Comparative finite element analysis of fixations for posterior malleolar fracture

Objective To compare the tube plate,T-plate and screws in fixation of posterior malleolar fracture in terms of biomechanical stability.Methods The CT data of the ankle obtained from a normal male volunteer was used to make a three-dimensional reconstruction by software mimics 14.0 and geomagic 2012.After we built a three-dimensional finite element model of the ankle along with its stimulated ligaments in software ANSYS,the validity of the model was verified.The model of posterior malleolar fracture was cut from the posteromedial point of the tibia to the one-fourth point of the distance from the posterior to the anterior margin in the software Solidworks 2012.Models of screws,1/4 tube plate and T-plate were also constructed in Solidworks 2012.According to the established method in the literature,2 screws,a 1/4 tube plate and a T-plate were applied respectively.Under the same neutral weight bearing,the flexion and external loadings,the fragmental displacement,the stresses of fracture and fixation were calculated by finite element analysis.Results Under neutral or external loading,T-plate fixation caused the smallest fragmental displacement compared with the other 2 fixations and the 2 plate fixations caused a smaller displacement in Z-axis under neutral loading than screws fixation.However,similar displacements were identified in all fixations under flexion loading.Under all loading conditions,excessive concentration of the stress was not observed.Conclusions T-plate shows a better biomechanical stability than 1/4 tube-plate and screws while plating reduces the upward displacement than screws.All the 3 fixations show no obvious excessive concentration of the stress. Key words: Hock;  Fracture fixation, internal;  Bone nails;  Bone plates;  Finite element analysis