2.5. Finite element analysis

Before implementing the in vivo animal experiments, we used finite element analysis (FEA) to stimulate and compare the effects of different repair materials and internal fixation modes for subarticular cancellous defects accompanied by split fractures in the distal femur. FEA could demonstrate the biomechanical distribution and concentration of the skeletal tissues and implants. As shown in Supplementary Figure B, the FEA model comprised the fracture fragment, femoral shaft, screws, plate, scaffold, and cement particles. We established a model of a lateral split fracture accompanied by cancellous bone defects. Four models were set up: Blank model (defects were left blank), Cement model (defects were filled with incompact cement particles), Scaffold I and II models (defects were filled with anatomical WE43 scaffolds). The difference between the latter two models was that part of the screws in Scaffold I penetrated the scaffolds, while the screws in Scaffold II avoided penetration. The elastic moduli of bone, plate, screw, cement, and scaffold were assigned values of 16,600 MPa, 110,000 MPa, 110,000 MPa, 3000 MPa, and 30,230 MPa, respectively. The Poisson's ratio of all the materials was set as 0.3. While applying the press, the proximal end of the femur was fixed, and the presses were applied separately from the unilateral or overall directions. The pressure was set at 50 N. We recorded and compared the von Mises values of the fracture fragment, femoral shaft, screws, plate, and scaffold.