Unstable proximal extraarticular tibia fractures - A biomechanical evaluation of four methods of fixation

Objective: To compare the biomechanical stability of extraarticular proximal tibia fractures reconstructed using a double-plate construct, locking plate system, hybrid external fixator, and single lateral periarticular plate, all from the same manufacturer. Design: Standardized proximal fibial fractures (AO classification 41-A3.2 and A3.3) in synthetic tibiae were stabilized using one of the four constructs. Load versus proximal fragment translation and rotation were monitored in each case. Fixation was evaluated for moderately unstable and completely unstable fractures simulated by wedge and gap osteotomies of the proximal femur. Setting: Academic medical center biomechanical engineering laboratory. Main Outcome Measurements: Proximal fragment axial displacement, varus rotation, and posterior rotation versus applied load for each of the constructs. Results: The double-plate construct was significantly stiffer than all other constructs with regard to resistance to axial displacement, varus rotation, and posterior rotation for both types of unstable fractures. With regard to axial stiffness, the double-plate construct was statistically similar to an intact tibia for moderately stable fractures. The locking plate and the external fixator were similar for stabilization of moderately unstable fractures, whereas the locking plate and the periarticular plate were significantly stiffer than the external fixator construct for completely unstable fractures. Conclusion: For axial load applied to a wedge or gap osteotomy of the proximal tibia, the double-plate construct provided significantly more rigidity than the other constructs. The locking plate, periarticular plate, and hybrid external fixator tested provided similar rigidity for the wedge osteotomy, but for the gap osteotomy the external fixator could not support 600N without complete closure of the gap.