Desiré Brits

The effects of freezing, boiling and degreasing on the microstructure of bone

The histology of bone has been a useful tool in research. It is commonly used to estimate the age of an individual at death, to assess if the bone is of human or non-human origin and in trauma analysis. Factors that affect the histology of bone include age, sex, population affinity and burning to name but a few. Other factors expected to affect bone histology are freezing, boiling and degreasing but very little information is available for freezing and the effect thereof, and it is unknown if boiling and degreasing affects bone histology. The aim of this study was to assess the effects of freezing, freezing and boiling, and freezing, boiling and degreasing on the histological structure of compact bone. Five cadaver tibiae were frozen at -20°C for 21 days followed by segments being boiled in water for three days and degreased in trichloroethylene at 82°C for three days. Anterior midshaft sections were prepared as ground sections and for Scanning Electron Microscopy (SEM). Quantitatively, there were no significant differences between freezing, boiling and degreasing; however, qualitative differences were observed using SEM. After being frozen the bone displayed cracks and after boiling the bones displayed erosion pits on the surface. It is suggested that further research, using different durations and temperatures for boiling and freezing be undertaken on bone samples representing different ages and various skeletal elements.

Estimating stature in South African populations using various measures of the sacrum

The accurate estimation of stature can meaningfully contribute to the positive identification of skeletal remains of unknown individuals. Regression equations are most commonly used to estimate stature and have been derived from numerous bones. Little is however known about stature estimation from the sacrum and therefore the aim of the current study was to evaluate whether it is possible to estimate stature from various sacral measurements in South African populations. A total of 210 sacra representing 50 black males, 51 white males, 58 black females and 51 white females were measured. These measurements included anterior sacral height, anterior sacral width, maximum transverse diameter of the base, anterior sacral height of individual sacral segments (S1, S2, S3, S4, S5) as well as combinations of anterior sacral heights of segments, (i.e. S1+S2). The correlation of these measures to stature was calculated using Pearsons correlation coefficient, followed by the calculation of linear least square and multiple regression equations for the estimation of stature. Statistical analyses indicated differences between sexes and population groups with multiple regressions being slightly more accurate than regression equations derived from single variables. Standard error of estimate values for the present study fall within the ranges stated by previous researchers, with smaller stature estimation intervals reported for black South Africans and females. This study suggests that regression equations derived from the sacrum of South Africans can be used to calculate reasonable estimates of stature, in the absence of bones that yield more accurate results.

Quantification of the subpubic angle in South Africans

Due to the high crime rate in South Africa, forensic anthropologists are increasingly approached to aid in the identification of skeletonized remains, with sex and population affinity assignment being some of the most critical tasks they face. For over a century, the pelvis has been known to be one of the most sexually dimorphic bones of the human body and the subpubic angle is one of the most accurate, albeit scarcely quantified, features thereof. Hence, the aim of this study was to quantify the size of the subpubic angle and compare it between male and female South Africans of African (black) and European (white) descent. One hundred and forty five (145) pelves were selected, consisting of 68 white (43 male and 25 female) and 77 black South Africans (44 male and 33 female), from the Raymond A. Dart Collection of Human Skeletons housed at the University of the Witwatersrand, Johannesburg, South Africa. Each of the pelves were articulated and placed into a custom built stand for photographing. Measures of the subpubic angle from these digital images were subjected to numerous statistical analyses. Results indicated that significant differences exist between the sexes, as well as between the two population groups. For black individuals it was found that males generally possessed a subpubic angle of 74.9° or less, with larger values being indicative of the female sex. For white individuals, subpubic angles of 81.4° and less indicated males whilst larger values indicated females, with an average accuracy of 86% for both population groups. These results illustrate the advantages of using the subpubic angle to assist in the estimation of sex and population affinity and also reinforce the need for population specific parameters to be applied.

Assessing the effects of tooth loss in adult crania using geometric morphometrics

With high numbers of unidentified skeletonised remains recovered annually in South Africa and an increased number of edentate individuals being reported, the question arises as to whether tooth loss would result in craniofacial changes which might alter the accuracy of osteological analyses. Forty-five fixed landmarks together with sliding semilandmarks were collected from 229 white South African crania and were used to capture curve data pertaining to the basicranium, alveoli, zygomatic arches, nasal aperture and orbits. Geometric morphometric methods were employed to assess the effects of tooth loss on these structures. Although a number of effects were seen when the skull was analysed in its entirety, only the alveoli proved to be significantly affected when regions were analysed individually. Both upper facial height and palate shape were affected by tooth loss, which may influence various osteometric measurements and qualitative traits that are used during the assessment of ancestry and sex.

Stature estimation from the femur and tibia in Black South African sub-adults

Stature estimation can play a role in the positive identification of unknown individuals and as such it is routinely assessed during the examination of adult remains. Unfortunately, this is not a standard procedure when dealing with sub-adult remains due to the general lack of standard procedures for the estimation of sub-adult stature. The aim of this study was therefore to derive regression equations for the estimation of stature in black South African sub-adults. Fifty nine black South African sub-adult males and females, aged 10-17 years, voluntarily participated in the study by undergoing a full body Magnetic Resonance Imaging (MRI) scan. Living stature was measured with a stadiometer and the maximum and diaphyseal lengths of the femur and tibia were measured from the MRI scans using the image processing software OsiriX. Pearsons correlation coefficients and linear least square regression analyses were used to assess the correlations between living stature and the measurements and to generate sub-adult stature estimation equations for males, females and a combined sex sample. Measurements of the femur, tibia and the combined measures thereof showed strong statistically significant positive correlations with living stature, while the obtained regression equations were characterized by low standard error of estimates. The strong correlations and low standard error of estimates are comparable to stature estimation models reported for Black South African adults and therefore these variables can be considered good estimators of sub-adult stature which will contribute valuable information to the biological profile of unidentified sub-adult skeletal remains.

The accuracy of the anatomical method for stature estimation in Black South African females

The anatomical method is considered the most accurate stature estimation method, but investigation has shown that it continuously underestimates stature. This underestimation is believed to be related to the use of universal soft tissue correction factors. Therefore, the aim of this study was to assess the accuracy of the soft tissue correction factors in a living population of Black South African females and to subsequently calculate a new soft tissue correction factor, specific for stature estimation in this population group. Thirty Black South African adult females voluntarily participated in this study and underwent a full body Magnetic Resonance Imaging (MRI) scan. Living stature was measured with a stadiometer and total skeletal height (TSH) was calculated from the MRI measurements. Stature was estimated from the TSH of each participant using Fullys (1956) [17], Raxter et al.s (2006) [38] and Bidmos and Mangers (2012) [5] methods. Results indicated strong, statistically significant positive correlations between living and estimated statures, however, paired t-tests revealed that living stature was significantly underestimated using Fullys and Raxter et al.s methods, while the method by Bidmos and Manger significantly overestimated stature. A lack of statistically significant correlations between soft tissue correction factors and the total skeletal height was found. Likewise, an absence of statistically significant correlations between age and the estimation error, with and without age adjustments were also observed. A new soft tissue correction factor, specific for stature estimation in Black South African females was calculated. The newly proposed regression equation presented improved stature estimation accuracies for this population group.

Age estimation accuracies from black South African os coxae

The accurate estimation of age is considered important from an ethical, legal and archaeological perspective. Among the numerous methods based on macroscopic skeletal studies for age estimation, the Brooks and Suchey (1990) method for aging from the pubic symphysis and the Buckberry and Chamberlain (2002) method for aging from the auricular surface are considered more reliable. However, both these methods have been derived from American populations. Therefore, the following study aimed to assess the accuracy of the estimation of age-at-death from morphological age related changes seen on the pubic symphysis and the auricular surface in a black South African population. A total of 197 individuals of known age of both sexes using both left and right ossa coxae were investigated. Age was estimated using descriptions stipulated by Brooks and Suchey (1990) and Buckberry and Chamberlain (2002). Correlation coefficients, inaccuracies and bias were calculated for both skeletal elements for both sexes and sides. Inaccuracies and bias were lower in the pubic symphysis than in the auricular surface thus making the pubic symphysis a more reliable age estimator. Similarly, males indicated lower inaccuracies and bias than did females. Overall, the pubic symphysis outperformed the auricular surface, even though the method described by Buckberry and Chamberlain (2002) is considered more reliable. It is advised that these two methods be improved to produce better accuracies, particularly when applying the methods to a black South African population.

Three-dimensionally derived interlandmark distances for sex estimation in intact and fragmentary crania

The skull is the element most frequently presented to forensic anthropologists for analysis yet weathering, corpse maiming, and scavenger activity often result in damage and fragmentation. This fragmentation results in a reduction in the number of traditional calliper derived measurements that can be obtained and subjected to discriminant based analyses for sex estimation. In this investigation, we employed three-dimensional geometric morphometric methods to derive novel interlandmark distance measures across six regions of the cranium including the basicranium, basipalate, zygoma, orbits and the cranium globally to create functions to discriminate sex with high efficacy, even in the event of fragmentation. Forty-five homologous landmarks were digitised across each of 227 (114 males and 113 females) South African crania of European descent (white) sampled from the Raymond A Dart Collection of Human Skeletons, housed in the School of Anatomical Sciences, University of the Witwatersrand, South Africa. A total of 990 interlandmark distances (ILDs) were mathematically derived using Pythagorean geometry. These ILDs were then filtered by region and subjected to both direct and stepwise discriminant function analyses. Discriminant equations where derived for each region and achieved the following average cross-validated sex estimation accuracies: basicranium-74%; basipalate-80.2%; zygomatic-82.4; orbits-71.8%; nasomaxilla-83.7%; global cranium-88.2%. A large number of the ILDs used to derive the discriminant functions are novel, demonstrating the efficacy of geometric morphometric methods and illustrating the need to reassess old methods of data collection using modern methods to determine whether they best capture biological differences. The results of this study provide an invaluable contribution to forensic anthropology in South Africa as it provides an accurate, practical means of assessing sex using fragmentary material that may otherwise have been disregarded. These will undeniable aid in accurate sex estimation and ultimately, victim identification.

Assessing the use of the anatomical method for the estimation of sub-adult stature in Black South Africans

Stature estimation is rarely attempted in sub-adults due to the general lack of available standards as a result of the dearth of sufficiently large sub-adult skeletal collections with known demographic information. To overcome this problem sub-adult research mainly relies on modern imaging modalities. In the current study Magnetic Resonance Imaging (MRI) scans were used to assess the use of the anatomical method for stature estimation in sub-adults. A total of 53 Black South African sub-adult males (n=24) and females (n=29) aged between 10 and 17 years participated in the study by voluntarily completing a full-body MRI scan. A stadiometer was used to measure living stature prior to all MRI scans. Skeletal elements that contribute directly to stature were measured from the MRI scans using OsiriX and summed to compute the total skeletal height. Total skeletal height was calculated using the diaphyseal, maximum and physiological long bone lengths and correlated to living stature using Pearsons correlations. Subsequently least squares regression equations were generated for the estimation of sub-adult stature. Results indicated strong, statistically significant positive correlations between living stature and total skeletal heights in sub-adult males, females and a combined sex sample. The regression equations were characterized by small standard error of estimates which are comparable to that reported for Black South African adults. Based on these results the anatomical method can be used to accurately describe living stature in Black South African sub-adults. This method is therefore encouraged as it will add valuable information when dealing with unknown sub-adult skeletal remains.