Age at death estimation in adults by computer-assisted histomorphometry of decalcified femur cortex

In 1965, Kerley pioneered histomorphometry of bone as an aging method. The technique has been modified by several authors, and some have used computer-assisted image analysis. Undecalcified bone sections used in these methods are obtained with a diamond wafer saw or by grinding the sections manually or automatically with abrasive paper. In the present study, we examined the application of histomorphometry to decalcified bone sections, routinely obtained in every pathology lab, from paraffin blocks cut with a standard microtome. This study was divided into two parts: in the first, we tested different decalcifying methods to determine the most appropriate for femoral bone; in the second part, we used computer-assisted histomorphometry to estimate age at death in 29 samples of femoral bone. We measured intact osteon density (N.On), fragmented osteon density (N.On.Fg) and percentage of lamellar bone surface per unit area (Lm.B.Ar) in the cortex of the femoral midshaft, on four or 20 fields per section. We found that 20% nitric acid solution at room temperature proved to be the best decalcifying method, with a mean decalcification duration of 1 week. Fragmented osteon density was found to be the morphometric feature most closely correlated with age, followed by intact osteon density; Lm.B.Ar. did not increase accuracy. The best accuracy (4.1 +/- 3.5 years) was obtained for individuals under the age of 70 when measurements of 20 fields were used for the analysis. For all individuals, the inaccuracy was 6.1 +/- 6.2 years and 8.1 +/- 8 years, with 20 and four fields respectively. The present study shows that decalcification of bone sections can be used for age estimation at death. This procedure is particularly useful in case of mass disaster as it is easily done in any pathology department.