Abstract: BACKGROUND: The C1 type fracture of the distal radius is an intraarticular unstable fracture, which is difficult to treat. At present, there are few clinical studies about the comparison of the biomechanical differences of different internal fixation plates for distal radius fractures under different loading conditions, and there are still controversies in the selection of internal fixation plates.
OBJECTIVE: To compare the biomechanical properties of different internal fixation plates for C1 type fractures of distal radius using a finite element analysis method.
METHODS: The distal radius model of a healthy female volunteer was used, and the files were sequentially imported into Mimics 21.0, Geomagic Wrap 2017, and Solid Works 2021 for processing. The C1 type fracture of the distal radius was modeled. According to the plate data provided by the manufacturer, the volar oblique T-locking plate, volar fixed-angle anatomical plate, volar variable-angle locking plate and screws three-dimensional model were created and assembled with the fracture model. The material properties were given in ANSYS 19.0 to set up the relationship of interaction between the contact surfaces, and to define the loads and boundary conditions. Four load cases, including compression, dorsal flexion, palmar flexion and torsion, were applied to compare the biomechanical properties.
RESULTS AND CONCLUSION: (1) In the three groups of internal fixation models, the overall displacement of the internal fixation model was mainly concentrated on the articular surface of the distal radius under four load conditions. The maximum displacement of the model under the dorsal, palmar and torsion load conditions was 2-6 times that of the displacement under the axial load, indicating that the internal fixation system was the most stable under the axial load condition. (2) The stress on the internal fixation was much greater than the stress on the bone fracture fragments. The stress of the internal fixation was mainly concentrated in the area that near to the fracture end of the bone plate, among which the stress distribution of the volar fixed-angle anatomical plate, volar variable-angle locking plate was relatively uniform, and the stress concentration of the oblique T-locking plate was the most obvious. (3) Under compressive and torsional loads, the stress of the fracture fragments was mainly concentrated in the area that around the screw holes. Under dorsal and palmar flexion, it gradually expanded from the distal end to the proximal radius. Under the same load condition, the stress of the fracture block in the oblique T-locking plate fixation state was the highest, and the peak stress of the fracture fragments in the volar variable-angle locking plate fixation system was the lowest. The difference between the peak stress of the bone fracture fragments in the fixed state of the volar fixed-angle anatomical plate and the volar variable-angle locking plate was only in the range of 0.2-6.0 MPa. (4) It is indicated that compared with the oblique T-locking plate and the volar fixed-angle anatomical plate, the volar variable-angle locking plate has more uniform stress distribution, less displacement of articular surface, and the best stability in the internal fixation in the C1 type fracture of the distal radius.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

Key words: distal radius fracture, internal fixator, oblique T-locking plate, fixed-angle locking plate, variable-angle locking plate, displacement, stress, finite element analysis