Biomechanical comparison of spatial weaving and conventional calcaneal plate fixation for calcaneal fracture / 中华骨科杂志

ABSTRACT

Objective:To compare the biomechanical characteristics of screw only spatial weaving fixation and calcaneal plate fixation in calcaneal fractures.Methods:Sanders type III calcaneus fracture model was established by using calcaneus model specimens the physiological model group were the normal calcaneal models; the steel plate group were conventional steel plate fixation fracture models; the metal screw group were fracture models with only metal screw weaving fixation; seven and nine absorbable screw spatial weaving groups (seven absorbable screw group, nine absorbable screw group) were used to weave and fix fracture models with seven and nine absorbable screws. Cyclic test and mechanical compression test were carried out, and load-displacement curves were recorded. The material properties of metal screw spatial weaving and calcaneal anatomical plate system were replicated, finite element fracture models were established, and the calcaneal internal fixation models of plate screw group and spatial weaving screw group were completed by reverse processing. The changes of biomechanical characteristics of calcaneal bone in human (70 kg) standing on one foot were simulated, and the distribution of structural strength was analyzed by Von Mises equivalent stress cloud diagram and displacement cloud diagram.Results:In the cyclic test of 20-200 N load, the physiological model group, the plate group, the metal screw group, the absorbable 7 screw group, the absorbable 9 screw group were 0.87±0.22, 0.82±0.08, 0.70±0.12, 1.04±0.13 and 0.83±1.76 mm, the difference in model gap was statistically significant ( F=3.16, P=0.037). Among them, the absorbable 7 screws group was larger than the metal screws group ( t=4.28, P=0.003), and the other pin-two comparisons were not statistically significant ( P>0.05). The deformation of the five groups was 0.37±0.06, 0.38±0.07, 0.38±0.06, 0.52±0.07 and 0.42±0.07 mm, and the difference was statistically significant ( F=4.39, P=0.010). The deformation of absorbable 7 screws group was greater than that of physiological model group, the plate group and metal screw group ( t=3.69, P=0.006; t=3.25, P=0.012; t=3.51, P=0.008). In static test, compression displacement was 7.14±0.79, 7.30±0.66, 6.95±0.28, 8.19±0.61 and 7.16±0.55 mm, the difference was statistically significant ( F=3.28, P=0.032). The displacement of the absorbable 7 screws group was greater than that of the metal screws group ( t=4.13, P=0.003). The stiffness changes were 570.60±122.62, 512.86±80.77, 497.40±66.50, 456.21±58.19 and 560.39±94.40 N/mm, respectively, with no statistical significance ( F=1.44, P=0.258). The results of finite element analysis showed that under 3 500 N axial pressure load, the maximum compression displacement and stiffness of the plate and screw set were 6.47 mm, 540.96 N/mm, and the Von Mises equivalent stress peaks were 450.31 and 353.15 MPa, respectively. The maximum compression displacement and stiffness of the braided screw group were 5.25 mm, 666.67 N/mm, and the peak Von Mises equivalent stress of the screw was 396.20 MPa. Conclusion:Compared with lateral plate fixation, spatial weaving fixation can provide sufficient biomechanical stability for calcaneal healing and is superior to plate fixation in terms of structural stability, which may help to improve the effectiveness of calcaneal fracture fixation.