Knoop microhardness anisotropy of the ovine radius

The Knoop indenter has been used to characterise fully the Knoop microhardness (H-K) 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 (p much less than 0.001). H-K increased significantly with ash fraction (p much less than 0.001), but decreased with atmospheric vapour pressure (p < 0.05). A significant interaction was found between ash fraction and atmospheric vapour pressure (p < 0.01). H-K significantly varied with indentation position along the diaphysis and around the cortex (both p much less than 0.001), however radial Variation in H-K was not statistically significant. The Variation of ash fraction showed similar trends. These data show that H-K 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. (C) 2000 Elsevier Science Ltd. All rights reserved.