Microindentation on cortical human bone: effects of tissue condition and indentation location on hardness values

The hardness of cortical human bone has been measured on osteons in different conditions. However, no data are reported in the literature regarding the effect of cortical tissue condition and indentation location on the measured hardness values. This study aimed to investigate whether the hardness of the human cortical bone evaluated by micro-indentation is influenced, first, by the tissue condition and, second, by the distance of the indentation from the edge of the Haversian canal. Two femura were collected from a subject without musculoskeletal disease. The Vickers hardness was measured by means of microindentation (applied load, 100 gf) on osteons with a cross-section greater than 200 microm. The tests were performed on wet and embedded tissue at different distances from the Haversian canal edge (30-150 microm). No significant differences were found in hardness values between the two contralateral femura. Embedded tissue was significantly harder (12 per cent) than wet tissue. No significant differences were found in hardness values measured at different distances from the Haversian canal edge except for those closer than 60 microm. Therefore, indentations cannot be performed on osteons small in cross-section, since the distance from the closer pore has to be controlled. They should be performed on wet tissue, to avoid an offset in the measured hardness.