteroposterior flexion, and the triangular configuration of the AO device in mediolateral flexion. A total stiffness index of each configuration as an average of the behavior against all loading modahties was obtained. The indications, advantages, complications and the biology of bone consolidation wien regards to external fixation are considered. As conclusion, progressive loading of the extremity with unstable fracture requires a close monitorization, since most of the device configurations analyzed allow more than 1 mm displacement of bone fragments at the fracture site, even with low axial loading.