Changes in Vickers hardness during the decomposition of bone: Possibilities for forensic anthropology

Cetaceans Humerus Radiodensity by CT: A Useful Technique Differentiating between Species, Ecophysiology, and Age

Cetaceans are mammals that underwent a series of evolutionary adaptations to live in the aquatic environment, including morphological modifications of various anatomical structures of the skeleton and their bone mineral density (BMD); there are few studies on the latter. BMD is related to the radiodensity measured through computed tomography (CT) in Hounsfield units (HU). This work aimed to test and validate the usefulness of studying humeral bone radiodensity by CT of two cetacean species (the Atlantic spotted dolphin and the pygmy sperm whale) with different swimming and diving habits. The radiodensity was analysed at certain levels following a new protocol based on a review of previous studies. Humeral radiodensity values were related to four aspects: species, diving behaviour, swimming activity level, and age. We observed that the consistent differences in the radiodensity of the cortical bone of the distal epiphysis between animals of different life-history categories suggest that this bone portion could be particularly useful for future ontogenetic studies. Hence, this technique may be helpful in studying and comparing species with different ecophysiologies, particularly distinguishing between swimming and diving habits.

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

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.

Scratches and grazes: a detailed microscopic analysis of trampling phenomena

Sedimentary abrasion and postdepositional damage to fossil remains are of great interest if considering the possible distortion they could produce in the archaeological and paleontological record. Since their discovery, natural agents such as trampling phenomena have been a topic of great taphonomic interest. Nevertheless, the majority of investigation into these traces has focused almost exclusively on their differentiation from other anthropic agents such as cut marks. In recent years, advances into bone surface modification analysis via geometric morphometrics have proven useful for in-depth characterization of different taphonomic traces; including cut, tooth and percussion marks. Through this, a preliminary study of trampling marks using advanced 3D digital microscopy was able to detect differences between what have since been known as scratch and graze marks. The present study expands from this, developing a more detailed analysis of these traces. Here, we use advanced data science techniques to provide a means of understanding trampling mark variations, contributing to our knowledge of site formation processes. Our results show how scratch and graze marks are a product of progressional decay and changes in cortical hardness, providing a new means of understanding taphonomic processes. LAY DESCRIPTION: The study of microscopic bone surface modifications in archaeology and palaeontology is of great importance, allowing for a detailed reconstruction of the formation of a site and providing a means of interpreting the fossil register. The damage that sedimentary abrasion can produce, however, is likely to distort and influence these studies, thus requiring a detailed understanding of the different traces that can be found on different materials. Here, we use advanced 3D digital microscopy and pattern recognition algorithms to analyse the different marks produced in different sedimentological contexts, also controlling for other variables such as the state of the bone when buried, the type of bone and the time exposed to these types of damages. Through this detailed microscopic analysis of these types of damages, we are able to conclude that morphological variations in trampling marks are product of the state of decay when the bones are buried.

Bone Hardness of Different Anatomical Regions of Human Radius and its Impact on the Pullout Strength of Screws

OBJECTIVE

To investigate the bone hardness of different anatomical regions of the human radius and its impact on the pullout strength of screws.

METHODS

Fresh radius bones were obtained from three donated cadavers. They were divided into three parts: proximal metaphysis, shaft, and distal metaphysis. The proximal metaphysis contains the head, neck, and radial tuberosity. The distal metaphysis includes the palmaris radius and the styloid process. The shaft of the radius was divided into nine segments of equal length. The bone hardness of three radiuses, one from each cadaver, was measured by Vickers microindentation hardness tests, and the screw pullout strength was examined in the other three radiuses using a materials testing machine. The trend between radius hardness and pullout strength was analyzed by using an analysis of variance randomized block design. Pearson correlation analysis was performed to evaluate the linear correlation between the bone hardness and the pullout strength of the human radius.

RESULTS

The mean hardness ranged from 33.30 HV (the head) to 43.82 HV (the diaphysis). The hardest part of the radius was the shaft, with a value of 42.54 ± 5.59 HV. The proximal metaphysis had a hardness value of 34.15 ± 6.48 HV, and the distal metaphysis hardness value was 35.24 ± 5.17 HV. The shaft was 23.5% harder than the proximal metaphysis and 20% harder than the distal metaphysis. The microhardness test demonstrated that the bone hardness value of the diaphysis was significantly higher than those of both the proximal and distal metaphysis of the radius (both P < 0.05). The mean pullout strength values ranged from 552 N (the distal metaphysis) to 2296 N (the diaphysis). The greatest pullout strength of the radius was observed for the shaft, with a pullout strength of 1727.96 ± 111.44 N. The pullout strength of the proximal metaphysis was 726.33 ± 236.39 N, and the pullout strength of the distal metaphysis was 590.67 ± 36.30 N. The pullout strength of the shaft was 138% greater than that of the proximal metaphysis and 190% greater than that of the distal metaphysis. The pullout strength was also higher in the diaphysis than at both ends of the radius (both P < 0.05). A positive correlation was found between bone hardness and pullout strength (R = 0.927, P < 0.001).

CONCLUSIONS

Bone hardness and screw pullout strength are higher in the diaphysis of the radius than at either end. The pullout strength is positively related to bone hardness in the human radius.