A novel external fixation for treating tibial fractures: a finite element and biomechanical study

Design a new type of external fixation device that is small in size, high in strength, and capable of achieving the mechanical requirements for fracture healing. Verify the rationality and effectiveness of the device in treating tibial fractures through finite element analysis and biomechanical comparative tests.

Finite element simulation was performed on the new external fixation device to treat fractures, to verify whether the mechanical properties of the device meet the requirements of fracture healing. A fracture gap model was created using Sawbones to simulate midshaft tibial comminuted fractures. The experiment was divided into four groups, testing the mechanical characteristics of the new external fixation (NEF), locking compression plate (LCP), the unilateral external fixation (UEF), and the externalized locking compression plate (E-LCP). The axial compression, torsion, fatigue and ultimate load tests were performed separately. Data were collected and statistical analysis was performed to verify whether there were statistical differences between the four groups.

The finite element analysis of NEF demonstrated that the fracture end was displaced by 0.512 mm under 700 N loading, and the maximum stress value of the device was 189 MPa, which met the mechanical requirements. Axial compression tests showed that LCP (2108.596 N/mm) had the highest stiffness, and NEF (519.489 N/mm) had higher stiffness than both UEF (327.153 N/mm) and E-LCP (316.763 N/mm) (p < 0.05), but no significant difference between UEF and E-LCP (p = 0.313). There was a significant difference in mean torsional stiffness among UEF (1.412 N·m/deg), NEF (1.398 N·m/deg), LCP (1.128 N·m/deg), and E-LCP (0.838 N·m/deg). No structural failures occurred during fatigue testing spanning 108,000 cycles. In ultimate load tests, NEF withstood the highest load, followed sequentially by LCP, UEF, and E-LCP. Significant differences were found between the groups (p < 0.05), with frame bending and secondary bone fractures noted in post-test evaluations.

The NEF for tibial fractures is well-designed to meet the fracture healing requirements. It has certain advantages in comparison with other fixation methods and can be used as a new method for the treatment of tibial fractures.