Hollow screw fixation of type II avulsion fractures of the calcaneal tuberosity using the finite element analysis.

We aimed to establish a model of type II avulsion fractures of the calcaneal tuberosity treated with 2 hollow screws implanted in different directions and to analyze the biomechanical properties of the model using the finite element method. The Dicom data of the calcaneal bone obtained after computed tomography scan were inputted into Mimics 21.0 software and Geomagic Studio software to generate a 3D finite element digital model of the calcaneal bone. The model was then imported into SOLIDWORKS 2020 software. Based on the Beavis theory, the calcaneal bone was cut to build a type II avulsion fracture model of the calcaneal tuberosity; the calcaneal fracture was then simulated by internal fixation using hollow screws. Two screws were used to fix the calcaneal bone from the calcaneal tuberosity in different ways, resulting in 3 different calcaneal models (Model 1 involved 2 screws for fixing the fracture vertically; Model 2 had 2 screws for fixing the fracture cross-wise; and Model 3 had 2 screws for fixing the fracture parallelly). Three internal fixation models were loaded under the same conditions, and lines finite element analysis was then performed to calculate the stress distribution of the generated internal fixation models. Under the same loading conditions, compared with Models 2 and 3, Model 1 exhibited smaller maximum displacement values of the heel bone, maximum equivalent force values of the screws, and more dispersed stresses. Avulsion fractures of the calcaneal tuberosity can be treated using 2 screws to fix the fracture vertically (Model 1), which is more biomechanically relevant.