Designing Composite External Fixator For Intertrochanteric Fracture Treatment Based On Vietnamese Femur Morphological Parameters

Abstract

Aim — 60 Vietnamese dry femurs were studied to design a carbon composite external fixator for intertrochanteric fracture. Its mechanical strength was evaluated. Material and Methods — The femurs were measured by standard goniometers. The fixator injection mold was created by a CNC machine. The fixator material included carbon fiber (30 – 40% content), BT4, and PA12 plastic. The fixator strength was calculated based on the Finite Element Method. Results — The average femoral neck-shaft angle, anteversion angle, bowing angle, head diameter, and neck width were respectively 124.850 (±7.12), 20.240 (±4.49), 14.900 (±3.27), 4.12cm (±0.30), and 3.05cm (±0.34). A mold and its resulting fixator were designed accordingly. The fixator elasticity modulus, tensile strength, Poisson ratio, and safety factor (K) were 1.32x1010 Pa, 2.21x108 Pa, 0.25, and 1.5, respectively, and max load, stress and transposition were 50-150 N, 1.21-1.38 x 108 Pa, and 0.4-1.27 mm, respectively. The composite fixator was more resistant against pressure across the x-axis but less against the y-axis than the chrome and Inox304 devices. Transposition was the smallest due to its tiny size. Load against z-axis pressure was safe for the patients. Conclusion — This study succeeded to design a prototype carbon composite external fixator with favorable mechanical traits compared with available metal fixators. Further clinical studies are needed to achieve an accurate evaluation of its effectiveness.