Stability Assessment of Unilateral External Fixator Configurations for Open Tibial Fractures: An Experimental Study

The primary objective of external fixation is to stabilize bone fractures, with the mechanical characteristics of the fixation system playing a critical role in shaping the biomechanical environment of the fracture and, consequently, the healing process. This study presents an experimental investigation of the stability of eight unilateral external fixation configurations applied to an open tibial fracture. The stiffness of each configuration was evaluated under axial compression, anterior–posterior (AP) bending, medial–lateral (ML) bending, and torsional loading. In addition, the effects of structural parameters—such as the number of half-pins, planarity of the configuration, and interfragmentary distance—on fixator stiffness and generated stresses were examined. The results revealed a linear relationship between applied load and both bone segment displacement and principal stresses. Biomechanical tests demonstrated that biplanar configurations provide sufficient stability for open tibial fractures, while simultaneously offering an optimal structural design for the fixation system. Moreover, the number of half-pins was identified as a statistically significant factor influencing configuration stiffness under axial loading and torsion, with biplanar configurations proving particularly effective in torsional scenarios. However, in AP and ML bending tests, neither configuration type nor any individual parameter produced statistically significant differences in bending stiffness. Interestingly, interfragmentary distance did not exert a statistically significant effect on configuration stiffness under any loading condition. Furthermore, neither configuration type nor the analyzed parameters had a notable influence on the principal stresses measured at the control points.