| Objective To investigate the stability and biomechanical properties of different distal locking nail states in the fixation of distal tibial fractures with interlocking intramedullary nails. Methods CT Dicom data of a healthy adult tibia were selected. 3D models of the tibia, intramedullary nail and locking nail were constructed by mimics, geomagic and solidworks software. Then, according to the different locking states of the distal end of the intramedullary nail, the models were divided into the test group (two transverse locking nails and one longitudinal locking nail) and the control group (two transverse locking nails), and different loads were applied in the axial, lateral, and torsional directions to simulate the stress and displacement distribution of the normal human tibia and the internal fixation system under different stress conditions. Results There was no significant difference in stress distribution between the test group and the control group, both of which were concentrated at the bone-screw junction. However, the maximum equivalent stress in the test group was slightly lower than that in the control group under different loads in the axial, lateral and torsional directions. Under axial loads of 300, 600, and 900 N, the maximum equivalent stress of the test group was 24.84, 49.68, 74.52 MPa, and that of the control group was 27.80, 55.51, 83.27 MPa, respectively. Under the torsional load of 2, 4, and 6 N/m, the maximum equivalent stress of the test group was 144.87, 290.92, 431.80 MPa, and that of the control group was 146.01, 292.03, 434.80 MPa, respectively. Under the lateral load of 300, 600, and 900 N, the maximum equivalent stress of the test group was 209.79, 419.58, and 629.37 MPa, and that of the control group was 210.47, 420.94, and 631.41 MPa, respectively. In terms of deformation and displacement, there was no significant deformation of the internal fixation system in the two groups, and the maximum displacement of the test group was slightly smaller than that of the control group. Under the axial load of 300, 600, and 900 N, the maximum displacement of the test group was 0.022 9, 0.045 8, 0.068 7 mm, and that of the control group was 0.024 1, 0.048 1, and 0.072 3 mm, respectively. Under the torsional load of 2, 4, and 6 N/m, the maximum displacement of the test group was 0.217 8, 0.428 8, and 0.597 8 mm, and that of the control group was 0.218 5, 0.436 9, and 0.607 2 mm, respectively. Under the lateral load of 300, 600, and 900 N, the maximum displacements of the test group were 0.949 2, 1.898 5, and 2.847 7 mm, and those of the control group were 0.952 5, 1.905 0, and 2.857 6 mm, respectively. Conclusion By comparative analysis of stress and displacement, when using intramedullary nails to fix distal tibial fractures, the distal fixation of two locking nails has provided sufficient stability, and two locking nails can reduce additional operation time, patient cost, and unnecessary radiation exposure compared with the use of three locking nails. In clinical practice, it is also necessary for the surgeon to select the most appropriate surgical plan for the patients according to the specific situation. |
