Objective: To explore biomechanical characteristics of minimally invasive different screw fixations in treating Sanders typeⅡcalcaneal fractures.
Methods: Dicom data of calcaneus by CT scan were input into Mimics 21.0 software and Ansys15.0 software to construct three-dimensional finite element digital model of calcaneus;this model was input into UG NX 10.0 software, and calcaneus was cut according to Sanders classification to establish Sanders typeⅡ calcaneus model with posterior articular surface collapse;then simulated minimally invasive screw internal fixation after calcaneal fracture:a screw from posterior articular surface was used to outside-in fix sustentaculum tali, other 4 screws were used to fix calcaneus by different methods through calcaneal tuberosity, and 4 different calcaneal models were obtained. Under the same conditions, 4 types of internal fixation models were loaded respectively, and nonlinear finite element analysis was performed to calculate the stress distribution of different internal fixation models.
Results: Under the same condition of loading, the model 3 had smaller displacement value, maximum calcaneus displacement value and maximum equivalent stress value of the screw than other three internal fixation models, and the stress was more dispersed.
Conclusion: In minimally invasive screw internal fixation of calcaneus fracture, after 1 sustentaculum tali screw fixation, 2 screws crossed fix posterior articular surface from calcaneal tuberosity, 2 screws fix parallelly calcaneocuboid joint from calcaneal tuberosity are more suitable for biomechanical requirements, and could provide basic theory for clinical treatment.
Keywords: Calcaneus; Finite element analysis; Fractures; Minimally invasive.