Nanoindentation differentiates tissue‐scale functional properties of native articular cartilage

Abstract

Cartilage mechanical properties are typically tested at the macroscale. To demonstrate the ability of nanoindentation to characterize in situ articular cartilage properties at the tissue scale, we investigated the local structure-property relationships of intact articular cartilage of a normal rabbit metacarpophalangeal joint. We calculated the mechanical parameters of stiffness, S, resistance to penetration, R, and volumetric creep strain, dV/V, from nanoindentation of the articular surface at specific regions of interest. We measured morphological parameters of superficial zone thickness, middle zone thickness, total uncalcified thickness, and cell density from corresponding regions with light and polarized light microscopy. Mechanical parameters were compared to morphological parameters. There were significant positive correlations (r = 0.98, p < 0.05) between superficial zone thickness and both S and R. However, we found no significant correlation between dV/V and the zone sizes. There were moderate, negative correlations between cell density and both S and R, suggesting an effect of cell volume on cartilage behavior at the tissue scale. We opine that the superficial zone plays important role in load support, as evidenced by correlations between zone size and intact cartilage mechanical properties.

Cell‐based resurfacing of large cartilage defects: Long‐term evaluation of grafts from autologous transgene‐activated periosteal cells in a porcine model of osteoarthritis

“…Stimulation (38). Nevertheless, it has to be pointed out that the superficial layer is of highest importance for the function of repair tissue, because degeneration of the articular surface, e.g., fibrillation and fissuring, begins in the superficial zone.…”

A fiber reinforced poroelastic model of nanoindentation of porcine costal cartilage: A combined experimental and finite element approach

“…Soft tissues, on the other hand, are hydrated materials with complex constitutive behaviors that violate all the aforementioned analytical assumptions. Limited nanoindentation work has been conducted on soft tissues, including repair cartilage, fibrocartilage, vascular tissue, and the healing fracture callus, with the authors generally reporting elastic properties or functional parameters Ebenstein et al, 2004;Ebenstein and Pruitt, 2004;Li et al, 2006;Franke et al, 2007;Li et al, 2007;Leong and Morgan, 2008). This is due in large part to the fact that analytical solutions to the indentation, whether macroscale, microscale, or nanoscale, are very limited, existing only for select tip geometries, loading profiles, and simple material models including linear elastic, linear viscoelastic models, and in the case of porous, freedraining flatpunch indentation, linear poroelastic materials (Hertz, 1881;Sneddon, 1965;Mak et al, 1987;Sakai, 2002;Mattice et al, 2006;Oyen, 2006).…”

Dynamic impact indentation of hydrated biological tissues and tissue surrogate gels

“…A growing number of reports have quantified mechanical properties of soft tissues via a variety of quasistatic methods including macroscale tension, unconfined compression and microscale indentation experiments [4][5][6][7][8][9][10][11]. Further, dynamic mechanical analysis of soft tissues have been explored via methods such as oscillatory loading [12][13][14][15] and indentation recovery [16].…”