Anthropological Age Estimation with Bone Histomorphometry from the Human Clavicle

The purpose of present study was to apply histomorphometry to estimate the age at death using the clavicular osteonal remodeling rate and to develop an age-predicting equation. 46 clavicular samples consisting 28 males and 18 females were obtained from Korean cadavers. Two sequential 1-mm-thick sections, were prepared using a diamond wheel, and a 100 um-thick section was then made by manual grinding with polarizing filter optical microscopy. Three histomorphometric variables, including relative cortical area (RCA), osteon population density (OPD), and mean osteon area (OA), were measured. The mean values are indicated because no significant difference in any variable was noted by a paired t test between the two sequential sections. Analysis of covariance demonstrated that stratification of the statistical results of OPD and OA based on sex was unnecessary, except for RCA. Regression analysis indicated that the highest coefficient value was OPD (R2 = 0.583), which was selected as a significant value with RCA for an age-predicting equation (R2 = 0.628) by the multiple regression analysis stepwise method. In conclusion, a histomorphometric method using the clavicle is reliable for age estimation in physical and forensic anthropological fields. Address for correspondence: Dr. Yi-Suk Kim Department of Anatomy, Ewha Womans University School of Medicine 911-1, Mok-5-dong, Yangcheon-gu, Seoul 158-710, Republic of Korea Fax: 82-2-2650-5716, E-mail: [email protected] INTRODUCTION In forensic anthropology, biological profiles including age, sex, and populations group should be assessed to identify skeletal remains (Trotter and Gleser 1958; Han et al. 2009). To do this, it is crucial to first distinguish human bones from animal bones (Mughal et al. 2013; Formicola 1993). If the skeletal remains are confirmed to be human, procedures for assessing the biological profiles depend on individual skeletal measurements (Balseven-Odabasi et al. 2013; Absolonova et al. 2013; Buikstra and Ubelaker 1994). Among the biological profiles, the age at death provides significant information about the cause of death, irrespective of the elapsed time after death. Therefore, it is vital to determine the age at death of unidentified remains, especially in forensics. Until now, two major methods have been used for age estimation: the conventional method of visual inspection and a histomorphometric method (Kerley 1965). In visual inspection, the examiners study a specific articulation surface with the naked eye and measure the level of aging-related degeneration. However, the outcome is likely to produce a wide range and a large standard error of estimate. In addition, if the articulation surface is severely damaged, visual inspection might be difficult to satisfy the scientific demands. In contrast, the histomorphometric method is a quantitative determination based on the measurable morphology of the osteon (Frost 1987). Microscopic examination of a cross-section of the bone is used to measure the histomorphometric features of the osteon and the measured variables are applied to confirm the regression relationship between bone and age at death. The histomorphometric method reduces subjective judgments and the level of experience needed for age estimation, and this method is available even for small fragmentary. Currently, histomorphometric age estimation is widely performed for a number of population groups and various types of bone elements (Frost 1958; Thompson 1983). The osteonal remodeling process that contributes to bone variation 930 U-YOUNG LEE, GO-UN JUNG, SEUNG-GYU CHOI ET AL. differs among population groups and bone types (Thompson and Guness-Hey 1981; Stout and Lueck 1995). In addition, age-estimating research based on diverse population groups with different materials has been expanded, especially in Korean populations. In 2007 and 2009, the sternal end of the 4th rib and anterior cortex of the femur were tested for use to as materials (Kim et al. 2007; Han et al. 2009). However, previous research has not examined the extent and range for applying additional bone materials that can be assessed in diverse forensic situations. Moreover very few studies have focused on the clavicle, except in Caucasian populations (Stout and Paine 1992) The clavicle has several clear benefits and was selected as the target material in this study. First, the size determines the relatively high ratio of compact bone to spongy bone, so there is little possibility of damage to the clavicle by a fracture. Second, the bone is likely to be found intact rather than in fragments. Third, the clavicle is not a weight-bearing bone, so few factors, including daily lifestyle, can affect the bone remodeling rate over time. Finally, the clavicle does not influence other anthropological tests (Stout and Paine 1992); the bone is not an essential elements for tests that determine utile biological profiles such as statue and sex. The purpose of this study is to provide a new regression equation using various histomorphometric features of the clavicle for age estimation that can be applied in different forensic situations. Additionally, this study also aimed to show a positive application of the equation, which is founded on histomorphometric methods. In future studies that utilize diverse bone materials for age estimation, histomorphometric age estimation methods can be applied in the forensic field.