Bone and Joint Institute

Title

Biomechanical Response under Stress-Controlled Tension-Tension Fatigue of a Novel Carbon Fiber/Epoxy Intramedullary Nail for Femur Fractures

Document Type

Article

Publication Date

6-1-2020

Journal

Medical Engineering and Physics

Volume

80

First Page

26

Last Page

32

URL with Digital Object Identifier

10.1016/j.medengphy.2020.04.001

Abstract

© 2020 IPEM Metallic intramedullary nails are the “gold standard” implant for repairing femur shaft fractures. However, their rigidity may eliminate axial micromotion at the fracture (causing delayed healing) and they may carry too much load relative to the femur (causing “stress shielding”). Consequently, some researchers have proposed fiber-reinforced composite nails, but only one evaluated cyclic fatigue performance. Therefore, this study assessed the cyclic fatigue response of a carbon fiber/epoxy nail with a novel ply stacking sequence of [02/-45/452/-45/0/-45/452/-452/452/-45/902] previously developed by the present authors. Nails were cyclically loaded in tension-tension at 5 Hz with a stress ratio of R=0.1 from 30% - 85% of the material's ultimate tensile strength (UTS). Thermographic stress analysis, rather than conventional fatigue testing, was used to obtain high cycle fatigue strength (HCFS), below which the nail can be cyclically loaded indefinitely without damage. Also, the mechanical test machine's built-in load cell and an extensometer were used to create stress-strain curves, from which the change in static EO and dynamic E* moduli were obtained. Results showed that HCFS was 70.3% of UTS (or about 283 MPa), while EO and E* remained at 42 GPa without any dRegradation during testing. The current nail shows potential for clinical use.

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