Experimental study on the biomechanical loading of a four-dimensional plate for the fixation of femoral shaft fractures.

Abstract

Objective: To explore the biomechanical properties of a four-dimensional structure locking osteosynthesis plate that can alter its structure and functionality over time.

Methods: According to the AO classification (AO-A2) standard, 18 artificial femoral shaft oblique fracture models with the same position and shape were generated and subsequently randomly divided into 2 groups (n = 9). In the experimental group, the four-dimensional locking plate was fixed, and in the control group, the locking plate was fixed. In vitro loading experiments were carried out under three conditions: 1400 N axial compression, 500 N internal and external four-point bending, and 15 N·m torsion. The average compression stiffness, average bending stiffness, average torsional stiffness, and displacement were compared between the two groups.

Results: Under vertical loading, the average compression stiffness of the experimental group (558.7 ± 39.1) N/mm was greater than that of the control group (548.8 ± 24.5) N/mm, (P = 0.73); and the average displacement of the fracture end of the experimental group (3.3 ± 0.2) mm was lower than that of the control group (3.4 ± 0.3) mm, (P = 0.47). The differences were not statistically significant. Under four-point bending loading, the average bending stiffness of the experimental group (466.6 ± 85.8) N/mm was lower than that of the control group (542.5 ± 43.2) N/mm, and the difference was not statistically significant (P = 0.24). The average displacement of the fracture ends in the experimental group (1.6 ± 0.2)mm was greater than that in the control group (1.2 ± 0.1)mm, and the difference was statistically significant (P = 0.02). Under torsional loading, the average torsional stiffness of the experimental group (1.0 ± 0.1) N·m/deg was lower than that of the control group (1.1 ± 0.1) N·m/deg, (P = 0.27); and the average angular displacement of the fracture end of the experimental group (15.9 ± 1.3) deg was greater than that of the control group (14.6 ± 1.3) deg, (P = 0.26). There was no significant difference between the two groups.

Conclusion: The anti-compression, anti-bending and anti-torsion properties of four-dimensional locking plates are similar to those of conventional locking plates and can meet the mechanical requirements of internal fracture fixation.