Design and linear statics finite element analysis of screw hole filler for titanium locking plate system / 中华创伤骨科杂志

ABSTRACT

Objective To investigate the conceptual feasibility and biomechanical advantages of our self-designed screw hole filler for a lateral bamboo-raft-type titanium locking plate in a digital model of proximal tibial fracture using linear statics finite element analysis.Methods A nut-type screw hole filler was designed.Four different idealized finite element models of proximal tibial fracture fixed by a lateral bamboo-raft-type anatomic locking plate were established on the basis of three-dimensional CT reconstruction and digital orthopedic techniques.The first one was assembled with the filler and stabilized fibula,the second with stabilized fibula but without the filler,the third with the filler and unstabilized fibula,and the fourth with unstabilized fibula but without the filler.Linear statics finite element analyses were conducted for the 4 models under the same 26 groups of loads.The 4 models were compared in terms of maximum relative displacement on fracture surface,average relative displacement on fracture surface,maximum Von Mises stress of internal fixation,maximum contact stress on fracture surface,maximum contact stress between plate and tibial surface,maximum contact pressure on fracture surface,and maximum contact pressure between plate and tibial surface.Outcomes of the analyses for the 4 models were harvested and treated with Wilcoxon Signed Ranks Test.Results There were significant differences between using filler and not using filler in maximum relative displacement on fracture surface,average relative displacement on fracture surface,maximum Von Mises stress of internal fixation and maximum contact pressure between plate and tibial surface (P ＜ 0.05),but no significant difference was found in maximum contact pressure on fracture surface (P ＞ 0.05).The model assembled with the filler and unstabilized fibula led to the greatest improvement in maximum Von Mises stress of internal fixation (P ＜ 0.05).Conclusions Since use of nut-type screw hole filler may increase the contact pressure between plate and bone surface,reduce the maximum Von Mises stress of internal fixation,the maximum displacement of the whole model,and the relative and average displacements on fracture surface,but has insignificant effect on the contact pressure on fracture surface,it improves the biomechanical performance of internal fixation.The filler deserves further study.