Recalibration of the Klales et al. (2012) method of sexing the human innominate for Mexican populations.

OBJECTIVES: The aim of this study was to test the accuracy of the Klales et al. (2012) equation for sex estimation in contemporary Mexican population. MATERIALS AND METHODS: Our investigation was carried out on a sample of 203 left innominates of identified adult skeletons from the UNAM-Collection and the Santa María Xigui Cemetery, in Central Mexico. The Klales' original equation produces a sex bias in sex estimation against males (86-92% accuracy versus 100% accuracy in females). Based on these results, the Klales et al. (2012) method was recalibrated for a new cutt-of-point for sex estimation in contemporary Mexican populations. RESULTS AND DISCUSSION: The results show cross-validated classification accuracy rates as high as 100% after recalibrating the original logistic regression equation. Recalibration improved classification accuracy and eliminated sex bias. This new formula will improve sex estimation for Mexican contemporary populations.

Molar size and shape in the estimation of biological ancestry: A comparison of relative cusp location using geometric morphometrics and interlandmark distances.

Human molars exhibit varying shapes when viewed from the occlusal surface. Available methods for quantifying molar occlusal shape have historically been confined to qualitative descriptions. The present study utilized geometric morphometric analyses to capture molar shape as defined through relative cusp locations. Cusp apices of maxillary and mandibular first and second molars were digitized from 190 American Blacks and Whites to estimate biological affinity through the shape of relative cusp locations. The coordinate data were subjected to a Generalized Procrustes Analysis to generate Procrustes coordinates and calculate centroid sizes. Procrustes coordinates were then subjected to a principal component analysis to examine the direction and magnitude of shape change inherent in the sample. Centroid size and major shape component group means were compared with t-tests. Interlandmark distances were then calculated from the raw coordinate information and also subjected to a principal components analysis. Procrustes coordinates and the principal components derived from them with and without centroid size, along with the interlandmark distances and the principal components derived from them, were each subjected to a discriminant function analysis to examine which methods yielded the highest correct classification between population groups. Total correct classifications ranged from 62.7% to 87.9% depending on the variables forward stepwise selected for each analysis. Using a combination of the second maxillary molar and first mandibular molar yielded the most optimistic results and corroborates theoretical models of molar development.

A review of anatomical terminology for the hip bone.

Anatomists have been attempting to standardize anatomical terminology of the human body and in doing so created the Terminologia Anatomica as a standard language of anatomy. Despite developments such as the Terminologia Anatomica, a lack of consistency of anatomical terminology is still seen across and within disciplines. This study explores the variation in terminology for the hip bone through a literature review. In total, ten terms used to describe the hip bone were searched in PubMed, JSTOR, and EBSCO databases: "coxal bone," "hip bone," "innominate bone," "os coxa," "os coxae," "ossa coxa," "ossa coxae," "os innominatum," "os pelvicum," and "pelvic bone." Results found that the terms "hip bone" and "pelvic bone" were the most commonly used terms, with the most frequently used discipline being medicine. However, we argue against the use of these terms in favor of "coxal bone" or "innominate bone." "Hip bone" should be avoided due to its colloquial nature, and "pelvic bone" is not specific enough to the structure of the hip. Latin terms are often incorrectly conjugated (e.g., "os coxae"); therefore, the English equivalent should be used when possible. Regardless, standardization of anatomical terminology should be adopted through consensus by practitioners, researchers, and stakeholders.

A revised method of sexing the human innominate using Phenice's nonmetric traits and statistical methods.

The traits of the pubis described by Phenice (Am J Phys Anthropol 30 (1969) 297-302) have been used extensively by physical anthropologist for sex estimation. This study investigates all three of Phenice's characteristics in an approach similar to Walker's (Am J Phys Anthropol 136 (2008) 39-50) study using observations from the cranium and mandible. The ventral arc, the subpubic contour, and the medial aspect of the ischio-pubic ramus were scored on a five-point ordinal scale from a sample of 310 adult, left innominates of known ancestry and sex from the Hamann-Todd Human Osteological Collection and the W.M. Bass Donated Skeletal Collection. Four observers with varying levels of experience blindly scored each trait using new descriptions and illustrations adapted from those originally created by Phenice. The scores were then analyzed with ordinal logistic regression. Using all three traits for sex classification, the mean correct classification rate was 94.5% cross-validated for experienced observers. Intra- and interobserver error in trait scoring was low for all three traits and agreement levels ranged from moderate to substantial. Tests of the method on an independent validation sample provided a classification accuracy of 86.2%. This revision of the Phenice (Am J Phys Anthropol 30 (1969) 297-302) technique is a reliable and valid method of sex estimation from the human innominate that meets the Daubert criteria for court admissibility.

The importance of processing procedures and threshold values in CT scan segmentation of skeletal elements: An example using the immature os coxa.

As the accessibility and utility of virtual databases of skeletal collections continues to grow, the impact that scan processing procedures has on the accuracy of data obtained from virtual databases remains relatively unknown. This study quantifies the intra- and inter-observer error generated from varying computed tomography (CT) scan processing protocols, including re-segmentation, incrementally varying thresholding value, and data collectors' selection of the threshold value on a set of virtual subadult pelves. Four observers segmented the subadult ossa coxarum from postmortem CT scans of the fully-fleshed bodies of eleven individuals of varying ages. Segmentation protocol was set, with the exception of each observer selecting their own thresholding value for each scan. The resulting smoothed pelvic surfaces were then compared using deviation analyses. Root mean square error (RMSE), average distance deviation, and maximum deviation distances demonstrated that thresholding values of ∼50 HU (Hounsfield units) are easily tolerated, the surfaces generated are robust to error, and threshold value selection does not systematically vary with user experience. The importance of consistent methodology during segmentation protocol is highlighted here, especially with regards to consistency in both selected thresholding value as well as smoothing protocol, as these variables can affect subsequent measurements of the resultant surfaces.

A Validation Study of the Langley et al. (2017) Decision Tree Model for Sex Estimation.

Langley et al. (2017) developed a sex estimation decision tree utilizing two traditional cranial traits (glabella and mastoid) and a new trait: zygomatic extension. This study aimed to test the reliability of their zygomatic extension scoring method and validate their sex estimation method. Ordinal score data were collected from 281 male and female U.S. White and Black individuals. The five traditional cranial traits were collected from physical specimens, while zygomatic extension was scored from 3D cranial models. Intra- and interobserver analyses carried out on a subsample of 30 individuals indicate good agreement between zygomatic scores. The decision tree correctly sexed 71.5% of the sample, but a strong sex bias (94.2% correct for females, 49.3% correct for males) severely limits the utility of this method. The Walker (2008) and Stevenson et al. (2009) methods produced higher accuracy rates (80.8% and 82.6%, respectively), although these methods also produced sex and ancestry biases.

Adapting and Applying the Phenice (1969) Adult Morphological Sex Estimation Technique to Subadults.

This research evaluated whether adult morphological sex estimation methods of the innominate could be adapted and applied to subadults. The subpubic concavity, described by Phenice (1969) and revised by Klales et al. (2012), was modified for use with subadults. Two observers scored radiographic images from the PATRICIA database of 334 individuals of both sexes aged between 1.19 and 20.47 years. Score frequencies shifted from score 2 (straight) to higher frequencies of score 3 (convexity) in males and score 1 (concavity) in females with increasing age. Using ordinal logistic regression, sex classification was highest for the oldest age cohort at 97.2% and then decreased by age cohort. Interobserver error rendered a high level of agreement (0.806) using the intraclass correlation coefficient. Results indicate that the Klales method can be modified and applied to subadults to accurately estimate sex following the onset of puberty with a high degree of reliability and validity.

Improving Nonmetric Sex Classification for Hispanic Individuals.

Current techniques used by forensic anthropologists for the identification of unknown human skeletal remains have largely been created using U.S. Black and White samples. When applied to Hispanics, these techniques perform poorly and can lead to misclassifications; consequently, there is an imperative need for population-specific standards for Hispanics. This research examines the classification accuracies obtained by the original Walker (Am J Phys Anthropol, 136, 2008) and Klales et al. (Am J Phys Anthropol, 149, 2012) methods for nonmetric sex estimation and provides recalibrated regression equations specifically for Hispanics. Ordinal data were collected for five skull and three pelvic traits from a sample of 54 modern Hispanic individuals. Recalibration of the Klales et al. equation improved accuracy (90.3% vs. 94.1%), while recalibration of the Walker method equation decreased accuracy (81.5% vs. 74.1%), but greatly improved sex bias (22.2% vs. -7.4%), thereby making the recalibrated equations more appropriate for use with Hispanics.

The Optimized Summed Scored Attributes Method for the Classification of U.S. Blacks and Whites: A Validation Study.

Recently, Hefner and Ousley (2014) introduced the optimized summed scored attributes (OSSA) method that maximizes between-group differences in U.S. black and white populations by dichotomizing six cranial morphoscopic trait scores. This study tests OSSA using an independent skeletal sample (Hamann-Todd, n = 208) and positively identified forensic cases (Mercyhurst University, n = 28, and New York City Office of Chief Medical Examiner, n = 38). An evaluation of trait frequencies suggests shifting the heuristically selected sectioning point separating U.S. black and white populations from ≤ 3 to ≤ 4. We found a total correct classification of 73.0% (B = 50.9%, W = 89.2%) using the originally suggested sectioning point of ≤3, while the total correct classification increases to 79.2% (B = 80.2%, W = 78.5%) with a modified sectioning point of ≤4. With the increased total correct classification and reduced classification bias between ancestry groups, we suggest the modified sectioning point of ≤4 be used when assessing ancestry in forensic unknowns.

Worldwide population variation in pelvic sexual dimorphism: A validation and recalibration of the Klales et al. method.

Sex estimation is an integral aspect of biological anthropology. Correctly estimating sex is the first step to many subsequent analyses, such as estimating living stature or age-at-death. Klales et al. (2012) [6] provided a revised version of the Phenice (1969) [3] method that expanded the original three traits (ventral arc, subpubic concavity/contour, and medial aspect of the ischio-pubic ramus) into five character states to capture varying degrees of expression within each trait. The Klales et al. (2012) [6] method also provided associated probabilities with each sex classification, which is of particular importance in forensic anthropology. However, the external validity of this method must be tested prior to applying the method to different populations from which the method was developed. A total of 1915 innominates from four diverse geographic populations: (1) U.S. Blacks and Whites; (2) South African Blacks and Whites; (3) Thai; and (4) unidentified Hispanic border crossers were scored in accordance with Klales et al. (2012) [6]. Trait scores for each innominate were entered into the equation provided by Klales et al. (2012) [6] for external validation. Additionally, recalibration equations were calculated with logistic regression for each population and for a pooled global sample. Validation accuracies ranged from 87.5% to 95.6% and recalibration equation accuracies ranged from 89.6% to 98% total correct. Pooling all samples and using Klales' et al. (2012) [6] equations achieved an overall validation accuracy of 93.5%. The global recalibration model achieved 95.9% classification accuracy and can be employed in diverse worldwide populations for accurate sex estimation without the need for population specific equations.

Secular Change in Morphological Pelvic Traits used for Sex Estimation.

This research evaluates secular change in Phenice's (Am J Phys Anthropol, 30, 1969 and 297) three morphological traits of the pubis, as described by Klales et al. (Am J Phys Anthropol, 149, 2012 and 104): medial aspect of the ischio-pubic ramus, subpubic contour, and ventral arc. Ordinal scores were collected for these traits and compared between a sample of innominates from the historical Hamann-Todd Collection (n = 170) and modern Bass Donated Collection (n = 129). Using the Freeman-Halton test, significant differences between temporal sample score frequencies were found for all traits in females and for the subpubic contour and ventral arc in males. Despite these findings, classification accuracy using logistic regression between the temporal periods remained low (68.7%). These results suggest that secular changes in trait expression are occurring; however, sex estimation methods using these traits and created with historical samples are still applicable to modern forensic cases. In fact, the secular changes occurring in these traits contribute to better classification accuracy between sexes in modern populations.

Morphological assessment of ancestry using cranial macromorphoscopics.

Ancestry estimation is essential for biological profile estimation in forensic anthropology. Hefner (2009) and Osteoware (Smithsonian Institution, 2011) presented 16 macromorphoscopic traits that can be scored for standardized data collection and can also be used within a statistical framework to estimate ancestry. The primary purpose of this research was to examine the utility of these traits for assessing ancestry. Tests of observer agreement and the range of variation in trait expression were evaluated. A sample of 208 American whites and blacks from the Hamann-Todd Collection were scored, and several classification methods were utilized in accordance with Hefner (2009). Correct classifications for the pooled sex analyses ranged from 73.3% to 86.6% and from 46.7% to 64.3% when the sexes were analyzed independently. Interobserver agreement was variable and was found to be lower than that presented in Hefner (2009). Trait expression was variable in both groups and was generally consistent with Hefner's findings.