Anisotropic properties of human tibial cortical bone as measured by nanoindentation

Abstract

The purpose of this study was to investigate the effects of elastic anisotropy on nanoindentation measurements in human tibial cortical bone. Nanoindentation was conducted in 12 different directions in three principal planes for both osteonic and interstitial lamellae. The experimental indentation modulus was found to vary with indentation direction and showed obvious anisotropy (oneway analysis of variance test, P < 0.0001). Because experimental indentation modulus in a specific direction is determined by all of the elastic constants of cortical bone, a complex theoretical model is required to analyze the experimental results. A recently developed analysis of indentation for the properties of anisotropic materials was used to quantitatively predict indentation modulus by using the stiffness matrix of human tibial cortical bone, which was obtained from previous ultrasound studies. After allowing for the effects of specimen preparation (dehydrated specimens in nanoindentation tests vs. moist specimens in ultrasound tests) and the structural properties of bone (different microcomponents with different mechanical properties), there were no statistically significant differences between the corrected experimental indentation modulus (M,:np) values and corresponding predicted indentation modulus (M,J values (two-tailed unpaired t-test, P > 0.5). The variation of M,,, values was found to exhibit the same trends as the corrected McTp data. These results show that the effects of anisotropy on nanoindentation measurements can be quantitatively evaluated.

Mechanical property determination of bone through nano- and micro-indentation testing and finite element simulation

“…An increasing number of measurements of hardness and Young's modulus of bone have been made using different nano-instruments (Turner et al, 1999;Hengsberger et al, 2003;Rho and Pharr, 1999;Hoffler et al, 2005;Ashman and Rho, 1988;Fan et al, 2002;Garner et al, 2000;Fan and Rho, 2003). However, testing conditions have not been uniform.…”

“…For example, Turner et al (1999) indented to a depth of 1000 nm at 750 μN/s, an unloading rate of 375 μN/s, and a hold time of 10 s. Rho et al (2002), Rho and Pharr (1999), and Fan and Rho (2003) performed tests using a maximum load of 8 mN, and a 400 μN/s load rate in studying the microstructural elasticity and heterogeneity in human femoral bone. Additional researchers (Hengsberger et al, 2003;Ashman and Rho, 1988;Fan et al, 2002;Garner et al, 2000) utilized other indentation testing conditions. Micro-indentation tests have also been used to probe the micro-scale properties of bone (Weaver, 1966;Hodgskinson et al, 1989;Carlstrom, 1954;Amprino, 1958;Currey and Brear, 1990;Evans et al, 1990; Blackburn *Corresponding author.…”

Variations of mechanical property of out circumferential lamellae in cortical bone along the radial by nanoindentation

“…As shown in Fig.1, the cortical bone is made up of haversian system, interstitial lamellae and circumferential lamellae. Up to now, the structure [1][2][3][4] and mechanical properties [5][6][7][8][9] of bone have been widely studied in micro/nano scale, and the majority of the researches concentrate on the haversian system and interstitial lamellae. Although the haversian system and interstitial lamellae occupy mostly in bone compared with circumferential lamellae, the inner circumferential lamellae and outer circumferential lamellae also play an important role in practice, especially the outer circumferential lamellae.…”

The Effect of Antiresorptives on Bone Quality

“…The technology for measuring this in humans is under development. One promising method is ''nanoindentation'' where embedded iliac specimens are obtained and an instrument is used to make small indents (*5 lm) while monitoring the force used and the tissue's ability to return to the preindented state [28]. Of course, this requires iliac biopsy and ex vivo measurements on the specimens.…”