Biomechanical stability of three-dimensional external fixator applied in early-stage senile osteoporotic fracture

Liu Yao1; Huang Yue2; Liu Yong3; Luo Yuru1; Luo Jing1; Ju Mei1

Abstract：BACKGROUND: Improved three-dimensional external fixator can obtain good treatment effect and is expected to become a new effective fixation method for osteoporotic fracture in the elderly for minimally invasion. However, little is reported on its mechanical stability after fixation. OBJECTIVE: To investigate the biomechanical effect of three-dimensional external fixator for aged patients with osteoporotic fractures and provide evidence for its clinical application. METHODS: From June 2017 to June 2018, 36 aged tibial specimens were selected to prepare the tibia osteoporosis specimen models by 18% EDTA decalcification. After successful modeling, the short oblique osteoporosis fracture model of the middle tibia was established. Then these tibial specimens were randomly divided into three groups (n=12 per group), and fixed with steel plate, intramedullary nail, and three-dimensional external fixator, respectively. Four specimens randomly from each group were measured by compression test, bending test, and torsion test with the BOSE3300 biomechanical testing machine, and the differences in biomechanical stability among groups were determined. RESULTS AND CONCLUSION: (1) Under 250 and 500 N of axial force, the displacement value in the three-dimensional external fixator group was significantly higher than that in the intramedullary nail group, and lower than that in the plate group (both P < 0.05). The displacement value under 750 N of axial force in the three-dimensional external fixator group was significantly lower than that in the other two groups (P < 0.05). (2) In the bending test, the deflection under different bending forces in the three-dimensional external fixator group was smaller than that in the other two groups (P < 0.05). The deflection in the intramedullary nail group was smaller than that in the plate group (P < 0.05). (3) The torsional angle in the three-dimensional external fixator group was smaller than that in the other two groups under different torsion forces (P < 0.05). The torsional angle in the intramedullary nail group was smaller than that in the plate group (P < 0.05). (4) In summary, from the perspective of biomechanics, the three-dimensional external fixator can be widely applied in elderly osteoporotic fractures due to its good biomechanical stability.