Biomedical Engineering Reference
In-Depth Information
Figure 9-2.
Load-displacement curves and histological sections from three different
cartilage regions: control cartilage, hyaline-like repair tissue, and fibrocartilage repair
tissue.
18
Note the variations in load-displacement behavior between the three tissue
regions, with the control cartilage showing the stiffest response and the fibrocartilage
repair tissue showing the most compliant behavior. The hyaline-like repair tissue had
intermediate mechanical behavior. As illustrated in the histological sections, the hyaline-
like repair tissue was histologically more similar to the control cartilage, with intense
staining for proteoglycans and depth dependent distribution of cells. In contrast, the
fibrocartilage repair tissue did not stain strongly for proteoglycans and had evenly
distributed cells as a function of depth. Bars on histological images = 50
μ
m. (Data
adapted from cartilage study by Ebenstein
et al.
18
)
and peak indent loads were much higher than in the previous cartilage
repair study (loads up to 10 mN, displacements over 100
m in some
cases). In addition, multiple load-unload cycles were used to investigate
changes in mechanical properties as a function of penetration depth, and
the effect of fixing cartilage tissue in paraformaldehyde (PFA) on the
mechanical properties was investigated.
19
The authors in this study
reported contact stiffness, reduced modulus, and hardness, relying on tip
calibration in fused silica (
E
= 72 GPa, ν = 0.18) to determine the tip
shape and estimate the contact area between the tip and the sample and
using the compliance method
6
of analysis to calculate reduced modulus.
The reduced modulus values reported were approximately 3 MPa for
the intact cartilage, 0.5 MPa for repair tissue, and 10 MPa for PFA-fixed
μ
Search WWH ::
Custom Search