Cortical bone histomorphology of known-age skeletons from the Kirsten collection, Stellenbosch university, South Africa

Age estimation in the combined long bones and ribs by histomorphometry: Past, present, and future

Numerous age estimation methods in unidentified bone have been a long time developing for application in forensic anthropology. The histomorphometric technique is one of the alternative methods that relied upon the evaluation of the cortical bone microstructure over the lifespan as a result of the remodeling process in bone. Remodeling is a sophisticated event occurring from the coupled function of bone formation and resorption cells for maintaining mineral homeostasis and repairment of microdamage in bone tissue. Products derived from remodeling are primary changes in the osteon or haversian system in various regions in the cortical bone, including periosteum, endosteum, and trabecular bone. Throughout life, bone remodeling rate with osteon alteration can be predictable. In the forensic field, histological methods are getting more attention due to the unavailability of macroscopic methods. Histomorphometry approach can be accomplished in fragmentary or incomplete bone remains indicating the limited use of gross morphological methods. In addition, the microscopic methods can aid to increase the more accuracy of analyses and diminish the biased subjective assessment for determining age. Most histomorphometry method utilizes a cross-section of the midshaft of the long bones including the mandible, rib, and clavicle. This review provides the basic knowledge of bone biology and anatomy, several age-estimating methods of histology, and crucial factors for age methods. Studies regarding overall age determination methods from the past until now contribute to obtaining more benefits for developing methods of histomorphometry using human bone in forensic identification.

The Effects of Experimental Whole-Body Burning on Histological Age-at-Death Estimation from Human Cortical Bone and Dental Cementum

Whole-body donations (n = 6) were placed in various experimental fire-death scenarios to understand the histological effects of thermal alteration on bones and teeth. Midshaft samples of the femur, 6th rib, and metatarsal were removed from each donor pre- and post-burning to examine histomorphometric differences and test established age-at-death estimation methods. Dental samples were taken post-burning to test the applicability of dental cementum analysis for age-at-death estimation. Significant differences in osteon area or Haversian canal area between some pre- and post-burn samples were found although no patterns related to temperature or element were observable. The femoral age estimates across pre- and post-burn samples were 91% accurate across all donors. The point age estimates from the ribs compared to known age were significantly different (t(10) = 6.88, p < 0.001) with an average difference of −18.53 years. Dental age estimates of post-burn samples were not significantly different from the known donor age (t(3) = −0.74, p = 0.512) with an average difference of −3.96 years. Overall, the results of this study show that thermally altered remains can be used for histologic age-at-death analysis of cortical bone and dental cementum, within certain burning parameters.

Age estimation for two Mediterranean populations: rib histomorphometry applied to forensic identification and bone remodelling research

Numerous intrinsic and extrinsic factors influence bone remodelling rates and have shown to affect the accuracy of histological aging methods. The present study investigates the rib cortex from two Mediterranean skeletal collections exploring the development of population-specific standards for histomorphometric age-at-death estimation. Eighty-eight standard ribs from two samples, Cretans and Greek-Cypriots, were processed histologically. Thirteen raw and composite histomorphometric parameters were assessed and observer error tested. The correlation between age and the parameters and the differences between sex and population subsamples were explored through group comparisons and analysis of covariance. General linear models assessed through data fit indicators and cross-validation were generated from the total dataset, and by sex and population subsamples. Most of the histological variables showed a statistically significant correlation with age with some differences observed by sex and by sample. From the twelve models generated, the optimal model for the whole sample included osteon population density (OPD), osteon perimeter, and osteon circularity producing an error of 10.71 years. When sex and samples were separated, the best model selected included OPD and osteon perimeter producing an error of 8.07 years for Greek-Cypriots. This research demonstrates the feasibility of quantitative bone histology to estimate age, obtaining errors rates in accordance with macroscopic ageing techniques. Sex and sample population differences need further investigation and inter-population variation in remodelling rates is suggested. Moreover, this study contributes to the creation of population-specific standards for Cretans and Greek-Cypriots.

Rib histomorphometry: A reliability and validation study with a critical review of histological techniques for forensic age estimation

Fragmented human remains present a challenge for forensic experts as they attempt to identify individuals using standard forensic methods. Several histological age estimation techniques have been developed during the last fifty years to aid in this process. However, very few validation studies have been conducted in order to test their accuracy and bias, and thus, validation assessment is required as we employ them while testifying in court. Histological variables are assessed from rib thin sections from two Mediterranean samples; Cretans (N = 41) and Greek-Cypriots (N = 47). Intra and inter-observer errors are assessed through TEM analysis and Intra-class Correlation Coefficient by testing observers with different levels of experience as they collected data on osteon counts and area measurements. The relation between the variables and age is determined using correlation coefficients. Histomorphometric data are applied to four widely used age estimation formulas assessing the performance of the methods for the entire sample. Inaccuracy and bias are calculated with age estimations and known age tested for significance and proportional bias assessed. Overall, histological parameters presented acceptable intra- and inter-observer errors. All variables exhibited statistically significant correlation with age (P < 0.01). For three of the techniques, data showed a systematic underestimation of age with an increase in inaccuracy in older individuals. One of the age estimation formulas produced overestimation of young individuals yet, it more accurately estimated the age of older individuals. This validation study explores inter-population variation in bone remodeling dynamics and presents a critical evaluation on methodological issues that can affect the performance of existing histological techniques.

Using histomorphometry for human and nonhuman distinction: A test of four methods on fresh and archaeological fragmented bones

Positive identification of human remains is the very first step in anthropological analysis, and the task may be particularly difficult in the case of fragmented bones. Histomorphometry methods have been developed to discriminate human from nonhuman bones, based on differences in the size and shape of Haversian systems between the two groups. Those methods all focus on a very specific type of bone, section, and zone. Therefore, the objective of this study was to test the efficiency of four histomorphometric methods on a sample of fragmented bones. The sample is composed of 37 archaeological and fresh specimens, 25 nonhumans (Bos taurus, Equus caballus, Sus scrofa, Capreolus, Canis familiaris, Cervus elaphus, Ovis, and Capra) and 12 humans (Homo sapiens). Eight histomorphometric criteria were collected from all intact osteons visible on each fragment and then inserted into the corresponding discriminate function of each method. The results were compared with the real origin to establish rates of correct classification for each method. The methods of Martiniaková et al. (2006) and Crescimanno and Stout (2012) obtained very low percentages of good classification (32 % and 67 %). Those of Cattaneo et al. (1999) obtained 94 % correct classification, but only after a correction of the units of measurement for Haversian canal area in their formula. The methods of Dominguez and Crowder (2012) obtained an 86 % rate for well-classified specimens. Some of the methods tested here contain errors in the original publication that make them unusable in their current state. Plus, it seems that histomorphometric methods developed from specific areas are more difficult to apply to fragments. A reduced number of intact osteons analyzed may partially affect the reliability of the method by being unrepresentative of the entire microstructure. Therefore, this study demonstrates that one should be cautious with the use of histomorphometric methods to distinguish human and nonhuman fragmented bone until further research can refine these methods to achieve greater reliability.

Histological age-at-death estimation in white South Africans using stereology

Various methods are available for estimating age from skeletal remains, amongst them the use of histomorphometry. It is generally argued that age estimation standards are population specific, but this in itself creates problems as the reference samples used are often not large enough and/or lack substantial representation of all age cohorts. Traditional age methods have been shown to suffer from problems such as age mimicry. This paper aims at establishing histological age-at-death standards for the white South African population by supplementing the available sample (lacking an adequate number of young adults) with another sample of European descent to avoid over-estimation of age in younger individuals caused by age mimicry. Bone microstructures related to the number of osteons and fragments, osteon size and Haversian canal size that change with advancing age were used for the development of regression formulae. A histomorphometric assessment of the anterior cortex of the femur was done using stereology for the estimation of age at death. All sections were analysed using the optical fractionator and nucleator probes. A sample of 94 bone sections (n = 50 male, n = 44 females) of white South African individuals were used. A sample of Danish individuals (n = 14 males, n = 16 females) was combined with the South African sample to create a normal age distribution for the reference sample. Single and multiple regression equations were developed after randomly selecting a hold-out sample (n = 14) for validation. Osteon size (average length, surface area and volume) showed the highest correlation with age, followed by the number of osteons and fragments per grid area. Haversian canal size showed inconsistent changes with advancing age. Using the regression equations, predicted ages were obtained for the 14 individuals. RMSE values ranged between 14 and 17 years, which we deemed acceptable.

Diet and adult age-at-death among mobile foragers: A synthesis of bioarcheological methods

OBJECTIVES

The research explores whether the combined study of cortical bone histology, bone morphology, and dietary stable isotopes can expand insights into past human health and adaptations, particularly dietary sufficiency and life span.

MATERIALS AND METHODS

Midthoracic rib cortices from 54 South African Late Holocene adult skeletons (28 M, 24 F, two sex undetermined) are assessed by transmitted-light microscopy for cross-sectional area measurements, osteon area (On.Ar), osteon population density, and presence/absence of secondary osteon variants. Values for δ¹³ C_{bone collagen} , δ¹⁵ N_{bone collagen} , ¹⁴ C dates, Southwestern and Southern Cape geographic regions, body size measures, estimated ages-at-death from both morphological and histological methods are integrated into analyses, which include Spearman correlations, χ² tests and Kruskal-Wallis ANOVAs.

RESULTS

There is reduced On.Ar variability with higher δ¹⁵ N (r = -.41, p = .005); rib %cortical area and δ¹⁵ N are negatively correlated in the Southern Cape group (r = -.60, p = .03). Osteon variants are more common in older adults; histological ages at death are significantly older than those determined from gross morphology.

DISCUSSION

We found bone tissue relationships with measures of diet composition, but indicators of dietary adequacy remain elusive. Relationships of tissue quality and isotopes suggest that some Southern Cape adults lived long lives. Osteon variants are associated with age-at-death; some association with diet remains possible. Gross morphological methods appear to underestimate adult ages-at-death, at least among small-bodied adults.

Inter-population variation of histomorphometric variables used in the estimation of age-at-death

Population variation of several microscopic structures used in age-at-death estimation was assessed for three different population samples. The aim of the study was to determine if the need exists for population-specific standards when dealing with individuals of African and European origin. A total sample 223 bone sections from the anterior cortex of the femur (n = 99 black South Africans, n = 94 white South Africans and n = 30 Danish individuals) were analysed using a stereological protocol. Variables assessed included the average number of osteons per grid area (OPD), osteon size and Haversian canal size. ANCOVA was employed for assessment of statistically significant differences. The results indicated that OPD differed significantly between the three groups, but that osteon size was similar for all individuals. Haversian canal size showed unpredictable changes with age and high levels of variation, making it unsuitable to use for age estimation as a single factor. As there are conflicting opinions in the literature on whether to use population-specific equations for the estimation of age-at-death or not, this paper provided additional insight into the use of specific variables and its related variation between groups.

The influence of biological affinity and sex on morphometric parameters of the clavicle in a South African sample

OBJECTIVES

The present study aims to investigate the influence of environmental and functional factors associated with biological affinity and musculature on sexual dimorphism of the clavicle, and to develop population-specific methods of sex estimation from the clavicle.

METHODS

The maximum length of the clavicle (MAXL), the sagittal diameter of the clavicle (SAGD), and the vertical diameter of the clavicle (VERD) were measured. The left clavicles of 198 South African coloured individuals (108 males and 90 females) were examined.

RESULTS

Overall, the results of this study indicate that the SAGD of the clavicle is more sexually dimorphic than the VERD in the South African coloured sample. When the black American, white American, and Greek discriminant functions were applied to the South African coloured metric data, females were more accurately classified than males overall. Population-specific discriminant functions were created for the South African coloured sample. The original accuracy showed that females (85.5%) were more accurately classified than males (78.1%). Overall, the multivariate discriminant function demonstrated a higher correct classification of South African coloureds than the univariate discriminant functions. The results also suggest that univariate discriminant function equations are more accurate for sex estimation than univariate sectioning points in the South African coloured sample.

CONCLUSIONS

Overall, the results of the present study indicate that the clavicle is an accurate predictor of sex and its dimensions are population-specific. Therefore, discriminant functions of the clavicle should only be used for sex estimation in forensic anthropology with the populations from which they were derived. © 2018 Wiley Periodicals, Inc.

Sex-specific patterns in cortical and trabecular bone microstructure in the Kirsten Skeletal Collection, South Africa

OBJECTIVES

The purpose of this study was to provide bone histomorphometric reference data for South Africans of the Western Cape who likely dealt with health issues under the apartheid regime.

METHODS

The 206 adult individuals (_n female = 75, _n male = 131, mean = 47.9 ± 15.8 years) from the Kirsten Skeletal Collection, U. Stellenbosch, lived in the Cape Town metropole from the late 1960s to the mid-1990s. To study age-related changes in cortical and trabecular bone microstructure, photomontages of mid-thoracic rib cross-sections were quantitatively examined. Variables include relative cortical area (Rt.Ct.Ar), osteon population density (OPD), osteon area (On.Ar), bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp).

RESULTS

All cortical variables demonstrated significant relationships with age in both sexes, with women showing stronger overall age associations. Peak bone mass was compromised in some men, possibly reflecting poor nutritional quality and/or substance abuse issues throughout adolescence and early adulthood. In women, greater predicted decrements in On.Ar and Rt.Ct.Ar suggest a structural disadvantage with age, consistent with postmenopausal bone loss. Age-related patterns in trabecular bone microarchitecture are variable and difficult to explain. Except for Tb.Th, there are no statistically significant relationships with age in women. Men demonstrate significant negative correlations between BV/TV, Tb.N, and age, and a significant positive correlation between Tb.Sp and age.

CONCLUSIONS

This research highlights sex-specific differences in patterns of age-related bone loss, and provides context for discussion of contemporary South African bone health. While the study sample demonstrates indicators of poor bone quality, osteoporosis research continues to be under-prioritized in South Africa.

Rib biomechanical properties exhibit diagnostic potential for accurate ageing in forensic investigations

Age estimation remains one of the most challenging tasks in forensic practice when establishing a biological profile of unknown skeletonised remains. Morphological methods based on developmental markers of bones can provide accurate age estimates at a young age, but become highly unreliable for ages over 35 when all developmental markers disappear. This study explores the changes in the biomechanical properties of bone tissue and matrix, which continue to change with age even after skeletal maturity, and their potential value for age estimation. As a proof of concept we investigated the relationship of 28 variables at the macroscopic and microscopic level in rib autopsy samples from 24 individuals. Stepwise regression analysis produced a number of equations one of which with seven variables showed an R2 = 0.949; a mean residual error of 2.13 yrs ±0.4 (SD) and a maximum residual error value of 2.88 yrs. For forensic purposes, by using only bench top machines in tests which can be carried out within 36 hrs, a set of just 3 variables produced an equation with an R2 = 0.902 a mean residual error of 3.38 yrs ±2.6 (SD) and a maximum observed residual error 9.26yrs. This method outstrips all existing age-at-death methods based on ribs, thus providing a novel lab based accurate tool in the forensic investigation of human remains. The present application is optimised for fresh (uncompromised by taphonomic conditions) remains, but the potential of the principle and method is vast once the trends of the biomechanical variables are established for other environmental conditions and circumstances.