Multi-objective design optimization of high tibial osteotomy for improvement of biomechanical effect by using finite element analysis.

Medial opening wedge high tibial osteotomy (HTO) makes the proximal tibia a highly unstable structure and causes plates and screws to be the potential sources for mechanical failure. However, asymmetrical callus and incomplete bone formations underneath the plates (TomoFix) have been recent concerns in clinical and experimental studies related to HTO due to the high stiffness. The purpose of this study was to evaluate the biomechanical effect of the TomoFix plate system with respect to changes in design using a computational simulation. A parametric three-dimensional model of HTO was constructed from medical image data. The design parameters for the HTO plate were evaluated to investigate their influence on biomechanical effects, and the most significant factors were determined using Taguchi-style L27 orthogonal arrays. Multi-objective optimization was used to identify the wedge micromotion stability without the stress shielding effect that occurs in the bone plate. The initial design showed that the high stiffness of the plate caused stress shielding on the bone and plate. However, the optimal design led to sharing the stress and load with the bone plate to eliminate stress shielding. In addition, the stability required for the plate could be found in the micromotions of the wedge for the optimal design. The optimal condition of design parameters was successfully determined using the Taguchi and multi-objective optimization method, which was shown to eliminate stress shielding effects. The results showed that an optimal design demonstrated the feasibility of design optimization and improvements in biomechanical stability for HTO.