Biomedical Engineering Reference
In-Depth Information
Fig. 11.1 Photography of a
representative specimen for a
delamination test showing the
through-thickness incision for
creating the initial dissection
plane. Taken from Pasta et al.
( 2011 )
A constant crosshead speed of 1 mm/min was used to pull apart the two free flaps
of the tissue specimen whereas the applied load and resulting displacement were
recorded continuously using the Instron-packaged software (Bluehill v.2). The two
delaminated halves resulting from each delamination test (i.e., the one between the
intimal surface and the delaminated plane (INT-DEL), and the one between the ad-
ventitial surface and the delaminated plane (ADV-DEL)) were stretched to failure
in the uniaxial tensile testing system to evaluate the tensile strength of each. None
of specimens failed for technical reason during biomechanical testing.
11.2.3 Data Analysis
'Delamination curves' were generated from each test, and consisted of a plot of the
'peel tension' ( T peel , defined as the applied force normalized by the width of the
specimen) as function of the elongation (displacement). The mean value of T peel
after the initial peak was taken as the delamination strength S d of the specimen. The
S d values calculated for multiple LONG and CIRC specimens tested for a given
patient were taken as the overall S d , LONG and S d , CIRC for that specific patient. For
the tensile tests, we utilized the approach published previously by our laboratory
(Raghavan et al., 1996 ). In short, the Cauchy stress T was calculated as the applied
force normalized by the deformed cross-sectional area, and stretch was calculated
as the deformed length normalized by the original length of each specimen. The
tensile strength S T was taken as the peak value of stress attained prior to complete
specimen failure.
One-way ANOVA, followed by Holm-Sidak post-hoc test for all pair-wise
comparisons, was performed using SigmaPlot software (SYSTAT Software Inc.,
Chicago, Ill) to determine significance among groups. Level of statistical signifi-
cance was set as p
=
0 . 05. Data are shown as mean
±
SEM.
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