Bagheri_Zahra.pdf (15.25 MB)

Biomechanical development and analysis of a new carbon-fiber/flax/epoxy plate for repairing femur fractures

Download (15.25 MB)
thesis
posted on 23.05.2021, 17:35 by Zahra Bagheri
Femur fracture at the tip of a total hip replacement (THR), commonly known as Vancouver B1 fracture, is mainly treated using rigid metallic bone plates, which may result in "stress shielding" leading to bone resorption and implant loosening. To minimize "stress shielding", a novel carbon fiber (CF)/Flax/Epoxy composite plate with a “sandwich structure” has been developed and characterized mechanically, biologically and biomechanically compared to a standard clinical metal plate. The CF/Flax/Epoxy composite material showed no cytotoxicity with no negative influence on the expression level of bone formation genes at all incubation time. The results of mechanical tests revealed a considerably high ultimate strength in tension (399.8 MPa), flexion (510.6 MPa) and fatigue loading (200-220 MPa). The composite plate showed higher elastic modulus in bending tests (57.4 GPa) compared to tension tests (41.7 GPa). The dynamic modulus (E*) was found to stay almost constant versus the number of cycles, which can be related to the contribution of both flax/epoxy and CF/epoxy laminae to the stiffness of the composite. The results of biomechanical assessment of the plate showed that the bone beneath the CF/Flax/Epoxy plate was the only area that had a significantly higher average surface stress (fractured = 2.10 ± 0.66 MPa; healed = 1.89±0.39 MPa) compared to bone beneath the metal plate (fractured = 1.shielding” effect. The CF/Flax/Epoxy plated femur had comparable axial stiffness (fractured = 645 ± 67 N/mm; healed = 1731 ± 109 N/mm) to the metal plated femur (fractured = 658 ± 69 N/mm; healed = 1751 ± 39 N/mm) (p=1.00). These results confirm that the new CF/Flax/Epoxy material could be a potential candidate for bone fracture plate applications as it shows good biocompatibility and considerably higher strength in tension, flexion and fatigue than actual clinical load level experienced by femur during daily normal activities. Moreover, it can simultaneously provide similar mechanical stiffness and lower “stress shielding” (i.e. higher bone stress) compared to commercially-used metal bone plates.18 ± 0.93 MPa; healed = 0.71 ± 0.24 MPa) (p<0.05), cause less “stress

History

Degree

Doctor of Philosophy

Program

Mechanical and Industrial Engineering

Granting Institution

Ryerson University

LAC Thesis Type

Dissertation