Hybrid external fixation of proximal tibia fractures: biomechanical analysis of four commercial systems.

To compare commercially available hybrid external fixator systems, mechanical testing was performed on fiberglass composite tibias with proximal metaphyseal fractures fixed with 4 hybrid systems (Ace-Fischer, Hoffmann II, Synthes Hybrid, and EBI DynaFix) and a custom "rigid" frame. The only significant difference between commercial systems was in axial loading where the Ace-Fischer allowed less motion than the other frames. In all cases the "rigid" reference frame allowed significantly less motion than the commercial systems. Approximately 50% of the motion comes from frame deformation and 50% from deformation of the pins and wires.