Abstract:

BACKGROUND: Most of the external fixator is a rigid structure with too much stress shielding on the fracture end which can affect the fracture healing speed and quality of callus, and even lead to fracture nonunion.
OBJECTIVE: To compare the difference of biomechanical strength between normal tibia and the tibia with middle transverse fracture after treated with vertical physiological external pressure fixator.
METHODS: Twelve fresh tibial specimens were obtained and randomly divided into experimental group and control group, tibia with middle transverse fracture caused by wire saw and fixed with vertical physiological external pressure fixator was the experimental group; the tibias in the control group were the normal tibias. The mechanical loading experiment was performed on the axial load, bending load and torsional load, and the displacement of the tibia and the torsion angle were recorded after each level of load, the axial compression stiffness, bending stiffness and torsional stiffness were calculated.
RESULTS AND CONCLUSION: Loading within the physiological range, the left and right strain in the experimental group were slightly larger than those in the control group, but there was no significant difference of overall stiffness after fixation between two groups (P > 0.05); the bending strain in the experimental group was larger than that in the control group, but there was no significant difference of overall stiffness after fixation between two groups (P > 0.05); there was no significant difference of overall torsional stiffness between two groups (P > 0.05); the ultimate bending load in the experimental group was significantly larger than that in the control group (P < 0.05). The vertical physiological external pressure fixator has a sufficient biomechanical strength and good stability, and plays an important role in the biological fixation of fracture.