Age related changes of rib cortical bone matrix and the application to forensic age-at-death estimation

Abstract

Forensic anthropology includes, amongst other applications, the positive identification of unknown human skeletal remains. The first step in this process is an assessment of the biological profile, that is: sex, age, stature and ancestry. In forensic contexts, age estimation is one of the main challenges in the process of identification. Recently established admissibility criteria are driving researchers towards standardisation of methodological procedures. Despite these changes, experience still plays a central role in anthropological examinations. In order to avoid this issue, age estimation procedures (i) must be presented to the scientific community and published in peer reviewed journals, (ii) accurately explained in terms of procedure and (iii) present clear information about the accuracy of the estimation and possible error rates. In order to fulfil all these requirements, a number of methods based on physiological processes which result in biochemical changes in various tissue structures at the molecular level, such as modifications in DNA-methylation and telomere shortening, racemization of proteins and stable isotopes analysis, have been developed. The current work proposes a new systematic approach in age estimation based on tracing physicochemical and mechanical degeneration of the rib cortical bone matrix. This study used autopsy material from 113 rib specimens. A set of 33 parameters were measured by standard bio-mechanical (nanoindentation and microindentation), physical (TGA/DSC, XRD and FTIR) and histomorphometry (porosity-ImageJ) methods. Stepwise regressions were used to create equations that would produce the best ‘estimates of age at death’ vs real age of the cadavers. Five equations were produced; in the best of cases an equation counting 7 parameters had an R2 = 0.863 and mean absolute error of 4.64 years. The present method meets all the admissibility criteria previously described. Furthermore, the method is experience-independent and as such can be performed without previous expert knowledge of forensic anthropology and human anatomy.

Assessing bone maturity: Compositional and mechanical properties of rib cortical bone at different ages

“…In between the two different cycles the powder was filtered using a 106 μm sieve to produce a more uniform size mixture and eliminate larger particles that could affect heat absorption and X-ray diffraction [13]. Full details of these preparation protocols and methods are also contained in two recent studies [14,15] produced to predict the 'age-at death' of individuals for use with recovered skeletal remains in the forensic context.…”

“…Each picture was cropped to select areas completely occupied by bone and converted into 16-bit images (Image > Type > 16-bit). The plugin BoneJ was employed to automatically calculate area fraction by applying a threshold mask (Plugins > BoneJ > Volume Fraction) [14,15].…”

Innovative Vibrational Spectroscopy Research for Forensic Application

“…FTIR spectroscopy was used because it could quantify the components of interest in the bones and could act as a supplemental technique to others, such as histomorphometry, or the study of bone structure and remodeling, to gather the most information. 272 As mentioned, it is common for bones to not be discovered whole. This can be due to several factors, such as evidence disposal, animal interference, and burial.…”

“…Other researchers have also investigated the use of FTIR spectroscopy to estimate the age at the death of bone samples in tandem with other techniques, using the previous study to support other findings. FTIR spectroscopy was used because it could quantify the components of interest in the bones and could act as a supplemental technique to others, such as histomorphometry, or the study of bone structure and remodeling, to gather the most information …”

Analysis of 14C, 13C and Aspartic Acid Racemization in Teeth and Bones to Facilitate Identification of Unknown Human Remains: Outcomes of Practical Casework

“…Anthropological analyses based on morphological changes typically provide age estimation errors for adults of ±10 years [ 1 , 2 , 3 , 4 , 5 , 6 ], which imply intervals that are too wide to offer meaningful help in practical casework. A number of chemical and molecular analytical methods have therefore been developed to improve the accuracy of predicting the age of deceased subjects [ 1 , 2 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. One of the most useful chemical methods to assess age is aspartic acid racemization (AAR) analysis, which is based on the gradual increase in the D-form of aspartic acid in tissues with age.…”