Scanning electron microscope observations of incinerated human femoral bone: a case study

Fragments of the incinerated remains of a fire victim were studied using scanning electron microscopy and microradiography. These observations were then compared with the heat-induced alterations found in laboratory heat-treated human bone. The incinerated bone fragments exhibited a range of colours, including black, grey and white, concomitant with alterations to the ultrastructure and microstructure of the bone tissue. The colour of the incinerated bone tissue, and the crystal habit and size associated with each region of colour, indicated a gradual decrease in the temperature attained in the bone, as a function of the radial distance from the outer cortical bone surface. A maximum temperature in the range approximately 1000-1200 degrees C had been attained in the outer cortical bone regions that were white in colour. A minimum temperature of 300 degrees C had been attained in the inner cortical bone regions that were black in colour. The period of time over which the fire attained the maximum temperature was inferred to be too short for the bone tissue to have reached an equilibrium with the surrounding environment, as the fire was due to a sudden ignition. However, the minimum temperature recorded was attained for a longer period of time as the organic contents of the Haversian canals and the medullary cavity had been completely combusted. From examinations of the spherical-type crystal size in the grey regions of cortical bone, the habit of the hexagonal-type crystals in the white regions of bone, and the preferred orientation of the mineralised collagen fibrils in the Haversian canals situated in the black regions of cortical bone, it was suggested that the deceased person was a young-to-mature adult, possibly aged 20-40 years.