Mechanical strength of aneurysmatic and dissected human thoracic aortas at different shear loading modes

Gerhard Sommer, Selda Sherifova, Peter J. Oberwalder, Otto E. Dapunt, Patricia A. Ursomanno, Abe DeAnda, Boyce E. Griffith, Gerhard A. Holzapfel

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Rupture of aneurysms and acute dissection of the thoracic aorta are life-threatening events which affect tens of thousands of people per year. The underlying mechanisms remain unclear and the aortic wall is known to lose its structural integrity, which in turn affects its mechanical response to the loading conditions. Hence, research on such aortic diseases is an important area in biomechanics. The present study investigates the mechanical properties of aneurysmatic and dissected human thoracic aortas via triaxial shear and uniaxial tensile testing with a focus on the former. In particular, ultimate stress values from triaxial shear tests in different orientations regarding the aorta׳s orthotropic microstructure, and from uniaxial tensile tests in radial, circumferential and longitudinal directions were determined. In total, 16 human thoracic aortas were investigated from which it is evident that the aortic media has much stronger resistance to rupture under ‘out-of-plane’ than under ‘in-plane’ shear loadings. Under different shear loadings the aortic tissues revealed anisotropic failure properties with higher ultimate shear stresses and amounts of shear in the longitudinal than in the circumferential direction. Furthermore, the aortic media decreased its tensile strength as follows: circumferential direction <longitudinaldirection> radial direction. Anisotropic and nonlinear tissue properties are apparent from the experimental data. The results clearly showed interspecimen differences influenced by the anamnesis of the donors such as aortic diseases or connective tissue disorders, e.g., dissected specimens exhibited on average a markedly lower mechanical strength than aneurysmatic specimens. The rupture data based on the combination of triaxial shear and uniaxial extension testing are unique and build a good basis for developing a 3D failure criterion of diseased human thoracic aortic media. This is a step forward to more realistic modeling of mechanically induced tissue failure i.e. rupture of aneurysms or progression of aortic dissections.

Original languageEnglish (US)
Pages (from-to)2374-2382
Number of pages9
JournalJournal of Biomechanics
Volume49
Issue number12
DOIs
StatePublished - Aug 16 2016

Keywords

  • Aortic aneurysm
  • Aortic dissection
  • Connective tissue disorder
  • Thoracic aorta
  • Ultimate stress

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Biomedical Engineering
  • Rehabilitation

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    Sommer, G., Sherifova, S., Oberwalder, P. J., Dapunt, O. E., Ursomanno, P. A., DeAnda, A., Griffith, B. E., & Holzapfel, G. A. (2016). Mechanical strength of aneurysmatic and dissected human thoracic aortas at different shear loading modes. Journal of Biomechanics, 49(12), 2374-2382. https://doi.org/10.1016/j.jbiomech.2016.02.042