Biomechanical study of a low-cost external fixator for diaphyseal fractures of long bones

BACKGROUND: External fixation improves open fracture management in emerging countries. However, sophisticated models are often expensive and unavailable. We assessed the biomechanical properties of a low-cost external fixation system in comparison with the Hoffmann ® 3 system, as a reference. METHODS : Transversal, oblique, and comminuted fractures were created in the diaphysis of tibia sawbones. Six external fixators were tested in three modes of loading– axial compression, medio-lateral (ML) bending, and torsion – in order to determine construction stiffness. The fixator construct implies two uniplanar (UUEF1, UUEF2) depending the pin-rods fixation system and two biplanar (UBEF1, UBEF2) designs based on different bar to bar connections. The designed low-cost fixators were compared to a Hoffmann ® 3 fixator single rod (H3-SR) and double rod (H3-DR). Twenty-seven constructs were stabilized with UUEF1, UUEF2 and H3-SR (nine construct each). Nine constructs were stabilized with UBEF1, UBEF2 and H3-DR (three construct each). RESULTS : UUEF2 was significantly stiffer than H3-SR (p<0.001) in axial compression for oblique fractures and UUEF1 was significantly stiffer than H3-SR (p=0.009) in ML bending for transversal fractures. Both UUEFs were significantly stiffer than H3-SR in axial compression and torsion (p