Knoop microhardness anisotropy of the ovine radius

The Knoop indenter has been used to characterise fully the Knoop microhardness (HK) anisotropy of compact bone. 2120 indentations were performed on mature ovine radii and a linear relationship was found between H
K and the angle between the major diagonal of the indenter and the lamella boundaries ([email protected]). HK increased significantly with ash fraction ([email protected]), but decreased with atmospheric vapour pressure (p(0.05). A significant interaction was found between ash fraction and atmospheric vapour pressure (p(0.01). HK significantly varied with indentation position along the diaphysis and around the cortex (both [email protected]), however radial variation in H
K was not statistically significant. The variation of ash fraction showed similar trends. These data show that HK varies similarly to Vickers microhardness, but in addition, can provide clear information on the anisotropy of Haversian bone
without the need for excising many different indentation planes. A large number of indentations are required to obtain low type I and type II errors in the statistical analysis.