Relative stiffness, transverse displacement and dynamization in comparable external fixators

Several unilateral external fixators were laboratory tested under applied axial, bending, and torsional loads. In certain cases the shear movement at the fracture site was substantial, up to 4 mm, and in all cases it was as significant as axial displacement. Also, under average full weight bearing, all the fixator/bone screw frameworks will allow too much axial movement at the fracture. This could inhibit healing and cause peak bone and screw stresses to approach yield.