Finite element analysis on fixation of Sanders II type of calcaneal fracture

[Objective]To analyze the effect of multi-fixation and plate fixation for the treatment of calcaneal fracture,and to provide biomechanical evidence for internal fixation selection. [Methods]CT scan was made on a normal male right calcaneus weighting 64kg,and a complete three-dimensional finite element model calcaneus was established for simulation of Sanders Ⅱ type fracture of calcaneus.Plate fixation and multi-pin fixation were simulated for analysis of post-surgery Achilles tendon loading condition.Stress distribution,relative displacement of the fracture line and the max principle stress value were compared respectively in two fixations. [Results]With 160 Newton of Achilles tendon loading and 0? angle in 3 groups of fracture fixation model groups,the maximum principal stress value reached to 85.452 in plate group,87.378 in multi-pin functional position group,120.58 in multi-pin plantar flexion group,all less than the yield strength of fixation of 225 MPa.Relative displacement of fracture line in three groups was less than fracture line displacement requirement ≥1 mm.When loading 1～1 000 Newton loading condition,internal fixation failure occurred at 487.38 N,465.45 N,340.28 N in 3 groups respectively,all greater than 160 N.Stress loading was equally distributed in both plate and multi-pin fixations,according to stress distribution analysis. [Conclusion]The fixation stability and loading stress is similar for both multi-pin and plate fixation in treatment of calcaneau fracture.Compared with plate fixation,multi-pin fixation is preferred to Sandders Ⅱ fracture,in order to reduce the risk of postoperative soft tissue complications.