There is added stability when plate fixation of the fibula supplements the external fixator used in treating tibial fractures associated with a segmental defect. An anatomic specimen model of a Grade III open fracture of the tibia with an associated fibular fracture was used in this study. Fibular internal fixation using an AO standard plate was performed on one of each of five matched pairs of legs. These were then subjected to identical loads in compression and torsion. The numeric values obtained during loading in all modes were converted to ratios between each of the tested pair to directly compare the effect of stabilization of the fibula. The final results showed that in each case, the preparation with fibular plating had improved resistance to deformation in axial loading. On average, the plated specimens were 2.2 times stiffer. In torsion, plating the fibula did not appear to affect the resistance of the construct to the applied load. Supplemental plate fixation of the fibula in fractures of the tibia with segmental defects may improve subsequent morbidity. The increased rigidity of the system may be sufficient to allow partial to full weight bearing immediately after surgery. This may have significant value in the management of the polytraumatized patient.