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

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.