TY - JOUR
T1 - The effects of aneurysm on the biaxial mechanical behavior of human abdominal aorta
AU - Vande Geest, Jonathan P.
AU - Sacks, Michael S.
AU - Vorp, David A.
N1 - Funding Information:
This work was supported by grants from the NIH (R01-HL-60670) to DAV as well as The Pittsburgh Foundation (♯M2000-0027) to DAV. The authors would like to acknowledge the assistance from the Engineered Tissue Mechanics Laboratory, Larry Nichols MD, Elena Di Martino PhD, Ajay Bohra MS, as well as Michel Makaroun, MD and the rest of the Division of Vascular Surgery at the University of Pittsburgh Medical Center. MSS is an Established Investigator of the AHA.
PY - 2006
Y1 - 2006
N2 - The biomechanical response of normal and pathologic human abdominal aortic tissue to uniaxial loading conditions is insufficient for the characterization of its three-dimensional (3D) mechanical behavior. Planar biaxial mechanical evaluation allows for 3D constitutive modeling of nearly incompressible tissues, as well as the investigation of the nature of mechanical anisotropy. In the current study, 26 abdominal aortic aneurysm (AAA) tissue samples and 8 age-matched (>60 years of age) nonaneurysmal abdominal aortic (AA) tissue samples were obtained and tested using a tension-controlled biaxial testing protocol. Graphical response functions (Sun et al., 2003. J. Biomech. Eng. 125, 372-380) were used as a guide to describe the pseudo-elastic response of AA and AAA. Based on the observed pseudo-elastic response, a four-parameter exponential strain energy function developed by Vito (1990. J. Biomech. Eng. 112, 153-159) was used from which both an individual specimen and group material parameter sets were determined for both AA and AAA. Peak Green strain values in the circumferential ( Eθ θ,max) and longitudinal ( ELL, max) directions under an equibiaxial tension of 120 N/m were also compared. The strain energy function fit all of the individual specimens well with an average R2 of 0.95±0.02 and 0.90±0.02 (mean±SEM) for the AA and AAA groups, respectively. The average Eθ θ, max at 200 N/m equibiaxial tension was found to be significantly smaller for AAAs as compared to AAs (0.07±0.01 versus 0.13±0.03, respectively; p < 0.01). There was also a pronounced increase in the circumferential stiffness for AAA tissue as compared to AA tissue, indicating a larger degree of anisotropy for this tissue as compared to age-matched AA tissue. We also observed that the four-parameter Fung-elastic model was not able to fit the AAA tissue mechanical response using physically realistic material parameter values. It was concluded that aneurysmal degeneration of the abdominal aorta is associated with an increase in mechanical anisotropy, with preferential stiffening in the circumferential direction.
AB - The biomechanical response of normal and pathologic human abdominal aortic tissue to uniaxial loading conditions is insufficient for the characterization of its three-dimensional (3D) mechanical behavior. Planar biaxial mechanical evaluation allows for 3D constitutive modeling of nearly incompressible tissues, as well as the investigation of the nature of mechanical anisotropy. In the current study, 26 abdominal aortic aneurysm (AAA) tissue samples and 8 age-matched (>60 years of age) nonaneurysmal abdominal aortic (AA) tissue samples were obtained and tested using a tension-controlled biaxial testing protocol. Graphical response functions (Sun et al., 2003. J. Biomech. Eng. 125, 372-380) were used as a guide to describe the pseudo-elastic response of AA and AAA. Based on the observed pseudo-elastic response, a four-parameter exponential strain energy function developed by Vito (1990. J. Biomech. Eng. 112, 153-159) was used from which both an individual specimen and group material parameter sets were determined for both AA and AAA. Peak Green strain values in the circumferential ( Eθ θ,max) and longitudinal ( ELL, max) directions under an equibiaxial tension of 120 N/m were also compared. The strain energy function fit all of the individual specimens well with an average R2 of 0.95±0.02 and 0.90±0.02 (mean±SEM) for the AA and AAA groups, respectively. The average Eθ θ, max at 200 N/m equibiaxial tension was found to be significantly smaller for AAAs as compared to AAs (0.07±0.01 versus 0.13±0.03, respectively; p < 0.01). There was also a pronounced increase in the circumferential stiffness for AAA tissue as compared to AA tissue, indicating a larger degree of anisotropy for this tissue as compared to age-matched AA tissue. We also observed that the four-parameter Fung-elastic model was not able to fit the AAA tissue mechanical response using physically realistic material parameter values. It was concluded that aneurysmal degeneration of the abdominal aorta is associated with an increase in mechanical anisotropy, with preferential stiffening in the circumferential direction.
KW - Aneurysm
KW - Anisotropy
KW - Biaxial
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U2 - 10.1016/j.jbiomech.2005.03.003
DO - 10.1016/j.jbiomech.2005.03.003
M3 - Article
C2 - 15885699
AN - SCOPUS:33646041941
SN - 0021-9290
VL - 39
SP - 1324
EP - 1334
JO - Journal of Biomechanics
JF - Journal of Biomechanics
IS - 7
ER -