A geometric-morphometric study of the cretan humerus for sex identification

Sex estimation research trends in forensic anthropology between 2000 and 2022 in five prominent journals

In forensic anthropology, osteological sex estimation methods are continuously reevaluated and updated to improve classification accuracies. Therefore, to gain a comprehensive understanding of recent trends in sex estimation research in forensic anthropology, a content analysis of articles published between 2000 and 2022 in Forensic Science International, the Journal of Forensic Sciences, the International Journal of Legal Medicine, the American Journal of Biological Anthropology, and Forensic Anthropology, was performed. The main goals of this content analysis were to (1) examine trends in metric versus morphological research, (2) examine which areas of the skeleton have been explored, (3) examine which skeletal collections and population affinities have been most frequently utilized, and (4) determine which statistical methods were commonly implemented. A total of 440 articles were coded utilizing MAXQDA and the resulting codes were exported for analysis. Statistical analyses were conducted utilizing the Cochran-Armitage and Jonckheere-Terpstra tests for trends, as well as Fisher-Freeman-Halton tests. The results demonstrate that sex estimation research published in these journals has prioritized metric over morphological methods. Further, the most utilized skeletal regions continue to be the skull and pelvis, while the most popular classification statistics continue to be discriminant function analysis and logistic regression. This study also demonstrates that a substantial portion of research has been conducted utilizing U.S. and Europe-based collections and limited populations. Based on these results, future sex estimation research must continue exploring the use of long bones and other postcranial elements, testing newer methods of analysis, as well as developing population-inclusive methods.

TestDimorph: An R package for analysis of interpopulation sexual dimorphism differences using summary statistics

OBJECTIVE

The degree of sexual dimorphism in certain traits between males and females differ from one sample to another. Although trait differences by sex are often reported in bioanthropological research, few studies test for statistical significance or make raw data available. TestDimorph is the first R package dedicated to testing and comparing the degree of sexual dimorphism among different samples by leveraging summary statistics.

MATERIALS AND METHODS

We provide two approaches of analysis of inter-sample differences in degree of sexual dimorphism: univariate and multivariate for two or more samples. The methods follow upon publications primarily from the AJBA. Within-sex size variability between samples is compared using one-way ANOVA followed by control for multiple pairwise comparisons. In addition, we compute the overlapping area between the density functions of two normal distributions from the mixture intersection index or the non-overlapping area using the dissimilarity index as well as Hedges' g with inferential support using the 95% confidence interval. Finally, we use a multivariate analysis of differences in patterning of sexual dimorphism between samples.

RESULTS

We demonstrate various results from applying TestDimorph functions to data supplied with the package.

DISCUSSION

The package has many features including functionality for working with summary statistics, simulating data from summary statistics, and the extraction of summary statistics from raw data, so that the entire analysis can be performed through the package.

Glenohumeral joint reconstruction using statistical shape modeling

Evaluation of the bony anatomy of the glenohumeral joint is frequently required for surgical planning and subject-specific computational modeling and simulation. The three-dimensional geometry of bones is traditionally obtained by segmenting medical image datasets, but this can be time-consuming and may not be practical in the clinical setting. The aims of this study were twofold. Firstly, to develop and validate a statistical shape modeling approach to rapidly reconstruct the complete scapular and humeral geometries using discrete morphometric measurements that can be quickly and easily measured directly from CT, and secondly, to assess the effectiveness of statistical shape modeling in reconstruction of the entire humerus using just the landmarks in the immediate vicinity of the glenohumeral joint. The most representative shape prediction models presented in this study achieved complete scapular and humeral geometry prediction from seven or fewer morphometric measurements and yielded a mean surface root mean square (RMS) error under 2 mm. Reconstruction of the entire humerus was achieved using information of only proximal humerus bony landmarks and yielding mean surface RMS errors under 3 mm. The proposed statistical shape modeling facilitates rapid generation of 3D anatomical models of the shoulder, which may be useful in rapid development of personalized musculoskeletal models.

Sex estimation of the humerus: A geometric morphometric analysis in an adult sample

Sex estimation is the keystone for positive identification when an unidentified human body is recovered in forensic contexts. However, in complex death scenes such as mass disasters, the remains are often fleshed, mutilated, burned, and/or commingled. In situations such as these where it is not possible to analyze pelvis and/or cranium data, traditional metric and qualitative morphological methods on postcranial bones can yield unsatisfactory results. In such cases, geometric morphometric techniques offer an alternative to the analysis of both shape and size components of morphological variation that can be of great utility for sex estimation in forensic investigations. The study population consisted of 72 well-preserved adult humeri (40 males and 32 females; mean age of 62 years) that were photographed in standardized positions with landmarks located in four two-dimensional views of the humerus (anterior surface of the proximal epiphysis, and anterior, posterior and inferior surface of distal epiphysis). Principal components analysis, canonical variates analysis and discriminant analysis were applied. The data indicated that males and females were classified with low levels of accuracy (54.95-77.92% for males; 56.87-71.78% for females) based on shape variables. However, when the shape variable was combined with the centroid size, the levels of accuracy increased (81.86-94.92% for males; 84.08-94.88% for females). To obtain larger differences between males and females, it is necessary the combination of centroid size with shape variables; the shape of the humerus is insufficient to discriminate sex with accuracy.

Exploring sexual dimorphism of the modern human talus through geometric morphometric methods

Sex determination is a pivotal step in forensic and bioarchaeological fields. Generally, scholars focus on metric or qualitative morphological features, but in the last few years several contributions have applied geometric-morphometric (GM) techniques to overcome limitations of traditional approaches. In this study, we explore sexual dimorphism in modern human tali from three early 20th century populations (Sassari and Bologna, Italy; New York, USA) at intra- and interspecific population levels using geometric morphometric (GM) methods. Statistical analyses were performed using shape, form, and size variables. Our results do not show significant differences in shape between males and females, either considering the pooled sample or the individual populations. Differences in talar morphology due to sexual dimorphism are mainly related to allometry, i.e. size-related changes of morphological traits. Discriminant function analysis using form space Principal Components and centroid size correctly classify between 87.7% and 97.2% of the individuals. The result is similar using the pooled sample or the individual population, except for a diminished outcome for the New York group (from 73.9% to 78.2%). Finally, a talus from the Bologna sample (not included in the previous analysis) with known sex was selected to run a virtual resection, followed by two digital reconstructions based on the mean shape of both the pooled sample and the Bologna sample, respectively. The reconstructed talus was correctly classified with a Ppost between 99.9% and 100%, demonstrating that GM is a valuable tool to cope with fragmentary tali, which is a common occurrence in forensic and bioarchaeological contexts.

Outline Shape Analysis on the Trochlear Constriction and Olecranon Fossa of the Humerus: Insights for Sex Estimation and a New Computational Tool

Sex estimation through visual analysis of the distal humerus can contribute to establishing the biological profile of an unidentified skeletal individual. Using statistical shape modeling, the trochlear constriction open curves and olecranon fossa closed outlines of 151 humeri were digitized and analyzed. The shape configurations exhibited strikingly different degrees of sexual dimorphism when evaluated using linear discriminant analysis with leave-one-out cross-validation. The trochlear constriction performed poorly, correctly classifying 63.6% of the individuals. However, the olecranon fossa showed high sexual dimorphism, presenting a 94.0% accuracy. A simpler model using only two principal components was also generated. While the accuracy is slightly inferior (88.1%), it has the advantage of being constrained to bidimensional components that were translated into morphoscopic variables within a simulator interface. This allowed us to implement the method through a web application that does not require users to be trained in landmark digitization or have knowledge of geometric morphometrics.

Three-dimensional analysis of sexual dimorphism in ribcage kinematics of modern humans

OBJECTIVES

Sexual dimorphism is an important biological factor underlying morphological variation in the human skeleton. Previous research found sex-related differences in the static ribcage, with males having more horizontally oriented ribs and a wider lower ribcage than females. Furthermore, a recent study found sex-related differences in the kinematics of the human lungs, with cranio-caudal movements of the caudal part of the lungs accounting for most of the differences between sexes. However, these movements cannot be quantified in the skeletal ribcage, so we do not know if the differences observed in the lungs are also reflected in sex differences in the motion of the skeletal thorax.

MATERIALS AND METHODS

To address this issue, we quantified the morphological variation of 42 contemporary human ribcages (sex-balanced) in both maximal inspiration and expiration using 526 landmarks and semilandmarks. Thoracic centroid size differences between sexes were assessed using a t test, and shape differences were assessed using Procrustes shape coordinates, through mean comparisons and dummy regressions of shape on kinematic status. A principal components analysis was used to explore the full range of morphological variation.

RESULTS

Our results show significant size differences between males and females both in inspiration and expiration (p < .01) as well as significant shape differences, with males deforming more than females during inspiration, especially in the mediolateral dimension of the lower ribcage. Finally, dummy regressions of shape on kinematic status showed a small but statistically significant difference in vectors of breathing kinematics between males and females (14.78°; p < .01).

DISCUSSION

We support that sex-related differences in skeletal ribcage kinematics are discernible, even when soft tissues are not analyzed. We hypothesize that this differential breathing pattern is primarily a result of more pronounced diaphragmatic breathing in males, which might relate to differences in body composition, metabolism, and ultimately greater oxygen demand in males compared to females. Future research should further explore the links between ribcage morphological variation and basal metabolic rate.

Distinct Proximal Humeral Geometry in Chinese Population and Clinical Relevance

BACKGROUND

Replicating humeral anatomy during shoulder arthroplasty is important for good patient outcomes. The proximal humeral geometry of the Chinese population has been rarely reported. We analyzed the geometry of the proximal part of the humerus in Chinese subjects and compared it with that of Western populations and the dimensions of available prostheses.

METHODS

Eighty healthy Chinese subjects underwent computed tomography (CT)-arthrography. Three-dimensional (3D) digital humeral and glenoid models were reconstructed, and geometric parameters were measured. Humeral measurements included the radius of curvature, articular surface diameter and thickness, anterior-posterior/superior-inferior (AP/SI) articular surface diameter ratio, articular surface thickness/radius of curvature ratio, surface arc, inclination angle, retroversion angle, and medial and posterior offsets. Glenoid measurements included SI length, AP length, SI radius, and AP radius.

RESULTS

The average radius of curvature (and standard deviation) of the humeral head was 22.1 ± 1.9 mm, the articular surface diameter averaged 42.9 ± 3.6 mm, and the articular surface thickness averaged 16.9 ± 1.5 mm. There was strong linear correlation between the articular surface diameter and thickness (r = 0.696, p = 0.001), with a linear regression relationship of thickness = 0.357 × diameter + 1.615. The AP/SI articular surface diameter ratio averaged 0.93 ± 0.03; the articular surface thickness/radius of curvature ratio, 0.77 ± 0.05; the surface arc, 153° ± 5.6°; the inclination angle, 133° ± 3.1°; and the retroversion angle, 22.6° ± 10.2°. The medial and posterior offsets averaged 6.3 ± 0.9 mm and 0.4 ± 0.78 mm, respectively; the SI and AP lengths, 30.15 ± 3.70 mm and 20.35 ± 2.56 mm; and the SI and AP radii, 23.49 ± 2.48 mm and 25.54 ± 3.07 mm. Compared with the Western population, the Chinese cohort had a smaller radius of curvature (p < 0.001), smaller articular surface diameter (p = 0.009), larger articular surface thickness/radius of curvature ratio (p < 0.001), larger surface arc (p < 0.001), smaller inclination angle (p < 0.001), and smaller posterior offset (p < 0.001). Unlike the Western population, the Chinese population had higher glenohumeral conformity in the coronal plane than in the axial plane. Many manufacturers' shoulder prostheses do not adequately cover the range of humeral head dimensions in our Chinese cohort.

CONCLUSIONS

The geometric parameters of the humeri in the Chinese population differ from those in other populations. These differences have clinical relevance with regard to implant design and arthroplasty technique and likely affect clinical outcomes.

Diachronic changes in size and shape of human proximal tibia in Central Europe during the latest 1200 years

During the past twelve centuries, the stature of Central European inhabitants has increased significantly with corresponding changes in the size of lower limb bones. The aim of our study was to determine whether these changes have occurred strictly in relation to size or if the shape of skeletal structures has been altered simultaneously. Diachronic size and shape changes in the proximal part of tibia in a Central European population (Czech Republic) were studied using geometric morphometrics (principal components analysis, Hotelling's test, linear discriminant analysis). The study sample consisted of 183 three-dimensional (3D) models of adult tibiae dating to the early Middle Ages (N=65), early 20th century (N=60), and from a modern Czech population (N=57). A positive secular trend in size manifested only between the two modern Czech populations (the 20th century vs. the 21st century), a time range shorter than one century. By contrast, landmark-based shape analyses revealed significant differences in tibial morphology over the three periods covered in the study. In particular, progressive changes were observed in the position of tibial tuberosity (shifted medially), the inclination of the line connecting tuberosity with anterior edge of the tibial plateau (sloped down), the reshaping of the lower back condyle boundary (shifted posteriorly), and reshaping of the medial contour of the medial condyle (shifted anteriorly). Changes in the shape of the proximal tibial extremity across the chronologically distinct groups indicated the existence of discreet but convincing microevolutionary trends involving this anatomical structure.

Sexual Dimorphism of the Human Tibia through Time: Insights into Shape Variation Using a Surface-Based Approach

In this paper we present a three-dimensional (3D) morphometrical assessment of human tibia sexual dimorphism based on whole bone digital representation. To detect shape-size and shape differences between sexes, we used geometric morphometric tools and colour-coded surface deviation maps. The surface-based methodology enabled analysis of sexually dimorphic features throughout the shaft and articular ends of the tibia. The overall study dataset consisted of 183 3D models of adult tibiae from three Czech population subsets, dating to the early medieval (9-10th century) (N = 65), early 20th century (N = 61) and 21st-century (N = 57). The time gap between the chronologically most distant and contemporary datasets was more than 1200 years. The results showed that, in all three datasets, sexual dimorphism was pronounced. There were some sex-dimorphic characteristics common to all three samples, such as tuberosity protrusion, anteriorly bowed shaft and relatively larger articular ends in males. Diachronic comparisons also revealed substantial shape variation related to the most dimorphic area. Male/female distinctions showed a consistent temporal trend regarding the location of dimorphic areas (shifting distally with time), while the maximal deviation between male and female digitized surfaces fluctuated and reached the lowest level in the 21st-century sample. Sex determination on a whole-surface basis yielded the lowest return of correct sex assignment in the 20th-century group, which represented the lowest socioeconomic status. The temporal variation could be attributed to changes in living conditions, the decreasing lower limb loading/labour division in the last 12 centuries having the greatest effect. Overall, the results showed that a surface-based approach is successful for analysing complex long bone geometry.

A method for sex estimation using the proximal femur

The assessment of sex is crucial to the establishment of a biological profile of an unidentified skeletal individual. The best methods currently available for the sexual diagnosis of human skeletal remains generally rely on the presence of well-preserved pelvic bones, which is not always the case. Postcranial elements, including the femur, have been used to accurately estimate sex in skeletal remains from forensic and bioarcheological settings. In this study, we present an approach to estimate sex using two measurements (femoral neck width [FNW] and femoral neck axis length [FNAL]) of the proximal femur. FNW and FNAL were obtained in a training sample (114 females and 138 males) from the Luís Lopes Collection (National History Museum of Lisbon). Logistic regression and the C4.5 algorithm were used to develop models to predict sex in unknown individuals. Proposed cross-validated models correctly predicted sex in 82.5-85.7% of the cases. The models were also evaluated in a test sample (96 females and 96 males) from the Coimbra Identified Skeletal Collection (University of Coimbra), resulting in a sex allocation accuracy of 80.1-86.2%. This study supports the relative value of the proximal femur to estimate sex in skeletal remains, especially when other exceedingly dimorphic skeletal elements are not accessible for analysis.

Determination of sex from radiographic measurements of the humerus by discriminant function analysis in Saudi population, Qassim region, KSA

BACKGROUND

Diagnosis of sex from skeleton or individual bone plays an important role in identifying unknown bodies, parts of bodies or skeletal remains for forensic purposes. This study aims to examine the applicability of the measurements taken from the humerus to assess sex, and to contribute to establishing discriminant function equations for Saudi populations for medico legal applications.

MATERIAL & METHODS

Archived X-ray radiographs of humerus for 387 patients (216 males & 171 females) who attended the orthopedic clinics at Suleiman Al-Habib Hospital, Qassim region, KSA in the period from January 2011 to December 2013 were reviewed and analyzed. Five dimensions, including maximum length, vertical head diameter, diameter of head+greater tubercle, right-left diameter at midshaft, and epicondylar breadth were taken and subjected to Univariate and multivariate discriminant function analysis.

RESULTS

The studied radiographic dimensions of the humerus indicate that there are significant differences (p<0.05) between the males and females measurements while the difference between right and left measurements was not significant. The findings revealed that the proximal part of the humerus has greater diagnostic accuracy than distal and middle parts. Accuracy of correct classification varies between 68.0% (epicondylar breadth) and 90.4% (vertical head diameter) for univariate analyses. When the multivariate analyses were conducted, three functions were produced, with the accuracy of ranging between 88.4% and 94.3%.

CONCLUSION

These findings suggested that the dimensions of the humerus, especially the measurements taken from the proximal parts, could be used successfully for sex diagnosis.

Sex classification using the three-dimensional tibia form or shape including population specificity approach

The aims of this study were to enable geometric morphometric sex classification using tibial proximal and distal sexual dimorphism and to evaluate the secular trend of tibial shape/form from the early 20th century to the present day. The study samples consisted of 61 adult tibias from an early 20th-century Czech population and 57 three-dimensional tibias from a 21st-century population. Discriminant function analysis with cross-validation was carried out to assess the accuracy of sex classification. Shape analysis revealed significant sex differences in both tibial extremities of the 21st-century sample and in the proximal tibia of the 20th-century population. Sex-based divergence varied between the analyzed samples, raising the issues of population specificity and diachronic change. Classification using tibial form was more successful than using tibial shape. The highest values of correct assignment (91.80% and 88.52%) were found using the form from the early 20th Czech population.

Sex determination using upper limb bones in Korean populations

The purpose of this research is to establish metric standards for the determination of sex from the upper limb bones of Korean. We took a set of eleven measurements on each of 175 right sides of adult skeletons chosen at Korean sample. Classification accuracy dropped only one or two individuals when only vertical head diameter of humerus is used. Variables in relation with maximal length were less accurate than head diameter of humerus. Two variables were selected by the stepwise procedure: maximal length of humerus, vertical head diameter of humerus. The combined accuracy was 87%. This study of modern Korean skeletons underscores the need for population-specific techniques, not only for medicolegal investigations, but also for the study of population affinities and factors affecting bone configurations.

Three-dimensional analysis of sexual dimorphism in human thoracic vertebrae: implications for the respiratory system and spine morphology

Sexual dimorphism is important for intraspecific variation and well studied in the human skeleton. In the thoracic part of the spine sexual dimorphism is expected for differences in the respiratory system related to body mass, lung capacity, and energetics, and in the reproductive system for adaptations to pregnancy (lower spine lordosis, posture). However, little is known about sexual dimorphism in this anatomical region. We use three-dimensional (3D)-geometric morphometrics to test hypotheses on sexual dimorphism in the first 10 thoracic vertebrae (T1-T10). Forty-six 3D-landmarks were measured on vertebrae of 24 adult females and males of known age and sex. Results confirm that male vertebrae are consistently larger than female ones. Males show more dorsally oriented transverse processes and relatively larger vertebral bodies in upper and lower thoracic vertebrae. Sexual dimorphism in lower thoracic vertebrae affects the orientation of the spinous processes, which is more horizontal in females but more caudal in males. Such regional pattering of sexual dimorphism emerges also from principal component analyses reflecting a complex interaction between the effects of sex and serial position on shape variation. Greater dorsal orientation of male transverse processes reorients the ribs and could lead to greater radial thorax diameters. This fits with greater male respiratory capacities, but may indicate also greater invagination of the male spine within the thorax. Horizontal orientation of the spinous processes in females could allow for a greater thoraco-lumbar lordosis during pregnancy, but more comparative research is necessary to test these hypotheses.

Estimation of sex from index and ring finger in a North Indian population

Estimation of sex is an important parameter in the examination of unknown dismembered and commingled remains. The present study explores the possibility of estimation of sex from length of index and ring finger and the index and ring finger ratio in 140 individuals (70 boys and 70 girls) from North India. Index finger length (IFL) and ring finger length (RFL) of the participants were measured following standard procedures and landmarks. Sex differentiation in the present study was based on sectioning point analysis. The 'sectioning point' for the IFL, RFL and the index and the ring finger ratio was estimated from the average of the mean of male and female values. Binary logistic regression (BLR) analysis was employed to derive a predicting equation for estimation of sex. The results of the present study indicate that significant sex differences exist in the IFL and RFL and index and ring finger ratio. Among finger lengths, RFL is a better predictor of sex than IFL. It is further concluded that the index and ring finger length is of limited utility in estimation of sex in forensic casework and should be employed only in cases when no other means of sexing are available. The study suggests that the index and ring finger ratio should not be employed in estimation of sex in forensic casework due to considerable overlap in male and female values.

Nonmetric sex determination from the distal and posterior humerus in black and white South Africans

The successful identification of human skeletal remains relies on proven diagnostic techniques for sex determination. This research utilized 608 individuals from South Africa (420 men, 188 women) to conduct a blind nonmetric determination of sex from three features of the distal humerus: olecranon fossa shape, angle of the medial epicondyle, and trochlear extension. A scoring system between males and females was implemented, and the aggregate score of the three features determined the estimated sex of the skeletal element in question. With all features combined, black and white South Africans were categorized successfully as either male or female 75.5% (77% accuracy rate for females, 74% accuracy rate for males). This classification rate is lower than what was found in previous studies, but suggests that characteristics of the distal humerus are still quite valuable when estimating skeletal sex. More research is needed to assess reasons for the differential expression of these traits in different populations and to determine whether the method is nonpopulation specific.

Sex estimation of the Cretan humerus: a digital radiometric study

Sex estimation based on measurements of unidentified skeletal remains recovered in crime and death scenes can be accomplished with accuracy. In mass disasters, however, the remains are often fleshed, burned, and/or commingled. As a result, osteometric methods are difficult to apply. In such cases, radiography can be of great use during the examination process. A total of 101 (53 males and 48 females) adult humeri were radiographed using digital equipment (Technix TCA 4R PLUS). Specific measurements were taken on the radiographs and then analyzed. Multivariate discriminant function analysis was applied, and the results showed up to 89.1% classification accuracy. Single variables performed equally well for both epiphyses reaching 86.1% correct group membership. The method proposed here is successful, offering an alternative sex estimation technique applicable to the identification of deceased individuals whose remains are semi-fleshed, burned, mutilated, or otherwise unrecognizable. Specifically, this method is extremely useful when maceration of the remains is not an option.