Abstract: BACKGROUND: The types of acetabular double-column fractures are complex and common. At present, the traditional reconstructed bone plates are used to treat the double-column fractures, and the mismatch between them and the bone surface will increase the difficulty of surgery. Personalized bone plate can realize the adhesion of bone plate and bone surface, but the biomechanical comparison between personalized bone plate and traditional reconstructed bone plate in fixation of acetabular double column fracture is few, and the simulated posture is relatively simple.
OBJECTIVE: Three-dimensional finite element method was used to analyze the biomechanical characteristics of different internal fixation methods of complex acetabular double-column fractures in various positions, providing the necessary biomechanical basis for clinical application.
METHODS: The most representative two-column fracture model of complex acetabular fractures involving square area was established. A three-dimensional finite element model was established for the fixation of complex acetabular double-column fractures by four different internal fixation methods: special-shaped titanium plate fixation (group A), anterior and posterior column double titanium plate fixation (group B), anterior column reconstruction titanium plate + posterior column lag screw fixation (group C), and anterior column reconstruction titanium plate + subacetabular screw fixation (group D). Four kinds of complicated acetabular double-column fracture models with different internal fixation were simulated in the position of sitting, standing, affected side extension, affected side abduction, and affected side standing on one leg. The biomechanical properties of the four internal fixation methods were compared.
RESULTS AND CONCLUSION: (1) The node displacement and mean displacement on fracture line were presented as group A < group B < group C < group D in all postures. The displacement value in the one-leg standing position on the affected side was the largest compared with other postures, and the maximum displacement of the internal fixation system in group A was the smallest among the four models. There was no significant difference between the four groups in the standing position and the one-legged standing position (P > 0.05). In the position of sitting, affected side extension, and affected side abduction, there was no significant difference between group A and group B, group B and group C, and group C and group D (P > 0.05), but there was significant difference between group A and group C, group A and group D, and group B and group D (P < 0.05). (2) The maximum stress of each fracture block in group A was smaller than that in other groups, and the stress distribution of fracture block was more uniform. The stress of the internal fixator was mainly concentrated in the area near the fracture end of the bone plate. The stress distribution of the internal fixator was more uniform in groups A and B, while the stress concentration of the internal fixator in groups C and D was more obvious, and the maximum stress value of the internal fixator in group A decreased by 4.86%-54.61% compared with the other three groups. (3) In the affected side extension and abduction position, both groups A and B had a large stress shielding rate, and the maximum difference between the two groups was 5.67%. In the one-legged standing position on the affected side, the internal fixed stress shielding rate of group A was the highest, while that of group D was the lowest. (4) It is indicated that shaped personalized titanium plate fixation (group A) has better biomechanical stability than the other three groups of traditional reconstructed bone plate fixation.

Key words: shaped personalized titanium plate, traditional reconstructive plate, acetabular double column fracture, fracture internal fixation, multi-position, displacement, stress, finite element analysis, biomechanics