Evaluation of Stress and Fatigue in Femoral Hip Implants
Date of Award
Peter J. Laz
Femoral hip implant, Mechanical engineering
To expedite the design cycle of a device within new product development, an accurate theoretical assessment of fatigue life is critical. In order for a femoral implant design to be launched to the market, fatigue testing is required by regulatory bodies as evidence of the implant strength to different potting scenarios. The time required to cut forging dies, finish manufacturing processes, complete inspection, and fatigue test takes the majority of a year and is very costly. Therefore, understanding the fatigue properties of the design early is imperative to the success of product launches. Computational analysis, via a finite element analysis (FEA), can be used to assess early phase design iteration and aids in resource efficiency. This study will evaluate the stress and fatigue life prediction process used to design femoral hip implants.
The use of a validated FEA is needed to accurately determine the long-term survivorship success of an orthopaedic implant. This study investigates the ISO-7206-4 (2010) distal fatigue setup using a common implant configuration. Within this study theoretical calculations and material fatigue testing were used to validate the FEA. Fatigue life was also calculated and compared to laboratory fatigue testing.
Theoretical calculations accurately validated the FEA within an error of 1.2%. Strain gauging validation was also accurate and had an error of 3.4%. For fatigue, the stress-life theory, along with the Goodman method, were used to predict the fatigue life cycle of a femoral implant. A comparison between the predicted and experimental load endurance limit were within 16%.
This research gives confidence in the use of theoretical and FE methods to capture the stress and fatigue behavior of femoral implants. The insights gained can improve the design and product development process. The fatigue life and the endurance load can be predicted successfully by using stress-life theory. However, engineers need to understand the variability of test results, driven by specimen dimensional changes, material differences, and test potting setup variability.
Copyright is held by the author. Permanently suppressed.
Satterthwaite, Rodney E., "Evaluation of Stress and Fatigue in Femoral Hip Implants" (2018). Electronic Theses and Dissertations. 2197.
Received from author
Rodney E. Satterthwaite